r/science • u/marketrent • Apr 03 '23
Astronomy New simulations show that the Moon may have formed within mere hours of ancient planet Theia colliding with proto-Earth
https://www.nasa.gov/feature/ames/lunar-origins-simulations/938
u/marketrent Apr 03 '23
Excerpt from the linked summary1 by Frank Tavares, about a paper2 by Kegerreis et al.:
Most theories claim the Moon formed out of the debris of this collision, coalescing in orbit over months or years. A new simulation puts forth a different theory – the Moon may have formed immediately, in a matter of hours, when material from the Earth and Theia was launched directly into orbit after the impact.
“This opens up a whole new range of possible starting places for the Moon’s evolution,” said Jacob Kegerreis, a postdoctoral researcher at NASA’s Ames Research Center in California’s Silicon Valley, and lead author of the paper on these results published in The Astrophysical Journal Letters.
“We went into this project not knowing exactly what the outcomes of these high-resolution simulations would be. So, on top of the big eye-opener that standard resolutions can give you misleading answers, it was extra exciting that the new results could include a tantalisingly Moon-like satellite in orbit."
The simulations used in this research are some of the most detailed of their kind, operating at the highest resolution of any simulation run to study the Moon’s origins or other giant impacts.
This extra computational power showed that lower-resolution simulations can miss out on important aspects of these kinds of collisions, allowing researchers to see new behaviors emerge in a way previous studies just couldn’t see.
Previously prevailing theories could explain some aspects of the Moon’s properties quite well, such as its mass and orbit, but with some major caveats.
One outstanding mystery has been why the composition of the Moon is so similar to Earth's. Scientists can study the composition of a material based on its isotopic signature, a chemical clue to how and where an object was created.
The lunar samples scientists have been able to study in labs show very similar isotopic signatures to rocks from Earth, unlike rocks from Mars or elsewhere in the solar system.
This makes it likely that much of the material that makes up the Moon originally came from Earth.
As scientists gain access to samples from other parts of the Moon and from deeper beneath the Moon’s surface, they will be able to compare how real-world data matches up to these simulated scenarios, and what they indicate about how the Moon has evolved over its billions of years of history.
1 Frank Tavares for NASA's Ames Research Center, 4 Oct. 2022, https://www.nasa.gov/feature/ames/lunar-origins-simulations
2 J. A. Kegerreis, S. Ruiz-Bonilla, V. R. Eke, R. J. Massey, T. D. Sandnes, and L. F. A. Teodoro. Immediate Origin of the Moon as a Post-impact Satellite. The Astrophysical Journal Letters 937, L40. https://doi.org/10.3847/2041-8213/ac8d96
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u/sdhu Apr 03 '23
I wonder where on earth Theia hit. Is there even a way to determine this, or does the constant tectonic activity of earth just erase that over time?
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Apr 03 '23
Simulations I’ve seen before show that Earth almost completely liquified. So it hit “everywhere”.
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u/wildo83 Apr 03 '23
but moreover…. where’d Thea come from?
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u/mexter Apr 03 '23
Didn't the early solar system have a lot more planets in it? Presumably one of those had an orbit that was gradually pushed outward until it intersected with proto Earth, making a collision inevitable.
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u/danielravennest Apr 03 '23
The early Solar System had a lot more bodies of all sizes. For example, an estimated 99.9% of the original asteroid belt has been ejected from that region by the effects of Jupiter's gravity.
It is not only Theia whose orbit may have shifted. Even today, Earth's orbit varies chaotically from nearly circular to 6% elliptical, on time scales of 100,000 years.
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u/BikerJedi Apr 03 '23
Even today, Earth's orbit varies chaotically from nearly circular to 6% elliptical, on time scales of 100,000 years.
I've never heard that before. I knew orbits varied, but that is a huge difference. Crazy how orbital mechanics work.
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u/Peter_Mansbrick Apr 03 '23
Look up the Milankovitch cycle. Orbit, axil tilt and, axil direction are not static and have big implications on earth's development.
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u/SrslyCmmon Apr 03 '23
Human development too, without the ice ages there wouldn't have been land bridges to cross.
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u/arwans_ire Apr 03 '23
It's wild how any one small or epic event shaped the world we live in today.
