Why Are Craters Always Round?

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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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Sources:
www.sciencefocus.com/space/wh...
www.britannica.com/science/me...
www.scientificamerican.com/ar...
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arxiv.org/ftp/arxiv/papers/19...
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astronomy.com/magazine/ask-as...
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Images:
www.nasa.gov/multimedia/image...
commons.wikimedia.org/wiki/Fi...
www.flickr.com/photos/edsween...
commons.wikimedia.org/wiki/Fi...
www.flickr.com/photos/edsween...
www.gettyimages.com/detail/vi...
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www.nasa.gov/mission_pages/LR...
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commons.wikimedia.org/wiki/Fi...
www.nasa.gov/content/elliptic...
www.nasa.gov/mission_pages/me...
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• Massive Crater Discove...
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www.gettyimages.com/detail/vi...
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mars.nasa.gov/resources/22477...
www.jpl.nasa.gov/images/pia15...
climate.nasa.gov/news/2948/mi...

Опубликовано:

16 май 2023

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Комментарии : 276

@SciShow Год назад

Visit brilliant.org/scishow/ to get started learning STEM for free. The first 200 people will get 20% off their annual premium subscription and a 30-day free trial.

@Chris_winthers Год назад

The real question is: why do asteroids always fall into craters?

@KOKO-uu7yd Год назад

🤣 Sounds like a real question, honestly, from a certain population segment that tends to distrust science. 😵‍💫😩

@Arthera0 Год назад

Same for rivers. Why do they always flow to larger bodies of water like Lakes seas and oceans.

@NeoTechni Год назад

they look like comfy beds

@nuttin2chereur2late74 Год назад

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.

@LightBlueVans Год назад

big brain

@captain_context9991 Год назад

Wow 3:18 Look how close that asteroid came to hitting the visitation centre.

@ShahWirana-bq9hv 6 месяцев назад

Well, if you ever go to huge concerts, you'd be hating the visitor centres too

@FosukeLordOfError Год назад

John is staring into my soul

@1224chrisng Год назад

Now I want Pizza

@DoctorX17 Год назад

They wore that shirt specifically so John could stare at your soul

@Chris_winthers 5 месяцев назад

He may not be the scishow brother, but he still finds his way on there

@YoungGandalf2325 Год назад

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.

@Makabert.Abylon Год назад

And crash here, we just have a too short of a lifespan to take it seriously

@bernier42 Год назад

I mean we’re hurtling through space pretty quickly…

@kirkmorrison6131 Год назад

More like a Gatling Gun

@fancyincubus Год назад

I'm underground in my war bunker eating beanies brains I'm not dodging nothing but my taxes

@thomasgoodwin2648 Год назад

Don't forget the Comets. 😉

@jupiter1217 Год назад

"It's the kind of research that leaves a bigger impact than you might think." LOL

@spidermanandsnape Год назад

I will never get over learning fascinating scientific facts and ideas while John's pizza face stares back at me. Truly stellar fashion

@filonin2 Год назад

RIP SciShow Space. We miss you.

@johncaze757 Год назад

Why what happened?

@fishstix4209 Год назад

@johncaze757 they stopped their spin-off channels and re-merged them into the base....just another rip

@LightBlueVans Год назад

✌️😔

@geoffreymartin6363 Год назад

Pizza John, stop guilting me with those eyes while I'm trying to learn

@James-hn8yi Год назад

I wear my sunglasses at night 🎶

@chiliwithonel Год назад

So I can, so I can

@captain_context9991 Год назад

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.

@pierrecurie Год назад

I don't think angular momentum is significant (99% of the time).

@koubenakombi3066 Год назад

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.

@joehorn1762 Год назад

@koubenakombi3066 no, no it doesn't.

@zed1stwizard Год назад

@@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.

@DemPilafian Год назад

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).

@OnTheRiver66 Месяц назад

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.

@thedayb4tomorrow Год назад

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.

@filonin2 Год назад

Had no idea there was a difference between momentum and kinetic energy.

@captain_context9991 Год назад

@@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.

@1224chrisng Год назад

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

@tinglin6121 Год назад

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.

@thedayb4tomorrow Год назад

@@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.

@oma15 Год назад

Never really thought about it. Interesting.

@ihcfn Год назад

"Bigger impact than you think," I see what you did there!

@sagetmaster4 Год назад

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

@maksphoto78 Год назад

And don't forget the massive Valles Marineris.

@NirvanaFan5000 Год назад

was just wondering about this a few days ago!

