Spaghettification in “linear” free-fall motion or Spaghettification in “orbital” free-fall motion? hmm… (get you with the long words and caps-locks!) I don’t know what the Earth is thinking!! but, I think I’ll stick with Dr Becky’s explanation - thank you very much - As I have a liking to staying alive! It’s called the tidal force, why is this so difficult for you to understand?
It may surprise a lot of people that the centrifugal “effect” has something to do with tides, but it’s really just “Inertia” in action, and all the matter in the Universe is accelerating away from each other, at an ever increasing rate (?) because, the gravity is unable to negate the expansion.
@@JarredDavidson And I totally agree, although I prefer to describe gravity strictly in terms of inertial mass curving spacetime, and as inertia herself once told me, _"the doors a jar, but it doesn't matter, because we're only travelling at 4mph."_ Those people who think inertia hasn't done anything good for us, should just go home, and take all those great tapes and albums...and burn them! What do you think about that then?
The universe isn't accelerating away from us. All matter is accelerating away from each other; where gravity isn't so strong that it negates the effect.
@@Ominousheat Brilliant! I stand corrected, and will make the appropriate correction in due course. You're absolutely right. In my defence however, I would like say that I only wrote this comment in response to the one below mine, which said there was no acceleration (?). Would you mind if I use your informative reply on my cartoon about the misperception of tides? Thanks
The two tides are of approximately equal height on both sides of the globe shaped planet, because in the *equilibrium* of tides theory, the centrifugal effect is the same across the whole earth, whilst the moon’s gravity diminishes with distance by the inverse square. 👇 Thank you.
That doesn’t seem to make sense.. I remember that the centrifugal force would be F=m \omega^2 r, where the angular velocity \omega is the same across the whole earth (1 rotation per month), but the distance to rotation center r is different, since (as Dr Becky pointed out) the barycenter of the earth-moon system is not at the center of the earth, but about 2/3 of the earth radius to the moon’s side. This would mean that the centrifugal force at the far side would be 5 times as high as the close side of the earth to the moon.. right?
@@CM-cr8wq Hello CM, thank you for the reply, you do realise that I have made a short video, which attempted to dispel the ridiculous claim and fraudulent myth, that centrifugal force was incapable of having any *real* effect in a dynamic Earth-Moon system, and instead they performed some crazy start-stop motion towards each other? And, that I'm more than willing to continue any discussion with you there...if you can find it? 🙄 Anyhow, I will provide you with an answer to your interesting question, seeing as no one is that interested in critical thinking anymore, and it only seems polite of me to do so... You're equation for the centrifugal force is entirely correct, and it's just your definition of the Inertial motion that needs to be re-evaluated. The Earth's motion around the CM (😅 Common Centre of Mass) or the Barycentre, is *not* a rotational motion. It is a translating motion, or as Dr Becky described, an Orbital Motion, which implies one complete revolution per monthly cycle. Whereas, with the Earth's axial rotation, the value of (r) would increase towards the equator, increasing the centrifugal effect, as you correctly suggested, and reducing the effective *'weight'* of an object at that point. With orbital motion around a barycentre, however, every point of mass on or within the Earth, will map out a circle of equal radius (r=4671km) as it completes one revolution around the CM. Therefore, the centrifugal force will remain constant across the Earth, during this monthly cycle, assuming that the orbital path is perfectly circular? I hope that was helpful, and apologise for the lengthy use of numerous words, but it does become increasingly boring having to repeat myself over and over, without any reward for my efforts. Best wishes and kind regards.
@wavydaveyparker in other words. The earth spinning on its axis while it orbits the sun is what creates the tides. There is no gravitational attraction between the earth and the moon. This was disproven by multiple experiments on earth and the moon. The earth is orbiting the sun in a counterclockwise direction. The entire mass of the earth is being accelerated in a counterclockwise direction with the sun as the center of the frame. As the earth rotates on its axis, the ocean is accelerated first in a clockwise direction in respect to the Earth's orbit and then a counterclockwise direction. This creates the daily high tides. The annual high tide occurs the first of the year as the planets elliptical path brings it the closest to the sun. As shown by Kepler's Laws of Motion, the Earth's ocean experiences the greatest rate of acceleration on the side opposite of the sun causing the water to be lifted into a higher radius/orbit. The surface of the earth does not experience the same amount of acceleration from pole to pole. This is why the tides are more pronounced at the equator. To reiterate. The moon has no influence on the Earth's ocean's other than the reflected light.
@@wavydaveyparker Thanks for the reply! I am not sure I quite understand you when you say "With orbital motion around a barycentre, however, every point of mass on or within the Earth, will map out a circle of equal radius (r=4671km) as it completes one revolution around the CM." How can that be? If we imagining at any snapshot of time, the distance between the barycenter (which is at a given point location within earth) and any given point on or within earth is clearly NOT the same, since the far-side of the earth is 5 times as far away to the barycenter as the close side. If the distance is different at a given time, how can they map out a circle of the same radius at a period of time? ... Unless when you say "the centrifugal effect is the same across the whole earth" and all of the above, you mean that it is the same across time instead of across space? i.e. it is the same for a fixed location (with respect to the earth-moon system, not a fixed a location on earth, since earth is rotating one revolution every day) at any time, but it can still be different for different location? The circle they map out would still be circles, but of different radius for different places? That would makes sense! I tried to do a simple calculation to verify this: 1) The force per unit mass of water (aka acceleration) from moon's gravity would be a_g2 = G m_2 / (R_2 - r)^2, where moon mass m_2 = 7.342e22 kg; distance from the moon center of mass to the barycenter R_2 = D - R_1 = 3.797e5 km; the distance from the earth's surface to the barycenter is r=1709km and r=-11046km for the closest point and the furtherest point from earth to moon respectively. This gives us a_g2 = 3.4e-5 m/s^2 and 3.2e-5 m/s^2 in the two scenarios; 2) The centrifugal force per unit mass is a_c = \omega^2 * r, where angular velocity \omega = sqrt(G * m_2 / D^2 / R_1) = 2.665e-6 s^(-1) (i.e. 2 pi per 27.28 days), so a_c = 1.215e-5 m/s^2 and -7.847e-5 m/s^2 for the closest point and the furtherest point respectively; 3) combining the two effects, total force from centrifugal effect and luna gravity effect is a = a_g2 + a_c, which gives 4.644e-05 m/s^2 (pulling towards moon) for the cloest point -4.638e-05 m/s^2 (pulling away from moon) for the furtherst point on earth from earth to moon. (Edit: Made a mistake about the plus/minus sign! I have fixed it in the above. Now the numbers agree!) These two numbers agrees with each other nicely. So nice that I am starting to wonder if there is a mathematical reason behind this.. If it would be true as well, in an alien planet? Thanks for listening. All the best!
It's obvious from your reply that these calculations of tidal accelerations means a great deal to you, and I'm thoroughly honoured that you would consider my appraisal worthy enough for you to share your workings. Please just do me a favour and drop a comment on my cartoon, because I've worked through these calculations on many occasions, and might be able to point you in the direction of some useful resource material. Thanks again. Addition: In the meantime, try calculating the gravitational force of the moon on the centre of the earth, and equate that against the centrifugal force of the earth's motion around the barycentre. You should find that the *net* result is a *zero* acceleration. Good luck.
Thank you Dr. Becky - I could not get my head around this for years and this is the 1st time someone actually explained it so clearly! I love your videos.
@@strong507 Well Stephen, I’m exceedingly happy for you and Tomas and I’m glad it finally added up for you, because when we ‘add’ the acceleration vectors at the centre of the Earth they equal zero! Thanks to the beloved Barycentre, where would we be without eh! Take care.
Dear Dr Becky, this video is exceptional and I sincerely apologise for not arriving earlier - _sorry!_ - seeing as I’m having trouble making a video myself, to correctly explain tides to a younger audience and have only produced something to dispel the totally incorrect assumption that the Earth moves directly towards the Moon in a straight line filling up bulges. This seems like the perfect place to post my boring lengthy comment on the matter…so here goes! Enjoy: When Isaac Newton first proposed the theory of Gravitation in his _‘Principia’,_ around 300 years ago! He unfortunately, neglected to give us the mechanism by which _‘gravity’_ worked! However, he did provide us with some very beautiful and simple equations, to correctly calculate the movement of Planets. His problem started with his acceptance of _‘absolute time’_ and distinguishing the difference between _‘gravitational’_ and _‘inertial’_ mass, which he considered to be equivalent, but being the genius he undoubtedly was, he agonised over that conclusion and knew it might not be completely accurate. It wasn’t until Albert Einstein around 200 years later, that we were finally given the more complete answer to gravity, when he told us that the natural state of things is _‘free fall’_ ... and the _‘mass’_ of an object had the potential to curve the space around itself, within the confines of his proposed idea of _‘spacetime’,_ which he presented in his brilliant theory of General Relativity.... _I hope that helped?_ 🙃 As for the tides... Well, they’re not that difficult to understand really? Think of it like this... At the very centre of the Earth, there is a centripetal ‘force’ of gravity pulling it towards the Moon... And there is also a centrifugal ‘force’ _(I use the term loosely, because it’s a ‘apparent’ force in an inertial frame, but the Earth-Moon system is definitely a rotating, non-inertial frame and it exists)_ due to the inertia of the moving objects wanting to continue in straight lines! These two effects ‘balance’ according to Newton’s Third Law and the orbits continue, because the ‘net’ forces at there centres are zero. The centres of the Earth and Moon are indeed moving on spacetime paths, and don’t experience a ‘net’ acceleration, because they are in free-fall around each other, but still under the influence of a non-uniform gravitational field. When we work out the tides, we use the ‘tidal force’ equations, which effect an object from the centre outwards. Therefore, ‘No!’ pulling, or tugging away from oceans or moving towards the moon filling up bulges is necessary. Just the knowledge to realise that the Earth-Moon system operates like any two-body problem. Of course, we then have to correctly apply the method of resolving these associated acceleration vectors into there respective components and recognise the buildup of sideways pressure in the underlying water column, which is what actually drives the tidal systems, but that’s not my particular area of expertise? Take care and thank you so much for making this video. Kind regards, Wavy 👋.
Yes, I’m afraid what you say is a bit of a misunderstanding. Look up Laplace’s Tidal Equations, which are differential equations that are still used today to accurately predict the tides. There is no involvement of any vertical or axial components, or centripetal forces. The tides are raised by the horizontal tractive forces in the plane of the oceans. Earth’s gravity swamps any vertical components by a factor of about ten million, but the horizontal components of the Moon’s gravity are at right angles to the Earth’s field and aren’t swamped. They are tiny, but crucially they are cumulative over thousands of square miles of ocean, and above all are convergent and are acting on an incompressible fluid. These factors combine to raise tides of a few metres in magnitude and also account for the second or antipodal tidal bulge due to the symmetry of the off-axis forces. The second tide is smaller due to the greater distance from the Moon. The Euler-Laplace model explains why tides don’t arise in small bodies of water and correctly models the domed shape of the tidal bulges. It’s a closed book. There’s an awful lot of rubbish on the web purporting to explain the tides, hardly any of it is correct, yet this was all solved by Euler and Laplace over 200 years ago.
@@oneeleven7897 Oh really!! So, you’re saying that Newton and Einstein are wrong are you! Well I happily pitch either of them against your Euler and Laplace equations any day. You obviously didn’t read the whole comment…at no point did I say that the water is pulled upwards. I even said at the end we have to resolve these acceleration vectors into the horizontal and vertical components and neglect the vertical component, because it is overwhelmed by the earth’s own gravitational attraction. The barycentre is a fundamental, undeniable fact of nature, the earth and moon are both in a freefall motion around their common centre of mass, which Einstein spent ten years contemplating about before publishing his general theory. Are you really going to try and go up against that? Under General Relativity! Gravity isn’t considered as a real force either! Gravity and Centrifugal forces only appear in an accelerated frame of reference, one that is non-inertial…where the apparent force becomes valid. Maybe you should look up the Jean Le Rond d’Alembert principal - it states, that at the centre of an object in rotational motion we can consider the centre of the object as having zero net acceleration. Please read the entire comment again and reflect on what you said? What I said here, did not go against the Euler-Laplace equations in the slightest, as they were both great mathematicians which I still admire greatly.
@@oneeleven7897 And I’ll continue…I also said that to work out the tides we use the ‘tidal force’ equations, which actually don’t involve centrifugal forces only the gravitational differential. Please try and keep up! Orbital motion is a whole different ball game and does involve d’Alembert forces. And I’ll also add that Dr Becky’s video here is a perfectly valid explanation for the *equilibrium* of tides. If you’ve got a problem with that, then I suggest you take it up with her or make a video yourself, which illustrates these wonderful and totally correct Euler-Laplace equations you keep telling everyone about. Take care.
@@wavydaveyparker Dr. Becky clearly claims in the first few minutes of this video that the sub-lunar tide is caused by the Moon’s upward gravitational pull and that the antipodal tide is caused by a centrifugal force. This is completely wrong. The tides arise from the horizontal tractive forces that I have already mentioned. The effect is subtle and could be said to be counterintuitive because the Moon is from our point of view ‘up’ in the sky so might be assumed to pull things up towards it. The real mechanism is like squeezing a soft ball around a circumference; it will distort on both sides of that circumference into an approximate ellipsoid. Newton was the first person to assign the tides to the Moon’s gravity but was unable to produce a mathematical model for them, as he too missed the subtlety of the effect. It was Euler who first worked out he truth, and later Laplace who derived the partial differential equations that accurately account for and predict the tides. So Newton was half right, and there is no need at all to invoke Einstein as it all works perfectly well in the low field classical limit. If you choose to picture the tides under General Relativity that’s fine but it makes no practical difference. The Euler-Laplace model of the tides remains the definitive explanation, and this is not subjective but is the history of science.
A brilliant question Stephen. Yep! The earth and moon are both moving further apart, by approximately 4cms every year…so, the tides will gradually decrease over time! And the length of a day on earth will increase by approximately 1.8 milliseconds every century. This will continue until the earth and moon are no longer in orbit around the barycentre…but, that won’t happen for a few billion years yet, and the Sun would have extinguished itself by then, so don’t worry about it! Ok! 👇
Actually, while it's true that the Earth had been slowing down century by century, that was only true until recently when it began speeding up again and days began to get shorter once again culminating in the shortest and second shortest days on record on june 29th and 30th, 2022, respectively , since the start of the use of the atomic clock. most scientists believe that this increased rate of rotation is probably explained somewhere between the Chandler Wobble and Glacial isostatic lateralization (the melting of polar glacial masses due to Climate change reducing mass pressure on the Earth's crust on the poles exerted by Glacial masses. It may not be long-lived and we may go back to steadily and slowly increasing day lengths/slower rate of Earth's rotation, but for the time being days are getting shorter and the Earth is spinning faster despite the Moon's enlarging orbit.
Interestingly, the solid ground beneath our feet also rises and falls in tides, though this is much harder to see. One way scientists have observed it is through pressure variations in oil bodies deep beneath the surface, directly attributable to the Moon. And in many high-energy accelerators in which sub-atomic particles travel at near-light speeds in tunnels beneath the ground, we need to apply corrections to the magnetic fields that guide them to compensate for the physical distortion of the ground as the Moon passes overhead. In all of these systems, we see tides
Yes, the Earth squishes together as the poles are compressed from tidal (directional) forces, so bulges at the middle a bit. But this confuses many people who believe the Moon is pulling. The Moon can't pull or lift water, it's smaller than Earth, and the gravity is far too weak for that. Lateral hydrostatic flow along Earth surface towards the equator is the cause of the ocean "tides". No tides in lakes or coffee cups. It's amazing what happens when all the stuff agrees on a single direction to move in.
@@glennbabic5954 I have also heard that explanation before, but the sources were less qualified than Becky. There may be some combination of the two effects at play.
Would be interesting to see how this plays out on water planets with more than one moon. Thank you for the bloopers Dr B you always know how to make us laugh!
not really a water planet doesn't really have tides in the sens we see them on earth. Tidal forces still apply of course, but there are no visible local effects.
@@MusikCassette So we need a bit of land mass to better measure the tides. But the whole point would be the different moons magnifying or cancelling out tidal effect.
Sort of like the sun and moon but more layered on top of each other. The moons would likely be in orbital resonances so you'd get one killer tide at some interval!
„Centrifugal force“? I can still hear my physic professor shouting „Don’t call inertia a force!“😂 (I get it’s a question of reference….). Many thanks for the best tide explanation I have seen so far 😀
Sorry for spamming this link, but Dr. Becky's explanation is actually not complete and actually a bit misleading in my opinion. Space Time a couple of years ago presented a much better picture of what is actually happening. ua-cam.com/video/pwChk4S99i4/v-deo.html
This makes total sense. It’s extremely difficult to visualise the effects of gravity in a four-dimensional manifold, using a two-dimensional rubber sheet, in a three-dimensional time space. All you achieve is a demonstration of gravity, using gravity! Which, rather defeats the objective. The gravitational and centrifugal effects of motion around a barycentre, both alleviate the gravimetric tensor of the earth’s own gravitational attraction, and allows water to flow in sideways from the adjoining areas to equalise the system…and, we call this movement of vast quantities of water…tides. All perfectly sensible. Thank you, Dr Becky.
@@davidmudry5622 Hello David, how’s it going? I think we first have to firmly establish exactly what “time” and “space” actually are? Although, we both achieved that sometime ago in our pleasant conversation. So, you already know the answer…but, it’s nice to hear from you again. Take care my friend and keep critically thinking…go
@@wavydaveyparker No, I understand gravity doesn't pull only because light can't be pulled, yet light bends near a massive body. I understand when things are weightless is because no force is accelerating them, and anytime a body has weight is because a force is accelerating them. But when it comes to a high tide on opposite sides of the earth at the same time I need some help as to how space-time can explain it.
@@davidmudry5622 Oh right! I see, but you shouldn’t be so down on yourself, because I don’t think you realise how agonisingly close you are to solving this problem. What you just said there was exceptional, and clearly shows a structured way of thinking, very reminiscent of a certain Mr Einstein. I’ll tell you what…drop that exact comment on my video and I’ll give you a link to someone, who asked the same questions and we can discuss it there. I think the two of you have a lot in common. Take care.
Yes, you’re absolutely right, it’s all to do with Newton’s Laws of Motion, as easy as one, two, three. Nothing is static in the universe, it’s all relative. The action is centrifugal, and the reaction is gravity. For every push, there is a pull, or as Einstein might say, the Earth is balancing on a free-falling bicycle, whilst it’s cycling around the barycentre, it’s just that the oceans have trouble remaining balanced occasionally. Thanks
Sorry Becky, but this explanation is simply wrong. PBS Spacetime made a video about this years ago (ua-cam.com/video/pwChk4S99i4/v-deo.html). The second bulge is caused not be centrifugal force. Actually the pulling force of the moon on the water doen't act on the bulges outwards. It acts on the inward bulges. It pulls the water closer to the ground and the water displaces other water and that water gets "lifted".
We need to get these comments higher, I'd like to see a second video from becky realising about being mistaken! I really think as a scientist & influencer, this is one of the most interesting topic she can discuss (the search for the truth, research in the internet era, and the fact that even the most intelligent and qualified people can be very sure of themselves and very wrong, even close to their own field of expertise)
Nah. As the guy says in the video, tidal acceleration is not real, its just an apparent effect produced by our constantly moving frame of reference. The same is true of centrifugal force. Her explanation and his are just different ways to imagine the same thing. Also, his claim that the effect is mainly caused by the sea being pulled in the middle seems off, to me. You can clearly see from his diagram that the forces "pulling" on the sea are significantly greater than the forces "pushing" on the sea.
Oh God are you saying centrifugal force create the opposing tide??? That's the biggest misconception about tides. Even a stationary system with no rotation would have 2 tides. The gradient of the gravitational field is enough to explain both tide. Just like when falling into a black hole one would get spaghettified, not just half spaghettified.
@@perseverancerover No, it is not a perfectly valid explanation. And no you do not need rotation or any sort of movement to have 2 tides. Tidal forces simply arise from the fact that the gravity force changes with the square of the distance, it does not need movement to take effect. That's basic physics. And the Wikipedia article on tidal forces is enough to understand there is absolutely no need for movement.
@@perseverancerover Just go read the formula for tidal force and tell me where you see the speed or rotation appear in this formula (spoiler alert: they do not). And if you cannot read equations just go watch the PBS video on tides. They explain very well how the shape of the gravitational field creates a pressure gradient on the water on Earth which translates into water level difference. No need for movement.
@UCSgdjTSWiZT8MZTCmom46gw Ok, that's my last response, because obviously you do not understand the basic of physics. We are not having a polite discussion. I am trying to educate you while you make an effort to not understand. The gravitational force is in 1/r², because it is in 1/r² any non punctual object placed in a gravitation field "feels" a different force in its different part. Regardless of its motion, the object will feel stretch and squeezed by the different values of the gravitational force. This stretching and squeezing is what we call tidal force and it is what is causing tides and spaghettification. Now this tidal force is in 1/r^3. And when I say that you make an effort to not understand is that obviously you went to look for the equation. Instead of seeing that speed and motion does not appear in the equation, you jumped directly to the 1/r^3. Felt clever to have something to say I am wrong. But you failed to understand that 1. I was talking about gravitational force, not tidal force. 2. Would it be in 1/r² or 1/r^3 it does not change that the speed does not appear in the equation. Oh and free fall motion, is like no motion at all. And free fall motion is only mentioned to justify we can change referential so that we can ignore the first term in 1/r².
@@gehngis this is the explanation I got in college. I got very confused at the time, but knowing a bit more today, it sounds more correct than the explanation on the video for sure.
In the UA-cam video, *“Why are there two high tides per day?”* the speaker _(Dr Becky)_ says… the earth is not static during all of this, and is in an orbital motion around a common centre of mass, called the barycentre. So, if we look at the gravitational and centrifugal effects closer to the poles, which are nearly tangential to the earth’s surface. Then, they are both right to claim, that these forces CAN accumulate to produce the observed tides.