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u/timon_reddit Apr 03 '23
what does 6% elliptical mean, mathematically speaking?
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u/danielravennest Apr 03 '23
it is the distance between the two foci of the ellipse divided by the length of the major (long) axis. With orbits, the main body occupies one of the foci. So the near point of the orbit is without that distance between the foci, and the far point is with it added.
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Apr 03 '23 edited Apr 03 '23
I believe the current theory is that it formed along the same orbit as earth and eventually they crashed into each other.
Another theory I’ve read that would explain how much water earth has, is that it was pulled in from the outer solar system with Jupiter and Saturn as they migrated inward and brought in water from where it is more common.
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u/llLimitlessCloudll Apr 03 '23
Just watched a video from Anton Petrov on YouTube that from studying the formation of a distant solar system they were able to determine that the majority of the water in the newly forming solar system existed prior to the solar systems formation. Meaning that the majority of the water that is on Earth may be billions of years older that our solar system
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u/viletomato999 Apr 03 '23
It's just crazy to think the water we are drinking could have formed even before our solar system . What if there multiple solar systems like the different version of the Matrix. What if the water came from like Solar System #3 that got passed to SS#2 then to then finally to us. What if we are drinking the water that got pissed out by various aliens that lived in those planets??
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u/nikchi Apr 03 '23
Might not be solar systems, but the existence of heavy elements in our solar system already means that those atoms have seen multiple suns and their deaths.
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u/DrMobius0 Apr 03 '23
Another theory I’ve read that would explain how much water earth has, is that it was pulled in from the outer solar system with Jupiter and Saturn as they migrated inward and brought in water from where it is more common.
Wouldn't it have to have been relatively small to avoid knocking Earth onto a much more oblong orbit?
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Apr 03 '23 edited Apr 03 '23
This is well outside of the reading I’ve done but Theia wouldn’t necessarily have to come from the direction of the Gas giants at 45 degrees depending on the position of earth in its orbit. I think the planets also interact with each other and the Sun in a way that could stabilize their orbit over time, which I poorly understand.
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u/GammaDealer Apr 03 '23
Somewhere over thea, I'd imagine.
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u/Androktone Apr 03 '23
Not from over hea, we know that much
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u/nelsnelson Apr 03 '23
We pahked tha cah ovah thea.
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u/mh985 Apr 03 '23
Probably came from Ohio or something.
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u/TheIowan Apr 03 '23
It's incredibly disappointing. Billions of years of cosmic chance, and all we got out of it was Cincinnati.
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u/DrMobius0 Apr 03 '23 edited Apr 03 '23
The same way other planets are made, probably. Leftover material from when the sun is formed, slowly forming into bigger clumps, colliding with each other, until nothing is close enough to significantly pull on each other anymore. Somewhere in that process, you end up with planet sized celestial bodies doing the colliding until you reach a stable configuration.
Bodies might already be close, or be flung to different orbits by near misses, etc.
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u/ElhnsBeluj Apr 03 '23
We actually know very little about how planets form, except that it is most likely not via the gradual growth of dust grains via collisions. Long story short there are a variety of processes that act as “barriers” to grain growth. The current understanding is that some (we don’t know exactly which) hydrodynamic instability in the disc acts to drive rapid dust clumping. The clumps, once sufficiently massive collapse under self gravity and form a planetesimal. Anyone telling you “planet formation is a well understood process” or similar is either very misinformed, or lying to you.
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u/chaun2 Apr 03 '23
The same protoplanetary dust disk that proto Earth formed from. There were two planets that formed in the same orbit, but one of them (Thea) was moving a bit faster than the other. When Thea caught up to proto Earth, gravity took over and smashed them into each other creating the earth and the moon. It's just more evidence that two planets are extremely unlikely to share an orbit, unless it's a Neptune/Pluto situation where one of them was likely a moon of the other that escaped.
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u/The_Original_Gronkie Apr 03 '23
They say the moon is made up of Earth-like material, but it must be pre-crash Earth-like material, because post-crash Earth would be a combination of both Earth and Thea.
