Why Are Craters Always Round?
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- Опубліковано 20 вер 2024
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If you take a look at all the impact craters in our solar system, the vast majority are nice, neat circles. But why? Meteorites and asteroids strike planets and moons at all sorts of angles. Where are all the elliptical craters?
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Wow 3:18 Look how close that asteroid came to hitting the visitation centre.
Well, if you ever go to huge concerts, you'd be hating the visitor centres too
The real question is: why do asteroids always fall into craters?
🤣 Sounds like a real question, honestly, from a certain population segment that tends to distrust science. 😵💫😩
Same for rivers. Why do they always flow to larger bodies of water like Lakes seas and oceans.
they look like comfy beds
We find a small rock in a huge crater & assume it crashed there from space. Maybe that little rock & crater are what's left behind when the actual asteroid launches itself into space. Space is full of asteroids & they have to come from somewhere.
big brain
John is staring into my soul
Now I want Pizza
They wore that shirt specifically so John could stare at your soul
He may not be the scishow brother, but he still finds his way on there
RIP SciShow Space. We miss you.
Why what happened?
@johncaze757 they stopped their spin-off channels and re-merged them into the base....just another rip
✌️😔
The solar system is firing a machine gun of asteroids and meteors at us, and we're just standing in place admiring the pretty holes they make as they crash all around us.
And crash here, we just have a too short of a lifespan to take it seriously
I mean we’re hurtling through space pretty quickly…
More like a Gatling Gun
I'm underground in my war bunker eating beanies brains I'm not dodging nothing but my taxes
Don't forget the Comets. 😉
Why are craters always round..... This was explained to me by a physicist once. He said if the angular momentum is greater than the power that keeps the bits of the asteroid together, then it doesnt matter how fast it goes or where it comes from, it will explode equally fast and strong to every direction. And make a circular crater.
I don't think angular momentum is significant (99% of the time).
Why there is nothing at its center? Because it was not made by impact. In fact, the moon shows a reflection of our bigger earth, where you live.
@koubenakombi3066 no, no it doesn't.
@@koubenakombi3066 The velocity of an Impacter determines If anything is left at the impact site. Simply put, the higher the velocity the higher the energy converted from the impacter mass. So you can have one chunk left of a larger body at lower velocities. Or small bits even dust from higher velocity impacts that are found far from the impact site. As explained in the video.
I will never get over learning fascinating scientific facts and ideas while John's pizza face stares back at me. Truly stellar fashion
A big rock going *10 km/s…* that'll hurt! I love these videos that give me a new _visual understanding_ of an important aspect of space science. Thank you SciShow for all this great content (especially the space videos).
The explanation I found really helpful is to look at how momentum, which is a vector, scales differently from kinetic energy, which is a scalar. e.g. if you have an object moving at 1m/s, then the ratio between kinetic energy and momentum is 0.5s. If the object is moving at 20km/s, which is not unreasonable for an asteroid impact, the ratio is 10,000s. Effectively, the momentum is completely irrelevant compared to the kinetic energy.
Had no idea there was a difference between momentum and kinetic energy.
@@filonin2
This was explained to me by a physicist once. I may be using the wrong words here, but.... He said if the angular momentum is greater than the power that keeps the bits of the asteroid together, then it doesnt matter how fast it goes or where it comes from, it will explode in a circular detonation. And make a circular crater.
They had to find an explanation to this because people found it weird how every crater on the moon were circular and not showing the angle from which the asteroid came from.
yeah, as Scott Manley says, momentum grows linearly and energy grows quadratically, if they're coming in at 30km/s it's no wonder why they're circular
This is unfortunately an incorrect argument. We can very well define energy as the amplitude of momentum instead of its square; the formulas will be different but the physics will not be affected. To understand it better, try to use the energy unit of kg*km^2/s^2 instead of kg*m^2/s^2 and see how your said ratio changes. Physical values with different units should not be compared in scales.
@@tinglin6121 while I made a mistake in the second ratio (whoopsie, corrected now), changing units does not affect my argument at all. The factor by which the ratio changes as you move from 1m/s to 20km/s stays precisely the same. Obviously when comparing quantities with different units you need to be aware of the units. Which is why the ratios are in seconds. But whether you use m/s or furlongs per fortnight, the difference between the energy momentum ratios when moving from 1m/s to 20km/s will always be 20,000. This can very easily be seen if you just write out the ratio of ratios without any specific values and you will see that everything except for the ratio between the 2 velocities - which is a dimensionless number - cancels out.
