"Standing on the shoulders of giants." How all progress has ever been made, in any field. We should always remember to be humble, because without them, we would not be where we are today.
The start of Cavendish's paper, which you flashed briefly around 12:48, gives due credit to John Michell, FRS, for both the concept and the construction of his torsion balance. Michell was also the first to suggest (in 1783) that a sufficiently massive star could be what we now call a black hole. ⚫
The fact that you can measure the force of gravity from something simple like Cavendish's experiment absolutely blows my mind. I always think of gravity as such a small force that you wouldn't really be able to notice it with such relatively small masses compared to the Earth. That's crazy!
A few years back My little boy transferred school at the start of Year 1 , and so had an induction day at the new school At the end of the day the teacher asked him if he had any questions “How heavy is the earth?” Proudest dad moment ever
Deriving the motion of a pendulum involves sin(x), x being the angle from the horizontal, and sin(x) can be replaced for small angles with just the simple 'x'. This may seem obvious, but it's actually the first taylor polynomial of sin(), just simply x. That is a huge simplification that may not have occured to the people before calculus was invented. Tho, now that I write that last sentence, I realized the idea of gravity and calculus where coined in the same book, so it's a moot point.
I retired a little of a year ago from 28 years of teaching high school physics, and watching this video was a lot of fun and kind of nostalgic. Thanks.
Truly excellent video, a big science question answered by breaking down the math and tying in history, I plan on showing this to my kids when they are older.
Cavendish is probably my favourite historical scientist. From Bill Bryson's (excellent) 'A Short History of Nearly Everything': "He suffered, in the words of one of his biographers, from shyness to a degree "bordering on disease." Any human contact was for him a source of the deepest discomfort. Once he opened his door to find an Austrian admirer, freshly arrived from Vienna, on the front step. Excitedly, the Austrian began to babble out praise. For a few moments Cavendish received the compliments as if they were blows from a blunt object and then, unable to take anymore, fled down the path and out the gate, leaving the front door wide open. It was some hours before he could be coaxed back to the property. Even his housekeeper communicated with him by letter."
What a freak. I know no one that would want to live that way. Nor do I think it's healthy for you to do so. Not long run anyway. Of course this opinion comes from my own drawn out thoughts.
Really love these type of videos! They don’t state the facts but tell us how we know the facts. A great representation of the scientific method and really interesting to watch!!
I’m going to steal, I mean borrow your experiment to measure gravity for the spring. The kits sound like fun and I’m going to share it with my students. TY.
Cavendish's method of weighting the earth absolutely blew my mind in school last year, when we covered that topic. Still one of the things in physics I'm most fascinated by :-)
I love the use of the iPad and Pencil to draw your notes and formulae 👍 makes it both clear and look a bit more interactive (as opposed to post-prod animations) as we see you draw and reason about it live
Really enjoyed this video. Especially including the math. It's a good refresher for those of us who have been out of school for decades and don't really need to use algebra and beyond in our everyday lives. Would like to see more like this. Thanks!
You are so much fun! These simple ways of experimenting and explaining are what drew me to science 70 years ago, and has held me ever since. Here's a story I heard as a child about the earth's shape. Around 1900 a ship was loaded with gold in Alaska, but when it was weighed in San Francisco they thought some had been stolen. It took a while before someone figured out the problem was the curvature of the earth!
Becky: “Thankyou to this week’s sponsor Kiwi Co, who provide...” Me: “Kiwi’s by mail...?” Becky: “...science experiments for kids.” Me: “Oh. I suppose that makes a bit more sense...”
I'm so glad to have @Dr. Becky as my professor of astrophysics! Carl Sagan, who enriched my knowledge and curiosity of the cosmos, I think would be proud of Dr. Becky's love to freely educate us masses. 😃
I love these videos where we see the experiments that show us how theories were confirmed or how important parameters (which are usually treated as a given) were derived.
People have asked what would happen to the Earth if everyone jumped up at the same time. Well, if my calculations are correct the planet is roughly 11.5 trillion times heavier than its inhabitants. So I suppose the answer is: not a lot!
Especially not since the impact is spread all over the planet :) Look up "xkcd everybody jump" to see how it would go if we collected all the people in one location.
Indeed, for the mass of the Earth you have to ask the turtle who carries the world on its back. Just make sure you ask the top turtle, because you don't want to get the mass of all the other turtles all the way down.
It is kind of a pointless question for the following: 1/ It is floating in space 2/ it depends on who's gravitational force is exerting on it What is the mass
Thank you for this amazing video, yet again! Your videos are the most admirable and extraordinary content, Dr. Becky! Honestly your UA-cam channel has been the best discover from this 2020! Thank you! 😀
That was entertaining and very educational. It's so great that you can break down those complex topics for people like me, who never understood this at school. And your sponsor seems real fun!