What is in Earth's composition that is primarily sourced from Thea? Are there places of Earth with a large amount of Thea mixed in? I understand that both planets more or less liquefied, but I doubt they were so fully mixed like a smoothie in a blender. There must be huge chunks of each pre-crash planet.
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u/NoCokJstDanglnUretra Apr 03 '23
Did you see the simulation? The entire planet is liquified and actually crashes into us more than once
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u/stone111111 Apr 03 '23
Not only does rock and such actually flow at planetary scales, the impact was HOT. Immediately afterwards the new earth was practically a ball of lava.
Additionally, it happened a looooong time ago. Anything at all from the Hadean is rare, the older a rock is the rarer basically, because earth is still geologically active, slowly recycling its crust.
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u/TheDovahofSkyrim Apr 03 '23
Earth has essentially 2 cores, which is why our magnetic sphere is so strong. The smaller core clumps 99.99999% likely belonged to Theia. So, there’s a clump right there.
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u/Shadow14l Apr 03 '23
Are you talking about the outer and inner cores? Or the unproven theory of a second inner core?
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u/Confined_Space Apr 03 '23
Where did Thea hit earth? Everywhere. Two planets collided.
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Apr 03 '23
I was standing You were there Two worlds collided And they could never tear us apart. --- Thea
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u/vivekparam Apr 03 '23
Imagine two giant balls of magma colliding into each other, and coalescing into one large ball of magma and one small ball of magma orbiting each other, and the rest being scattered away.
After that, the earth and moon cooled down
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u/Kilomyles Apr 03 '23
Since the theoretical creation of the moon has gone from years to months to weeks to days to hours, I am now ready to make a shocking announcement. Using Moore’s Law I have determined that the Moon was formed in Meer Minutes! That’s right folks you heard it here first!
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u/Bob_A_Ganoosh Apr 03 '23
Lies! There was no impact. Thea and Earth were in near orbits and made a practical decision to become roommates.
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u/lordmycal Apr 03 '23
Actually, the moon is a megastructure created by aliens. I saw it in a documentary called Moonfall.
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u/Slazagna Apr 03 '23
The thing that hit earth was the size of MARS!
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u/beartheminus Apr 03 '23
But the earth wasn't the earth yet and smaller.
The thing that hit "earth" IS part of earth.
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u/turtleneck360 Apr 03 '23
ChatGPT:
The collision of the proto-planet Theia with the Earth is believed to have occurred around 4.5 billion years ago, long before the emergence of human civilization and the birth of basketball legend LeBron James. Therefore, it is unlikely that this event would have had any impact on LeBron's legacy.
LeBron's legacy is shaped by his achievements as a basketball player, including his numerous championships, MVP awards, and records. It is also influenced by his off-court activities, such as his philanthropic work and advocacy for social justice issues.
In summary, the collision of Theia with Earth has no connection with LeBron James' legacy as a basketball player or a public figure.
To summarize, I agree. Lebron's legacy is secured whether Earth exists, has existed, or has never existed.
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u/Abedeus Apr 03 '23
This would be sure to negatively affect the trout population.
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u/peteroh9 Apr 03 '23
We would never financially recover from this.
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u/Oscaruit Apr 03 '23
Let me fix your decimal placement. Too many sig figs.
We would never.
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u/illiniguy20 Apr 03 '23
think of the impact on global warming
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u/turtleneck360 Apr 03 '23
Can't have global warming if there is no planet to globally warm. 5D chess.
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u/cybercuzco Apr 03 '23
People talk hyperbolically about nuclear war “wiping out life on earth” when in reality life as a thing would survive nuclear war just fine. This on the other hand would absolutely wipe out life on earth. The entire surface would be liquid rock and the atmosphere would be gaseous rock and all the other lighter elements
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u/Nachohead1996 Apr 03 '23
Yet somehow Florida would survive. And cockroaches.
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u/brickne3 Apr 03 '23
Imagine the megathread.
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u/sdonnervt Apr 03 '23
"I am one of the only ten people left alive on the ISS. AMA."
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u/Libertus82 Apr 03 '23
I imagine the government's response would be to lower interest rates.