Grew up in a small village on the coast. Tides can be massive. On the fridge was a tide table so we didn't get caught out by the the tide when going to Mersea Island. The Strood can really catch you.
My favorite way of explaining it is this: objects in orbit are in free fall, and even as the Moon falls toward the Earth (bending its path through space into a curve)... the Earth falls toward the Moon too. But the Moon's gravity is a little bit stronger on the side of the Earth facing it, and a little bit weaker on the side of the Earth facing away. And that causes the water on the near side to fall a bit more rapidly toward the Moon, and on the far side, the Earth is falling away from the water. Thus, two bulges. Tides are caused by *differences* in gravity, and they tend to stretch out objects that are in free fall in a varying gravitational field. In general relativity, in fact, tides are treated as more fundamental than the net force of gravity--they have a more coordinate-independent existence. (Extra credit: figure out how this is equivalent to the explanation Dr. Becky gave.)
I couldn't understand what you wrote, but it seems you are smart :) Becky basically explained the second tide as being due to centrifugal force - but I can't see how there could be one when objects in orbit are going around in a circle due to being in free fall, not because they are being prevented from going in a straight line by a mechanical linkage (like in a fairground ride).
@@gavinmetzler858 From a Newtonian perspective, the mechanical linkage works just like a gravitational force. There's no such thing as a centrifugal force in either case, if you do your calculations in the non-rotating frame; all that's happening is that some force prevents objects from moving in a straight line. But if you consider the *rotating* frame of reference (in this case, rotating around the barycenter), then there's a centrifugal force.pushing outward from the center on both the Earth and Moon, increasing with distance from the barycenter, and also a gravitational force that is greatest where they're closest. And all of that tends to stretch everything out. But it's just the same forces computed in a different reference frame, which is non-inertial (rotating and therefore accelerating).
@@gavinmetzler858 The roundabout is not moving because of the centripetal force, it’s moving because someone or something is pushing it around. If they pushed harder, then the roundabout would go faster and you’d better hold on tighter, otherwise you might come flying off and travel away from the roundabout in a straight line motion. That’s what inertia does to you. The Earth’s *centre* is in freefall, which means at that point the opposing accelerations cancel. That’s what weightlessness does to you. The points nearer and further away from the moon aren’t balanced and move slightly outwards. That’s what the tidal force does to you. Take care.
@@MattMcIrvin All very interesting Matt, but couldn’t we just say, that gravity and centrifugal are both ‘apparent’ forces, which only appear in an accelerated frame of reference. And this leads to a zero ‘net’ acceleration at the centre (ie. Free-fall) and…an ‘outward’ acceleration on either side, leading to a tidal force. Of course the barycentre is what prevents the whole thing from collapsing and becoming spaghetti?
over simplified. the high tide (even at spring tide) is not always "under the moon" . more over, there are places (at least one) that are within the same time zone (in fact, under 200 miles apart) where one will be experiencing a high tide, and another will be experiencing a low tide (at the same time). tides are not caused by the pulling on the water under the moon; but more by the "squeezing" on the water from the poles and topics, towards the earth-moon line (this pull is effect by the ocean floor and land, making "irregular", but periodic).
Right, it's more like squeezing a balloon at the poles. Ocean tides are hydrostatic pressure resulting in lateral flow to a common point. Moon is too small to lift water away from Earth's core.
Thank you Dr. Becky. In the 90's I worked in the local (Tampa, Florida) Planetarium. I got pretty good at explaining this, but I ALWAYS like to hear how others explain it. It gives me different ways of phrasing it when my first attempt doesn't work. On another note: here on the Gulf of Mexico we don't get those regular tides. Technically we do, but a low tide can sometimes be all of 2cm lower than the previous high tide. I have yet to find track down an expert to ask, but I'm pretty sure that the Gulf has a particular rhythm for the water to slosh from Florida to Texas and back, and that interferes (in the physics sense of that word) with the 12 hour rhythm of the lunar tides.
Dr. Becky , I think there is 2 forces first one the gravity of the moon pulls up the oceans from one side of the earth cause the high tide and the second force comes from the rotation of the earth around its axis pushes the water of the oceans to other side of the earth cause another high tide even though it is on the opposite direction of the moon ...
The problem really is that no one actually understands everything about tides. So no one can explain exactly why they work the way they do. For us common folks all we need to know is this, gravity is alive and well and tides on Earth are influenced by both the Moon and the Sun. Why would any of us need to understand it in more detail than that?
@@asthmasayshi131 It wouldn't, no. If there wasn't an orbit, the moon would crash into the earth. If there were a magic non-orbiting levitating moon, all the water would pool on the near side.
Sorry, I have absolutely no idea what a "Double torus *OOrt cloud* magnetoglobe" thingy is? You're just making this stuff up, but I can assure you, that it had nothing to do with me, Gregory. And if I was God, which thankfully I'm not, then I would have left that bit out of my creation, for fear of being mocked, by my minions. Oort bless you.
Yes, but the auestion is then: what is creating the differential pressure? And the answer: is the gradient of gravitational forces. No need for rotation amd centrifugal force.
@@MrGonzonator Yes, and what I said does not say otherwise. Both the squeezing and the pushing/pulling are caused by the shape of the moon gravitational field. My point is that there is no need to invoke rotation or centrifugal forces, unlike @DrBecky does in this video.
*bows down with raised hands* I've always wanted to know the exact reason for this. Schoolbooks just said "it's because of centrifugal force" which was so inadequate that I would go "huh?" Thank you Dr. Becky!!!
Hmm, I watched and read a lot of explanations about the physics of the tides. And most of them - especially on the internet - *does not match with physics textbooks.* Even some physics websites and Becky oversimplify it. Some sources are totally wrong. For those interested in the physics of tides, a good (school) physics textbook is recommended. It is much more complicated than described here or on some websites or YT videos. *In short:* It is the resultant acceleration due to the superposition of the tidal and centripetal (or centrifugal if you will) accelerations. Combined these push the water perpendicular from the earth-moon line to the two water mountains along the earth-moon line, like squeezing a pimple . So, both tidal bulges are caused by the same accelerations, not different ones as mentioned here. Because not only tidal acceleration, but also centripetal or centrifugal acceleration acts on every point on the earth, not just on one side. Of course, this is also simplified. But so it is written in physics textbooks. A pretty good brief visualization can be found at www .geological-digressions .com/wp-content/uploads/2018/08/tides-forces.jpg?ssl=1 (remove the blanks) If you want to stick to YT, PBS Space Time “What Physics Teachers Get Wrong About Tides!” (watch?v=pwChk4S99i4) is a good starting point. But even this video lets some questions unexplained. You can't avoid picking up a physics textbook. PS: I'm not usually the type to explain their job to professionals. And I am also aware that Becky cannot reading along all comments.
Hello Schlaf, why didn’t you mention my “daft” little video in your excellent appraisal? where did you go? I was all ready to discuss the ins and outs of tides with you…and then you disappeared…anyway, you’re right! dr becky probably isn’t reading this, but I just wanted to let you know that I did, and found it all very interesting. Apart from the *fact* that the Earth and Moon are both in a *freefall* orbital motion around a *barycentre* and *not* accelerating towards each other in a straight line, as is depicted in many incorrect tidal explanations. Thank you and take care.
@@wavydaveyparker _"... why didn’t you mention my “daft” little video ..."_ Because I did not know it before and it criticizes only one point of an explanation in another video if we mean the same one. And this is not a problem in Becky's explanation. _"... and then you disappeared..."_ I assume you mean the video from Atomic School. It was a pretty long time ago and I don't remember getting a notification on my comment from YT. _"... the fact that the Earth and Moon are both in a freefall ..."_ Exactly. But that wasn't explained incorrectly by Becky.
@@schlafschafweb Yep! You’re right…it was a long time ago, but I’d remember that sheep anywhere! You’re more than welcome to comment again, because I was attempting to address your concerns over the pbs video you, and everybody else keeps mentioning. The real key to this whole tidal thing is *Balance* - No balance! No Universe! No Universe! No us! It’s just that the oceans are temporarily out of balance twice a day in some places? Whilst the whole Earth remains balanced in its motion around the common centre of gravity.
I agree. Her explanation was pretty incomplete... The video you linked is the most complete explanation I've seen. But in his video, he also fails to mention the wobbling of the planet in the Earth-Moon barycenter and the centrifugal force that it causes. But still, the MAIN explanation is simply the "gravity differential (or tidal force)" between the different points on the planet, but also the fact that the water gets "squeezed" by it... So I think his video is better.
So, essentially what your saying is that you’d like to see a tidal explanation video, or read a definition in a scientific journal, that says, the tides are caused by the inertial momentum of planets and oceans, in orbital motion around a common centre of mass, in a non-uniform gravitational field. That gives rise to a tidal force from the centre outwards, and tractive acceleration vector components, that accumulate pressure across the surface of the water. Well, unfortunately that doesn’t exist presently, so you’ll just have to content yourself with watching both of these correct explanations in conjunction with one another. Good luck
An important note is that the Moon doesn't actually "lift" water. Its gravity is far less than Earth's. Water flows from the poles towards the equator, causing a hydrostatic bulging. The Moon's gravity is enough to cause water flow to change direction, but not to lift it. This is why there are no tides in lakes or bathtubs or coffee cups. Water is not lifted by the Moon. Rather, the tidal forces are lines converging on the Moon. The Earth is larger diameter, so those lines converge rather than being parallel. Water flow follows those lines, converging and so bulging at the equator. Another way to consider this is as a balloon being squeezed between your hands: it bulges in the center as it is compressed.The geology below water level also feels this compression, and bulges in the perpendicular slightly. Even if the Moon was 1 meter away from Earth, it still would not lift water away from the Earth, as the Earth gravity is stronger. Hence why water reservoirs do not lift even a millimeter during High Tide. (Maybe too technical for the video, but i meet a lot of people who were told in school the Moon actually "lifts" the water on Earth. But those teachers didn't calculate the gravity first, (obviously). They probably assumed somebody else did the calculation, because their teachers told them the same thing. It happens.)
This is also why the few lakes that do have tides, tend to be the ones with their long direction oriented north-south, and located close to the 45 degree latitude line. Lake Michigan has a very subtle tide. It can be hard to notice that it is a tide, but you can conclude that there is a cycle to Lake Michigan's level that is consistent with tidal cycles.
Eben if it could "lift" it ina sense that you describe, it would look like bubles of water floating up, not sea level rise. (and the whole earth would shatter as well, so thats not very useful)
@@carultch "True tides-changes in water level caused by the gravitational forces of the sun and moon-do occur in a semi-diurnal (twice daily) pattern on the Great Lakes. *Studies indicate that the Great Lakes spring tide, the largest tides caused by the combined forces of the sun and moon, is less than five centimeters in height.* These minor variations are masked by the greater fluctuations in lake levels produced by wind and barometric pressure changes." -- NOAA Yes, it would indeed by difficult to measure 5 cm level change. Especially when temperature, air pressure, and wind dwarf that variance. Longitudinal lakes on a calm, steady day. And only then from the height of Spring Tide to the absolute antithesis... 5 cm. Tides in the oceans however: 40 FEET in Bay of Fundy, Nova Scotia. To quote by paraphrase Crocodile Dundee: "That's not a tide. THIS is a tide".
That is actually the effect of the Moon lifting the water. It just happens that the lift is less on the poles that on the equator (because is further away). The difference is very small, but enough to cause a current flowing to the equator. Lakes and the mall seas, don't have this effect, because they are not big enough i the north-south direction to sense the difference , and in the Mediterranean case in addition to being "flat" north-south wise, is connected to the rest of the oceans by a very small channel, not big enough to allow enough water to bulge.
This is the correct explanation. A *revolving, translating* coordinate system is not assumed for the purpose of analysis. It is a *fact* of orbital motion around a common centre of mass. The inertial forces from such a motion can raise tides. *Gravity is an inertial force.* The tides are due to a combination of the gravitational and inertial effects of the Earth, Moon and Sun in orbital motion around a barycentre. The problem stems from the fact that gravity isn't actually a force, and is incapable of pulling water upwards across empty space. However, everything in the Solar System is in orbital motion around a *barycentre,* and that means it is subject to the influence of a host of *apparent* accelerating forces. I could continue, but I've discussed this at length elsewhere and just wanted to reassure you that the subject of tides has been thoroughly examined by science for over three centuries, *by the likes of real astrophysicists including: Johannes Kepler, Galileo Galilei, Issac Newton and Pierre Laplace.* The *udiprod* and *pbs* explanations are both correct explanations in accordance with *Dr Becky's* and the waterlust farse is a complete waste of time. Have a nice day! 😁
Thanks, you explained that very clearly. Any tidal explanation is dependent on the facts acquired through experimental data and observations. *These are the facts about tides:* *Lunar tides:* The Earth is in orbital motion around a barycentre with the Moon, and the tides are caused by the gravitational interaction with Inertial forces. Gravity is an inertial force. *Solar tides:* The Earth is in orbital motion around a barycentre with the Sun, and the tides are caused by the gravitational interaction with Inertial forces. Gravity is an inertial force. *The equation for inward inertial action:* *F = GMm/R²* ~ Newton's Universal Law of Gravitation, by Sir Isaac Newton 1687. The experiment that validated this equation for mass attraction: *The Henry Cavendish experiment* ~ Conducted by Henry Cavendish in 1797, which determined the value of *Newton's Gravitational Constant,* and allowed us to calculate the average density of the Earth. *The equation for outward inertial reaction:* *F = mrω²* ~ where *(r)* is the distance to the *Barycentre.* You're welcome. 🙂
I think you are mistaken. Its not that gravett pulls up the tide. It minutely squeezes the ocean. Check space time. ua-cam.com/video/pwChk4S99i4/v-deo.html this is the best description I've seen.
The funniest part of this excellent explanation is: 06:55 Here you go! _"You say either, and I say eyether._ _You say neither and I say nyther._ _Either, eyether, neither, nyther..."_ *Let's call the whole thing off!* ~ written by George Gershwin and Ira Gershwin. You're so funny Dr Becky. Thanks for that appraisal of reference frames, it was hilarious! 😄
My physics teacher was a strong proponent of the, "there's no centrifugal force" argument. Unfortunately, never explain why which made the video we watched on centripetal, centrifugal, et.al. forces tricky to digest :/ - until now! Thx, Dr Becky!
Mademoiselle, this tidal presentation is exquisite, the wolves below doth protest too much, methinks? _"Sköll the wolf who shall scare the Moon,_ _Till he flies to the Wood-of-Woe:_ _Hati the wolf, Hridvitnir's kin,_ _Who shall pursue the Sun."_ ~ *A quote from Grimnismál, from the Poetic Edda.* Thank you for sharing your knowledge with us Dr Becky, and for scaring the wolves of ignorance. 👇
It would all make more sense, if we had a 13 month calendar @ 28 days. And start the new year with a 0-day. It would be so much easier to calculate/plan stuff.
One thing I think you forgot to mention is the fact that gravity is dependent on distance. The side of earth facing the moon is slightly closer to the moon so the gravitational pull is stronger than the centrifugal force. On the other side, the moon is slightly further away so the gravitational pull is weaker than the centrifugal force.
The explanation I once saw was to imagine three balls lined up vertically to the moon. Allow the balls to fall under the moon's gravity. The ball closest to the moon gets attracted slightly more than the middle ball, which gets attracted slightly more than the outer ball. The result is that the two outer balls move away from the center ball.
@@charlesgantz5865 That is an excellent way to imagine it Charles. In Physics, it’s called the ‘spaghettification’ effect. Unfortunately, in your example those balls are still free falling towards the moon in a straight line. And, that’s where the barycentre, orbital motion and the centrifugal effect of inertia suddenly appear.
So a few things... first thank you for staying away from mis-leading clickbait titles on your videos. It drives me insane when science channels do this. Second, thanks for just educating us on random things. It's really fun, and this is information I didn't know I needed but now I can't wait to blow my friends minds telling them the Earth and moon actually revolve around each other. And lastly... love the blooper reels. WOBBLE WOBBLE WOOBLE WOBBLE.
The laws of Physics are equally applicable to all observers, regardless of there frame of reference. As far as a photon is concerned, it's moving with a constant velocity in a straight line motion, in its inertial frame of reference. However, it can still be affected by the gravitational field strength of the Sun, and is therefore deflected from its straight line trajectory. That is why we see a change in the position of distant stars, during a total eclipse of the Sun. Newton's Laws of Motion and Gravitation are both valid in a given timeframe.
Sorry but you are wrong. The MATTER AROUND the star is what deflects the photon. It's called refraction and is explained with Lenz's law dealing with current flow. The magnetosphere will redirect the light around a planet or star but the mass itself doesn't.
What a surprise! I'm actually quite relieved, if you had said, You are right! Then, I might have considered re-evaluating my position. 😆 Photons don't have an electric charge and thus are not affected by electromagnetic fields. Refraction and Diffraction are another matter, and involve the motion through differing mediums.
@wavydaveyparker refraction applies to both light and sound waves. That's why I don't understand all this gravitational attraction nonsense. It's flat earth/ stationary plane garbage that was disproved back in Galileo's day. And yet idiots like Hawkings and Einstein and even Newton still think the earth is a stationary frame and the center of the universe in which everything revolves around it. Didn't a king use his body measurements to establish the imperial units? They are doing the same, only measuring the universe using the earth as the unit of measure. Sure if you want to know things like Mars' gravity is 80% that of Earth's. The universe deals in Absolutes. It doesn't even know the earth exists so how can the earth define the universe. Nobody understands what a frame of reference is. The earth, rotating on its axis, that's one frame on reference. The earth orbiting the sun, that's the second frame of reference. Gravity decreases as one nears the pole because motion in space decreases. 1000 mph at the equator to zero at the poles, but you still have the earth in motion around the sun of 67000 mph. Then there is atmospheric pressure. Not only is the ground accelerating your mass, but you are also accelerating the air above you. Which is why gravity decreases with altitude. Since gravity comes from acceleration, it can't affect light waves that are pure acceleration. You can aim two light beams at each other and the forces cancel each other out. But light is not going to be pulled into the planet by its mass. Black holes aren't sucking in light no more than planets suck in sound waves. You can't fix stupid. The church of relativity have dug themselves a hole so deep, they can't climb out of it without looking stupid in not understanding basic physics.
Added to the possible fact, that if we were somehow able to place ourselves in a photons frame of reference, which is almost completely impossible! Then, we'd have no concept of space or time, because everything would be happening everywhere at the same time, and we would feel motionless to do anything about our predicament.
@cybermonkeys wrong. Beside the fact that your atomic energy is converted to radiant energy, the laws of physics still apply. The photon is accelerating itself. Dropping little atomic bombs out the back to accelerate itself forward. That's what redshift is. The loss of energy as the photon travels through space. Applying the Lorentz transforms, INFORMATION about your destination will be sped up while INFORMATION about your departure will be slowed down. Traveling to Alpha Centari, you will fly through the INFORMATION stream at 2x the speed of light. What is coming towards you and what you are traveling towards. Warping acceleration, so you are not converted to radiant energy, leaves you witnessing the forward view screen at 2x and the rear at 0x while normal time passes within your frame.
Hello Dominic, The acceleration due to gravity at the surface of the earth is 9.8m/s2. The acceleration due to gravity at the surface of the moon is 1.6m/s2. However, the pulling force between the two is the same, because gravity is proportional to the product of both the masses and indirectly proportional to the square of the distance they are apart. Does that help or would you like me to use actual numbers?
@@DOM_4GOOD wow, thanks very clear 10/10 ! It was nothing really 😄 just the simple use of F=ma, but your great question did get me thinking about some follow up questions. Maybe you’d like to drop a comment on my channel and we can work on some more simple math together. Thank you for replying. Take care.
Oh, Cherry Oh Baby, that's really interesting, thank you. Did Eric know Bob Marley? The Rolling Stones covered that track on their _"Black and Blue"_ album in 1976. Brilliant.
The tides can easily be explained using Galileo's principle of inertia, Kepler's laws of planetary motion and Newton's universal law of gravitation. The accelerated motion of freefall was used to demonstrate why all objects fall in a vacuum at the same rate, regardless of there mass. The ground is not a stationary plane and moves with an orbital motion around a common centre of mass, called the Barycentre. It does not float off into space with a straight line motion, unless someone miraculously manages to remove the Sun from our solar system, and then it will still take approximately eight minutes, for the structure of spacetime to adapt to this change in motion. The effects of gravity also travel at the speed of light. The National Aeronautics and Space Administration courageously planned and meticulously calculated several excellent missions to the Moon, not only to prove Galileo, Newton and Einstein correct, but to also show that the Earth was in orbit around the Sun and rotating on its axis. A delicate balance between inertial and gravitational mass, along with the necessary existence of a curved spacetime. Galileo clearly showed in the 16th century, that there was an attraction between objects of mass, by rolling objects of mass, down an inclined plane, and calculating the observed rate of acceleration. The tides are the natural result of the centrifugal effects of motion, whilst moving through a non-uniform gravitational field, that fortunately obeys an inverse square law geometry. Flat earth is not a science, and is devoid of any examinable evidence or able to make any viable predictions and just resorts to making unfounded claims that follow on from the ridiculous assumption, that the earth is stationary, two dimensional and pristinely flat, and is somehow sitting motionless at the centre of our galaxy.
Thank you dear Dr. Becky ❤️ .... And I'm always waiting for your videos about *Hubble* please make more video about it and its discovery and news (you are the best person for it).
One other interesting thing about tides, they don’t effect rivers or lakes. The actual tidal forces are minuscule, the only reason why we see tides at all is because the water allows circumnavigational flow of water. This allows basically a standing wave to rotate around the world. If the flow of water was blocked off then the tidal forces would be virtually imperceptible. As it is the current tidal bulge is just over 50cm (1’ 8”). It is higher on coast lines and river outlets for the same reason tsunamis are small bumps in the deep ocean but huge waves on land. It amazes me on how weak gravity is and yet its influence goes so far.