@taimunozhan Год назад

Thanks for making these educational videos, they are very impactful!

@Aaron_b_c Год назад

Fascinating

@bernier42 Год назад

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.

@janetf23 Год назад

👍Savannah gets my engaging presenter of the day award!🏆

@h7opolo Год назад

also, impact zones are composed of heterogenous composition of materials with different hardnesses, thus, not all material will be ablated uniformly. doy.

@arnavkaushik3373 Год назад

your t-shirt was a jumpscare

@jeremywinters2020 Год назад

Why are craters always round? Because you can't be a square in space, ya dig?

@guntherultraboltnovacrunch5248 Год назад

GREAT QUESTION! Edit: GREAT ANSWER!

@heavymetalbassist5 Год назад

Great stuff. Is that a John Green shirt?

@CL-go2ji Год назад

Yes. "Pizza John".

@danny234555 Год назад

Same reason ripples are round

@MyManMeli Год назад

Read that as nipples at first

@awaredeshmukh3202 Год назад

Oh wow you're absolutely right! Thanks!

@NeutronicalGaming Год назад

what other shape should they be?

@cyberherbalist Год назад

As Lucy van Pelt used to say, "Because they aren't triangular, blockhead!"

@mattkrumm8141 Год назад

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.

@DracoOmnia Год назад

What does a "crazy high pressure gun" look like? Any idea about the name of the documentary?

@mattkrumm8141 Год назад

@@DracoOmnia look up asteroid impact experiment.

@mattkrumm8141 Год назад

@@DracoOmnia from Berkley, MIT, or Cal tech.

@yellowflowerorangeflower5706 Год назад

Cool

@sagittariusa2008 Год назад

Why do meteorites always fall into craters

@thewalkingcrow8946 Год назад

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.

@winterwatson6811 Год назад

nice pizza john shirt savannah :D

@all3ykat79 Год назад

Clever

@mikebauer6917 Год назад

Sounds like normalization with anti-tank rounds; the impact on a somewhat plastic surface can pull/redirect the trajectory into the surface.

@willywokeup9112 3 месяца назад

Your next mission if you choose to accept it: why are some craters inverted?

@vazwan Год назад

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

@ConnorNolan Год назад

Cause of how it is

@Fiyaaaahh Год назад

1:03 Did NASA of all people really make an animation that shows how a falling rock hitting rock creates a fiery cloud?

@maksphoto78 Год назад

What's wrong with that? If the energy of the impact is strong enough, it will be like a nuclear explosion.

@Fiyaaaahh Год назад

@@maksphoto78 Rock can melt/glow/evaporate under extreme force or heat, but it doesn't burn (just like lava doesn't burn).

@maksphoto78 Год назад

@@Fiyaaaahh ok, so what creates the fireball in a nuclear explosion?

@Fiyaaaahh Год назад

@@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.

@St8Genesis Год назад

I knew this since third grade.

@diegofernandez4789 Год назад

Interesting! Thanks moon for letting 3have a habitable planet.

@edserembus9651 Год назад

BIG DUH !!!IF THEY WERE HIT BY SQUARE ROCKS THE CRATERS WOULD BE SQUARE!!!

@kisakisakura6663 Год назад

Coming from the video about the shape of black holes, I know what that hair tie ...

@BensCoffeeRants Год назад

We owe a lot to our moon it seems!

@jonathanrobles3753 Год назад

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 ❤

@klaus7164 Год назад

This was a weapon grade pun. 😂

@thomasgoodwin2648 Год назад

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.

@maksphoto78 Год назад

Some might have disintegrated due to tidal forces, and created a chain of smaller craters.

@DracoOmnia Год назад

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.

@maksphoto78 Год назад

@@DracoOmnia Thanks for the info. At cosmic speeds, pretty much every impact is like a nuclear explosion.

@ShahWirana-bq9hv 6 месяцев назад

I asked my grandma once and she said the same reason why I have pimples

@tonymaccaroni5744 10 месяцев назад

What about these dome looking things perfectly round, they are everywhere. What are these?

@ChimeraZone Год назад

Hell Yeah Pizza

@terencevanriesen9745 4 месяца назад

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.

@Astrofrank Год назад

Several craters are polygonal.

@christianheichel Год назад

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

@lincolnrock9158 Год назад

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?

@Hydroverse 4 месяца назад

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.

@amehak1922 Год назад

10 to 30 degrees? Wow that's a lot of perturbation.

@anthimeria4994 Год назад

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.

@wasyertakeawaythaturmadeofcorn Год назад

47!