"It's the kind of research that leaves a bigger impact than you might think." LOL
I wear my sunglasses at night 🎶
So I can, so I can
Pizza John, stop guilting me with those eyes while I'm trying to learn
Good video! People also seem to be concerned that craters are the same depth. This is explained is that the impact is basically an explosion and not a penetration. It blasts everything away just like a huge bomb going off. This has been demonstrated by hitting ground with high velocity particles. The depth is the same.
I think olympus mons is a big contributor to the variability in Mars's tilt, all of that mass in one area makes it much less well balanced than Earth. Plus our massive moon stabilizes us
And don't forget the massive Valles Marineris.
"Bigger impact than you think," I see what you did there!
also, impact zones are composed of heterogenous composition of materials with different hardnesses, thus, not all material will be ablated uniformly. doy.
Not every impact has to be a high speed collision. Abnormally slow impacts would tend to push the dirt around a bit more rather than tossing it like the high speed, high energy impacts.
One also has to consider the spin of the impacting object as well.
Some crater chains bare more resemblance to a skipping rock than a series of impacts from a tidally broken object.
All I'm saying is that there may be many different causes for elongated craters despite their relative rarity.
Some might have disintegrated due to tidal forces, and created a chain of smaller craters.
I feel like the spin of the impacting object is fairly irrelevant, much like it's momentum, in comparison to the astronomical kinetic energy... Using a more earth based Example, bullets rotate around 300krpm's, presuming a .308 (7.62mm) round, it's rotating 466 fps which is a not insigificant (somewhere between half and nearly 1/6th depending on distance from muzzle to target and many other less relevant factors) fraction of its forward rate of travel. Yet on impact with a solid object the spin is utterly irrelevant as the kinetic energy destroys the projectile before the spin can be factored. The impacted object has to be very soft to take in and slow down the projectile, at which point the spin can have some effect on the wound channel, which is still minor and mostly irrelevant to the hole in the impacted soft body.
@@DracoOmnia Thanks for the info. At cosmic speeds, pretty much every impact is like a nuclear explosion.
Same reason ripples are round
Read that as nipples at first
Oh wow you're absolutely right! Thanks!
Never really thought about it. Interesting.
Thanks for making these educational videos, they are very impactful!
I watched this video two days before belatedly watching the Veritasium video from several months ago where he asks these exact questions and wonders why no one thinks about them. That was an experience.
Why are craters always round? Because you can't be a square in space, ya dig?
Fascinating
Why do meteorites always fall into craters
what other shape should they be?
your t-shirt was a jumpscare
👍Savannah gets my engaging presenter of the day award!🏆
Essentially in highly kinetic impacts or explosive detonation, the force of the blast radiates out in a spherical pattern, only when an asteroid hits at an angle of less than 10 degrees (I think?) will there be any elongation of the crater, and that is only very slight depending on the angle of impact, relative velocity, size and mass of the asteroid.
was just wondering about this a few days ago!
As Lucy van Pelt used to say, "Because they aren't triangular, blockhead!"
There was a guy who did a crap ton of research on this. It's a shame you didn't look his stuff up or recognize him for his work.
Sounds like normalization with anti-tank rounds; the impact on a somewhat plastic surface can pull/redirect the trajectory into the surface.
I watched a documentary decades ago where they proved crater angles and impacts at Berkeley, where they used a crazy high pressure gun to shoot packed sand.
What does a "crazy high pressure gun" look like? Any idea about the name of the documentary?
@@DracoOmnia look up asteroid impact experiment.
@@DracoOmnia from Berkley, MIT, or Cal tech.
Probably from the NASA Ames Vertical Gun Range. Pete Schultz did a tonne of stuff in experiments there.
What about these dome looking things perfectly round, they are everywhere. What are these?
1:03 Did NASA of all people really make an animation that shows how a falling rock hitting rock creates a fiery cloud?
What's wrong with that? If the energy of the impact is strong enough, it will be like a nuclear explosion.
@@maksphoto78 Rock can melt/glow/evaporate under extreme force or heat, but it doesn't burn (just like lava doesn't burn).
@@Fiyaaaahh ok, so what creates the fireball in a nuclear explosion?
@@maksphoto78 Had to look this up: "The heat of the explosion causes air in the vicinity to become ionized, creating the fireball" (from en.wikipedia.org/wiki/Effects_of_nuclear_explosions). Pretty cool and I actually didn't know this. So it's actually the air itself that's burning.
So the question now becomes if kinetic energy can approximate nuclear fission. My gut feeling says 'no', but NASA seems to think otherwise and I have no proof to the contrary. Thanks to your skepticism this just became a lot more interesting lol.