I think we did this during a physics lesson, teacher made us do some experiments with a stick and swapped with another school. And a pendulum but didn't tell us where we were going with it. We then did another lesson where we ended up working out the mass of the earth, moon and sun, and then the orbits and stuff all with maths I could actually follow.. My mind was thoroughly blown. I also felt for the first time there was a point to algebra. Really think the UK should stop teaching maths and other subjects in isolation and start teaching what you can do with the tools they give ya
It's also si-MONE, not si-MONE-ee, but I figure by now she probably just collects pronunciations, and this may be a new one, so if anyone knows her, send her this one to add to the set. She just moved house (and shop), so she maybe could use a laugh. Also, yes, per Mr. Ormundson's link, she suggests Yetch, and when I listen to her say it there and elsewhere, heck, it could be Yetch, it could be Yatch, it could be Yutch. Pick a vowel. I'm still trying to figure out if Saoirse Ronan is SER-sha or SEER-sha.
l4pin It’s was a news story @ 8 o clockish talking about black holes feeding and it was observed over a short period of time. It only last a couple of minutes
The problem is that of density. The earths rock is much more dense than the earth's atmosphere (5480 kg/m3 to 1.225 kg/m3), so the addition of the atmosphere is basically negligable. However, with the gas giants, the atmospheres are so thick and dense that they contribute a significant amount to the mass of the planet. Also, as far as I am aware, we are still not sure where the atmosphere stops and the planet begins with the gas giants like Saturn and Jupiter.
Because Gas giants do not have a surface. Their atmosphere transitions into a supercritical state, so there's actually no sharp boundary between the gaseous atmosphere and the liquid underneath. From what I can tell, their size is calculated from top of the clouds, aka. the topmost opaque layer of the planet.
@@KohuGaly Their atmospheres are also way more significant that Earth's for very simple calculations the only terrestrial bodies which have a more significant atmosphere are Venus and Saturn's moon Titan. Personally the ignoring of the atmosphere has always bothered me since the comparison is different between the terrestrial and giant planets with the typical atmosphere height of giant planets being rather arbitrarily defined by convention rather than dynamics. Probably the best analog if one wants to use a more consistent metric for representing their "surface" for the gas giants is the critical phase transition from a conventional convective fluid towards a fluid layer that rotate more like a solid rigid body. Where this occurs varies based on the planets mass starting out deep down for less massive giant planets and becoming more shallow as more and more of the planet and or brown dwarf occurs ~9000+km down in Saturn and ~3500 km down in Jupiter. When you do that you would find that their atmospheres are a small fraction of their total mass (Jupiter's atmosphere calculated this way accounts for about 1% of its total mass) but due to their sheer mass the layers are many times the Earth's mass ~1.9 e+25 kg nearly 22% of the planet Uranus's total mass! For the ice giants I think the Hydrogen & Helium envelope is what is considered the planets atmosphere which account for a few Earth masses worth of hydrogen and Helium but we lack the observations to really quantify those layers... Getting more data will be critical to redefine the "surface" boundary.
We are on the surface, inside the atmosphere. The gravity from the atmosphere above us cancels the gravity from the atmosphere on the other side of the earth. To calculate the gravity on a satellite, we should include the mass of the atmosphere.
≈ 10m30s Galileo almost surely didn't actually drop weights off the Leaning Tower. But much more importantly, he performed many careful experiments timing balls rolling down inclined planes. Incidentally, you can also "measure" g by timing an accurately known-length pendulum, along with the correction needed for the slight change of period with angular amplitude. You do an amazing job bringing us these videos. I love the extra details you get into, that your typical physics course won't even usually cover. Keep 'em coming! Fred
Hello Dr. Becky, I used to have that very same problem with Eratosthenes's name. Somehow it feels more natural for me to say Erastosthenes. All the best and many thanks, Peter Nolan. Ph.D.(physics). Dublin. Ireland.
If earth was discovered by Something like Kepler from another solar system the mass detected would include the moon. Kepler 62E&F size & Mass only makes sense when you include moons
If it were discovered by something like Kepler, the mass would be completely unknown, because transit method only allows you to measure the ratio of angular areas of the object vs. the star and the length of the year. You can't even tell the size without measuring the distance to the star.
Isnt it so amazing that you can approximate gravity with something as simple as a piece of paper, a highlighter and a SLOW MOTION CAMERA, just like they could have done in 200BC!