Right, the Moon doesn't "lift" or "pull" water away from Earth. It changes the flow direction. All the water flowing towards the equator causes the bulge due to hydrostatic pressure. Water flows towards the equator because the Earth is larger than the Moon, so those force lines converge towards the center. It's amazing what happens when a single direction is agreed on. Be it tides, or magnetism, or tornados and hurricanes. Motion is the same magnitude, momentum is conserved. But when it all agrees on a single direction: it's nothing short of amazing.
It also amazes me that tides still work even though there are multiple landmasses blocking water from flowing around the Earth near the equator - South America (plus Central and North America for a big blockage in the northern hemisphere), Africa (plus Eurasia for another northern blockage) and Indonesia. The tides require a significant current to move water to where the high tides are - mostly the high tide itself moving, but that's clearly complicated by the land masses. The only major current that circumnavigates the globe is around Antarctica. I would have thought there's some degree of tide circumnavigating the globe around the Arctic too - there's no continent, the ice is floating on the surface so water can flow underneath and the ice is presumably vertically mobile, and that ice doesn't always reach Canada, Greenland, Scandinavia and Russia anyway - but I don't see anything marked around the Arctic on maps of ocean currents. So yes, it's pretty impressive that there's enough flow to maintain this standing wave, given that the tidal forces are highest at the equator which is obstructed by land. I guess that depends on the Pacific, Indian and Atlantic oceans covering large chunks of the equator, leaving enough room for tides to occur, and creating enough pressure to maintain the needed currents around the barriers?
@@onebylandtwoifbysearunifby5475 The whole planet deforms, as does the moon. It's just that in rotation the solid part of the Earth is attempting to pass through the much more fluid oceans.
"they don’t effect rivers or lakes" - nope. Larger lakes can experience tides. See for example the North American Great Lakes. It's just that the tides on said lakes are much smaller than ocean tides.
@@stevehorne5536 There are certainly strong global oceanic currents. They are strong enough to maintain direction of flow through tides. The longitudinal directions are not to be overlooked. There isn't much obstruction between N and S hemispheres, most of the landmass is in the Northern hemisphere. So the flow in largely N-S unobstructed. Where it meets land, there are tides of course. But water pushes equally in all directions. Water pressure increases with depth, not surface area. (And even the surface area is 70% water). Pressure equalizes in all directions, pushing the water higher where there is more of it. Persistent force and small accumulations make a startling difference, yes. It's not something one would predict as obvious. One interesting thing to think about is how pressure increases on deep sea life at high tide areas. All that water stacked on them probably is rather noticeable. Probably a lot of cycles we don't even know about in marine life.
Ive heard it explained completely differently but in the linear reference frame. I suspect theyre the same explanation just with different reference frames, this one is easier for me to understand because of...the orbiting going on.
That is a superb comment Matt. Thank you for having the wherewithal to type such clear reasoning. Even though this wasn't my creation. There are only two reference frames we need to concern ourselves with here. An *inertial* reference frame, and a *non-inertial* reference frame. An inertial reference does *not* accelerate. Therefore, it does *not* contain any resultant action from any external forces. The Earth and Moon are in an orbital motion around a barycentre. Therefore, they are accelerating, and have to be considered in a non-inertial frame of reference. Where the external forces of gravity and inertia (centrifugal effect) have to be taken into consideration. Leading to the twice daily tides we observe on the surface of our precious planet Earth. Thank you.
I love the way you explain concepts. The questions you ask and the way you link all the components to clarify the explanation. This video is awesome but uses Southern Hemisphere orbits(clockwise). Could you also make one for Northern Hemisphere with counterclockwise graphics? The students of Georgia, USA would be very grateful!
That is a really brilliant comment, but must admit that I'm now completely confused. I might leave this to Dr Becky's expertise, seeing as she is in the northern hemisphere, and I'll just go and fly my battle kite instead. I thought the graphics were going counterclockwise, I must have been watching this, while standing on my head. Thanks for the heads-up! I wondered why I was beginning to feel dizzy.
Centrifugal force might explain high tides on the side of Earth opposite to the Moon because the barycenter is inside Earth. I don't think it can explain the effect of the Sun because that barycenter is inside the Sun.
Except it does explain the effect of the sun. Not the sun-Earth's barycenter, but the Earth's center of mass. What happens is that the Earth's acceleration due to the gravitational fields of the sun and moon, is based on the gravitational force on the average kilogram of Earth, summed up across the entire region of space that the Earth occupies. Locations on the side of Earth closest the source of the tidal force, receive greater force per unit mass than the average kilogram of Earth. Locations on the opposite side, receive less force per unit mass than the average kilogram of Earth, and therefore will lag behind the Earth. In the reference frame of the Earth's center, this will make it seem like that particular portion of the Earth's surface weighs less, and likewise, the side closest to the source of the tidal force, will seem like it weighs less as well. It is the locations where the body causing the tidal force see it at the horizon, where the apparent weight will be greater, which is where low tides happen when the moon is at the horizon.
Try to explain this to the infamous Fox News host, Bill O'Reilly, who in a news cast with an atheist said: "Tides go in, tides go out. You can't explain that!" The atheist was so baffled, he didn't know what to say, in reply to such stupidity.
I used to think that the explanation given of the moon's gravitational attraction pulling the water and thought each day only had one high tide When i saw the normal illustration shown I've been confused for a while ....now i know about tidal forces 👌
Hm, now I am confused. I learned that the Tidal Force is responsible for this effect of tides. Does this seeming "disagreement" have to do with different frame of reference being observed?
I am confused about your confusion. Why? Tidal Force is the result of Centrifugal Force + Gravitational Force. Both those forces act in nearly the opposite direction on any place of earth. So if you simply add up this both forces the result would be close to zero. You have to do it in an vector addition, so they don't cancel each other out completly. The resulting tiny vector represents the direction and strength of your tidal force. This only works because the angle between those two forces is less then 180°. This is also the reason why the tidal force of the moon is so much bigger then the tidal force of the sun. Although the gravitational force of the sun measured on earth is many times higher than that of the moon. It's ultimately all about the angle between the vectors.
Yes, good point. "Tides" are hydrostatic forces due to cumulative directional water flow, not "lifting". The Earth gravity is stronger than the Moon, so no lifting away from Earth surface. Smaller bodies don't lift larger ones. Rather, the Earth is larger diameter than the Moon, so the tidal forces converge towards the center, causing a bulge at the equator. This bulge is largely symmetric, hence the "tides" on the opposite side. That plus the barycenter rotational forces of the Earth-Moon system mentioned in this video. It's both, but mainly hydrostatic (lateral) water flow towards the equator.
You should look up the video on tides by PBS Spacetime. It goes into much more details. Tides are mainly caused by the oceans flowing towards the equator rather than being lifted up by moon's gravity. Other phenomena like the ones mentioned in this video are minor contributors. I'm no expert but this video seems incomplete
This is not the correct explanation. Even when a rotating coordinate system is assumed for the purpose of analysis, the centrifugal forces have the same size and direction anywhere on or within the earth. So they cannot raise tides. "Tidal bulges" are not due to rotation, but are simply due to the combined gravitational fields of the earth and moon, and the fact that the gravitational field due to the moon has varying direction and strength over the volume of the earth. I like many of Dr. Becky's explanations, but you can watch PBS Spacetime and other reliable physics channels to see why this is not the case. I recommend Waterlust and udiprod's videos on this topic to understand tides better.
Who said anything about the effect of a rotation on it's axis. That is not applicable in a equipotential tidal height analysis. It is an orbital motion around a common centre of mass that is important here. As is proposed by udiprod. Actually, what Sir Isaac Newton would say, instead of F=ma, is that at the centre of the Earth. The centrifugal force balances the centripetal force. So, *F= -ma* ~ Therefore, *GMm/R² + (-mrω²) = Zero* Where *(r)* is the distance to the *Barycentre.* The Moon's gravity at the centre of the Earth causes nothing whatsoever, because the the Earth is weightless in space. In a freefall motion around the common centre of mass, in the Earth-Moon system. A force is not required to maintain motion, and the so-called gravity at the centre is not a force. So what causes tides? The two tides are of approximately equal height on both sides of our globe shaped planet, because in an *equilibrium* of tides theory, as was proposed by Isaac Newton. The Earth is not static in space, and orbits a barycentre. The centrifugal effect from this inertial motion is the same across the whole earth, whilst the moon’s gravitational attraction diminishes with distance by the inverse square. This inevitably leads to an average tide height of approximately *0.54m* on either side of Earth, pointing away from, and towards the direction of the Moon. And an average tide height of approximately *0.25m* on either side of Earth, pointing away from, and towards the direction of the Sun. And an average tide height of approximately *0.79m* during a spring tide. Any other complications, then you'll have to consult with Pierre Laplace. Are you honestly trying to imply that Newton got his theory of gravitation incorrect? I'd think again if I was you. The pbs explanation is correct with reference to the tractive component, but the waterlust mistake is just flawed, because it holds to the idea that the ocean is left behind in a linear acceleration towards the moon.
This explanation is much better than others, because it’s simplified to a point that is correct and easy to understand. The tides are essentially caused by the inertial motion of planets and oceans around a common centre of gravity, in a non-uniform gravitational field. I see no reason to mention the SpaceTime extravaganza here, as it only deals with a misleading static scenario of tidal forces and makes no mention of the tidal effects produced by orbital motion around the sun.
I would move the Barry center closer to the 1/6 the distance to the moon since the moon's apparent mass is 1/6 the size of earth! Did you also knotice that the earth isspinning 28 times faster than the moon, so even though the earth volume is 50x bigger than the the moon, its gravity is only 6x bigger! We need to start using the mass on the moon so that we can accurately predict their true mass! I bet you guys underestimated the mass of Jupiter as well since it's rotates 2.6x faster than the earth!
Hey there, whilst most of what you say is correct. I personally think you’re getting slightly confused through the use of some of your terminology. The barycentre is the balance point of the system, around which objects of mass orbit. Its value can be calculated by using the relatively simple equation given here. Although, it can also be determined by equating the balance between the inertial motion of the earth, against its gravitational attraction to the moon, or its centripetal effects against its centrifugal effects. I would be glad to work with you through these calculations, in my own comment section, if you’re interested. Kind regards
@wavydaveyparker I agree! I think the mass that we are assigning to each planet/moon is obscure by the centrifugal force. That's why planets that are spinning faster than earth would be estimated lower and slower like moon or other planet with slower spin to be larger in mass. I am assuming you are calculating mass based on the gravity experienced. If we assume density is the same for all the objects, we should be able to find correction factors for the mass of objects with varying rotation speed.
@@kmyase1 That’s interesting, and I’m glad you agree, but I determine the mass of an object in orbital motion, by using Kepler’s third law of Planetary Motion, like most physicists have done, since the time that Cavendish correctly calculated Newton’s Universal Gravitational Constant. However, believe it or not, this is Dr Becky’s excellent tidal explanation, and you’re more than welcome to discuss this further with me, in my comment section if you can find it? Thanks
Centrifugal effects are capable of causing tidal forces, in conjunction with the inverse square law of gravity. Centrifugal and gravitational forces cause very little effect on tides, especially around the barycentre. Thank you for teaching this, it is a very accurate depiction of our twice daily tides. Tidal forces don't have to be orbital, but in a balanced orbital Earth-Moon system, around a barycentre, they are essential. Gravity is universal and non-uniform. All parts of the earth are accelerating towards and away, from all parts of the moon at different rates, and it is causing the Earth to squeeze and not the oceans to lift. If you want to truly understand tidal forces, then you need to understand General Relativity, because General Relativity is built upon an accurate description of tidal forces. Thanks
Aren't tidal forces themselves involved as well? Water on the opposite side of the Moon would be slightly further from it than the Earth itself, and hence pull would be a little less, so water would "lag" behind, causing a tide.
Tidal forces are the correct explanation because they elongate the objects, in this case the Earth, even if they do not rotate. Gravity and the centrifugal force are conveniently influencing the right sides of the Earth relative to the Moon in Becky's explanation.
Tidal forces are the correct explanation for tides, but if they didn’t revolve around the barycentre together, then they would accelerate towards each other and the tides would rapidly increase, until collision. In Dr Becky’s video the tidal forces are taken relative to the centre of the earth outwards, because that is the zero reference point.
I always thought it had to do with the fact that the Earth is in free-fall around the Earth-Moon center of mass, which cancels out the component of the Moon's gravity pointing directly toward the Moon's center of mass, leaving only the inward-pointing component due to the fact that the lines from the Moon's center of mass to the different points on the Earth are not parallel. The Sun's tidal influence on the Earth is less because being so much farther away, those lines are closer to parallel, and the inward component, after canceling out the component that points toward the sun, is smaller.
This is correct but misses some things. On the side of the planet facing the Moon, the gravitational acceleration caused by the Moon is stronger than that applied to the planet as a whole, so you could think of it as water falling slightly away from Earth - so you get a tidal bulge. On the side opposite the Moon, the Moon's gravity is weaker, so the acceleration applied to the water on the far side is less than the acceleration applied to the planet as a whole. The end result is the planet itself falling slightly away from the water, so you get a tidal bulge on the far side as well. But since the planet and the water sticks together by Earth's much stronger gravity and molecular bonds, this tidal force makes itself apparent as a "stretching" component - essentially it puts the whole planet under tension, not just the water on the surface. Additionally the inward-pointing component applies a compressive force on the globe. As far as tides are concerned, you could also look at it as the gradient of gravity applying a tangential acceleration to water all across the globe, pushing water towards the high tide bulges and away from the neap tide recesses. On top of that there is the centrifugal effects from the fact that Earth is rotating around the Earth-Moon barycenter, but that effect *stacks* on top of the tidal bulges caused solely by the gradient of gravity.
@@HerraTohtori Another thoughtful comment. Well done! But, can I politely suggest one slight correction? You said, _“The end result is the planet itself falling slightly away from the water…”_ That should read, “The end result is the water itself falling slightly away from the planet…” Because at the centre the opposing accelerations cancel. The Earth is in free-fall and the whole planet receives an ‘outward’ acceleration to balance the Moon’s gravitational attraction, which is weaker on the far-side. It’s really very simple.
@@wavydaveyparker It's all relative! The important thing to realize is that the difference in gravitational acceleration points away from the surface on both sides. I was attempting to use the linguistic inversion to highlight that, from the perspective of the water on the far side, Earth is being pulled more towards the Moon than the water itself is, leading to "planet falling away from the water" - or, in reality, leaving the tidal bulge slightly higher.
@@HerraTohtori Yes, it is all relative! At the centre of the Earth the acceleration vectors cancel, just like Daniel described. The tidal force acts in an outward direction from this point. There is no need to mention any other perspective. It’s unnecessary baggage.
There is a huge difference between a respected *Astrophysicist,* explaining tides correctly, without mentioning the motion of our planet around the *barycentre,* or the resulting effect from any apparent forces, which maybe present in a tractive component. And, a chemistry teacher telling you that these forces do not exist, and that the tides are solely caused by the Earth shifting position directly towards the Moon in a straight line motion, which quite frankly is totally ridiculous, and an insult to classical physics, classical music, and the obvious intelligence of any average human being. Thanks again for this interesting and accurate video.
Do you honestly think Becky is a true astrophysicist? You really are delusional. Galileo proved the non-existence of gravity. Of mass attraction. That the earth is a 3d sphere in orbit around a central star. He correctly theorized that the tides are the result of the Earth's motion around the sun. Rotating on its axis, the Earth's mass is being accelerated outward and forward accelerating its mass into a higher orbit/radius as evidenced by the tidal bulges. The fact that it is in orbit around the sun changes the direction of rotation twice a day. From clockwise to counterclockwise. Hence, tide comes in, tide goes out. Rivers and lakes don't have pronounced tides because the bank is pushing back and dirt has more force to resist acceleration than water. Becky is obviously unfamiliar with Kepler's Laws of Motion or she would know that the annual high tide occurs on the side opposite of the sun when the planet makes its closest path and experiences the most acceleration. There is no interaction between the earth and the moon because mass is not an actionable force. You would still get the same tidal effect without the moon in the sky. Any competent astrophysicist would know this and not be scamming you with gravitational attraction nonsense. So quit encouraging her to lie. Since Google refuses to flag her videos as flat earth physics, her viewers need to do so in the comments. If Becky has an issue with that, then she can address why Galileo is wrong. Why Newton's Law of Motion, F=ma, is wrong. Why Kepler's Laws of Motion, acceleration increases as the radius decreases in an elliptical orbit, is wrong. Three highly regarded physicist, all saying the same thing. There is no mass attraction. There isn't even an equation for mass attraction. Nor any experiment that validates mass attraction. You are being brainwashed by flat earth physics. Educate yourself because Becky is just regurgitating the nonsense she was told or read in a book.
Thanks, you really know your stuff. Here, this might help ease anyone's doubts, if they have the wherewithal to grasp the concept: The equation for mass attraction: *F = GMm/R²* ~ Newton Universal Law of Gravitational Attraction, by Sir Isaac Newton 1687. The experiment that validated this equation for mass attraction: *The Henry Cavendish experiment* ~ Conducted by Henry Cavendish, funnily enough! 😅 In 1797, which determined the average density of the Earth, and allowed us to calculate *Newton's Gravitational Constant.* If we take the time and do some real courses in *Physics.* Then, hopefully one day, we all might become respected *Astrophysicists,* like Dr Becky.😂
@@cybermonkeys you should go back to school and learn some real physics. Galileo proved in the 1590s that there is no mass attraction. When two objects of disproportionate mass fall at the same rate, where is the mass in the equation? There is only Acceleration. F=ma. Mass is not an actionable force. Newton's gravitational attraction equation. That just states that mass equals mass. Where is the action? The laws of physics are equally applicable in all frames of reference. Turn the frame horizontally. What happens then? Acceleration differences. Gravity is an artifact of Acceleration. Your god Einstein pointed this out himself. There is no difference in the orientation of the frame. The physics is still the same. Mass attraction came from the fact that you kids believe in a flat earth with everything else floating around it. How else do you expect to stay rooted to the ground? Galileo's ball drop experiment-> no mass attraction Newton's, F=ma. Force equals Acceleration. The earth spinning on its axis is accelerating its mass outward and forward creating curved space. Your are being accelerated outward. Not pulled inward. What? Do you think the Earth's mass force is greater than its acceleration force? You are a true flat earther there Skippy. F=ma. Mass TIMES Acceleration. Mass has no force without acceleration. Acceleration is the Acceleration force. Mass is just mass. Stored energy taking up space. E=mc. You don't even understand basic math and physics because you are stuck on stupid flat earth science. Why don't you go look at LIGO. Are the detectors being pulled towards the source or pushed out of alignment. Sounds like tractor beam technology if you can get an electromagnetic wave emanating outward to pull matter back towards it. You have to be really dumb to believe that mass is an actionable force. It's F=ma. Not m=a. Take a pan of hot water. Now add some ice (mass) do you get more acceleration-> increase in temperature? Go back to school there kid. You have a lot to learn yet.
Brilliant! I now understand. Your knowledgeable lessons have been invaluable. Thank you. The Centrifugal Force was an idea introduced by Newton himself, to explain the _'apparent'_ outward movement of an object in circular motion, very similar to the action of a *centrifuge,* but Newton had to concede that it wasn't a _'real'_ force, because there wasn't any agent to produce the desired effect, which is very similar to the action of gravity, which is the _'apparent'_ inward movement between objects of *mass,* across empty space. However, when questioned on this apparent mystery in his calculations, he had no answer and said, _"I'll leave that for the consideration of a future scientist?"_ And, that scientist was none other than Albert Einstein, who finally concluded, after ten long years, and lots of steamed clams, that gravity and centrifugal were both _'apparent'_ forces, which only appear in an *accelerated* frame of reference, and that both were contributing factors behind the *tidal force* phenomena we observe in our oceans, lakes and seas. Dr Becky summed it up perfectly at the very end of her tidal explanation, when she says, _"People start saying Centrifugal is fictitious, we know!"_ Many thanks for remaining truthful to science education. Astounding comments. 😅
Cool Video!!! Just out of curiosity, am I the only person who had a sudden desire to here Rowan Atkinson say the word wobble? I'm sure it would be funny... ;-)
You're not alone, as I had the same thought myself, but mine involved the character of "Blackadder" who, if I'm not mistaken, actually said something similar to "wobble" in a episode once?
In the UA-cam video "what physics teachers get wrong about tides" (ua-cam.com/video/pwChk4S99i4/v-deo.html), the speaker says... the grav and centrif forces (basically along the line joining moon and earth) are FAR too small to produce the observed tidal bulges. Instead, he looks at the forces somewhat closer to the poles (see that video at 5:20), which are nearly tangential to the earth's surface. He claims these forces ARE large enough to produce the observed tides.
Yes, yes…what’s your point? All vectors can be resolved into their vertical and horizontal components. The only thing that was demonstrated in the video you cited, was a stationary earth with extremely tiny forces at its surface, and about to start accelerating in free-fall motion directly towards the moon, because he forgot to mention inertia and the barycentre.
Yes indeed there are 2 high tides, 1st Ministers resigned and the 2nd Boris Johnson also resigned. I wonder what caused this gravitational pull Dr. Becky??🧐🤔😄❤️
I think if we didn’t have a unusual big moon (compared to other planets) we might not have a liquid molten core in the earth. Those tidal forces are massaging the earth and slowing down the cooling of the earth core. And certainly without a liquid core, no magnetic field, no protection against solar eruptions, loss of atmosphere. Mars has no big moon -> no liquid core -> no magnetic field-> a very thin atmosphere. I never thought of the barycenter being far away from the center being essential for the dynamo…I don’t know, but yes I think you might be correct in that assumption.
thanks for that simple and clear explanation, I'm very familiar with the tides but have always struggled to understand, let alone explain, this phenomenon, which makes it awkward when teaching tides to novices! All the models I'd seen before ignored this barycentre oscillation, so the idea of a centrifugal effect never really came up in the discussions. I'll forward this link to Physics teaching colleagues at work and may link it to a video in my own channel in due course. Many thanks and here's fingers crossed for a nice balmy, breathable atmosphere on Trappist d or whatever its proper name is!