Because the impactor, and much of the surface rock, vaporise. Literally. Have a look at the work of Prof. Pete Schultz at the NASA Ames Vertical Gun Range. I am sure there is some of his stuff on youtube as well.
Great stuff. Is that a John Green shirt?
Yes. "Pizza John".
GREAT QUESTION! Edit: GREAT ANSWER!
Wait I need to read more about tilting planets, right now I think if a planet is +- a sphere, does it change its position vs asteroid belt? How so, that now asteroids hit them in different angles even when the planet is technically a sphere... That would imply is not spherical more like an egg and it tilts very fast . But... Until I research more about tilting planets... I'm wrong... Thanks for reading my rampage ❤
BIG DUH !!!IF THEY WERE HIT BY SQUARE ROCKS THE CRATERS WOULD BE SQUARE!!!
Coming from the video about the shape of black holes, I know what that hair tie ...
Very neat!
I was wondering--would y'all consider doing a "state of covid" episode? I feel like all the media I get as an american is the GOP going "no more pandemic! no masking even if you want to!" and the democrats going "eh, sacrifices must be made for the economy," and meanwhile my disabled friends haven't eaten inside a restaurant in three years and sometimes I see articles about new variants and how people are still dying and long covid. I'd just like an unbiased overview.
Cause of how it is
nice pizza john shirt savannah :D
soon as an asstroid enters our gravity starts to bend towards us pulling it to be perpendicular but has limited time so the angle remines to a mazmum of 15 degrees thus making an elliptical creators
5 per cent of craters are oval in shape. And this happens when the angle the meteor is striking Earth is 15 degrees or less. Is this consistent with math? Yes.
If the direction of a meteor happens to be coming from the direction of the North Pole, the angle will be 15 degrees or less if it strikes the Earth at a latitude of 15 degrees or less. What is the radius of a circle that covers everything north of 15 degrees? cos(15). So, the percentage of meteors that will hit within this circle are:
cos(15) ^ 2 which works out to 0.933 or 93.3 per cent.
So the percentage of meteors that strike within 15 degrees of the equator is 6.7 per cent. Reasonably close to 5 per cent.
Turning the problem around, at what latitude would 95 per cent of meteors strike north of?
acos( sqrt(95) ) = 12.9 degrees
Again, reasonably close to 15 degrees.
Even deaper questions is well why do space rock knows only circle
Cool
Your next mission if you choose to accept it: why are some craters inverted?
If the moon is title locked to earth, how do you get perfectly round craters on the side we can see they should almost all be ovals, at least.
Interesting! Thanks moon for letting 3have a habitable planet.
Clever
Several craters are polygonal.
I knew this since third grade.
Why are a lot of craters on the moon look like an octagon or only so deep? And the asteroid belt. Do u think it use to be a planet the blew up?
Given the ratio of asteroids, meteoroids, and comets seem to match ratios of worlds in our Solar System, then you could hypothesize that a collision of worlds has taken place. Comets would match an icy crust. Then there is mostly rocky debris with fewer metallic objects floating around, which would be core remnants.
@@Hydroverse Comets did not come from any sort of larger body. They formed in the outer reaches of the solar system. And most of the asteroids did not come from larger bodies. A large body could never have formed in the asteroid belt due to gravitational influences, mainly from Jupiter.
We owe a lot to our moon it seems!
10 to 30 degrees? Wow that's a lot of perturbation.
Well we know from Wallace and Gromit that the moon and most likely other space bodies are made of cheese so asteroids hitting the moon are some cheese on cheese roughness😮
Maybe that makes some craters oblong due to a harder cheese for the asteroid
Why does a shockwave distribute the energy in a ring?
Circles are what happens when you put down a dot and spin a line that doesn't change its length around it like a clock. If your environment doesn't have strong irregularities the length and speed of the shockwave will stay the same regardless of the angle
Why don't mars' moons stabilize its wobble?
They are too small. Also, they are quite new.
So if the angle is low enough, by the time the shock-wave travels up the asteroid, the asteroid itself has moved sideways enough so that its a oblong explosion... huh.
This was a weapon grade pun. 😂
I asked my grandma once and she said the same reason why I have pimples
Hell Yeah Pizza
How are they hitting the moon if the earth is in the way?
They're not all perfectly aligned with the ecliptic.
It isn't! And for half its orbit the Moon is closer to the asteroid belt than the Earth is. Obviously.
1:42 Nice try Savannah, you can't get me to believe space rocks wear make-up.
47!
Is explosion the only reason for a round crater? Can you still have a round crater even when the object isn't falling straight down and doesn't explode?