"Simone Giertz" - I always pronounced her name like that, but as she isn't german, that's not right. It should sound like this: [ˈjæʈːʂ]. I learned this from Adam Savage. en.wikipedia.org/wiki/Simone_Giertz
"I feel like Simone Gee-ertz." Not picking on you - that's how I thought it was pronounced, too, but in one of her videos, she explains "Giertz" is pronounced "Yetch." She has a wonderful, quirky style. Like you. Love your channel.
Absolutely brilliant I love your stuff❤️. It’s been awesome watching you go from Sixty Symbols to DeepSky Videos to having your own super rad show. Keep it up!🙏
RE: Galileo "How he worked under those conditions, I'll never know" Dr. Becky I'm giggling something fierce to that one for some reason. Your sarcasm is funny.
I imagine that term comes from the type of scales you see outside courthouses that the blindfolded lady justice holds, the type that uses on object on both side to balance them
@@SpydersByte Exactly. The scale shown in the graphic would be called a set of scales in the US as well. A scale that you stand on would just be called a scale.
@pjd412 common knowledge in the UK circa 1950 is that 14lbs (pounds) = 1 stone....also for some reason equally unfathomable (pun intended) 8 stones = 1 hundredweight ((cwt) It's great fun being ancient, having to convert all the crazy metric terms back to proper ones in the head before they make sense. :)
@@wwoods66 Forget weight Bob. Your personal 'weight' depends on where you are on Earth. If you were to weigh yourself at the North Pole you would find that you are heavier. Do you understand why? Do you understand the difference between weight and mass? The Earth's mass is 5.9722×1024 kg.
Asimov wrote about this in his book The Stars in their Courses. It's an amazing book, if you can get your hands on a copy. So elegantly and simply written, well thought out, and a very educational read, delving into various properties of the universe. From the chapter on calculating the mass of the earth, he finishes with the following: Which leave one question: What _is_ the weight of the Earth? The answer is simple. The Earth is in free fall and, like any other object in free fall, it is responding in full to the gravitation fields to which it is subject. It is not 'attempting' to make any further response and therefor it is weightless. The weight of the Earth, then, is zero.
It is interesting also that the earth or any planet actually is not uniform in density and thus measurements are only approximations, thus gravitational measurements also have to account for these variations.
It' s nice that you found 9,5 m/s^2 as g...only a few % of the real value. I suppose it would be closer if you did not use that paper as holder for the pencil . When pushing away that paper you'll also move (relatively) a lot of air which will change the outcome of your test...making the pencil fall a little slower. At my highschool we used a kind of trigger system to let go a (hanging) weight....and also a relative heavy weight for minimizing the influence of air resistance. And of course a good measure of the height the lead ball was falling. We did not have a smartphone 45 years ago with speed camera, but this trigger was good for electrical starting a stopwatch and the plate on which the ball fell at the bottom stopped the stopwatch.
10:30 The experiments performed by Galileo used inclined planes (hence slow falling speeds), and he developed pretty good water-driven time measures. So, he determined the gravity acceleration in a totally accurate way. I mean, old Newt did a fantastic job on his own, no need for giving him credit for the work of other people...
There is a physical difference between „how heavy“ something is, what its „weight“ is and what its „mass“. And this difference is even more important in a physics education setting. And if we are using a modern phone anyways, way not just using its accelerometer?
@@little_forest ah, I think I see what you mean. Basically turn the accelerometer on, and then drop the phone? Sorry, I'm feeling the brain fog from changing shifts at work. I should have got that.
@@daddymuggle yes, that is how one would do it for example at school in science/physics courses. There are very good apps to read out all the sensors and display them against time. You even can just display the raw data and the acceleration of the axis that points up/down is g. Good luck with your brain fog, soon will be weekend! ;)
It's almost certain that Galileo never dropped anything off the Leaning Tower of Pisa. Instead, what he did was roll balls of various masses down an inclined plane. Attached to the plane was a series of bells whose position could be varied. As he rolled his balls down the plane, he adjusted the spacing of the bells so that the sounds were separated by equal intervals of time, as measured by a pendulum. He discovered that the distances between the bells required to achieve this increased as the square of the distance. He also discovered that the mass of the ball made no difference to its acceleration. I believe that it just took a little bit of trigonometry to convert the observed acceleration into the downward acceleration due to gravity.
42 km wider at the equator? 42! Everything else suddenly make sense!
Ah.. tha magical 42 pops up again.
You could measure the earth's circumference with *lots of towels.*
You didn't even tell properly about the scientist Al-Biruni who first measured and discovered radius of the Earth.
Just a tiny marathon. Nothing special...