What a wonderfully clear, interesting comment and accompanying channel. Yes, Isaac Newton firmly established that a common centre of gravity was a prerequisite for all celestial bodies in balanced motion. Otherwise the outcomes would be disastrous. This wobbly inertial movement is definitely a contributing factor behind the tides, and is often overlooked by some unscrupulous individuals, although it did later require the incredible insights of Pierre Laplace to complete the picture. Many thanks and please take care balancing on bicycles.
Earth's equatorial bulge is about 43 kilometers (27 miles). The equatorial bulge means that people standing at sea level near the poles are closer to the center of Earth than people standing at sea level near the Equator.Ocean has bulge?Earth has bulge ?Bulge within a bulge? This vlog🎥 👀took a year to pop in to my stream🎏. Compared to your comment?😒😒
You seem very obsessed with bulges. Next you'll be telling us Everest is a bulge. 😂 So, I'll just play along with the bulges for now. Yes, gravity causes a bulge, and Inertial motion through bulging space (also known as centrifugal bulging force) causes a bulge. So, the Sun causes two bulges and the Moon causes two bulges, and at full and new moon we get four bulges for the price of two bulges, with bulges moving within bulges. And the earth spins on its axis causing a equal bulge right around the equator. Having said all that, we don't actually notice any of these bulges, or pass through them twice a day, because they are extremely tiny and actually only exist as bulges of tidal energy that dissipate through the oceans and around the surface of the Earth causing Tides.
@@Romadedoniamace You're very welcome eduardo 🐒😅 but, to clarify I think I should add that all these apparent bulges, manifest from the centre of the earth, *outwards,* as it spins on its axis, whilst also revolving with the bulging moon around there barycentre, and all whilst that same barycentre, orbits around the Solar System barycentre with the bulging Sun, which probably gets 'spots' from all the bulging? 😒
@@cybermonkeyssome people just shouldn't be allowed to do physics. The moon has nothing to do with the tides. Nothing. Back in 1971, Scott dropped a hammer and feather on the moon proving that there is NO gravitational attraction between celestial objects. None whatsoever. This should have settled the gravity as a force debate waging since Galileo dropped balls from the Tower of Pisa back in the 1590s. But a bunch of flat earthers wrote Galileo's findings off as a thought experiment leading Newton to his gravitational attraction nonsense which later discombobulated Einstein into his nonsensical relativity and warped space bs. The tides are strictly the result of the Earth's motion in space as theorized by Galileo. The equator has more acceleration causing the ocean to be accelerated to a higher orbit/radius. The Earth is also in motion around the sun causing a change in direction of acceleration of the ocean twice a day. The highest tide of the year takes place the first of the year on the OPPOSITE side of the planet facing the sun when it makes its closet pass and experiences the greatest amount of acceleration at that point according to Kepler's laws of motion. If there was no moon, there would still be tides.
If there was no moon, there would still be *solar* tides, due to the combined effect of the Inertial motion of the Earth's orbit around the Sun, and the gravitational effect between them. And, the tide would be highest at closest approach or perihelion, due to the increased gravity and Inertial speed of its orbit, in direct accordance with Johannes Kepler's *Second* Law of Planetary Motion. Go back to atom-school stewie and get your teacher to take some proper Physics lessons. Good luck.
Sure the earth feels no force as it's travelling in a straight unaccelerated line along it's geodesic. Although, that's "net" unaccelerated. I suppose tidal bulges are parts that are being accelerated temporarily, as they are not at the centre of mass, rotating etc, but aways from it, but it all balances out.
That is actually a blindingly good comment Paul. Accurate and concise. You even managed to smuggle in the word ‘geodesic’ - brilliant! It’s just a shame some people won’t understand what you meant and just say, “Centrifugal” doesn’t exist. Thank you.
By far the best explanation I've seen! I tried to understand this concept a few months ago. And between wiki, forums and other videos I got no where. You did it in 4 minutes. Bravo!
@@marcelluswallace6240 It may not be fully correct for the front side facing the Moon, as the Moon cannot actually lift water away from Earth. ... But It does give an explanation to the opposite side of the Earth experiencing tides due to inertia of rotation. A "Tides Part 2" may be good.
@@onebylandtwoifbysearunifby5475 No, the opposite side bulge is actually explained in the same way that the moon-side bulge is explained. Neil Degrasse Tyson did a really excellent video on it.
No! NdT spoke about “Yoga” - Pbs spoke about “Pimples” - Dr Becky spoke about “Centrifugal” - they are all simple and correct mechanisms, which explain the far side tides. The main message you should takeaway from this video is the factual existence of a barycentre, and the fact that at the centre of the Earth the opposing acceleration vectors cancel.
Simply. Let's split Earth into water-Earth and rocky-Earth (hardly changing shape by the tidal forces). If we look at water-Earth only rotating with the Moon it would take an ellipsoidal shape for sure, like dual stars do. Now drop rocky-Earth into the water one. Where will it sink? INTO CENTRE of water one. It means that both tides would be exactly the same height, if the diameter of Earth would be meaningless to the distance to the Moon. But it's not.
Well, I need to admit one thing. It is a change in the way we think about the problem. Once the Moon changed shape on the water-Earth, there is no more about the Moon influence. It is about the gravitational relation between water-Earth and rocky-Earth. They HAVE TO line up with their centres, because they both free in space. Does not matter what wired shape water-Earth would take and why.
I love your pronouncing "Wobble" it sounded like Wooble I grew up right beside the highest tides in the famous Bay of Fundy, and had my own fishing skiff at the age of twelve - your explanation is much better than anything else I've heard. And I later worked as a geologist at Bedford Institute of Oceanography in Nova Scotia The funnel shape and the shallower (shoaling) depth towards land accentuates the tidal bulge in the Bay of Fundy One unusual effect is that during ebb flow you can catch a temporary eddy close to shore that actually carries you in the opposite direction to the tidal currents in the main channel- handy in a row boat -very localized by the current jetties or promomtories such as reefs - fly fishermen use the same technique in rivers
This explanation, which is the only correct explanation for the reasons behind two tides a day, in its simplest form, works perfectly fine with lakes and rivers. However, we have to take this explanation one step further to correctly answer your great question, as Dr Becky explains, "there are many factors which control when, and how high a tide will be, but on average..." lakes and rivers do experience tides, but geography plays an important role. A lake is not usually connected to the open ocean, so is unable to carry the necessary momentum, caused by the lateral inertial motion of water, to form a noticeable tide, but they do exist and can be measured. Did that answer your question?
The bank is pushing back against the water molecules preventing them from being accelerated to a higher orbit. Water pushing on water elevates itself to a higher radius whereas when water has to push against land, land has more force pushing back. Rivers and lakes aren't deep enough or wide enough to elicit tidal forces.
Thank you Dr. Becky, this was a great explanation! I've read about "wobble" before, mostly pertaining to the detection of exoplanets (as you mentioned), but I could never really get my mind around the idea. Seeing that time-lapse of Pluto and Charon blew my mind. It was a "light-bulb" moment for me, and finally I understand wobble. ❤
To: Dr Rebecca Smethurst From: HR Department, Oxford University Dear Dr Smethurst The Geography Department have put in a complaint, and would like an apology. Something about you infringing on their turf. Those people are all about 'turf'. Regards HR Manager
(04:00) _“NB: NOT TO SCALE“_ How amusing that you snuck in a Latin lesson there. Nice. “NB“ is an abbreviation (actually, an _initialism,_ because there are no periods) of _Nota Bene,_ a Latin phrase meaning _mark well,_ or _note this well._ Its modern interpretation is to call attention to something important, especially in legal writings. Isn´t it amazing how _everything,_ even the ostensibly simple, is also complex when expressed in context of such exegeses (or orbital dynamics)? That is why _NB_ was “invented“ thousands of years ago, to put the burden of understanding on the reader instead of the writer. (I´m only kidding!)
I am visiting my folks who live right on the ocean in Western Canada, I was just wondering this last night! Of course I knew it was from the moon but not all the exact details, you're so helpful
There is just one enormous, glaring mistake in your very first sentence, flipfake: 👇 _"Only the Flat earth model explains tides."_ ❌ And, without doubt, it's a huge non-sequitur - _if I'm using that term correctly?_ 🙂 Unfortunately, flat earth is *not* a science, and does *not* have *any* workable models. Therefore, it is totally *incapable* of *convincingly* explaining anything about the tides. All the slight discrepancies you foolishly listed, without any satisfactory explanation whatsoever, can be perfectly understood, if only you'd shown the true rigour of a *real* scientist, working in the field of Oceanography and fluid dynamics. Instead of behaving like a flat earth nincompoop, who actually doesn't have any answers, and just preys on people, who have the honesty and natural curiosity, to seek truthful answers to their questions. As was clearly highlighted by Dr Becky, at the very beginning of her excellent video. Thanks for commenting, and take care when swimming in the ocean. 😄
I'm sure many have said this already. I've tried wrapping my head around this reading, watching videos, discussing with others, thought experiments...a phenom woman in STEM explains it in 3 minutes. Now to have her explain literally everything else. Thank you. This was driving me bonkers.
I'm nktnsur this is accurate thoigh..think about if nothing is pulling the water away from the earth on the other side..there has to be a force there to pull the water.
@@leif1075 You're right, nothing is pulling the water on the far side. But something is pulling the earth more than the water, hence the water is 'left behind' slightly.If you use the earth as your inertial frame of reference, then it looks 'weird', but use the universe as your frame, then it looks 'normal'.
@@Chris-hx3om the way she says it in the video makes it seem like that..but what is that something..why do you just say something..don't youbjustmeam gravity of the moon? And earth's rotational momentum maybe squeezing the land spmehwat?
@@leif1075 Would you like me to attempt to answer some of your ‘apparent’ confusion? Unfortunately, it appears Chris is providing you with some mixed metaphors and personally I don’t think it’s helping you to understand tides correctly?
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So it’s centrifugal force that causes the other bulge , Thank you Dr. Becky for this explanation. I am an engineer but never properly understood this 2nd bulge. That Rose & Jack spinning around dance scene was killer explanation 😊
That is also unfortunately not the main explanation for that second tide, it just coincides with it (see pbs or ndt videos about this). I've been thinking that myself with complete certainty for years and realised a month ago that I was wrong. Seeing a youtuber & scientist I respect doing the same is making me feel a bit better now though ^^
@@dkey201 I had already seen their videos, unfortunately I was not convinced by their explanation. But after seeing Dr Becky’s I understand now that all those videos are ultimately talking about centrifugal force, they just don’t know it 😂. Let me explain, using Jack and Rose analogy. 1)Jack and Rose suddenly pull each other ( not yet spinning around) , what you will see, Rose hair suddenly flying outwards, well that is centrifugal force. So, in earth-moon scenario , that is 2nd bulge. 2)Jack and Rose now start moving around each other while pulling each other . You will see again , Rose’s hair again flying outwards, that’s centrifugal force. So all those tidal forces which pbs video was saying are just gravitational pull and centrifugal force(virtual force) created by this gravity . And centrifugal force is imaginary, so it’s just gravity and motion of moon that cause tides
@@sureshbesra466 That was an excellent appraisal Suresh, and seeing that ‘d’key’ hasn’t responded…please let me interject! What you’ve described there is the perfect explanation to ‘Inertia’ in action. That’s what centrifugal force is - The tendency of a object to want to continue in a straight line, but is pulled by a force at right angles to its motion, which results in an orbit. Quite simple really!! 😂 Now, if you’d like to hear what Einstein actually thought his General Theory was actually all about! … 😌 … Then you’ll have to comment on my video instead. 👍 Take care.
I'm never going to forgive you dr. Becky, for not using the meme where they add the cat to the couple spinning. 😕 But seriously, thanks for the lesson! 😊 Stay safe there with your family! 🖖😊
Thank you. There are so many ‘tides explained’ vids that don’t discuss the barycenter and the centrifugal force of the opposite tide. And when I point to a Dr Feynman vid describing the barycenter and opposite tide I get hand waved off.
Hey @Dr. Becky , PBS SPACE TIME made a video about this a couple of years ago. But they gave a completely different answer than you just did.... like completely and they included the math for the height off the tides might be worth checking that out
Great explanation. I understood this 40years ago from physics classes but had long since forgot the details. Nice to see it explained with no resort to the mathematics. I recently moved to a place where the tides are very high so have taken a bit more interest in how they vary day to day. It would be good to do a follow up on how the inclination of the moons orbit results in one high tide often being a bit higher than the other each day.
Hello doctor I still struggle with this... Isn't centrifugal force a fictitious force that has to be generated by a different force? I still don't get this after watching mutiple videos of different teachers
@@wavydaveyparker hmm. I always understood that the moon orbits the earth because the centrifugal force necessary to keep it in orbit is "generated" (maybe not the right word, English is not my native language) by the gravitational force of the earth. A weight on a rope swung around is kept in a circular motion by a centrifugal force generated by the tensile force of the rope. This is where my confusion lays
Maybe you would be kind enough to place that comment under my creation. As I've discussed this confusion in detail there? Anyway, while you're pondering that request, I'll give you a quick reply here, as I really like the doctors approach to science teaching. The gravitational force _(or the gravitational mass)_ provides the *centripetal* force to keep an object in orbit. It is the *inertia* _(or the inertial mass)_ of the object in orbital motion that provides the *centrifugal* force. At the centre of the Earth these two forces balance and the orbit continues. The tides are caused by the imbalance of these two forces. Does that help with the confusion.
@@wavydaveyparker it does help a little, although I find inertia a difficult concept to comprehend. I've been looking for your creation, but I'm unable to find it or your channel
@@ArjanD78 Brilliant! I suspected as much. 😐 That's because you-tube try and hide any discussion about fictitious forces, but I reassure you my creation does exist in an accelerated frame of reference. 😁 Which brings us to your understanding of the concept of inertia, or as Galileo might say, *The principle of Inertia.* Are you familiar with the concept of reference frames?
Hi Dr. Becky, are you SURE that's an accurate description of the principle forces involved? Doesn't sound right to me. My understanding is more closely related to the gravitational effect of the Moon diminishing with distance, plus the fact that the earth is (comparatively speaking) a rigid body - so the whole thing moves, whereas the body of water can display its experience of those gravitational forces by distorting (a lot more than the Earth does).
It’s not wrong what she said, but it’s not the full explanation. I highly recommend this UA-cam video of PBS Space Time: ua-cam.com/video/pwChk4S99i4/v-deo.html
@@jorgmintel3060 I mean it's not wrong, but if it isn't the main factor, then it's kind of wrong. But it's a good lesson in humility for all of us who fell into that trap :) (assuming she notices these comments and makes a corrective video)
Yeah, this is completely right though, the far side tide is more of a centrifugal effect. The graphics are wonderful and the explanation correct. Science does not rely on opinion, it’s all about examining the evidence and looking at the facts, which are acquired through experimentation. The centrifugal effect is responsible for tides on the opposite side, and the centripetal effect is gravity, but it’s easy to get confused if you are a *chemist,* and they haven’t got a clue what they’re talking about. It won’t be published within a week, because no one is interested. 😊 Take care and thanks for the comment.
Sorry, but I think you'll find that *"Cos"* is defined as the ratio of the length of the adjacent side to that of the longest side i.e. the hippopotamus. Just another one of my creations. Thank you.
Dr. Becky … fifty years in boating, including three decades in the USN, and you explained the system of tides better than anyone I’ve known. Well done!
@@Chris-hx3om No! I think you’ll find that the NdT video and this are both in direct accordance. NdT calls on the mechanism of tidal ‘Yoga’ - whatever that is? - And Dr Becky calls on ‘Centrifuge’ - I know what that is? - And they both yield the same results for tides.
Yes well, both Dr Becky and Dr Tyson got it not exactly right.... Here a link to a video of PBS Space Time about this topic: ua-cam.com/video/pwChk4S99i4/v-deo.html It’s not flat-earthier BS, I promise!
Wouldn't there be a tidal bulge on the opposite side even without the effect of the centrifugal effect from orbital rotation? I mean, just the gravitational gradient will produce a tension on the axis of the two bodies, and a compression towards that axis. The effects caused by orbiting a displaced barycenter are also an important factor, but that alone doesn't produce the bulge on the opposing side. To illustrate this - imagine a large planet orbited by a moon almost at the Roche limit. Because of the small distance between the bodies, the displacement of the barycenter would be quite small and centrifugal effects would be reduced, while the effect from the gravitational gradient would be enhanced. The large planet would still have two high tides and two neap tides. Also, it seems to me that the centrifugal effect is asymmetric and basically produces a larger bulge on the part of the planet that is "outside" of the barycenter relative to the Moon, and a smaller bulge on the "inside" segment. So it would partially increase the height of the neap tides as well - or rather it would all add up in such a way that it would shift the time of the lowest tide quite a bit towards the point facing the Moon. And then there's the part where the tides are "lagging" because all that water has a lot of inertia and doesn't just change its direction of flow immediately when the Earth's rotation causes the tangential component of Moon's gravity to switch from one side to another.
An excellent comment and very detailed. Thank you. However, there is a very simple answer to your confusion. No centrifugal effect means no orbital motion and no orbital motion means collapse and the earth and moon would eventually collide like in the film ‘Moonfall’ !! Take care.
@@wavydaveyparker I wasn't really confused about anything. My point is that the tidal bulges caused by gradient of gravitational attraction are separate from the tidal bulges caused by the system's rotation around its barycenter, and it isn't strictly speaking correct to say that the "off-side" bulge is caused by a different effect than the bulge on the side facing the Moon. The acceleration differences from gravitational gradient, and the acceleration differences from rotation both contribute to the total effect of tides, and the amount depends on the masses of, and the distance between the two orbiting bodies.
@@HerraTohtori Yep! I agree and maybe shouldn’t have used the word ‘confusion’ … I was only answering your first question, which might have got confusing if I had continued? There would be a tidal bulge on the opposite side even without the effect of the centrifugal effect from orbital motion around the barycentre. However, the Earth-Moon system would then be in a state of collapse…I did make a video explaining all this, if you’re interested and we can discuss it further there if you’d like. Thank you.
I think you have made a common error in your explanation about how the tides work. Watch this Spacetime video for the correct explanation: ua-cam.com/video/pwChk4S99i4/v-deo.html
Whoa!!!! 😲 The beloved BARYCENTRE!! ❤️😎 Thank you Dr Becky!!!
Spaghettification in “linear” free-fall motion or Spaghettification in “orbital” free-fall motion? hmm… (get you with the long words and caps-locks!) I don’t know what the Earth is thinking!! but, I think I’ll stick with Dr Becky’s explanation - thank you very much - As I have a liking to staying alive! It’s called the tidal force, why is this so difficult for you to understand?
It may surprise a lot of people that the centrifugal “effect” has something to do with tides, but it’s really just “Inertia” in action, and all the matter in the Universe is accelerating away from each other, at an ever increasing rate (?) because, the gravity is unable to negate the expansion.
I prefer to describe things strictly in terms of inertia rather than using the term centrifugal force.
@@JarredDavidson And I totally agree, although I prefer to describe gravity strictly in terms of inertial mass curving spacetime, and as inertia herself once told me, _"the doors a jar, but it doesn't matter, because we're only travelling at 4mph."_ Those people who think inertia hasn't done anything good for us, should just go home, and take all those great tapes and albums...and burn them! What do you think about that then?
The universe isn't accelerating away from us. All matter is accelerating away from each other; where gravity isn't so strong that it negates the effect.
@@Ominousheat Brilliant! I stand corrected, and will make the appropriate correction in due course. You're absolutely right. In my defence however, I would like say that I only wrote this comment in response to the one below mine, which said there was no acceleration (?). Would you mind if I use your informative reply on my cartoon about the misperception of tides? Thanks
@@wavydaveyparker No biggy. Pleasure is all mine. Only in the science community can one discover the magnanimity that you exhibit.
The two tides are of approximately equal height on both sides of the globe shaped planet, because in the *equilibrium* of tides theory, the centrifugal effect is the same across the whole earth, whilst the moon’s gravity diminishes with distance by the inverse square. 👇 Thank you.
That doesn’t seem to make sense.. I remember that the centrifugal force would be F=m \omega^2 r, where the angular velocity \omega is the same across the whole earth (1 rotation per month), but the distance to rotation center r is different, since (as Dr Becky pointed out) the barycenter of the earth-moon system is not at the center of the earth, but about 2/3 of the earth radius to the moon’s side. This would mean that the centrifugal force at the far side would be 5 times as high as the close side of the earth to the moon.. right?
@@CM-cr8wq Hello CM, thank you for the reply, you do realise that I have made a short video, which attempted to dispel the ridiculous claim and fraudulent myth, that centrifugal force was incapable of having any *real* effect in a dynamic Earth-Moon system, and instead they performed some crazy start-stop motion towards each other? And, that I'm more than willing to continue any discussion with you there...if you can find it? 🙄
Anyhow, I will provide you with an answer to your interesting question, seeing as no one is that interested in critical thinking anymore, and it only seems polite of me to do so...
You're equation for the centrifugal force is entirely correct, and it's just your definition of the Inertial motion that needs to be re-evaluated. The Earth's motion around the CM (😅 Common Centre of Mass) or the Barycentre, is *not* a rotational motion. It is a translating motion, or as Dr Becky described, an Orbital Motion, which implies one complete revolution per monthly cycle.
Whereas, with the Earth's axial rotation, the value of (r) would increase towards the equator, increasing the centrifugal effect, as you correctly suggested, and reducing the effective *'weight'* of an object at that point.
With orbital motion around a barycentre, however, every point of mass on or within the Earth, will map out a circle of equal radius (r=4671km) as it completes one revolution around the CM.
Therefore, the centrifugal force will remain constant across the Earth, during this monthly cycle, assuming that the orbital path is perfectly circular?
I hope that was helpful, and apologise for the lengthy use of numerous words, but it does become increasingly boring having to repeat myself over and over, without any reward for my efforts. Best wishes and kind regards.
@wavydaveyparker in other words.
The earth spinning on its axis while it orbits the sun is what creates the tides. There is no gravitational attraction between the earth and the moon. This was disproven by multiple experiments on earth and the moon.