@giniside89ovanim96 Год назад

Even deaper questions is well why do space rock knows only circle

@HandzSome 9 месяцев назад

How are they hitting the moon if the earth is in the way?

@Hydroverse 4 месяца назад

They're not all perfectly aligned with the ecliptic.

@TheRealSkeletor Год назад

1:42 Nice try Savannah, you can't get me to believe space rocks wear make-up.

@yoyoyohihihidude Год назад

Why does a shockwave distribute the energy in a ring?

@fabulousflufferbum2051 Год назад

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

@gregedwards1087 Год назад

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.

@joeelliott2157 4 месяца назад

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.

@YogaToSamadhi 10 месяцев назад

Boombs

@chrisg3030 Год назад

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" ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-bSVfItpvG5Q.html "Most collisions are secretly in one direction"

@synapse349 Год назад

Why don't mars' moons stabilize its wobble?

@maksphoto78 Год назад

They are too small. Also, they are quite new.

@Noam-Bahar Год назад

PIZZA

@maremacd Год назад

If they weren’t round they’d be ditches.

@MrStevenlynch Год назад

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.

@maksphoto78 Год назад

Not always, there can be very different angles of impact. Did the Chelyabinsk meteor go straight down?

@MrStevenlynch Год назад

@@maksphoto78 Isn't that what I said?

@maksphoto78 Год назад

@@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.

@MrStevenlynch Год назад

@@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.

@Henrydingus01123 Год назад

Anyone know who’s face is on that shirt?

@massimookissed1023 Год назад

Hank Green's brother John.

@michaelmicek Год назад

Not sure why she's wearing it now; Pizzamas is months away.

@randybugger3006 Год назад

They're not! Sometimes they're egg shaped! Now ask why craters are never _square._

@maksphoto78 Год назад

Sometimes, they are even hexagonal.

@Kratoseum Год назад

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.

@Aarygon Год назад

I dont mind watching longer videos if you want to take a breath at any point, lol. Nah fr tho hella fun topic ty

@borrellipatrick Год назад

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

@melorawr1608 Год назад

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

@anonimanonim2710 5 месяцев назад

All of the moon's craters are abuse from her ex, Meeteo Wright-Schauer

@EyesOfByes Год назад

0:47 Not as fast as throwing a tantrum amiright fellow ADHDs

@okman9684 Год назад

If we had square craters then we could have ended global hunger

@samwill7259 Год назад

So now we know that Mars is tilted Must be a Valorant player

@tbella5186 Год назад

Pizzamas???

@mamanoneyall51 Год назад

Beause if they were square, they would be Borg...and we would be assimilated

@TheRealInscrutable Год назад

Am I supposed to recognize the face on her shirt or is it some kind of _one off_?

@drain_001 Год назад

Pizza.

@outlawbillionairez9780 Год назад

Why are craters always round? ... Cause they got nowhere else to go.

@ericdoe2318 Год назад

Haven’t watched the videa but from my experience with playing asteroids they are coming for you… almost chasing you around.. constantly…

@RideAcrossTheRiver Год назад

The craters in this video's thumbnail are all hexagonal to some degree.

@Hydroverse 4 месяца назад

Hexagonal craters could form via wave interference. You'd just need multiple shockwaves overlapping each other.

@RideAcrossTheRiver 4 месяца назад

@@HydroverseNo. Rock is crystalline.

@Hydroverse 4 месяца назад

@@RideAcrossTheRiver Wow, really? Wave interference can still take place within a solid medium (e.g. cymatics).

@RideAcrossTheRiver 4 месяца назад

@@Hydroverse Oh, no, not that nonsense.

@RideAcrossTheRiver 4 месяца назад

@@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.

@ponyote Год назад

Thumbs up for that awful pun.

@jonatanromanowski9519 Год назад

Go Go Sci Show!

@nickinurse6433 Год назад

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.

@eroraf8637 Год назад

Uh, no. It's because of gravity and hydrostatic equilibrium. Dark matter is literally irrelevant at these scales.

@Bubble33333 Год назад

Those aren't craters, those are nostrils.

@phookadude Год назад

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.

@DemPilafian Год назад

The _hexagons are bestagons_ conspiracy has corrupted your brain.

@phookadude Год назад

@@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.

@DemPilafian Год назад

@@phookadude And if you look directly at the sun, you'll notice that it's actually a hexagon. For real bro!

@phookadude Год назад

@@DemPilafian An astronomy professor pointed it out to me in a course I took so I would suggest you just look.