OMG TRUE
"Standing on the shoulders of giants." How all progress has ever been made, in any field. We should always remember to be humble, because without them, we would not be where we are today.
The start of Cavendish's paper, which you flashed briefly around 12:48, gives due credit to John Michell, FRS, for both the concept and the construction of his torsion balance. Michell was also the first to suggest (in 1783) that a sufficiently massive star could be what we now call a black hole. ⚫
I'm like the earth. I bulge at the equator slightly.
"I'm not fat, I'm oblate"
Danny De Vito is thus oblate.
I used to have a six pack, but it's turned into a keg. 😋
And just like the Earth, the effect diminishes when you don't spin as quickly...
Fred
The problem is really if the radius of Your girth exceeds Your hight by any appreciable amount?
The fact that you can measure the force of gravity from something simple like Cavendish's experiment absolutely blows my mind. I always think of gravity as such a small force that you wouldn't really be able to notice it with such relatively small masses compared to the Earth. That's crazy!
A few years back My little boy transferred school at the start of Year 1 , and so had an induction day at the new school
At the end of the day the teacher asked him if he had any questions
“How heavy is the earth?”
Proudest dad moment ever
You can also calculate g using a pendulum, but the slo-mo camera method is pretty sweet.
It showed the heavier more massive highlighter accents quicker!😅
Umm, to a free fall state.
Why did he care about density when you have a particular relationship states with pendulum L1234 and heatsink with speeds?
Deriving the motion of a pendulum involves sin(x), x being the angle from the horizontal, and sin(x) can be replaced for small angles with just the simple 'x'. This may seem obvious, but it's actually the first taylor polynomial of sin(), just simply x. That is a huge simplification that may not have occured to the people before calculus was invented. Tho, now that I write that last sentence, I realized the idea of gravity and calculus where coined in the same book, so it's a moot point.
@@kindlin well said.
The pendulum method is a lot more accurate.
I retired a little of a year ago from 28 years of teaching high school physics, and watching this video was a lot of fun and kind of nostalgic. Thanks.
1:10 - "Now if we remember back to high school geometry..." I've just encountered our first problem.
Truly excellent video, a big science question answered by breaking down the math and tying in history, I plan on showing this to my kids when they are older.
Cavendish is probably my favourite historical scientist. From Bill Bryson's (excellent) 'A Short History of Nearly Everything':
"He suffered, in the words of one of his biographers, from shyness to a degree "bordering on disease." Any human contact was for him a source of the deepest discomfort.
Once he opened his door to find an Austrian admirer, freshly arrived from Vienna, on the front step. Excitedly, the Austrian began to babble out praise. For a few moments Cavendish received the compliments as if they were blows from a blunt object and then, unable to take anymore, fled down the path and out the gate, leaving the front door wide open. It was some hours before he could be coaxed back to the property. Even his housekeeper communicated with him by letter."
That was a very enjoyable book
What a freak. I know no one that would want to live that way. Nor do I think it's healthy for you to do so. Not long run anyway. Of course this opinion comes from my own drawn out thoughts.
This almost sounds like autism to me...
The earth is flat and Cavendish was a nutcase.
@@popcorn-uz3tn indeed. This video is hilarious btw.
Really love these type of videos! They don’t state the facts but tell us how we know the facts. A great representation of the scientific method and really interesting to watch!!
Hey becky by 13:08 you mean more* dense than water! It is written more but you said less.
Whoops brain typo!
@@DrBecky - Hahaha @ brain typo....I'm stealing that one. BTW, love watching your videos.
@@DrBecky Excellent demonstration using the pen, paper and phone!!!!
I was like what?
Oh my god I spent minutes trying to wrap my head around how Earth could be less dense than water… oof, thanks for pointing that out
Pretty sure Galileo actually rolled balls/cylinders down ramps for his actual measurements. Pisa is a legend that may be myth! :)
I’m going to steal, I mean borrow your experiment to measure gravity for the spring. The kits sound like fun and I’m going to share it with my students. TY.
Cavendish's method of weighting the earth absolutely blew my mind in school last year, when we covered that topic. Still one of the things in physics I'm most fascinated by :-)
I love the use of the iPad and Pencil to draw your notes and formulae 👍
makes it both clear and look a bit more interactive (as opposed to post-prod animations) as we see you draw and reason about it live
...and that handwriting. So neat. Mine is like a scrawl.
Really enjoyed this video. Especially including the math. It's a good refresher for those of us who have been out of school for decades and don't really need to use algebra and beyond in our everyday lives. Would like to see more like this. Thanks!