The earth is orbiting the sun in a counterclockwise direction. The entire mass of the earth is being accelerated in a counterclockwise direction with the sun as the center of the frame. As the earth rotates on its axis, the ocean is accelerated first in a clockwise direction in respect to the Earth's orbit and then a counterclockwise direction. This creates the daily high tides.
The annual high tide occurs the first of the year as the planets elliptical path brings it the closest to the sun. As shown by Kepler's Laws of Motion, the Earth's ocean experiences the greatest rate of acceleration on the side opposite of the sun causing the water to be lifted into a higher radius/orbit.
The surface of the earth does not experience the same amount of acceleration from pole to pole. This is why the tides are more pronounced at the equator.
To reiterate. The moon has no influence on the Earth's ocean's other than the reflected light.
@@wavydaveyparker Thanks for the reply!
I am not sure I quite understand you when you say "With orbital motion around a barycentre, however, every point of mass on or within the Earth, will map out a circle of equal radius (r=4671km) as it completes one revolution around the CM."
How can that be? If we imagining at any snapshot of time, the distance between the barycenter (which is at a given point location within earth) and any given point on or within earth is clearly NOT the same, since the far-side of the earth is 5 times as far away to the barycenter as the close side. If the distance is different at a given time, how can they map out a circle of the same radius at a period of time?
... Unless when you say "the centrifugal effect is the same across the whole earth" and all of the above, you mean that it is the same across time instead of across space? i.e. it is the same for a fixed location (with respect to the earth-moon system, not a fixed a location on earth, since earth is rotating one revolution every day) at any time, but it can still be different for different location? The circle they map out would still be circles, but of different radius for different places? That would makes sense!
I tried to do a simple calculation to verify this:
1) The force per unit mass of water (aka acceleration) from moon's gravity would be a_g2 = G m_2 / (R_2 - r)^2,
where moon mass m_2 = 7.342e22 kg;
distance from the moon center of mass to the barycenter R_2 = D - R_1 = 3.797e5 km;
the distance from the earth's surface to the barycenter is r=1709km and r=-11046km for the closest point and the furtherest point from earth to moon respectively.
This gives us a_g2 = 3.4e-5 m/s^2 and 3.2e-5 m/s^2 in the two scenarios;
2) The centrifugal force per unit mass is a_c = \omega^2 * r, where angular velocity \omega = sqrt(G * m_2 / D^2 / R_1) = 2.665e-6 s^(-1) (i.e. 2 pi per 27.28 days), so a_c = 1.215e-5 m/s^2 and -7.847e-5 m/s^2 for the closest point and the furtherest point respectively;
3) combining the two effects, total force from centrifugal effect and luna gravity effect is a = a_g2 + a_c, which gives
4.644e-05 m/s^2 (pulling towards moon) for the cloest point
-4.638e-05 m/s^2 (pulling away from moon) for the furtherst point
on earth from earth to moon.
(Edit: Made a mistake about the plus/minus sign! I have fixed it in the above. Now the numbers agree!)
These two numbers agrees with each other nicely. So nice that I am starting to wonder if there is a mathematical reason behind this.. If it would be true as well, in an alien planet?
Thanks for listening. All the best!
It's obvious from your reply that these calculations of tidal accelerations means a great deal to you, and I'm thoroughly honoured that you would consider my appraisal worthy enough for you to share your workings.
Please just do me a favour and drop a comment on my cartoon, because I've worked through these calculations on many occasions, and might be able to point you in the direction of some useful resource material. Thanks again.
Addition: In the meantime, try calculating the gravitational force of the moon on the centre of the earth, and equate that against the centrifugal force of the earth's motion around the barycentre. You should find that the *net* result is a *zero* acceleration. Good luck.
Thank you Dr. Becky - I could not get my head around this for years and this is the 1st time someone actually explained it so clearly! I love your videos.
And she got it WRONG!
This video (by PBS Space-time) is better and more accurate.
ua-cam.com/video/pwChk4S99i4/v-deo.html
Same here
@@sureshbesra466 same here I have been trying to understand for years and it never really added up
@@strong507 Well Stephen, I’m exceedingly happy for you and Tomas and I’m glad it finally added up for you, because when we ‘add’ the acceleration vectors at the centre of the Earth they equal zero! Thanks to the beloved Barycentre, where would we be without eh! Take care.
same here. Nobody could tell me. So thanks a lot
Dear Dr Becky, this video is exceptional and I sincerely apologise for not arriving earlier - _sorry!_ - seeing as I’m having trouble making a video myself, to correctly explain tides to a younger audience and have only produced something to dispel the totally incorrect assumption that the Earth moves directly towards the Moon in a straight line filling up bulges. This seems like the perfect place to post my boring lengthy comment on the matter…so here goes! Enjoy:
When Isaac Newton first proposed the theory of Gravitation in his _‘Principia’,_ around 300 years ago! He unfortunately, neglected to give us the mechanism by which _‘gravity’_ worked! However, he did provide us with some very beautiful and simple equations, to correctly calculate the movement of Planets. His problem started with his acceptance of _‘absolute time’_ and distinguishing the difference between _‘gravitational’_ and _‘inertial’_ mass, which he considered to be equivalent, but being the genius he undoubtedly was, he agonised over that conclusion and knew it might not be completely accurate.
It wasn’t until Albert Einstein around 200 years later, that we were finally given the more complete answer to gravity, when he told us that the natural state of things is _‘free fall’_ ... and the _‘mass’_ of an object had the potential to curve the space around itself, within the confines of his proposed idea of _‘spacetime’,_ which he presented in his brilliant theory of General Relativity.... _I hope that helped?_ 🙃
As for the tides... Well, they’re not that difficult to understand really? Think of it like this... At the very centre of the Earth, there is a centripetal ‘force’ of gravity pulling it towards the Moon... And there is also a centrifugal ‘force’ _(I use the term loosely, because it’s a ‘apparent’ force in an inertial frame, but the Earth-Moon system is definitely a rotating, non-inertial frame and it exists)_ due to the inertia of the moving objects wanting to continue in straight lines!
These two effects ‘balance’ according to Newton’s Third Law and the orbits continue, because the ‘net’ forces at there centres are zero. The centres of the Earth and Moon are indeed moving on spacetime paths, and don’t experience a ‘net’ acceleration, because they are in free-fall around each other, but still under the influence of a non-uniform gravitational field.
When we work out the tides, we use the ‘tidal force’ equations, which effect an object from the centre outwards.
Therefore, ‘No!’ pulling, or tugging away from oceans or moving towards the moon filling up bulges is necessary. Just the knowledge to realise that the Earth-Moon system operates like any two-body problem.
Of course, we then have to correctly apply the method of resolving these associated acceleration vectors into there respective components and recognise the buildup of sideways pressure in the underlying water column, which is what actually drives the tidal systems, but that’s not my particular area of expertise?
Take care and thank you so much for making this video.
Kind regards, Wavy 👋.
WRONG WRONG WRONG!
Just so completely WRONG!
Yes, I’m afraid what you say is a bit of a misunderstanding. Look up Laplace’s Tidal Equations, which are differential equations that are still used today to accurately predict the tides. There is no involvement of any vertical or axial components, or centripetal forces. The tides are raised by the horizontal tractive forces in the plane of the oceans. Earth’s gravity swamps any vertical components by a factor of about ten million, but the horizontal components of the Moon’s gravity are at right angles to the Earth’s field and aren’t swamped. They are tiny, but crucially they are cumulative over thousands of square miles of ocean, and above all are convergent and are acting on an incompressible fluid. These factors combine to raise tides of a few metres in magnitude and also account for the second or antipodal tidal bulge due to the symmetry of the off-axis forces. The second tide is smaller due to the greater distance from the Moon. The Euler-Laplace model explains why tides don’t arise in small bodies of water and correctly models the domed shape of the tidal bulges. It’s a closed book. There’s an awful lot of rubbish on the web purporting to explain the tides, hardly any of it is correct, yet this was all solved by Euler and Laplace over 200 years ago.
@@oneeleven7897 Oh really!! So, you’re saying that Newton and Einstein are wrong are you! Well I happily pitch either of them against your Euler and Laplace equations any day. You obviously didn’t read the whole comment…at no point did I say that the water is pulled upwards. I even said at the end we have to resolve these acceleration vectors into the horizontal and vertical components and neglect the vertical component, because it is overwhelmed by the earth’s own gravitational attraction. The barycentre is a fundamental, undeniable fact of nature, the earth and moon are both in a freefall motion around their common centre of mass, which Einstein spent ten years contemplating about before publishing his general theory. Are you really going to try and go up against that? Under General Relativity! Gravity isn’t considered as a real force either! Gravity and Centrifugal forces only appear in an accelerated frame of reference, one that is non-inertial…where the apparent force becomes valid. Maybe you should look up the Jean Le Rond d’Alembert principal - it states, that at the centre of an object in rotational motion we can consider the centre of the object as having zero net acceleration. Please read the entire comment again and reflect on what you said? What I said here, did not go against the Euler-Laplace equations in the slightest, as they were both great mathematicians which I still admire greatly.
@@oneeleven7897 And I’ll continue…I also said that to work out the tides we use the ‘tidal force’ equations, which actually don’t involve centrifugal forces only the gravitational differential. Please try and keep up! Orbital motion is a whole different ball game and does involve d’Alembert forces. And I’ll also add that Dr Becky’s video here is a perfectly valid explanation for the *equilibrium* of tides. If you’ve got a problem with that, then I suggest you take it up with her or make a video yourself, which illustrates these wonderful and totally correct Euler-Laplace equations you keep telling everyone about. Take care.
@@wavydaveyparker Dr. Becky clearly claims in the first few minutes of this video that the sub-lunar tide is caused by the Moon’s upward gravitational pull and that the antipodal tide is caused by a centrifugal force. This is completely wrong. The tides arise from the horizontal tractive forces that I have already mentioned. The effect is subtle and could be said to be counterintuitive because the Moon is from our point of view ‘up’ in the sky so might be assumed to pull things up towards it. The real mechanism is like squeezing a soft ball around a circumference; it will distort on both sides of that circumference into an approximate ellipsoid. Newton was the first person to assign the tides to the Moon’s gravity but was unable to produce a mathematical model for them, as he too missed the subtlety of the effect. It was Euler who first worked out he truth, and later Laplace who derived the partial differential equations that accurately account for and predict the tides. So Newton was half right, and there is no need at all to invoke Einstein as it all works perfectly well in the low field classical limit. If you choose to picture the tides under General Relativity that’s fine but it makes no practical difference. The Euler-Laplace model of the tides remains the definitive explanation, and this is not subjective but is the history of science.
A brilliant question Stephen. Yep! The earth and moon are both moving further apart, by approximately 4cms every year…so, the tides will gradually decrease over time! And the length of a day on earth will increase by approximately 1.8 milliseconds every century. This will continue until the earth and moon are no longer in orbit around the barycentre…but, that won’t happen for a few billion years yet, and the Sun would have extinguished itself by then, so don’t worry about it! Ok! 👇
Actually, while it's true that the Earth had been slowing down century by century, that was only true until recently when it began speeding up again and days began to get shorter once again culminating in the shortest and second shortest days on record on june 29th and 30th, 2022, respectively , since the start of the use of the atomic clock.
most scientists believe that this increased rate of rotation is probably explained somewhere between the Chandler Wobble and Glacial isostatic lateralization (the melting of polar glacial masses due to Climate change reducing mass pressure on the Earth's crust on the poles exerted by Glacial masses.
It may not be long-lived and we may go back to steadily and slowly increasing day lengths/slower rate of Earth's rotation, but for the time being days are getting shorter and the Earth is spinning faster despite the Moon's enlarging orbit.
*taking notes* "What causes two tides? Wobble... and... Sean Connery. Got it." - Thank you, Dr. Becky!
Interestingly, the solid ground beneath our feet also rises and falls in tides, though this is much harder to see. One way scientists have observed it is through pressure variations in oil bodies deep beneath the surface, directly attributable to the Moon. And in many high-energy accelerators in which sub-atomic particles travel at near-light speeds in tunnels beneath the ground, we need to apply corrections to the magnetic fields that guide them to compensate for the physical distortion of the ground as the Moon passes overhead. In all of these systems, we see tides
Woah! Cool! I guess I always assumed that was true but never gave it thought. Damn nature!
Yes, the Earth squishes together as the poles are compressed from tidal (directional) forces, so bulges at the middle a bit. But this confuses many people who believe the Moon is pulling. The Moon can't pull or lift water, it's smaller than Earth, and the gravity is far too weak for that. Lateral hydrostatic flow along Earth surface towards the equator is the cause of the ocean "tides". No tides in lakes or coffee cups.
It's amazing what happens when all the stuff agrees on a single direction to move in.
@@onebylandtwoifbysearunifby5475
But he clearly says that it puls
ua-cam.com/video/KlWpFLfLFBI/v-deo.html
@@onebylandtwoifbysearunifby5475 the great lakes have tides.
@@glennbabic5954 I have also heard that explanation before, but the sources were less qualified than Becky. There may be some combination of the two effects at play.
Would be interesting to see how this plays out on water planets with more than one moon. Thank you for the bloopers Dr B you always know how to make us laugh!
I would like a video on this!
not really a water planet doesn't really have tides in the sens we see them on earth. Tidal forces still apply of course, but there are no visible local effects.
sloshing. Lots of sloshing around.
@@MusikCassette So we need a bit of land mass to better measure the tides. But the whole point would be the different moons magnifying or cancelling out tidal effect.
Sort of like the sun and moon but more layered on top of each other. The moons would likely be in orbital resonances so you'd get one killer tide at some interval!
„Centrifugal force“? I can still hear my physic professor shouting „Don’t call inertia a force!“😂
(I get it’s a question of reference….).
Many thanks for the best tide explanation I have seen so far 😀
Aye, there was also a voice in my head shouting "centrifugal force does not exist!!" too.
It's a lack of centripetal force! Our physics teacher chastised anyone who dared utter the word centrifugal.
Sorry for spamming this link, but Dr. Becky's explanation is actually not complete and actually a bit misleading in my opinion. Space Time a couple of years ago presented a much better picture of what is actually happening. ua-cam.com/video/pwChk4S99i4/v-deo.html
And may not be correct! (See a Neil Degrasse Tyson 'Star-talk' video on it)
@@Chris-hx3om link?
This makes total sense.
It’s extremely difficult to visualise the effects of gravity in a four-dimensional manifold, using a two-dimensional rubber sheet, in a three-dimensional time space. All you achieve is a demonstration of gravity, using gravity! Which, rather defeats the objective.
The gravitational and centrifugal effects of motion around a barycentre, both alleviate the gravimetric tensor of the earth’s own gravitational attraction, and allows water to flow in sideways from the adjoining areas to equalise the system…and, we call this movement of vast quantities of water…tides. All perfectly sensible. Thank you, Dr Becky.
tides explained by space time...go
@@davidmudry5622 Hello David, how’s it going? I think we first have to firmly establish exactly what “time” and “space” actually are? Although, we both achieved that sometime ago in our pleasant conversation. So, you already know the answer…but, it’s nice to hear from you again. Take care my friend and keep critically thinking…go
@@wavydaveyparker No, I understand gravity doesn't pull only because light can't be pulled, yet light bends near a massive body. I understand when things are weightless is because no force is accelerating them, and anytime a body has weight is because a force is accelerating them. But when it comes to a high tide on opposite sides of the earth at the same time I need some help as to how space-time can explain it.
@@davidmudry5622 Oh right! I see, but you shouldn’t be so down on yourself, because I don’t think you realise how agonisingly close you are to solving this problem. What you just said there was exceptional, and clearly shows a structured way of thinking, very reminiscent of a certain Mr Einstein. I’ll tell you what…drop that exact comment on my video and I’ll give you a link to someone, who asked the same questions and we can discuss it there. I think the two of you have a lot in common. Take care.
@@wavydaveyparker Tidal Forces ua-cam.com/video/GuLL_upE4zk/v-deo.html
I knew it, it wasn't because of the beers it was the centrifugal force that made me wobble at the fare!! 🤔
Precisely, but it was the beers that forced you put that traffic cone on your head and buy that huge kebab on the way home!! 😂
@@cybermonkeys 🍻
? Fair ?
@@johnstarkie9948 Fair's fair, you're right! But, let's be fair here, we had been drinking and the ? centrifugal ? fairground ride had a fare to pay.
I always thought it was because of Newton's Third law. Learn something new every day.
Yes, you’re absolutely right, it’s all to do with Newton’s Laws of Motion, as easy as one, two, three. Nothing is static in the universe, it’s all relative. The action is centrifugal, and the reaction is gravity. For every push, there is a pull, or as Einstein might say, the Earth is balancing on a free-falling bicycle, whilst it’s cycling around the barycentre, it’s just that the oceans have trouble remaining balanced occasionally. Thanks
Sorry Becky, but this explanation is simply wrong. PBS Spacetime made a video about this years ago (ua-cam.com/video/pwChk4S99i4/v-deo.html). The second bulge is caused not be centrifugal force. Actually the pulling force of the moon on the water doen't act on the bulges outwards. It acts on the inward bulges. It pulls the water closer to the ground and the water displaces other water and that water gets "lifted".
We need to get these comments higher, I'd like to see a second video from becky realising about being mistaken! I really think as a scientist & influencer, this is one of the most interesting topic she can discuss (the search for the truth, research in the internet era, and the fact that even the most intelligent and qualified people can be very sure of themselves and very wrong, even close to their own field of expertise)
Nah. As the guy says in the video, tidal acceleration is not real, its just an apparent effect produced by our constantly moving frame of reference. The same is true of centrifugal force. Her explanation and his are just different ways to imagine the same thing. Also, his claim that the effect is mainly caused by the sea being pulled in the middle seems off, to me. You can clearly see from his diagram that the forces "pulling" on the sea are significantly greater than the forces "pushing" on the sea.
Oh God are you saying centrifugal force create the opposing tide???
That's the biggest misconception about tides.
Even a stationary system with no rotation would have 2 tides. The gradient of the gravitational field is enough to explain both tide.
Just like when falling into a black hole one would get spaghettified, not just half spaghettified.
@@perseverancerover
No, it is not a perfectly valid explanation.
And no you do not need rotation or any sort of movement to have 2 tides.
Tidal forces simply arise from the fact that the gravity force changes with the square of the distance, it does not need movement to take effect.
That's basic physics. And the Wikipedia article on tidal forces is enough to understand there is absolutely no need for movement.
@@perseverancerover Just go read the formula for tidal force and tell me where you see the speed or rotation appear in this formula (spoiler alert: they do not).
And if you cannot read equations just go watch the PBS video on tides. They explain very well how the shape of the gravitational field creates a pressure gradient on the water on Earth which translates into water level difference. No need for movement.
@UCSgdjTSWiZT8MZTCmom46gw
Ok, that's my last response, because obviously you do not understand the basic of physics.
We are not having a polite discussion. I am trying to educate you while you make an effort to not understand.
The gravitational force is in 1/r², because it is in 1/r² any non punctual object placed in a gravitation field "feels" a different force in its different part.
Regardless of its motion, the object will feel stretch and squeezed by the different values of the gravitational force.
This stretching and squeezing is what we call tidal force and it is what is causing tides and spaghettification.
Now this tidal force is in 1/r^3.
And when I say that you make an effort to not understand is that obviously you went to look for the equation.
Instead of seeing that speed and motion does not appear in the equation, you jumped directly to the 1/r^3. Felt clever to have something to say I am wrong.
But you failed to understand that
1. I was talking about gravitational force, not tidal force.
2. Would it be in 1/r² or 1/r^3 it does not change that the speed does not appear in the equation.
Oh and free fall motion, is like no motion at all. And free fall motion is only mentioned to justify we can change referential so that we can ignore the first term in 1/r².
@@gehngis this is the explanation I got in college. I got very confused at the time, but knowing a bit more today, it sounds more correct than the explanation on the video for sure.
In the UA-cam video, *“Why are there two high tides per day?”* the speaker _(Dr Becky)_ says… the earth is not static during all of this, and is in an orbital motion around a common centre of mass, called the barycentre. So, if we look at the gravitational and centrifugal effects closer to the poles, which are nearly tangential to the earth’s surface. Then, they are both right to claim, that these forces CAN accumulate to produce the observed tides.
ok that was about the most intuitive explanation I've ever heard for this phenomenon.
Grew up in a small village on the coast. Tides can be massive. On the fridge was a tide table so we didn't get caught out by the the tide when going to Mersea Island. The Strood can really catch you.
It's not that big here where I live, but I also have it on an app. It's useful to know when to go fishing or not. 😬
Same where I live.7 metre king tides. You really have to think about where you anchor your boat.
My favorite way of explaining it is this: objects in orbit are in free fall, and even as the Moon falls toward the Earth (bending its path through space into a curve)... the Earth falls toward the Moon too. But the Moon's gravity is a little bit stronger on the side of the Earth facing it, and a little bit weaker on the side of the Earth facing away. And that causes the water on the near side to fall a bit more rapidly toward the Moon, and on the far side, the Earth is falling away from the water. Thus, two bulges.
Tides are caused by *differences* in gravity, and they tend to stretch out objects that are in free fall in a varying gravitational field. In general relativity, in fact, tides are treated as more fundamental than the net force of gravity--they have a more coordinate-independent existence.
(Extra credit: figure out how this is equivalent to the explanation Dr. Becky gave.)
I couldn't understand what you wrote, but it seems you are smart :) Becky basically explained the second tide as being due to centrifugal force - but I can't see how there could be one when objects in orbit are going around in a circle due to being in free fall, not because they are being prevented from going in a straight line by a mechanical linkage (like in a fairground ride).
@@gavinmetzler858 From a Newtonian perspective, the mechanical linkage works just like a gravitational force. There's no such thing as a centrifugal force in either case, if you do your calculations in the non-rotating frame; all that's happening is that some force prevents objects from moving in a straight line. But if you consider the *rotating* frame of reference (in this case, rotating around the barycenter), then there's a centrifugal force.pushing outward from the center on both the Earth and Moon, increasing with distance from the barycenter, and also a gravitational force that is greatest where they're closest. And all of that tends to stretch everything out. But it's just the same forces computed in a different reference frame, which is non-inertial (rotating and therefore accelerating).