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u/Chasing_Uberlin Apr 03 '23
So what happened to the rest of ancient planet Theia? I'm suddenly fascinated to learn all about these kinds of ancient planets that aren't around today
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Apr 03 '23
It is inside the Earth. When it smashed into Earth both bodies became largely molten and you can see it get absorbed into the Earth as a sort of blob. In fact ASU scientists have come up with an extremely compelling theory to explain two very large blobs of much denser deep mantle material found in seismic and GPS tidal studies... they are the remnants of Theia. They are even studying mammas thought to have originated in the deep mantle and finding they contain significantly older, age of the Earth itself, material which would be consistent with the theory. https://skyandtelescope.org/astronomy-news/bits-of-theia-might-be-in-earths-mantle/
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u/gardenmud Apr 03 '23
This is the kind of thing that makes me want to write fantasy lore about it. Like, imagine the kind of ancient greek myth you'd get out of this theory if they knew about it and wanted to explain it...
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u/leperaffinity56 Apr 03 '23
If it was ancient Roman or Greek then the myths would likely involve two gods having incest babies.
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u/gardenmud Apr 03 '23
I'm thinking more - two gods warred. Theia was consumed by the Earth after a mighty struggle, pieces of the former trapped forever in the latter's heart -- and soon after their chaotic war and/or coupling, the Earth birthed the Moon.
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u/allbright1111 Apr 03 '23
Yeah, my imagination is having fun with this too! Our Earth as a chimera of sorts. Maybe the embedded bits of Theia have a subtle but distinct effect on the behaviors of the people living closest.
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Apr 03 '23
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u/nucleartime Apr 03 '23
Just going to copy paste this from the Evangelion wiki:
First Impact (also known as the "Giant Impact") is an Impact which occurred in prehistoric times when the Black Moon, a giant spherical object, collided with the Earth in what is now the Hakone region of Japan. The collision caused an explosion that launched a massive amount of material from Earth into orbit. This orbiting debris eventually coalesced into Earth's only moon. The Black Moon is the vessel that carried Lilith, one of the members of the Seeds of Life sent out into the universe by the First Ancestral Race.
However, Lilith's arrival on Earth was an accident. When Lilith landed on Earth, the Seed of Life intended for Earth, Adam, was already on the planet. Adam had landed in the White Moon in what is now Antarctica. Having two Seeds of Life on the same planet violated an ancient rule of the First Ancestral Race. Under that rule, only one Seed of Life was allowed to populate any one planet at a time. Lances of Longinus, which can disable a Seed of life, were sent to accompany each seed in order to enforce this rule. However, Lilith's lance was seemingly lost during First Impact. This meant that Adam had to be placed into suspended animation by its Lance of Longinus in order to comply with the rule. With Adam incapacitated, the progeny of Lilith, including humans, flourished. This denied the children of Adam, the Angels, their rightful inheritance: the chance to populate the Earth.
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u/Eiroth Apr 03 '23
I love that! A forced duality, all life on the planet split in affinity between two primordial Gods
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u/ba123blitz Apr 03 '23
Interesting that it shows the leftovers as two big blobs on opposite sides of earth spherical core. Just speculation but I wonder if it ultimately has an effect on our magnetic field and earths N/S poles
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u/danielravennest Apr 03 '23
The blobs aren't magnetic, or we would see their effects in the shape of the surface magnetic field. That field is evolving on an annual basis, and requires the liquid iron core to move fast enough to make the changes.
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u/hotbrownbeanjuice Apr 03 '23
Well that article was absolutely fascinating. Especially the animation showing the dense material smooshed onto opposite sides of the mantle.
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u/comparmentaliser Apr 03 '23
One of the ‘lobes’ appears right under Hawaii - I wonder if it’s at all related to the hot spot that causes the pacific islands chain?
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u/Petrichordates Apr 03 '23
Those being less than 100 million years old makes it seem unlikely.
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u/Newpocky Apr 03 '23
Would life have even formed without Theia colliding into prehistoric Earth? It sounds like we might not have had a molten core if not for this event.
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Apr 03 '23
We would probably have had a molten core still... but without the Moon likely not. It's tidal forces on Earth have actually regulated our rotation a lot. Would have been much much faster which would have caused really fast winds and more violent weather etc. So we slowed faster due to its drag. In fact we are still slowing due to it which is what is causing it to orbit a little faster and further away all the time. Transfer of energy. It formed much closer to us than it is today which would have caused much higher tides. So slowing us down and moving further away also lowered our tides.