Nice sponsor. Fun and interesting ways to get kids hooked on science kick ass.
Agreed. One of the few times I've enjoying seeing a sponsored segment in a video.
You are so much fun! These simple ways of experimenting and explaining are what drew me to science 70 years ago, and has held me ever since. Here's a story I heard as a child about the earth's shape. Around 1900 a ship was loaded with gold in Alaska, but when it was weighed in San Francisco they thought some had been stolen. It took a while before someone figured out the problem was the curvature of the earth!
I like the deep philosophical context in the statement about the last 2 thousand years... And on the shoulders of the Giants.
💫👽💫
But I don't like heights, I don't want to stand on the shoulders of giants. I want to stand on a solid floor.
1:10 - "Imagine, if you will, a perfectly spherical cow..."
...in vacuum
Becky, just came across your channel and I immediately became a huge fan. Thank you for doing what you do.
Best UA-cam Video thumbnail yet!! Awesome job, Dr. Becky!!!!!!!!!!!!!!
Becky: “Thankyou to this week’s sponsor Kiwi Co, who provide...”
Me: “Kiwi’s by mail...?”
Becky: “...science experiments for kids.”
Me: “Oh. I suppose that makes a bit more sense...”
😂
But which sort of kiwi?
@@daddymuggle maybe the fruit because I don't think they provide the birds or the people by mail. I don't think it's the galaxy either
OH MY GOD I LOVE THE ADDITION OF YOUR IPAD WHEN YOU EXPLAIN CONCEPTS!!!!!
Thanks 🤗
Dr. Becky you are awesome. I'm so glad you share your enthusiasm and not only that, but help to recognize the astronomers who were lost to history
This video is fabulous. You make the subject matter approachable (and understandable) for everyone. Thanks!
I loved the exercise left to the viewer. The type that you find on an a test and go crazy! 😂
Glad you noticed that 😂
Yup, don't we all hate those type of exerices? 😂
"Eratosthenes"
"I used to calculate the circumference of the earth, but then I took ArrowsToTheKnees"
"Have you seen those mathematicians from Alexandria? They've got curved measurements. CURVED. MEASURMENTS."
A pointed comment!
Gesundheit!
Dr. Becky , I enjoy all your videos, thanks for your hard work in producing them.
I'm so glad to have @Dr. Becky as my professor of astrophysics! Carl Sagan, who enriched my knowledge and curiosity of the cosmos, I think would be proud of Dr. Becky's love to freely educate us masses. 😃
The cover stills for the videos are getting cheesier - and it's fantastic 😄
Simone's surname is pronounced Yetch, apparently its a Swedish thing, and yes it makes no sense to them either.......she did a video on it. lol
Seeing the struggle with "Eratosthenes", perhaps "Giertz" is better left for the second semester :D :D
Well done! It is great to have access to such kind of content! Fun & Instructive!
I love these videos where we see the experiments that show us how theories were confirmed or how important parameters (which are usually treated as a given) were derived.
People have asked what would happen to the Earth if everyone jumped up at the same time. Well, if my calculations are correct the planet is roughly 11.5 trillion times heavier than its inhabitants. So I suppose the answer is: not a lot!
Especially not since the impact is spread all over the planet :)
Look up "xkcd everybody jump" to see how it would go if we collected all the people in one location.
@@WarpdriveEngineer thank you! That was great!
Why not ask Atlas? I'll show myself out now...
He knows the mass of the sky, because he has to hold it up, but he doesn't know the mass of the Earth.
Indeed, for the mass of the Earth you have to ask the turtle who carries the world on its back. Just make sure you ask the top turtle, because you don't want to get the mass of all the other turtles all the way down.
Herculean effort to get in before me. Yeah I know, Terra bull.
I feel better, leaving now.
@@johnladuke6475 But the turtle only knows the mass of the Earth plus the mass of the four elephants.
I'll get me cloak!
Loved this episode. And BTW I can tell you’re enjoying your new iPad. Great illustrations and math demonstration. 👍🏾❤️
It is kind of a pointless question for the following:
1/ It is floating in space
2/ it depends on who's gravitational force is exerting on it
What is the mass
"We're all weighin'! Weighin' up the worrrld today!"
Someone had to do it....
aww, you should have asked the Slow Mo Guys to help you out.
Thank you for this amazing video, yet again! Your videos are the most admirable and extraordinary content, Dr. Becky! Honestly your UA-cam channel has been the best discover from this 2020! Thank you! 😀
We did the Cavendish experiment in school and it blew my mind back then. It's still my favourite physics experiment :)
I already knew the weight of the world.. I carry it on my shoulders everyday
BlueMarbleScience is currently constructing the aparatus for the cavendish experiment. Check it out!