@@gavinmetzler858 The roundabout is not moving because of the centripetal force, it’s moving because someone or something is pushing it around. If they pushed harder, then the roundabout would go faster and you’d better hold on tighter, otherwise you might come flying off and travel away from the roundabout in a straight line motion. That’s what inertia does to you. The Earth’s *centre* is in freefall, which means at that point the opposing accelerations cancel. That’s what weightlessness does to you. The points nearer and further away from the moon aren’t balanced and move slightly outwards. That’s what the tidal force does to you. Take care.
@@MattMcIrvin All very interesting Matt, but couldn’t we just say, that gravity and centrifugal are both ‘apparent’ forces, which only appear in an accelerated frame of reference. And this leads to a zero ‘net’ acceleration at the centre (ie. Free-fall) and…an ‘outward’ acceleration on either side, leading to a tidal force. Of course the barycentre is what prevents the whole thing from collapsing and becoming spaghetti?
over simplified.
the high tide (even at spring tide) is not always "under the moon" .
more over, there are places (at least one) that are within the same time zone (in fact, under 200 miles apart) where one will be experiencing a high tide, and another will be experiencing a low tide (at the same time).
tides are not caused by the pulling on the water under the moon; but more by the "squeezing" on the water from the poles and topics, towards the earth-moon line (this pull is effect by the ocean floor and land, making "irregular", but periodic).
Right, it's more like squeezing a balloon at the poles. Ocean tides are hydrostatic pressure resulting in lateral flow to a common point. Moon is too small to lift water away from Earth's core.
Thank you Dr. Becky. In the 90's I worked in the local (Tampa, Florida) Planetarium. I got pretty good at explaining this, but I ALWAYS like to hear how others explain it. It gives me different ways of phrasing it when my first attempt doesn't work. On another note: here on the Gulf of Mexico we don't get those regular tides. Technically we do, but a low tide can sometimes be all of 2cm lower than the previous high tide. I have yet to find track down an expert to ask, but I'm pretty sure that the Gulf has a particular rhythm for the water to slosh from Florida to Texas and back, and that interferes (in the physics sense of that word) with the 12 hour rhythm of the lunar tides.
Dr. Becky , I think there is 2 forces first one the gravity of the moon pulls up the oceans from one side of the earth cause the high tide and the second force comes from the rotation of the earth around its axis pushes the water of the oceans to other side of the earth cause another high tide even though it is on the opposite direction of the moon ...
no, the effect would be there even if the earth was completely stationary without any orbit, wobling or whatever
dr blocky explains that incorrectly
The problem really is that no one actually understands everything about tides. So no one can explain exactly why they work the way they do. For us common folks all we need to know is this, gravity is alive and well and tides on Earth are influenced by both the Moon and the Sun. Why would any of us need to understand it in more detail than that?
@@asthmasayshi131 It wouldn't, no. If there wasn't an orbit, the moon would crash into the earth. If there were a magic non-orbiting levitating moon, all the water would pool on the near side.
@@txmike1945 Oh hey it's Bill O'Reilly.
Hello Elias, how are you? “For every action there is an equal and opposite reaction” - Elias koff - 2021
Sorry, I have absolutely no idea what a "Double torus *OOrt cloud* magnetoglobe" thingy is? You're just making this stuff up, but I can assure you, that it had nothing to do with me, Gregory.
And if I was God, which thankfully I'm not, then I would have left that bit out of my creation, for fear of being mocked, by my minions. Oort bless you.
Not quite right. It's differential pressure and hydraulic forces that cause tides. PBS Space Time covered this many years ago.
Here's a link maybe:
ua-cam.com/video/pwChk4S99i4/v-deo.html
Yes, but the auestion is then: what is creating the differential pressure?
And the answer: is the gradient of gravitational forces.
No need for rotation amd centrifugal force.
@@gehngis did you watch the video? It's tiny tangential forces that squeeze the oceans, rather than huge vertical "pulling".
@@MrGonzonator Yes, and what I said does not say otherwise.
Both the squeezing and the pushing/pulling are caused by the shape of the moon gravitational field.
My point is that there is no need to invoke rotation or centrifugal forces, unlike @DrBecky does in this video.
I live by the sea, its amazing. Tides are weird, yet no tides in the med???
*bows down with raised hands*
I've always wanted to know the exact reason for this. Schoolbooks just said "it's because of centrifugal force" which was so inadequate that I would go "huh?" Thank you Dr. Becky!!!
You are seriously a world treasure. Thank you for giving us these amazing concepts in ways that we can understand!
Hmm, I watched and read a lot of explanations about the physics of the tides. And most of them - especially on the internet - *does not match with physics textbooks.* Even some physics websites and Becky oversimplify it. Some sources are totally wrong. For those interested in the physics of tides, a good (school) physics textbook is recommended. It is much more complicated than described here or on some websites or YT videos.
*In short:* It is the resultant acceleration due to the superposition of the tidal and centripetal (or centrifugal if you will) accelerations. Combined these push the water perpendicular from the earth-moon line to the two water mountains along the earth-moon line, like squeezing a pimple . So, both tidal bulges are caused by the same accelerations, not different ones as mentioned here. Because not only tidal acceleration, but also centripetal or centrifugal acceleration acts on every point on the earth, not just on one side. Of course, this is also simplified. But so it is written in physics textbooks.
A pretty good brief visualization can be found at www .geological-digressions .com/wp-content/uploads/2018/08/tides-forces.jpg?ssl=1 (remove the blanks) If you want to stick to YT, PBS Space Time “What Physics Teachers Get Wrong About Tides!” (watch?v=pwChk4S99i4) is a good starting point. But even this video lets some questions unexplained. You can't avoid picking up a physics textbook.
PS: I'm not usually the type to explain their job to professionals. And I am also aware that Becky cannot reading along all comments.
Hello Schlaf, why didn’t you mention my “daft” little video in your excellent appraisal? where did you go? I was all ready to discuss the ins and outs of tides with you…and then you disappeared…anyway, you’re right! dr becky probably isn’t reading this, but I just wanted to let you know that I did, and found it all very interesting. Apart from the *fact* that the Earth and Moon are both in a *freefall* orbital motion around a *barycentre* and *not* accelerating towards each other in a straight line, as is depicted in many incorrect tidal explanations. Thank you and take care.
@@wavydaveyparker _"... why didn’t you mention my “daft” little video ..."_
Because I did not know it before and it criticizes only one point of an explanation in another video if we mean the same one. And this is not a problem in Becky's explanation.
_"... and then you disappeared..."_
I assume you mean the video from Atomic School. It was a pretty long time ago and I don't remember getting a notification on my comment from YT.
_"... the fact that the Earth and Moon are both in a freefall ..."_
Exactly. But that wasn't explained incorrectly by Becky.
@@schlafschafweb Yep! You’re right…it was a long time ago, but I’d remember that sheep anywhere! You’re more than welcome to comment again, because I was attempting to address your concerns over the pbs video you, and everybody else keeps mentioning. The real key to this whole tidal thing is *Balance* - No balance! No Universe! No Universe! No us! It’s just that the oceans are temporarily out of balance twice a day in some places? Whilst the whole Earth remains balanced in its motion around the common centre of gravity.
I agree. Her explanation was pretty incomplete... The video you linked is the most complete explanation I've seen. But in his video, he also fails to mention the wobbling of the planet in the Earth-Moon barycenter and the centrifugal force that it causes.
But still, the MAIN explanation is simply the "gravity differential (or tidal force)" between the different points on the planet, but also the fact that the water gets "squeezed" by it... So I think his video is better.
So, essentially what your saying is that you’d like to see a tidal explanation video, or read a definition in a scientific journal, that says, the tides are caused by the inertial momentum of planets and oceans, in orbital motion around a common centre of mass, in a non-uniform gravitational field. That gives rise to a tidal force from the centre outwards, and tractive acceleration vector components, that accumulate pressure across the surface of the water. Well, unfortunately that doesn’t exist presently, so you’ll just have to content yourself with watching both of these correct explanations in conjunction with one another. Good luck
An important note is that the Moon doesn't actually "lift" water. Its gravity is far less than Earth's. Water flows from the poles towards the equator, causing a hydrostatic bulging. The Moon's gravity is enough to cause water flow to change direction, but not to lift it.
This is why there are no tides in lakes or bathtubs or coffee cups.
Water is not lifted by the Moon. Rather, the tidal forces are lines converging on the Moon. The Earth is larger diameter, so those lines converge rather than being parallel. Water flow follows those lines, converging and so bulging at the equator.
Another way to consider this is as a balloon being squeezed between your hands: it bulges in the center as it is compressed.The geology below water level also feels this compression, and bulges in the perpendicular slightly. Even if the Moon was 1 meter away from Earth, it still would not lift water away from the Earth, as the Earth gravity is stronger. Hence why water reservoirs do not lift even a millimeter during High Tide.
(Maybe too technical for the video, but i meet a lot of people who were told in school the Moon actually "lifts" the water on Earth. But those teachers didn't calculate the gravity first, (obviously). They probably assumed somebody else did the calculation, because their teachers told them the same thing. It happens.)
This is also why the few lakes that do have tides, tend to be the ones with their long direction oriented north-south, and located close to the 45 degree latitude line. Lake Michigan has a very subtle tide. It can be hard to notice that it is a tide, but you can conclude that there is a cycle to Lake Michigan's level that is consistent with tidal cycles.
Eben if it could "lift" it ina sense that you describe, it would look like bubles of water floating up, not sea level rise.
(and the whole earth would shatter as well, so thats not very useful)
@@carultch "True tides-changes in water level caused by the gravitational forces of the sun and moon-do occur in a semi-diurnal (twice daily) pattern on the Great Lakes. *Studies indicate that the Great Lakes spring tide, the largest tides caused by the combined forces of the sun and moon, is less than five centimeters in height.* These minor variations are masked by the greater fluctuations in lake levels produced by wind and barometric pressure changes."
-- NOAA
Yes, it would indeed by difficult to measure 5 cm level change. Especially when temperature, air pressure, and wind dwarf that variance. Longitudinal lakes on a calm, steady day. And only then from the height of Spring Tide to the absolute antithesis... 5 cm.
Tides in the oceans however: 40 FEET in Bay of Fundy, Nova Scotia.
To quote by paraphrase Crocodile Dundee:
"That's not a tide. THIS is a tide".
@@Quickcat21MK lol, I knew a guy who went by the name "cryptman" and he was as incapable of rational thought as you are.
That is actually the effect of the Moon lifting the water. It just happens that the lift is less on the poles that on the equator (because is further away). The difference is very small, but enough to cause a current flowing to the equator.
Lakes and the mall seas, don't have this effect, because they are not big enough i the north-south direction to sense the difference , and in the Mediterranean case in addition to being "flat" north-south wise, is connected to the rest of the oceans by a very small channel, not big enough to allow enough water to bulge.
This is the correct explanation. A *revolving, translating* coordinate system is not assumed for the purpose of analysis. It is a *fact* of orbital motion around a common centre of mass. The inertial forces from such a motion can raise tides. *Gravity is an inertial force.* The tides are due to a combination of the gravitational and inertial effects of the Earth, Moon and Sun in orbital motion around a barycentre.
The problem stems from the fact that gravity isn't actually a force, and is incapable of pulling water upwards across empty space. However, everything in the Solar System is in orbital motion around a *barycentre,* and that means it is subject to the influence of a host of *apparent* accelerating forces.
I could continue, but I've discussed this at length elsewhere and just wanted to reassure you that the subject of tides has been thoroughly examined by science for over three centuries, *by the likes of real astrophysicists including: Johannes Kepler, Galileo Galilei, Issac Newton and Pierre Laplace.*
The *udiprod* and *pbs* explanations are both correct explanations in accordance with *Dr Becky's* and the waterlust farse is a complete waste of time.
Have a nice day! 😁
Thanks, you explained that very clearly. Any tidal explanation is dependent on the facts acquired through experimental data and observations.
*These are the facts about tides:*
*Lunar tides:* The Earth is in orbital motion around a barycentre with the Moon, and the tides are caused by the gravitational interaction with Inertial forces. Gravity is an inertial force.
*Solar tides:* The Earth is in orbital motion around a barycentre with the Sun, and the tides are caused by the gravitational interaction with Inertial forces. Gravity is an inertial force.
*The equation for inward inertial action:*
*F = GMm/R²* ~ Newton's Universal Law of Gravitation, by Sir Isaac Newton 1687.
The experiment that validated this equation for mass attraction:
*The Henry Cavendish experiment* ~ Conducted by Henry Cavendish in 1797, which determined the value of *Newton's Gravitational Constant,* and allowed us to calculate the average density of the Earth.
*The equation for outward inertial reaction:*
*F = mrω²* ~ where *(r)* is the distance to the *Barycentre.*
You're welcome. 🙂
I think you are mistaken. Its not that gravett pulls up the tide. It minutely squeezes the ocean. Check space time. ua-cam.com/video/pwChk4S99i4/v-deo.html this is the best description I've seen.
The funniest part of this excellent explanation is: 06:55 Here you go!
_"You say either, and I say eyether._
_You say neither and I say nyther._
_Either, eyether, neither, nyther..."_
*Let's call the whole thing off!* ~ written by George Gershwin and Ira Gershwin.
You're so funny Dr Becky. Thanks for that appraisal of reference frames, it was hilarious! 😄
My physics teacher was a strong proponent of the, "there's no centrifugal force" argument. Unfortunately, never explain why which made the video we watched on centripetal, centrifugal, et.al. forces tricky to digest :/ - until now! Thx, Dr Becky!
Mademoiselle, this tidal presentation is exquisite, the wolves below doth protest too much, methinks?
_"Sköll the wolf who shall scare the Moon,_
_Till he flies to the Wood-of-Woe:_
_Hati the wolf, Hridvitnir's kin,_
_Who shall pursue the Sun."_
~ *A quote from Grimnismál, from the Poetic Edda.*
Thank you for sharing your knowledge with us Dr Becky, and for scaring the wolves of ignorance. 👇
It would all make more sense, if we had a 13 month calendar @ 28 days. And start the new year with a 0-day. It would be so much easier to calculate/plan stuff.
One thing I think you forgot to mention is the fact that gravity is dependent on distance.
The side of earth facing the moon is slightly closer to the moon so the gravitational pull is stronger than the centrifugal force.
On the other side, the moon is slightly further away so the gravitational pull is weaker than the centrifugal force.
Same effect explained in two different but equally valid ways.
@@maximilianofonseca9013 Exactly and at the centre the centrifugal force = gravitational pull = free-fall = weightlessness. Thanks
The explanation I once saw was to imagine three balls lined up vertically to the moon. Allow the balls to fall under the moon's gravity. The ball closest to the moon gets attracted slightly more than the middle ball, which gets attracted slightly more than the outer ball. The result is that the two outer balls move away from the center ball.
@@charlesgantz5865 That is an excellent way to imagine it Charles. In Physics, it’s called the ‘spaghettification’ effect. Unfortunately, in your example those balls are still free falling towards the moon in a straight line. And, that’s where the barycentre, orbital motion and the centrifugal effect of inertia suddenly appear.
@@charlesgantz5865 this is the answer!
So a few things... first thank you for staying away from mis-leading clickbait titles on your videos. It drives me insane when science channels do this. Second, thanks for just educating us on random things. It's really fun, and this is information I didn't know I needed but now I can't wait to blow my friends minds telling them the Earth and moon actually revolve around each other. And lastly... love the blooper reels. WOBBLE WOBBLE WOOBLE WOBBLE.
Hoobble
Wobble.
And she got it WRONG!
This video (by PBS Space-time) is better and more accurate.
ua-cam.com/video/pwChk4S99i4/v-deo.html
“Hoobble, Wobble toil and trouble - Fire burn and cauldron bubble” - _Macbeth_
The laws of Physics are equally applicable to all observers, regardless of there frame of reference.
As far as a photon is concerned, it's moving with a constant velocity in a straight line motion, in its inertial frame of reference.
However, it can still be affected by the gravitational field strength of the Sun, and is therefore deflected from its straight line trajectory. That is why we see a change in the position of distant stars, during a total eclipse of the Sun.
Newton's Laws of Motion and Gravitation are both valid in a given timeframe.
Sorry but you are wrong. The MATTER AROUND the star is what deflects the photon. It's called refraction and is explained with Lenz's law dealing with current flow. The magnetosphere will redirect the light around a planet or star but the mass itself doesn't.
What a surprise! I'm actually quite relieved, if you had said, You are right! Then, I might have considered re-evaluating my position. 😆
Photons don't have an electric charge and thus are not affected by electromagnetic fields. Refraction and Diffraction are another matter, and involve the motion through differing mediums.
@wavydaveyparker refraction applies to both light and sound waves.
That's why I don't understand all this gravitational attraction nonsense.
It's flat earth/ stationary plane garbage that was disproved back in Galileo's day.
And yet idiots like Hawkings and Einstein and even Newton still think the earth is a stationary frame and the center of the universe in which everything revolves around it.
Didn't a king use his body measurements to establish the imperial units? They are doing the same, only measuring the universe using the earth as the unit of measure.
Sure if you want to know things like Mars' gravity is 80% that of Earth's.
The universe deals in Absolutes. It doesn't even know the earth exists so how can the earth define the universe.
Nobody understands what a frame of reference is. The earth, rotating on its axis, that's one frame on reference. The earth orbiting the sun, that's the second frame of reference.
Gravity decreases as one nears the pole because motion in space decreases. 1000 mph at the equator to zero at the poles, but you still have the earth in motion around the sun of 67000 mph.
Then there is atmospheric pressure. Not only is the ground accelerating your mass, but you are also accelerating the air above you. Which is why gravity decreases with altitude. Since gravity comes from acceleration, it can't affect light waves that are pure acceleration. You can aim two light beams at each other and the forces cancel each other out. But light is not going to be pulled into the planet by its mass.
Black holes aren't sucking in light no more than planets suck in sound waves.
You can't fix stupid. The church of relativity have dug themselves a hole so deep, they can't climb out of it without looking stupid in not understanding basic physics.
Added to the possible fact, that if we were somehow able to place ourselves in a photons frame of reference, which is almost completely impossible!
Then, we'd have no concept of space or time, because everything would be happening everywhere at the same time, and we would feel motionless to do anything about our predicament.
@cybermonkeys wrong. Beside the fact that your atomic energy is converted to radiant energy, the laws of physics still apply. The photon is accelerating itself. Dropping little atomic bombs out the back to accelerate itself forward. That's what redshift is. The loss of energy as the photon travels through space.
Applying the Lorentz transforms, INFORMATION about your destination will be sped up while INFORMATION about your departure will be slowed down.
Traveling to Alpha Centari, you will fly through the INFORMATION stream at 2x the speed of light. What is coming towards you and what you are traveling towards.
Warping acceleration, so you are not converted to radiant energy, leaves you witnessing the forward view screen at 2x and the rear at 0x while normal time passes within your frame.
The knights who say "Neap Tides"...
earth's gravity is stronger than the one on the moon BUT the moon is pulling earth ? how come ?
Hello Dominic, The acceleration due to gravity at the surface of the earth is 9.8m/s2. The acceleration due to gravity at the surface of the moon is 1.6m/s2. However, the pulling force between the two is the same, because gravity is proportional to the product of both the masses and indirectly proportional to the square of the distance they are apart. Does that help or would you like me to use actual numbers?
@@wavydaveyparker wow clear 10/10 ! i love when people knows their stuff and can easely explain it ! man science is a good thing for healt !
@@DOM_4GOOD wow, thanks very clear 10/10 ! It was nothing really 😄 just the simple use of F=ma, but your great question did get me thinking about some follow up questions. Maybe you’d like to drop a comment on my channel and we can work on some more simple math together. Thank you for replying. Take care.
Eric Donaldson (born 11 June 1947 in Bog Walk, Jamaica) is a Jamaican reggae singer-songwriter. He originated in Saint Catherine, Jamaica
Oh, Cherry Oh Baby, that's really interesting, thank you. Did Eric know Bob Marley? The Rolling Stones covered that track on their _"Black and Blue"_ album in 1976. Brilliant.
The tides can easily be explained using Galileo's principle of inertia, Kepler's laws of planetary motion and Newton's universal law of gravitation.
The accelerated motion of freefall was used to demonstrate why all objects fall in a vacuum at the same rate, regardless of there mass. The ground is not a stationary plane and moves with an orbital motion around a common centre of mass, called the Barycentre.
It does not float off into space with a straight line motion, unless someone miraculously manages to remove the Sun from our solar system, and then it will still take approximately eight minutes, for the structure of spacetime to adapt to this change in motion. The effects of gravity also travel at the speed of light.
The National Aeronautics and Space Administration courageously planned and meticulously calculated several excellent missions to the Moon, not only to prove Galileo, Newton and Einstein correct, but to also show that the Earth was in orbit around the Sun and rotating on its axis. A delicate balance between inertial and gravitational mass, along with the necessary existence of a curved spacetime.
Galileo clearly showed in the 16th century, that there was an attraction between objects of mass, by rolling objects of mass, down an inclined plane, and calculating the observed rate of acceleration.
The tides are the natural result of the centrifugal effects of motion, whilst moving through a non-uniform gravitational field, that fortunately obeys an inverse square law geometry.
Flat earth is not a science, and is devoid of any examinable evidence or able to make any viable predictions and just resorts to making unfounded claims that follow on from the ridiculous assumption, that the earth is stationary, two dimensional and pristinely flat, and is somehow sitting motionless at the centre of our galaxy.
Thank you dear Dr. Becky ❤️ ....
And I'm always waiting for your videos about *Hubble* please make more video about it and its discovery and news (you are the best person for it).