Here's something from a minutephysics vid: "Most of the time collisions in 2D or3D result in a net force between the objects which is only in one direction - typically perpendicular to the surface where the objects collide" ua-cam.com/video/bSVfItpvG5Q/v-deo.html "Most collisions are secretly in one direction"
Splash, next question.
If they weren’t round they’d be ditches.
Beause if they were square, they would be Borg...and we would be assimilated
Anyone know who’s face is on that shirt?
Hank Green's brother John.
Not sure why she's wearing it now; Pizzamas is months away.
Asteroids fall due to gravity, so all asteroids are on a parabolic path to the centre of gravity that makes nearly all of them fall almost vertically when they strike the surface.
Not always, there can be very different angles of impact. Did the Chelyabinsk meteor go straight down?
@@maksphoto78 Isn't that what I said?
@@MrStevenlynch ok, let me put it this way - asteroids don't fall due to gravity. It's more like a high-speed collision on a highway. The Moon's gravity is minuscule anyway, and even smaller moons and large asteroids have impact craters. It's just two cosmic bodies having a chance meeting while travelling at high velocity. Thus, impact angle could be literally anything.
@@maksphoto78 Everything in the Solar System is orbiting the Sun. The orbits of smaller bodies may be affected by a random larger body and change to a different orbit. That interaction may put it in an orbit that will take it close to another body. Millions of miles away and over millions of years that object will be affected by the gravity of that body. As the smaller object approaches, its orbit will be increasingly affected, veering to the centre of gravity, its trajectory becoming more vertical from the perspective of the larger body. The "start" position and masses will affect the angle but because of gravity it will tend to the vertical. Subsequently, more craters will be circular and only a very few will be elongated. There are other forces at play which are explained in this video. But I think my theory should be put in the mix too.
They're not! Sometimes they're egg shaped! Now ask why craters are never _square._
Sometimes, they are even hexagonal.
Curious of the t-shirt. I uh, don't understand it but would like to 👀👉👈
I don't know who's on it but i see pizza and i do like pizza
That is John Green, Hank Greens's brother. During one Christmas many years ago, John had a mustache for about 3 days. Hank found that funny and put it on advertisement for his venture about pizza. I don't know more about it, but John Green has a short on his channel explaining it
PIZZA
All of the moon's craters are abuse from her ex, Meeteo Wright-Schauer
Boombs
0:47 Not as fast as throwing a tantrum amiright fellow ADHDs
The craters in this video's thumbnail are all hexagonal to some degree.
Hexagonal craters could form via wave interference. You'd just need multiple shockwaves overlapping each other.
@@HydroverseNo. Rock is crystalline.
@@RideAcrossTheRiver Wow, really? Wave interference can still take place within a solid medium (e.g. cymatics).
@@Hydroverse Oh, no, not that nonsense.
@@Hydroverse Minerals such as olivine, basalt, and feldspar are crystalline in chemical structure. On the large scale, rock layers fracture generally along these chemical structure. Please don't prattle nonsense.
If we had square craters then we could have ended global hunger
Go Go Sci Show!
Why are craters always round?
... Cause they got nowhere else to go.
Haven’t watched the videa but from my experience with playing asteroids they are coming for you… almost chasing you around.. constantly…
Pizzamas???
So now we know that Mars is tilted
Must be a Valorant player
Am I supposed to recognize the face on her shirt or is it some kind of _one off_?
I dont mind watching longer videos if you want to take a breath at any point, lol. Nah fr tho hella fun topic ty
Thumbs up for that awful pun.
Pizza.
They arent.
Craters aren't round, they tend to be a rounded hexagonal shape. This is because the energy that creates them goes out in a circular pattern but the material it impacts along with any other irregularities will cause a reflection in part of the wavefront. The result is a hexagon.
The _hexagons are bestagons_ conspiracy has corrupted your brain.
@@DemPilafian No it's true just look. If you watch some slow motion videos of liquid drops hitting a pool they often form 6 nodes that peak around the rim for the same reason.
@@phookadude And if you look directly at the sun, you'll notice that it's actually a hexagon. For real bro!
@@DemPilafian An astronomy professor pointed it out to me in a course I took so I would suggest you just look.
I have always felt that planets n moons n stars are round because of dark matter. Like rolling a meatball the outer pressure on a rotating item makes it round.
Uh, no. It's because of gravity and hydrostatic equilibrium. Dark matter is literally irrelevant at these scales.
“Why is there hair around my anus?”
Prevents friction burns.
Those aren't craters, those are nostrils.
It would be a lot weirder if they were always triangular...#ijs
what a bunch of hogwash.
bs
They're not always round.... Sometimes they're oblong. 🤭
It's because theyre created by the moon rabbits digging their burrows