That was entertaining and very educational. It's so great that you can break down those complex topics for people like me, who never understood this at school. And your sponsor seems real fun!
I think we did this during a physics lesson, teacher made us do some experiments with a stick and swapped with another school. And a pendulum but didn't tell us where we were going with it.
We then did another lesson where we ended up working out the mass of the earth, moon and sun, and then the orbits and stuff all with maths I could actually follow.. My mind was thoroughly blown. I also felt for the first time there was a point to algebra. Really think the UK should stop teaching maths and other subjects in isolation and start teaching what you can do with the tools they give ya
I know simone wont care, but as a fan of her's I feel like it should be said. Its pronounced "Yatch" lol
I thought it was more like "Yetch"
No, it is pronounced as Yatsh [ˈjæʈːʂ].
@@erkinalp ua-cam.com/video/z8NIw1HeBBk/v-deo.html
Indeed it is pronounced [ˈjæʈːʂ], even with this source
It's also si-MONE, not si-MONE-ee, but I figure by now she probably just collects pronunciations, and this may be a new one, so if anyone knows her, send her this one to add to the set. She just moved house (and shop), so she maybe could use a laugh. Also, yes, per Mr. Ormundson's link, she suggests Yetch, and when I listen to her say it there and elsewhere, heck, it could be Yetch, it could be Yatch, it could be Yutch. Pick a vowel. I'm still trying to figure out if Saoirse Ronan is SER-sha or SEER-sha.
I heard you on radio four this morning talking about black holes 🌚
What show was that? I'd like to catch up
l4pin It’s was a news story @ 8 o clockish talking about black holes feeding and it was observed over a short period of time. It only last a couple of minutes
Fascinating !!! straight to my top 10 science Videos !!! Love it !!! Thanks Dr B. !!!
I really wish I'd seen this last year.
Cavendish's experiment was sooooo confusing for my 11th-grade finals.
Thank you for making this clear
Why is Earths size/mass/density etc only measured to its surface, but
planets like Jupiter and Saturn include their atmospheres?
The problem is that of density. The earths rock is much more dense than the earth's atmosphere (5480 kg/m3 to 1.225 kg/m3), so the addition of the atmosphere is basically negligable. However, with the gas giants, the atmospheres are so thick and dense that they contribute a significant amount to the mass of the planet. Also, as far as I am aware, we are still not sure where the atmosphere stops and the planet begins with the gas giants like Saturn and Jupiter.
Because Gas giants do not have a surface. Their atmosphere transitions into a supercritical state, so there's actually no sharp boundary between the gaseous atmosphere and the liquid underneath. From what I can tell, their size is calculated from top of the clouds, aka. the topmost opaque layer of the planet.
@@KohuGaly Their atmospheres are also way more significant that Earth's for very simple calculations the only terrestrial bodies which have a more significant atmosphere are Venus and Saturn's moon Titan. Personally the ignoring of the atmosphere has always bothered me since the comparison is different between the terrestrial and giant planets with the typical atmosphere height of giant planets being rather arbitrarily defined by convention rather than dynamics.
Probably the best analog if one wants to use a more consistent metric for representing their "surface" for the gas giants is the critical phase transition from a conventional convective fluid towards a fluid layer that rotate more like a solid rigid body. Where this occurs varies based on the planets mass starting out deep down for less massive giant planets and becoming more shallow as more and more of the planet and or brown dwarf occurs ~9000+km down in Saturn and ~3500 km down in Jupiter. When you do that you would find that their atmospheres are a small fraction of their total mass (Jupiter's atmosphere calculated this way accounts for about 1% of its total mass) but due to their sheer mass the layers are many times the Earth's mass ~1.9 e+25 kg nearly 22% of the planet Uranus's total mass!
For the ice giants I think the Hydrogen & Helium envelope is what is considered the planets atmosphere which account for a few Earth masses worth of hydrogen and Helium but we lack the observations to really quantify those layers... Getting more data will be critical to redefine the "surface" boundary.
We are on the surface, inside the atmosphere. The gravity from the atmosphere above us cancels the gravity from the atmosphere on the other side of the earth. To calculate the gravity on a satellite, we should include the mass of the atmosphere.
To be fair adding the atmosphere won't add that much. At least to the approximation we are talking about.
I think this video taught me more than physics class in my high school
Public schools fail thousands of children every day.
≈ 10m30s Galileo almost surely didn't actually drop weights off the Leaning Tower. But much more importantly, he performed many careful experiments timing balls rolling down inclined planes.