One other interesting thing about tides, they don’t effect rivers or lakes. The actual tidal forces are minuscule, the only reason why we see tides at all is because the water allows circumnavigational flow of water. This allows basically a standing wave to rotate around the world. If the flow of water was blocked off then the tidal forces would be virtually imperceptible. As it is the current tidal bulge is just over 50cm (1’ 8”). It is higher on coast lines and river outlets for the same reason tsunamis are small bumps in the deep ocean but huge waves on land. It amazes me on how weak gravity is and yet its influence goes so far.
Right, the Moon doesn't "lift" or "pull" water away from Earth. It changes the flow direction. All the water flowing towards the equator causes the bulge due to hydrostatic pressure. Water flows towards the equator because the Earth is larger than the Moon, so those force lines converge towards the center.
It's amazing what happens when a single direction is agreed on. Be it tides, or magnetism, or tornados and hurricanes. Motion is the same magnitude, momentum is conserved. But when it all agrees on a single direction: it's nothing short of amazing.
It also amazes me that tides still work even though there are multiple landmasses blocking water from flowing around the Earth near the equator - South America (plus Central and North America for a big blockage in the northern hemisphere), Africa (plus Eurasia for another northern blockage) and Indonesia. The tides require a significant current to move water to where the high tides are - mostly the high tide itself moving, but that's clearly complicated by the land masses. The only major current that circumnavigates the globe is around Antarctica. I would have thought there's some degree of tide circumnavigating the globe around the Arctic too - there's no continent, the ice is floating on the surface so water can flow underneath and the ice is presumably vertically mobile, and that ice doesn't always reach Canada, Greenland, Scandinavia and Russia anyway - but I don't see anything marked around the Arctic on maps of ocean currents. So yes, it's pretty impressive that there's enough flow to maintain this standing wave, given that the tidal forces are highest at the equator which is obstructed by land. I guess that depends on the Pacific, Indian and Atlantic oceans covering large chunks of the equator, leaving enough room for tides to occur, and creating enough pressure to maintain the needed currents around the barriers?
@@onebylandtwoifbysearunifby5475 The whole planet deforms, as does the moon. It's just that in rotation the solid part of the Earth is attempting to pass through the much more fluid oceans.
"they don’t effect rivers or lakes" - nope. Larger lakes can experience tides. See for example the North American Great Lakes. It's just that the tides on said lakes are much smaller than ocean tides.
@@stevehorne5536 There are certainly strong global oceanic currents. They are strong enough to maintain direction of flow through tides. The longitudinal directions are not to be overlooked. There isn't much obstruction between N and S hemispheres, most of the landmass is in the Northern hemisphere. So the flow in largely N-S unobstructed. Where it meets land, there are tides of course. But water pushes equally in all directions. Water pressure increases with depth, not surface area. (And even the surface area is 70% water). Pressure equalizes in all directions, pushing the water higher where there is more of it. Persistent force and small accumulations make a startling difference, yes. It's not something one would predict as obvious.
One interesting thing to think about is how pressure increases on deep sea life at high tide areas. All that water stacked on them probably is rather noticeable. Probably a lot of cycles we don't even know about in marine life.
This was enough to keep me tide over till your next James Webb video.
*[Enter your asinine and vacuous remark here]* 😂😂😂 And press enter.
Thank you for your contribution! 😌
I had always wondered this but never been curious enough to research it.
Ive heard it explained completely differently but in the linear reference frame. I suspect theyre the same explanation just with different reference frames, this one is easier for me to understand because of...the orbiting going on.
That is a superb comment Matt. Thank you for having the wherewithal to type such clear reasoning. Even though this wasn't my creation.
There are only two reference frames we need to concern ourselves with here. An *inertial* reference frame, and a *non-inertial* reference frame.
An inertial reference does *not* accelerate. Therefore, it does *not* contain any resultant action from any external forces.
The Earth and Moon are in an orbital motion around a barycentre. Therefore, they are accelerating, and have to be considered in a non-inertial frame of reference. Where the external forces of gravity and inertia (centrifugal effect) have to be taken into consideration.
Leading to the twice daily tides we observe on the surface of our precious planet Earth. Thank you.
@@wavydaveyparker Thank you for the kind words and for further explaining it!
@@MattH-wg7ou You're very welcome indeed Matt, I'm glad you found it helpful. In fact if you want to delve deeper into the mystery behind the discovery of gravitation. Then you'll have to wait for my new pop-up book to be published. 🤓 It's going to be called:
*Gravity roams the Universe with Newtonian tendrils* ~ _A brief story of Architects and Carpenters._ - by Wavy and Friends.© 2024
Available in all good secondhand bookshops at a very discounted price. 😆
@@wavydaveyparker Amazon will bankrupt you 🙄
This is exactly what I have been looking for! Nobody actually explains the bulge on the opposite side. Thanks!
hi. is that a scammer?
@@osalicsomonic6069 Possibly Osalic, I’ve tried telling Dr Becky, but she didn’t reply. My advice is to ignore it?
I love the way you explain concepts. The questions you ask and the way you link all the components to clarify the explanation. This video is awesome but uses Southern Hemisphere orbits(clockwise). Could you also make one for Northern Hemisphere with counterclockwise graphics? The students of Georgia, USA would be very grateful!
That is a really brilliant comment, but must admit that I'm now completely confused. I might leave this to Dr Becky's expertise, seeing as she is in the northern hemisphere, and I'll just go and fly my battle kite instead. I thought the graphics were going counterclockwise, I must have been watching this, while standing on my head. Thanks for the heads-up! I wondered why I was beginning to feel dizzy.
Centrifugal force might explain high tides on the side of Earth opposite to the Moon because the barycenter is inside Earth. I don't think it can explain the effect of the Sun because that barycenter is inside the Sun.
Except it does explain the effect of the sun. Not the sun-Earth's barycenter, but the Earth's center of mass. What happens is that the Earth's acceleration due to the gravitational fields of the sun and moon, is based on the gravitational force on the average kilogram of Earth, summed up across the entire region of space that the Earth occupies.
Locations on the side of Earth closest the source of the tidal force, receive greater force per unit mass than the average kilogram of Earth. Locations on the opposite side, receive less force per unit mass than the average kilogram of Earth, and therefore will lag behind the Earth. In the reference frame of the Earth's center, this will make it seem like that particular portion of the Earth's surface weighs less, and likewise, the side closest to the source of the tidal force, will seem like it weighs less as well. It is the locations where the body causing the tidal force see it at the horizon, where the apparent weight will be greater, which is where low tides happen when the moon is at the horizon.
Try to explain this to the infamous Fox News host, Bill O'Reilly, who in a news cast with an atheist said: "Tides go in, tides go out. You can't explain that!"
The atheist was so baffled, he didn't know what to say, in reply to such stupidity.
It would've been a more interesting exchange if Bill had actually done his research and found an example that scientists currently cannot explain.
I used to think that the explanation given of the moon's gravitational attraction pulling the water and thought each day only had one high tide
When i saw the normal illustration shown I've been confused for a while
....now i know about tidal forces 👌
Hm, now I am confused. I learned that the Tidal Force is responsible for this effect of tides. Does this seeming "disagreement" have to do with different frame of reference being observed?
I am confused about your confusion. Why? Tidal Force is the result of Centrifugal Force + Gravitational Force. Both those forces act in nearly the opposite direction on any place of earth. So if you simply add up this both forces the result would be close to zero. You have to do it in an vector addition, so they don't cancel each other out completly. The resulting tiny vector represents the direction and strength of your tidal force. This only works because the angle between those two forces is less then 180°. This is also the reason why the tidal force of the moon is so much bigger then the tidal force of the sun. Although the gravitational force of the sun measured on earth is many times higher than that of the moon. It's ultimately all about the angle between the vectors.
Yes, good point.
"Tides" are hydrostatic forces due to cumulative directional water flow, not "lifting". The Earth gravity is stronger than the Moon, so no lifting away from Earth surface. Smaller bodies don't lift larger ones. Rather, the Earth is larger diameter than the Moon, so the tidal forces converge towards the center, causing a bulge at the equator. This bulge is largely symmetric, hence the "tides" on the opposite side. That plus the barycenter rotational forces of the Earth-Moon system mentioned in this video. It's both, but mainly hydrostatic (lateral) water flow towards the equator.
You should look up the video on tides by PBS Spacetime. It goes into much more details. Tides are mainly caused by the oceans flowing towards the equator rather than being lifted up by moon's gravity. Other phenomena like the ones mentioned in this video are minor contributors. I'm no expert but this video seems incomplete
And Becky's explanation may not be correct! (See a Neil Degrasse Tyson 'Star-talk' video on it)
This is not the correct explanation. Even when a rotating coordinate system is assumed for the purpose of analysis, the centrifugal forces have the same size and direction anywhere on or within the earth. So they cannot raise tides. "Tidal bulges" are not due to rotation, but are simply due to the combined gravitational fields of the earth and moon, and the fact that the gravitational field due to the moon has varying direction and strength over the volume of the earth. I like many of Dr. Becky's explanations, but you can watch PBS Spacetime and other reliable physics channels to see why this is not the case. I recommend Waterlust and udiprod's videos on this topic to understand tides better.
Who said anything about the effect of a rotation on it's axis. That is not applicable in a equipotential tidal height analysis. It is an orbital motion around a common centre of mass that is important here. As is proposed by udiprod.
Actually, what Sir Isaac Newton would say, instead of F=ma, is that at the centre of the Earth. The centrifugal force balances the centripetal force.
So, *F= -ma* ~ Therefore, *GMm/R² + (-mrω²) = Zero* Where *(r)* is the distance to the *Barycentre.*
The Moon's gravity at the centre of the Earth causes nothing whatsoever, because the the Earth is weightless in space. In a freefall motion around the common centre of mass, in the Earth-Moon system. A force is not required to maintain motion, and the so-called gravity at the centre is not a force.
So what causes tides? The two tides are of approximately equal height on both sides of our globe shaped planet, because in an *equilibrium* of tides theory, as was proposed by Isaac Newton. The Earth is not static in space, and orbits a barycentre. The centrifugal effect from this inertial motion is the same across the whole earth, whilst the moon’s gravitational attraction diminishes with distance by the inverse square.
This inevitably leads to an average tide height of approximately *0.54m* on either side of Earth, pointing away from, and towards the direction of the Moon. And an average tide height of approximately *0.25m* on either side of Earth, pointing away from, and towards the direction of the Sun. And an average tide height of approximately *0.79m* during a spring tide. Any other complications, then you'll have to consult with Pierre Laplace.
Are you honestly trying to imply that Newton got his theory of gravitation incorrect? I'd think again if I was you.
The pbs explanation is correct with reference to the tractive component, but the waterlust mistake is just flawed, because it holds to the idea that the ocean is left behind in a linear acceleration towards the moon.
This explanation is much better than others, because it’s simplified to a point that is correct and easy to understand. The tides are essentially caused by the inertial motion of planets and oceans around a common centre of gravity, in a non-uniform gravitational field. I see no reason to mention the SpaceTime extravaganza here, as it only deals with a misleading static scenario of tidal forces and makes no mention of the tidal effects produced by orbital motion around the sun.
I would move the Barry center closer to the 1/6 the distance to the moon since the moon's apparent mass is 1/6 the size of earth! Did you also knotice that the earth isspinning 28 times faster than the moon, so even though the earth volume is 50x bigger than the the moon, its gravity is only 6x bigger! We need to start using the mass on the moon so that we can accurately predict their true mass! I bet you guys underestimated the mass of Jupiter as well since it's rotates 2.6x faster than the earth!
Hey there, whilst most of what you say is correct. I personally think you’re getting slightly confused through the use of some of your terminology. The barycentre is the balance point of the system, around which objects of mass orbit. Its value can be calculated by using the relatively simple equation given here. Although, it can also be determined by equating the balance between the inertial motion of the earth, against its gravitational attraction to the moon, or its centripetal effects against its centrifugal effects. I would be glad to work with you through these calculations, in my own comment section, if you’re interested. Kind regards
@wavydaveyparker I agree! I think the mass that we are assigning to each planet/moon is obscure by the centrifugal force. That's why planets that are spinning faster than earth would be estimated lower and slower like moon or other planet with slower spin to be larger in mass. I am assuming you are calculating mass based on the gravity experienced. If we assume density is the same for all the objects, we should be able to find correction factors for the mass of objects with varying rotation speed.
@@kmyase1 That’s interesting, and I’m glad you agree, but I determine the mass of an object in orbital motion, by using Kepler’s third law of Planetary Motion, like most physicists have done, since the time that Cavendish correctly calculated Newton’s Universal Gravitational Constant. However, believe it or not, this is Dr Becky’s excellent tidal explanation, and you’re more than welcome to discuss this further with me, in my comment section if you can find it? Thanks
Centrifugal effects are capable of causing tidal forces, in conjunction with the inverse square law of gravity. Centrifugal and gravitational forces cause very little effect on tides, especially around the barycentre.
Thank you for teaching this, it is a very accurate depiction of our twice daily tides. Tidal forces don't have to be orbital, but in a balanced orbital Earth-Moon system, around a barycentre, they are essential.
Gravity is universal and non-uniform. All parts of the earth are accelerating towards and away, from all parts of the moon at different rates, and it is causing the Earth to squeeze and not the oceans to lift.
If you want to truly understand tidal forces, then you need to understand General Relativity, because General Relativity is built upon an accurate description of tidal forces. Thanks
Thank you so much for explaining this it was terrifically eye-opening.
Aren't tidal forces themselves involved as well? Water on the opposite side of the Moon would be slightly further from it than the Earth itself, and hence pull would be a little less, so water would "lag" behind, causing a tide.
Tidal forces are the correct explanation because they elongate the objects, in this case the Earth, even if they do not rotate. Gravity and the centrifugal force are conveniently influencing the right sides of the Earth relative to the Moon in Becky's explanation.
Tidal forces are the correct explanation for tides, but if they didn’t revolve around the barycentre together, then they would accelerate towards each other and the tides would rapidly increase, until collision. In Dr Becky’s video the tidal forces are taken relative to the centre of the earth outwards, because that is the zero reference point.
I always thought it had to do with the fact that the Earth is in free-fall around the Earth-Moon center of mass, which cancels out the component of the Moon's gravity pointing directly toward the Moon's center of mass, leaving only the inward-pointing component due to the fact that the lines from the Moon's center of mass to the different points on the Earth are not parallel. The Sun's tidal influence on the Earth is less because being so much farther away, those lines are closer to parallel, and the inward component, after canceling out the component that points toward the sun, is smaller.
This is correct but misses some things.
On the side of the planet facing the Moon, the gravitational acceleration caused by the Moon is stronger than that applied to the planet as a whole, so you could think of it as water falling slightly away from Earth - so you get a tidal bulge.
On the side opposite the Moon, the Moon's gravity is weaker, so the acceleration applied to the water on the far side is less than the acceleration applied to the planet as a whole. The end result is the planet itself falling slightly away from the water, so you get a tidal bulge on the far side as well.
But since the planet and the water sticks together by Earth's much stronger gravity and molecular bonds, this tidal force makes itself apparent as a "stretching" component - essentially it puts the whole planet under tension, not just the water on the surface.
Additionally the inward-pointing component applies a compressive force on the globe. As far as tides are concerned, you could also look at it as the gradient of gravity applying a tangential acceleration to water all across the globe, pushing water towards the high tide bulges and away from the neap tide recesses.
On top of that there is the centrifugal effects from the fact that Earth is rotating around the Earth-Moon barycenter, but that effect *stacks* on top of the tidal bulges caused solely by the gradient of gravity.
@@HerraTohtori Another thoughtful comment. Well done! But, can I politely suggest one slight correction? You said, _“The end result is the planet itself falling slightly away from the water…”_ That should read, “The end result is the water itself falling slightly away from the planet…” Because at the centre the opposing accelerations cancel. The Earth is in free-fall and the whole planet receives an ‘outward’ acceleration to balance the Moon’s gravitational attraction, which is weaker on the far-side. It’s really very simple.
@@wavydaveyparker It's all relative! The important thing to realize is that the difference in gravitational acceleration points away from the surface on both sides. I was attempting to use the linguistic inversion to highlight that, from the perspective of the water on the far side, Earth is being pulled more towards the Moon than the water itself is, leading to "planet falling away from the water" - or, in reality, leaving the tidal bulge slightly higher.
@@HerraTohtori
Thank you. That makes sense.
@@HerraTohtori Yes, it is all relative! At the centre of the Earth the acceleration vectors cancel, just like Daniel described. The tidal force acts in an outward direction from this point. There is no need to mention any other perspective. It’s unnecessary baggage.
There is a huge difference between a respected *Astrophysicist,* explaining tides correctly, without mentioning the motion of our planet around the *barycentre,* or the resulting effect from any apparent forces, which maybe present in a tractive component.
And, a chemistry teacher telling you that these forces do not exist, and that the tides are solely caused by the Earth shifting position directly towards the Moon in a straight line motion, which quite frankly is totally ridiculous, and an insult to classical physics, classical music, and the obvious intelligence of any average human being. Thanks again for this interesting and accurate video.
Do you honestly think Becky is a true astrophysicist? You really are delusional.
Galileo proved the non-existence of gravity. Of mass attraction. That the earth is a 3d sphere in orbit around a central star. He correctly theorized that the tides are the result of the Earth's motion around the sun. Rotating on its axis, the Earth's mass is being accelerated outward and forward accelerating its mass into a higher orbit/radius as evidenced by the tidal bulges. The fact that it is in orbit around the sun changes the direction of rotation twice a day. From clockwise to counterclockwise. Hence, tide comes in, tide goes out. Rivers and lakes don't have pronounced tides because the bank is pushing back and dirt has more force to resist acceleration than water.
Becky is obviously unfamiliar with Kepler's Laws of Motion or she would know that the annual high tide occurs on the side opposite of the sun when the planet makes its closest path and experiences the most acceleration.
There is no interaction between the earth and the moon because mass is not an actionable force. You would still get the same tidal effect without the moon in the sky. Any competent astrophysicist would know this and not be scamming you with gravitational attraction nonsense.
So quit encouraging her to lie. Since Google refuses to flag her videos as flat earth physics, her viewers need to do so in the comments.
If Becky has an issue with that, then she can address why Galileo is wrong. Why Newton's Law of Motion, F=ma, is wrong. Why Kepler's Laws of Motion, acceleration increases as the radius decreases in an elliptical orbit, is wrong. Three highly regarded physicist, all saying the same thing. There is no mass attraction. There isn't even an equation for mass attraction. Nor any experiment that validates mass attraction. You are being brainwashed by flat earth physics. Educate yourself because Becky is just regurgitating the nonsense she was told or read in a book.
Thanks, you really know your stuff. Here, this might help ease anyone's doubts, if they have the wherewithal to grasp the concept:
The equation for mass attraction:
*F = GMm/R²* ~ Newton Universal Law of Gravitational Attraction, by Sir Isaac Newton 1687.
The experiment that validated this equation for mass attraction:
*The Henry Cavendish experiment* ~ Conducted by Henry Cavendish, funnily enough! 😅 In 1797, which determined the average density of the Earth, and allowed us to calculate *Newton's Gravitational Constant.*
If we take the time and do some real courses in *Physics.* Then, hopefully one day, we all might become respected *Astrophysicists,* like Dr Becky.😂
@@cybermonkeys you should go back to school and learn some real physics.
Galileo proved in the 1590s that there is no mass attraction. When two objects of disproportionate mass fall at the same rate, where is the mass in the equation?
There is only Acceleration. F=ma. Mass is not an actionable force. Newton's gravitational attraction equation. That just states that mass equals mass. Where is the action?
The laws of physics are equally applicable in all frames of reference. Turn the frame horizontally. What happens then? Acceleration differences.
Gravity is an artifact of Acceleration. Your god Einstein pointed this out himself. There is no difference in the orientation of the frame. The physics is still the same.
Mass attraction came from the fact that you kids believe in a flat earth with everything else floating around it. How else do you expect to stay rooted to the ground?
Galileo's ball drop experiment-> no mass attraction
Newton's, F=ma. Force equals Acceleration. The earth spinning on its axis is accelerating its mass outward and forward creating curved space. Your are being accelerated outward. Not pulled inward. What? Do you think the Earth's mass force is greater than its acceleration force? You are a true flat earther there Skippy.
F=ma. Mass TIMES Acceleration. Mass has no force without acceleration. Acceleration is the Acceleration force. Mass is just mass. Stored energy taking up space. E=mc. You don't even understand basic math and physics because you are stuck on stupid flat earth science.
Why don't you go look at LIGO. Are the detectors being pulled towards the source or pushed out of alignment. Sounds like tractor beam technology if you can get an electromagnetic wave emanating outward to pull matter back towards it.
You have to be really dumb to believe that mass is an actionable force. It's F=ma. Not m=a.
Take a pan of hot water. Now add some ice (mass) do you get more acceleration-> increase in temperature?
Go back to school there kid. You have a lot to learn yet.
Brilliant! I now understand. Your knowledgeable lessons have been invaluable. Thank you.
The Centrifugal Force was an idea introduced by Newton himself, to explain the _'apparent'_ outward movement of an object in circular motion, very similar to the action of a *centrifuge,* but Newton had to concede that it wasn't a _'real'_ force, because there wasn't any agent to produce the desired effect, which is very similar to the action of gravity, which is the _'apparent'_ inward movement between objects of *mass,* across empty space.
However, when questioned on this apparent mystery in his calculations, he had no answer and said, _"I'll leave that for the consideration of a future scientist?"_ And, that scientist was none other than Albert Einstein, who finally concluded, after ten long years, and lots of steamed clams, that gravity and centrifugal were both _'apparent'_ forces, which only appear in an *accelerated* frame of reference, and that both were contributing factors behind the *tidal force* phenomena we observe in our oceans, lakes and seas.
Dr Becky summed it up perfectly at the very end of her tidal explanation, when she says, _"People start saying Centrifugal is fictitious, we know!"_
Many thanks for remaining truthful to science education. Astounding comments. 😅
@@cybermonkeys Yes
Cool Video!!! Just out of curiosity, am I the only person who had a sudden desire to here Rowan Atkinson say the word wobble? I'm sure it would be funny... ;-)
You're not alone, as I had the same thought myself, but mine involved the character of "Blackadder" who, if I'm not mistaken, actually said something similar to "wobble" in a episode once?