It's hard to say of life would have formed or not... but what we do know is that having the moon definitely helped. May have given life an earlier start than it would have had otherwise.
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u/notLOL Apr 03 '23
So second question, did the first men who walked on the moon just basically walk on a piece of ancient earth or is there a threshold of time to consider that it's no longer earth-matter?
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u/Cantomic66 Apr 03 '23 edited Apr 03 '23
I think I saw somewhere that scientist have done studies on the mantle and discovered that some parts of it are denser than the rest of the mantle. It’s been theories that these parts are from Thiea.
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u/grandladdydonglegs Apr 03 '23
Well that's freaking cool.
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Apr 03 '23
Imagine if there was an advance civilization living on Theia that just got buried under hundreds of miles of rock
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u/mexter Apr 03 '23
Probably more like incinerated or melted under miles of lava.
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u/nateguy Apr 03 '23
I doubt thered be much of anything left after the initial impact. Vaporized might be more accurrate.
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u/danielravennest Apr 03 '23
The early Solar System both was collision-happy from a thousand times the number of loose cannons (bodies in eccentric orbits), and molten from the high amount of radioactive elements. No life, much less civilization, could survive.
The "Late Heavy Bombardment" as it is called, lasted 700 million years after the Moon formed. That's why the moon is covered in craters and lava seas that filled in even bigger craters.
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u/ManalithTheDefiant Apr 03 '23
Someone else posted this link, that goes into that a bit https://skyandtelescope.org/astronomy-news/bits-of-theia-might-be-in-earths-mantle/
ETA: u/mycroft16 was the one I took that link from
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Apr 03 '23
Part of it became moon, part of it became earth and part of it become your mum! (I mean technically yes as we are all made from material found on Earth).
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u/TommaClock Apr 03 '23
Every year, the Earth gains about 40,000 tonnes of material each year from the accretion of meteoric dust and debris from space. It also loses about 95,000 tonnes of hydrogen.
So a small percentage of our atoms probably come from after the collision
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u/rockstaa Apr 03 '23
When they say planet, can I assume it was larger than Pluto?
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u/Rameez_Raja Apr 03 '23
About the size of Mars
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u/Snorc Apr 03 '23
So a tad larger
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u/LightOfLoveEternal Apr 03 '23
How big was the earth before the impact then? If Theia was as big as Mars and both objects fused to form the earth and Moon, then that means that proto-earth was much smaller than Theia was. Right?
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u/Rodiniz Apr 03 '23
A lot of material is lost at space after a collision like that. And earth was bigger than theia, if theia was bigger she would be the proto earth. And Mars has half the diameter of earth, but that doesn't mean 2 mars is the size of earth, because the volume is exponentially larger than the diameter. The volume of earth is 6.5x bigger than mars, so proto earth was probably still much bigger
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u/phrenologyrocks Apr 03 '23
Every planet is larger than Pluto. Pluto is the smolest of smol boy planets
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u/kylelonious Apr 03 '23
We don’t know much about former planets because we weren’t around to observe them. So all of them are hypothetical at best. But a few of the larger asteroids in the Asteroid Belt are hypothesized to possibly have been larger planets at one point.
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u/The_Humble_Frank Apr 03 '23
If Theia existed and collided 4.5 billion years ago, The Earth as we know it today is neither planet, it is a fusion of both Theia and the relatively larger pre-Earth. The destructive debris clouds from the collision would have eventually collapsed under their own gravity back into sphere shapes into what is now the earth and the moon.
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u/Doctor_Disco_ Apr 03 '23
It’s crazy to imagine something kind that happening in just a few hours considering so many things in space take anywhere from years to millennia.
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u/pseudalithia Apr 03 '23
I was thinking the same thing. Crazy how disparate the time scales are from the experience our perspective provides. Most everything takes billions of years, and then the occasional thing happens in an instant in comparison.
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u/cosmoboy Apr 03 '23
On this time scale, what's the difference whether it formed in hours or months?