Incidentally, you can also "measure" g by timing an accurately known-length pendulum, along with the correction needed for the slight change of period with angular amplitude.
You do an amazing job bringing us these videos. I love the extra details you get into, that your typical physics course won't even usually cover. Keep 'em coming!
Fred
If anyone is interested "Blue Marble Science" has a few videos on his channel showing him building the Cavendish experiment from the original plans.
Ahh math...we meet again...my old nemesis
I tried to follow along, now I have to air the house out, smells like rubber burning. 😁 Definitely earned the doctor bit in front. 👍
welcome to my world!
3 thumbs down lol. 3 flat earthers were here 😅🤦♂️
Nah those were just Australians giving a thumbs up.
Six now, but I upvoted ;-)
Perfectly said at the end: Science has been built standing on the shoulders of giants. Thanks Dr. Becky!
Hello Dr. Becky,
I used to have that very same problem with Eratosthenes's name. Somehow it feels more natural for me to say Erastosthenes.
All the best and many thanks,
Peter Nolan. Ph.D.(physics). Dublin. Ireland.
If earth was discovered by Something like Kepler from another solar system the mass detected would include the moon.
Kepler 62E&F size & Mass only makes sense when you include moons
If it were discovered by something like Kepler, the mass would be completely unknown, because transit method only allows you to measure the ratio of angular areas of the object vs. the star and the length of the year. You can't even tell the size without measuring the distance to the star.
The mass of the Earth is 98.8% that of the Earth and Moon combined, which is within the margin of error of determining exoplanet masses.
@@denmaroca2584 Kepler 62E is twice earth size and 20 time as massive it the planet has more then one one or larger moons or both
I love the thumbnail photo!
Isnt it so amazing that you can approximate gravity with something as simple as a piece of paper, a highlighter and a SLOW MOTION CAMERA, just like they could have done in 200BC!
Heart wakes up and feels alive again to see Dr. Becky, such a Shiny Star.
"Simone Giertz" - I always pronounced her name like that, but as she isn't german, that's not right.
It should sound like this: [ˈjæʈːʂ]. I learned this from Adam Savage.
en.wikipedia.org/wiki/Simone_Giertz
If you can't read IPA, it's (very) approximately "Yetch"
@@thryduulf, I'm sure I said that the first time I tasted green beans!
@@thryduulf That's about right. And is also, what Simone says.
@Peter Mortensen Exactly. Thanks.
Becky is the modern day Atlas lifting the world out of ignorance.
"I feel like Simone Gee-ertz." Not picking on you - that's how I thought it was pronounced, too, but in one of her videos, she explains "Giertz" is pronounced "Yetch." She has a wonderful, quirky style. Like you. Love your channel.
Becky. You are amazing.. putting a lot of things in perspective.
Love the video thumbnail! Don't worry guys, Becky's got it
666 in the first 10 seconds of the video. Anything to declare Dr. Becky?
Declared!!!
Mummu Great becky is illuminati confirmed
Absolutely brilliant I love your stuff❤️. It’s been awesome watching you go from Sixty Symbols to DeepSky Videos to having your own super rad show. Keep it up!🙏
RE: Galileo
"How he worked under those conditions, I'll never know"
Dr. Becky I'm giggling something fierce to that one for some reason. Your sarcasm is funny.
Oh! Is "set of scales" a Briticism? Here in Yankland we'd say, "you can't put the earth on a scale."
I imagine that term comes from the type of scales you see outside courthouses that the blindfolded lady justice holds, the type that uses on object on both side to balance them
@@SpydersByte Exactly. The scale shown in the graphic would be called a set of scales in the US as well. A scale that you stand on would just be called a scale.
@@SpydersByte that's true, or the modern equivalent a triple beam balance, but we have those in the US as well.
@@essaboselin5252 Scales is plural in both cases in the UK. "Let me step on the bathroom scales and weigh myself."
@pjd412 common knowledge in the UK circa 1950 is that 14lbs (pounds) = 1 stone....also for some reason equally unfathomable (pun intended) 8 stones = 1 hundredweight ((cwt)
It's great fun being ancient, having to convert all the crazy metric terms back to proper ones in the head before they make sense. :)
16:55
Air-ah-toss-th-sneeze 🤣🤣
Dr. Becky, you make science extra fun!
Thanks for everything.
I suck at math. I love space and physics and stuff. This is math i can understand, great job Becky!
"the weight of the world"
... Trick question! Earth is in free fall around the Sun, so -- it's _weightless._
Who mentioned weight? Weight is not the same as mass.
JC Who ever wrote the title.