In the UA-cam video "what physics teachers get wrong about tides" (ua-cam.com/video/pwChk4S99i4/v-deo.html), the speaker says... the grav and centrif forces (basically along the line joining moon and earth) are FAR too small to produce the observed tidal bulges. Instead, he looks at the forces somewhat closer to the poles (see that video at 5:20), which are nearly tangential to the earth's surface. He claims these forces ARE large enough to produce the observed tides.
Yes, yes…what’s your point? All vectors can be resolved into their vertical and horizontal components. The only thing that was demonstrated in the video you cited, was a stationary earth with extremely tiny forces at its surface, and about to start accelerating in free-fall motion directly towards the moon, because he forgot to mention inertia and the barycentre.
Yes indeed there are 2 high tides, 1st Ministers resigned and the 2nd Boris Johnson also resigned. I wonder what caused this gravitational pull Dr. Becky??🧐🤔😄❤️
Off topic, but I wonder if the barycenter being so far from the center of the Earth helps generate the dynamo that creates our magnetic shield
I think if we didn’t have a unusual big moon (compared to other planets) we might not have a liquid molten core in the earth. Those tidal forces are massaging the earth and slowing down the cooling of the earth core. And certainly without a liquid core, no magnetic field, no protection against solar eruptions, loss of atmosphere. Mars has no big moon -> no liquid core -> no magnetic field-> a very thin atmosphere. I never thought of the barycenter being far away from the center being essential for the dynamo…I don’t know, but yes I think you might be correct in that assumption.
thanks a lot for this wonderful and simple explanation
lots of videos have uselessly complicated things
thanks for that simple and clear explanation, I'm very familiar with the tides but have always struggled to understand, let alone explain, this phenomenon, which makes it awkward when teaching tides to novices! All the models I'd seen before ignored this barycentre oscillation, so the idea of a centrifugal effect never really came up in the discussions. I'll forward this link to Physics teaching colleagues at work and may link it to a video in my own channel in due course. Many thanks and here's fingers crossed for a nice balmy, breathable atmosphere on Trappist d or whatever its proper name is!
What a wonderfully clear, interesting comment and accompanying channel. Yes, Isaac Newton firmly established that a common centre of gravity was a prerequisite for all celestial bodies in balanced motion. Otherwise the outcomes would be disastrous. This wobbly inertial movement is definitely a contributing factor behind the tides, and is often overlooked by some unscrupulous individuals, although it did later require the incredible insights of Pierre Laplace to complete the picture. Many thanks and please take care balancing on bicycles.
Came for the knowledge,, stayed for the bloopers 🥰
Earth's equatorial bulge is about 43 kilometers (27 miles). The equatorial bulge means that people standing at sea level near the poles are closer to the center of Earth than people standing at sea level near the Equator.Ocean has bulge?Earth has bulge ?Bulge within a bulge?
This vlog🎥 👀took a year to pop in to my stream🎏.
Compared to your comment?😒😒
You seem very obsessed with bulges. Next you'll be telling us Everest is a bulge. 😂 So, I'll just play along with the bulges for now. Yes, gravity causes a bulge, and Inertial motion through bulging space (also known as centrifugal bulging force) causes a bulge. So, the Sun causes two bulges and the Moon causes two bulges, and at full and new moon we get four bulges for the price of two bulges, with bulges moving within bulges. And the earth spins on its axis causing a equal bulge right around the equator.
Having said all that, we don't actually notice any of these bulges, or pass through them twice a day, because they are extremely tiny and actually only exist as bulges of tidal energy that dissipate through the oceans and around the surface of the Earth causing Tides.
🐒🐒🐒🐒🐒🤣🤣🤣
@@Romadedoniamace You're very welcome eduardo 🐒😅 but, to clarify I think I should add that all these apparent bulges, manifest from the centre of the earth, *outwards,* as it spins on its axis, whilst also revolving with the bulging moon around there barycentre, and all whilst that same barycentre, orbits around the Solar System barycentre with the bulging Sun, which probably gets 'spots' from all the bulging? 😒
@@cybermonkeyssome people just shouldn't be allowed to do physics. The moon has nothing to do with the tides. Nothing. Back in 1971, Scott dropped a hammer and feather on the moon proving that there is NO gravitational attraction between celestial objects. None whatsoever. This should have settled the gravity as a force debate waging since Galileo dropped balls from the Tower of Pisa back in the 1590s. But a bunch of flat earthers wrote Galileo's findings off as a thought experiment leading Newton to his gravitational attraction nonsense which later discombobulated Einstein into his nonsensical relativity and warped space bs.
The tides are strictly the result of the Earth's motion in space as theorized by Galileo. The equator has more acceleration causing the ocean to be accelerated to a higher orbit/radius. The Earth is also in motion around the sun causing a change in direction of acceleration of the ocean twice a day. The highest tide of the year takes place the first of the year on the OPPOSITE side of the planet facing the sun when it makes its closet pass and experiences the greatest amount of acceleration at that point according to Kepler's laws of motion.
If there was no moon, there would still be tides.
If there was no moon, there would still be *solar* tides, due to the combined effect of the Inertial motion of the Earth's orbit around the Sun, and the gravitational effect between them.
And, the tide would be highest at closest approach or perihelion, due to the increased gravity and Inertial speed of its orbit, in direct accordance with Johannes Kepler's *Second* Law of Planetary Motion.
Go back to atom-school stewie and get your teacher to take some proper Physics lessons. Good luck.
3:30 should have used Owl Kitty to illustrate centrifugal force
Sure the earth feels no force as it's travelling in a straight unaccelerated line along it's geodesic. Although, that's "net" unaccelerated. I suppose tidal bulges are parts that are being accelerated temporarily, as they are not at the centre of mass, rotating etc, but aways from it, but it all balances out.
That is actually a blindingly good comment Paul. Accurate and concise. You even managed to smuggle in the word ‘geodesic’ - brilliant! It’s just a shame some people won’t understand what you meant and just say, “Centrifugal” doesn’t exist. Thank you.
I never seen it explained so well, nice. well see ya in a week for JWST's first photos
By far the best explanation I've seen! I tried to understand this concept a few months ago. And between wiki, forums and other videos I got no where. You did it in 4 minutes. Bravo!
but unfortunately it's not really correct. Check the video by PBS spacetime to get a more accurate description.
@@marcelluswallace6240 It may not be fully correct for the front side facing the Moon, as the Moon cannot actually lift water away from Earth. ...
But It does give an explanation to the opposite side of the Earth experiencing tides due to inertia of rotation. A "Tides Part 2" may be good.
@@onebylandtwoifbysearunifby5475 No, the opposite side bulge is actually explained in the same way that the moon-side bulge is explained. Neil Degrasse Tyson did a really excellent video on it.
No! NdT spoke about “Yoga” - Pbs spoke about “Pimples” - Dr Becky spoke about “Centrifugal” - they are all simple and correct mechanisms, which explain the far side tides. The main message you should takeaway from this video is the factual existence of a barycentre, and the fact that at the centre of the Earth the opposing acceleration vectors cancel.
@@marcelluswallace6240 here is the link to the video you mentioned:
ua-cam.com/video/pwChk4S99i4/v-deo.html
Simply. Let's split Earth into water-Earth and rocky-Earth (hardly changing shape by the tidal forces). If we look at water-Earth only rotating with the Moon it would take an ellipsoidal shape for sure, like dual stars do. Now drop rocky-Earth into the water one. Where will it sink? INTO CENTRE of water one. It means that both tides would be exactly the same height, if the diameter of Earth would be meaningless to the distance to the Moon. But it's not.
Well, I need to admit one thing. It is a change in the way we think about the problem. Once the Moon changed shape on the water-Earth, there is no more about the Moon influence. It is about the gravitational relation between water-Earth and rocky-Earth. They HAVE TO line up with their centres, because they both free in space. Does not matter what wired shape water-Earth would take and why.
I love your pronouncing "Wobble" it sounded like Wooble
I grew up right beside the highest tides in the famous Bay of Fundy, and had my own fishing skiff at the age of twelve -
your explanation is much better than anything else I've heard.
And I later worked as a geologist at Bedford Institute of Oceanography in Nova Scotia
The funnel shape and the shallower (shoaling) depth towards land accentuates the tidal bulge in the Bay of Fundy
One unusual effect is that during ebb flow you can catch a temporary eddy close to shore that actually carries you in the opposite direction to the tidal currents in the main channel- handy in a row boat -very localized by the current jetties or promomtories such as reefs - fly fishermen use the same technique in rivers
How would that explanation work for lakes and rivers? Those don't experience tides, do they?
This explanation, which is the only correct explanation for the reasons behind two tides a day, in its simplest form, works perfectly fine with lakes and rivers.
However, we have to take this explanation one step further to correctly answer your great question, as Dr Becky explains, "there are many factors which control when, and how high a tide will be, but on average..." lakes and rivers do experience tides, but geography plays an important role.
A lake is not usually connected to the open ocean, so is unable to carry the necessary momentum, caused by the lateral inertial motion of water, to form a noticeable tide, but they do exist and can be measured.
Did that answer your question?
The bank is pushing back against the water molecules preventing them from being accelerated to a higher orbit.
Water pushing on water elevates itself to a higher radius whereas when water has to push against land, land has more force pushing back. Rivers and lakes aren't deep enough or wide enough to elicit tidal forces.
Thank you Dr. Becky, this was a great explanation! I've read about "wobble" before, mostly pertaining to the detection of exoplanets (as you mentioned), but I could never really get my mind around the idea. Seeing that time-lapse of Pluto and Charon blew my mind. It was a "light-bulb" moment for me, and finally I understand wobble. ❤
To: Dr Rebecca Smethurst
From: HR Department, Oxford University
Dear Dr Smethurst
The Geography Department have put in a complaint, and would like an apology.
Something about you infringing on their turf. Those people are all about 'turf'.
Regards
HR Manager
Thank you Dr Becky,
I was only wondering about this yesterday as I walked the Fleet on the Jurassic coast of Dorset.
What a Wonderful explanation Dr Rebecca.
Thank you 😊
You have the wrong explanation on tide, sorry Becky - ua-cam.com/video/pwChk4S99i4/v-deo.html
(04:00) _“NB: NOT TO SCALE“_
How amusing that you snuck in a Latin lesson there. Nice.
“NB“ is an abbreviation (actually, an _initialism,_ because there are no periods) of _Nota Bene,_ a Latin phrase meaning _mark well,_ or _note this well._ Its modern interpretation is to call attention to something important, especially in legal writings.
Isn´t it amazing how _everything,_ even the ostensibly simple, is also complex when expressed in context of such exegeses (or orbital dynamics)? That is why _NB_ was “invented“ thousands of years ago, to put the burden of understanding on the reader instead of the writer. (I´m only kidding!)
I am visiting my folks who live right on the ocean in Western Canada, I was just wondering this last night! Of course I knew it was from the moon but not all the exact details, you're so helpful
There is just one enormous, glaring mistake in your very first sentence, flipfake: 👇
_"Only the Flat earth model explains tides."_ ❌
And, without doubt, it's a huge non-sequitur - _if I'm using that term correctly?_ 🙂
Unfortunately, flat earth is *not* a science, and does *not* have *any* workable models. Therefore, it is totally *incapable* of *convincingly* explaining anything about the tides.
All the slight discrepancies you foolishly listed, without any satisfactory explanation whatsoever, can be perfectly understood, if only you'd shown the true rigour of a *real* scientist, working in the field of Oceanography and fluid dynamics. Instead of behaving like a flat earth nincompoop, who actually doesn't have any answers, and just preys on people, who have the honesty and natural curiosity, to seek truthful answers to their questions.
As was clearly highlighted by Dr Becky, at the very beginning of her excellent video. Thanks for commenting, and take care when swimming in the ocean. 😄
I'm sure many have said this already. I've tried wrapping my head around this reading, watching videos, discussing with others, thought experiments...a phenom woman in STEM explains it in 3 minutes.
Now to have her explain literally everything else.
Thank you. This was driving me bonkers.
And she got it WRONG!
This video (by PBS Space-time) is better and more accurate.
ua-cam.com/video/pwChk4S99i4/v-deo.html
I'm nktnsur this is accurate thoigh..think about if nothing is pulling the water away from the earth on the other side..there has to be a force there to pull the water.
@@leif1075 You're right, nothing is pulling the water on the far side. But something is pulling the earth more than the water, hence the water is 'left behind' slightly.If you use the earth as your inertial frame of reference, then it looks 'weird', but use the universe as your frame, then it looks 'normal'.
@@Chris-hx3om the way she says it in the video makes it seem like that..but what is that something..why do you just say something..don't youbjustmeam gravity of the moon? And earth's rotational momentum maybe squeezing the land spmehwat?
@@leif1075 Would you like me to attempt to answer some of your ‘apparent’ confusion? Unfortunately, it appears Chris is providing you with some mixed metaphors and personally I don’t think it’s helping you to understand tides correctly?
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So it’s centrifugal force that causes the other bulge , Thank you Dr. Becky for this explanation. I am an engineer but never properly understood this 2nd bulge. That Rose & Jack spinning around dance scene was killer explanation 😊
hi. is that a scammer?
That is also unfortunately not the main explanation for that second tide, it just coincides with it (see pbs or ndt videos about this). I've been thinking that myself with complete certainty for years and realised a month ago that I was wrong. Seeing a youtuber & scientist I respect doing the same is making me feel a bit better now though ^^
@@dkey201 I had already seen their videos, unfortunately I was not convinced by their explanation. But after seeing Dr Becky’s I understand now that all those videos are ultimately talking about centrifugal force, they just don’t know it 😂.
Let me explain, using Jack and Rose analogy.
1)Jack and Rose suddenly pull each other ( not yet spinning around) , what you will see, Rose hair suddenly flying outwards, well that is centrifugal force. So, in earth-moon scenario , that is 2nd bulge.
2)Jack and Rose now start moving around each other while pulling each other . You will see again , Rose’s hair again flying outwards, that’s centrifugal force.
So all those tidal forces which pbs video was saying are just gravitational pull and centrifugal force(virtual force) created by this gravity . And centrifugal force is imaginary, so it’s just gravity and motion of moon that cause tides
@@sureshbesra466 That was an excellent appraisal Suresh, and seeing that ‘d’key’ hasn’t responded…please let me interject! What you’ve described there is the perfect explanation to ‘Inertia’ in action. That’s what centrifugal force is - The tendency of a object to want to continue in a straight line, but is pulled by a force at right angles to its motion, which results in an orbit. Quite simple really!! 😂
Now, if you’d like to hear what Einstein actually thought his General Theory was actually all about! … 😌 … Then you’ll have to comment on my video instead. 👍 Take care.
I'm never going to forgive you dr. Becky, for not using the meme where they add the cat to the couple spinning. 😕
But seriously, thanks for the lesson! 😊
Stay safe there with your family! 🖖😊
Thank you. There are so many ‘tides explained’ vids that don’t discuss the barycenter and the centrifugal force of the opposite tide.
And when I point to a Dr Feynman vid describing the barycenter and opposite tide I get hand waved off.
Once upon a time there was an ‘AtomFool’ who said, that he respectfully disagreed with Feynman?
Hey @Dr. Becky , PBS SPACE TIME made a video about this a couple of years ago. But they gave a completely different answer than you just did.... like completely and they included the math for the height off the tides might be worth checking that out
hi. is that a scammer?
Great explanation. I understood this 40years ago from physics classes but had long since forgot the details. Nice to see it explained with no resort to the mathematics.
I recently moved to a place where the tides are very high so have taken a bit more interest in how they vary day to day. It would be good to do a follow up on how the inclination of the moons orbit results in one high tide often being a bit higher than the other each day.
Ah! I didn't know about that moon inclination bit ..... thank you! Another observation now makes sense!!
Hello doctor
I still struggle with this... Isn't centrifugal force a fictitious force that has to be generated by a different force? I still don't get this after watching mutiple videos of different teachers
Hello Arjan
Please read my comment directly below yours. A force is not generated by a different force. A force is either a force or not a force.
@@wavydaveyparker hmm. I always understood that the moon orbits the earth because the centrifugal force necessary to keep it in orbit is "generated" (maybe not the right word, English is not my native language) by the gravitational force of the earth.
A weight on a rope swung around is kept in a circular motion by a centrifugal force generated by the tensile force of the rope.
This is where my confusion lays
Maybe you would be kind enough to place that comment under my creation. As I've discussed this confusion in detail there?
Anyway, while you're pondering that request, I'll give you a quick reply here, as I really like the doctors approach to science teaching.
The gravitational force _(or the gravitational mass)_ provides the *centripetal* force to keep an object in orbit. It is the *inertia* _(or the inertial mass)_ of the object in orbital motion that provides the *centrifugal* force.
At the centre of the Earth these two forces balance and the orbit continues. The tides are caused by the imbalance of these two forces. Does that help with the confusion.
@@wavydaveyparker it does help a little, although I find inertia a difficult concept to comprehend.
I've been looking for your creation, but I'm unable to find it or your channel
@@ArjanD78 Brilliant! I suspected as much. 😐 That's because you-tube try and hide any discussion about fictitious forces, but I reassure you my creation does exist in an accelerated frame of reference. 😁
Which brings us to your understanding of the concept of inertia, or as Galileo might say, *The principle of Inertia.*
Are you familiar with the concept of reference frames?
Hi Dr. Becky, are you SURE that's an accurate description of the principle forces involved? Doesn't sound right to me. My understanding is more closely related to the gravitational effect of the Moon diminishing with distance, plus the fact that the earth is (comparatively speaking) a rigid body - so the whole thing moves, whereas the body of water can display its experience of those gravitational forces by distorting (a lot more than the Earth does).
It’s not wrong what she said, but it’s not the full explanation.
I highly recommend this UA-cam video of PBS Space Time:
ua-cam.com/video/pwChk4S99i4/v-deo.html
@@jorgmintel3060 I mean it's not wrong, but if it isn't the main factor, then it's kind of wrong. But it's a good lesson in humility for all of us who fell into that trap :) (assuming she notices these comments and makes a corrective video)
great description!
Yeah, this is completely right though, the far side tide is more of a centrifugal effect. The graphics are wonderful and the explanation correct. Science does not rely on opinion, it’s all about examining the evidence and looking at the facts, which are acquired through experimentation. The centrifugal effect is responsible for tides on the opposite side, and the centripetal effect is gravity, but it’s easy to get confused if you are a *chemist,* and they haven’t got a clue what they’re talking about. It won’t be published within a week, because no one is interested. 😊 Take care and thanks for the comment.
Sorry, but I think you'll find that *"Cos"* is defined as the ratio of the length of the adjacent side to that of the longest side i.e. the hippopotamus. Just another one of my creations. Thank you.
Dr. Becky … fifty years in boating, including three decades in the USN, and you explained the system of tides better than anyone I’ve known.
Well done!
And may not have got it right! (See a Neil Degrasse Tyson 'Star-talk' video on it)
@@Chris-hx3om No! I think you’ll find that the NdT video and this are both in direct accordance. NdT calls on the mechanism of tidal ‘Yoga’ - whatever that is? - And Dr Becky calls on ‘Centrifuge’ - I know what that is? - And they both yield the same results for tides.
Yes well, both Dr Becky and Dr Tyson got it not exactly right....
Here a link to a video of PBS Space Time about this topic:
ua-cam.com/video/pwChk4S99i4/v-deo.html
It’s not flat-earthier BS, I promise!
@@Chris-hx3om no
@@jorgmintel3060 Just watched it... Excellent video, and pretty much exactly what NDT said. (And not a single mention of any barycentre)...
Wouldn't there be a tidal bulge on the opposite side even without the effect of the centrifugal effect from orbital rotation?
I mean, just the gravitational gradient will produce a tension on the axis of the two bodies, and a compression towards that axis. The effects caused by orbiting a displaced barycenter are also an important factor, but that alone doesn't produce the bulge on the opposing side.
To illustrate this - imagine a large planet orbited by a moon almost at the Roche limit. Because of the small distance between the bodies, the displacement of the barycenter would be quite small and centrifugal effects would be reduced, while the effect from the gravitational gradient would be enhanced. The large planet would still have two high tides and two neap tides.
Also, it seems to me that the centrifugal effect is asymmetric and basically produces a larger bulge on the part of the planet that is "outside" of the barycenter relative to the Moon, and a smaller bulge on the "inside" segment. So it would partially increase the height of the neap tides as well - or rather it would all add up in such a way that it would shift the time of the lowest tide quite a bit towards the point facing the Moon.
And then there's the part where the tides are "lagging" because all that water has a lot of inertia and doesn't just change its direction of flow immediately when the Earth's rotation causes the tangential component of Moon's gravity to switch from one side to another.
An excellent comment and very detailed. Thank you. However, there is a very simple answer to your confusion. No centrifugal effect means no orbital motion and no orbital motion means collapse and the earth and moon would eventually collide like in the film ‘Moonfall’ !! Take care.
@@wavydaveyparker I wasn't really confused about anything.
My point is that the tidal bulges caused by gradient of gravitational attraction are separate from the tidal bulges caused by the system's rotation around its barycenter, and it isn't strictly speaking correct to say that the "off-side" bulge is caused by a different effect than the bulge on the side facing the Moon.
The acceleration differences from gravitational gradient, and the acceleration differences from rotation both contribute to the total effect of tides, and the amount depends on the masses of, and the distance between the two orbiting bodies.
@@HerraTohtori Yep! I agree and maybe shouldn’t have used the word ‘confusion’ … I was only answering your first question, which might have got confusing if I had continued? There would be a tidal bulge on the opposite side even without the effect of the centrifugal effect from orbital motion around the barycentre. However, the Earth-Moon system would then be in a state of collapse…I did make a video explaining all this, if you’re interested and we can discuss it further there if you’d like. Thank you.
Neil deGrasse Tyson has joined the chat.
and doesn't explain it as well as this.
I think you have made a common error in your explanation about how the tides work. Watch this Spacetime video for the correct explanation: ua-cam.com/video/pwChk4S99i4/v-deo.html