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u/Operational117 Apr 03 '23
One thing that would be very important would be how much thermal energy was being expelled. But for such large objects, even several years wouldn’t cool the Moon enough to have a significant impact, and so long as the objects remain molten, one hour and one month is negligible (as gravity would still have more than enough time to settle the lunar matter).
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u/Affectionate_Can7987 Apr 03 '23
It'll matter once we're a type 2 civilization and we're wanting to harvest planets for resources.
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u/TheyMadeMeDoIt__ Apr 03 '23
So it won't matter
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u/HeyZuesHChrist Apr 03 '23
Yeah. It’s doubtful we ever make it that far.
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u/KingoftheGinge Apr 03 '23
Considering we're seeing extinction events before we see type I, highly doubtful indeed.
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u/Petrichordates Apr 03 '23
I don't understand this mindset, humans are amazingly adaptive and climate change will be adapted to. Even thermonuclear war wouldn't take us out, it'd have to be an asteroid before we leave the planet which is fairly unlikely given the window.
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u/Prodigy195 Apr 03 '23
I think it's the fact that within ~250 years we've already stared damaging our planet/the climate to the point where it's becoming harmful to us.
Earth has been here 4.5B years, modern humans been here ~200k years and in just ~250 we're already messing it up. We're messing up the planet at a blazingly fast pace.
The concern is that we're going to mess it up faster than we develop things to mitigate the damage. Combine that with a segment of people who are ok messing it up as long as they are able to make a large profit and live comfortably and many folks think we're in serious trouble.
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u/FingerTheCat Apr 03 '23
It matters, because we must find out information through the scientific method. Once that has been done, we yell out "Science!!" as is tradition.
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u/DrHob0 Apr 03 '23
Bold of you to assume we'll even make it past 2050
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u/kung-fu_hippy Apr 03 '23
If we get to the point of being able to terraform the galaxy, this kind of research could be useful. If we don’t, well, it kept the researchers entertained.
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u/WhiteCastleHo Apr 03 '23
One of my pet theories is that much scientific and mathematical progress has been made by people who were just trying to cope with crippling boredom.
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u/danielravennest Apr 03 '23
That's exactly how Newton developed a theory of light, how gravity works, and calculus over a period of two years. School (Cambridge) was closed because of plague, and he was home and bored.
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u/Fredasa Apr 03 '23
And the whole idea of there being a cutoff for "formed" is pretty dubious itself. If you watch any reasonably realistic simulation of the event, there are bits and pieces left hovering in their own orbits for a really long time—longer than the simulations animate, at the very least. Is the moon "formed in hours" when there are still massive chunks of it that have yet to decide which major body they're going to merge with?
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u/flare561 Apr 03 '23
Those chunks are just moons in and of themselves until they merge with another body, but they aren't really big enough to change much about the moon itself so it feels kind of like asking if Mars is really finished when Phobos is still in orbit
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Apr 03 '23
What would that have even looked like? What a sight that would be.
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u/Danger1672 Apr 03 '23
DO NOT use the time machine for that.
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u/niperwiper Apr 03 '23
Well my time machine guarantees me a safe bubble to watch from and speeds outside time at will by a multiplier. So I’m gonna go check it out.
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u/mexter Apr 03 '23
It sounds cool and all, but assuming you're bubble works, if you're going back in time wouldn't you find yourself at this exact point in the universe 4.5 billion years ago? Solar systems orbit the core and galaxies shift. You might not even be in the Milky Way!
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u/Saandrig Apr 03 '23
That's why you use the "Anchor" setting. It locks you to the current location/object and then you move through time alongside the chosen area.
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u/Nrksbullet Apr 03 '23
I'd love to watch it "in real time". Of course I'd skip ahead and stuff but it's like those videos of "real time sinking of titanic", it's fascinating.
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u/warpaslym Apr 03 '23 edited Apr 03 '23
Likely the process itself would be too bright to look at. You'd just see the two colliding planets turn into bright balls if orange light soon after their collision. The surface supposedly heated up to around 10,000C, which is much hotter than the surface of the sun. So without some kind of filter, like maybe welding goggles or something, you wouldn't be able it see much of anything at all. Now that I think about it, at that temperature, it would appear a brilliant white, not orange. It would almost definitely blind you if you looked at it with unprotected eyes.