@@JC-gm3zs 0:32 "So how did we actually go about measuring _the weight of the world?"_
@@wwoods66 Forget weight Bob. Your personal 'weight' depends on where you are on Earth. If you were to weigh yourself at the North Pole you would find that you are heavier. Do you understand why? Do you understand the difference between weight and mass? The Earth's mass is 5.9722×1024 kg.
Raging S Yes they are weightless.
Weight is mass times acceleration.
Constant speed leaves only mass, so weight is zero.
It's easy, just change the units to "earths" piece of cake.
We measure other planets in "earth masses" so why not?
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That was fun! Thanks for explaining!
I wish my past teachers or professors were as skilled as Dr. Becky at teaching. Only a few were.
Hi Dr. Becky, you have finish the Masterclass of Thumbnailing OR you are really strong :-)
I'm from Iraq and you inspired me to make my space video. Thank you
I was legitimately blown away by the torsion bar tactic to measure the gravitational constant, measuring forces so small with such a simple technique.
Great video Dr. Becky!
Rude to ask a planet this....
especially when you know that equator is... bulging out.
Asimov wrote about this in his book The Stars in their Courses. It's an amazing book, if you can get your hands on a copy. So elegantly and simply written, well thought out, and a very educational read, delving into various properties of the universe.
From the chapter on calculating the mass of the earth, he finishes with the following:
Which leave one question: What _is_ the weight of the Earth?
The answer is simple. The Earth is in free fall and, like any other object in free fall, it is responding in full to the gravitation fields to which it is subject. It is not 'attempting' to make any further response and therefor it is weightless.
The weight of the Earth, then, is zero.
great video as always. great job becky
Love this stuff!
BTW, there is no S before the first T in Eratosthenes :)
It is interesting also that the earth or any planet actually is not uniform in density and thus measurements are only approximations, thus gravitational measurements also have to account for these variations.
It' s nice that you found 9,5 m/s^2 as g...only a few % of the real value.
I suppose it would be closer if you did not use that paper as holder for the pencil .
When pushing away that paper you'll also move (relatively) a lot of air which will change the outcome of your test...making the pencil fall a little slower.
At my highschool we used a kind of trigger system to let go a (hanging) weight....and also a relative heavy weight for minimizing the influence of air resistance. And of course a good measure of the height the lead ball was falling. We did not have a smartphone 45 years ago with speed camera, but this trigger was good for electrical starting a stopwatch and the plate on which the ball fell at the bottom stopped the stopwatch.
Very interesting, you really well illustrated how we get there, and how complicated the process was. Awesome.
I'd love that SloMoGuys colab!
Another great episode Becks. All good stuff. Keep ‘em coming.
10:30 The experiments performed by Galileo used inclined planes (hence slow falling speeds), and he developed pretty good water-driven time measures. So, he determined the gravity acceleration in a totally accurate way. I mean, old Newt did a fantastic job on his own, no need for giving him credit for the work of other people...
AND without a smartphone. I mean, how did he get selfies of his house arrest?
Loving all your vids Dr Becky! I always learn so much :)
There is a physical difference between „how heavy“ something is, what its „weight“ is and what its „mass“. And this difference is even more important in a physics education setting.
And if we are using a modern phone anyways, way not just using its accelerometer?
Because the accelerometer is built and calibrated using prior knowledge of the values of g and G.
daddymuggle It just measures acceleration in m/s^2, there is no, at least not necessarily, calibration to g.
@@little_forest ah, I think I see what you mean. Basically turn the accelerometer on, and then drop the phone? Sorry, I'm feeling the brain fog from changing shifts at work. I should have got that.
@@daddymuggle yes, that is how one would do it for example at school in science/physics courses. There are very good apps to read out all the sensors and display them against time. You even can just display the raw data and the acceleration of the axis that points up/down is g.
Good luck with your brain fog, soon will be weekend! ;)
It's almost certain that Galileo never dropped anything off the Leaning Tower of Pisa. Instead, what he did was roll balls of various masses down an inclined plane. Attached to the plane was a series of bells whose position could be varied. As he rolled his balls down the plane, he adjusted the spacing of the bells so that the sounds were separated by equal intervals of time, as measured by a pendulum. He discovered that the distances between the bells required to achieve this increased as the square of the distance.
He also discovered that the mass of the ball made no difference to its acceleration.
I believe that it just took a little bit of trigonometry to convert the observed acceleration into the downward acceleration due to gravity.
8:42 WHOOOO!
You have a lovely voice!!! A great singing voice. Reminded me of when I was listening to "The Opera Babes" singing "Beyond Imagination" a while back.
Great, great physik-lession. Thanks a lot !