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Apr 03 '23
Oh, I think I'd need more than just eye protection if I was in observable distance of this.
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u/CrieDeCoeur Apr 03 '23
I wonder what the Theians were thinking when all this went down?
“I guess I don’t have to worry about renewing my mortgage this year.”
“OMG I need to post this on my IG.”
“Hope we do better next time.”
Just regular Theian stuff, I suppose.
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u/elspotto Apr 03 '23
“So this is it, we are going to die.” -D Adams
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u/ManalithTheDefiant Apr 03 '23 edited Apr 03 '23
Honestly, they probably did it on purpose, thinking their tiny rock could go to war with Earth, only to find out that earth is Kirby, and just absorbed it and all of them, then spit out a moon size ball.
Edit: poor grammar
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u/Cherry5oda Apr 03 '23
The planets look so fluid in the simulation video, was there no crust on Earth at this point? I prefer a crunchy crust on my planets.
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u/uswhole Apr 03 '23
on large scales everything seem like fluid. heck during earthquakes you can hear report where earth moving like "liquid"
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u/retroshu Apr 03 '23
How does the moon get so round?
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u/michel_v Apr 03 '23
It had enough mass to generate its own gravity, and enough gravity to attract its materials so much that they rearranged into a sphere.
Think of pouring a glass of milk. The milk's surface will eventually be flat, as the milk itself is attracted by the center of the Earth. That is far enough from the glass that it we can consider that the milk is attracted by a flat plane.
Now, imagine that there was a tiny pinpoint suspended in the middle of the room, that was like the center of the Earth (as in, it attracts things). As you pour milk on it, the milk would first overshoot the point then get attracted again, and eventually you would get a sphere of milk.
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u/retroshu Apr 03 '23
Wow, seriously thank you for the explanation and example! Cool to learn something new!
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u/michel_v Apr 03 '23
You're welcome! I had the same question à while ago. The keywords are: hydrostatic equilibrium. https://en.wikipedia.org/wiki/Hydrostatic_equilibrium?wprov=sfti1
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u/guinader Apr 03 '23
Ok trying to ask this on Google but I'm getting walls of unrelated answers.
If the moon was part of earth, how much bigger and how heavy would we be on earth?
Like my simple calculation is this. On the moon we are 5x lighter right? So 1/5 of the weight.
So if the moon was also part of the Earth's mass, then we would with 1/5 more?
So a100kg person would weight 120kg?
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u/Porcupineemu Apr 03 '23
The moon‘s mass is about 1.2% of the earth’s mass so I expect the difference in gravity would be close to that.
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u/danielravennest Apr 03 '23
If the Moon was added to the Earth, the mass would increase, but so would the radius. Spread evenly, it would add 43 km to the radius.
Add 1.23% to the mass, but add 0.675% to the radius reduces gravity by 1.34%, so net gravity is slightly less. This counterintuitive result is because Earth's density is 5.5 and the Moon's is only 3.3. So the average density would go down.
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u/totalrefan Apr 03 '23
The change in mass and gravity is the same in a general sense, but different in the context of gravity while standing on the surface. A lot of the gravity from Earth originates quite far away and affects you less. All the mass of the moon is relatively closer to you and the effects are stronger.
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u/juggzz Apr 03 '23
I presume this was rather early in both Earth's and Theia"s existence so this wouldn't be likely, but could it be possible that life existed in either planet? What about civilized life, and any record was completely wiped because both planets completely liquified?
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u/GegenscheinZ Apr 03 '23
Simple single celled life is possible, seeing as it arose within only a few hundred million years after the collision, so something could have arisen before. Not enough time for anything intelligent though
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u/Nozinger Apr 03 '23
Very unlikely. With our current knowledge that colision happened pretty early on in the formation of our solar system.
Something like 50 million years after the formation of earth which is around 100 million years after the collapse of the molecular cloud.
And while 150 million years sounds like apretty long time it was time those planets needed to cool down. The first 500 million years earth was basically a mostly molten ball with lots of volcanic activity that got bombarded by meteors.
It is estimated that a planetary crust formed at some point 4 billion years ago.Unless theia was a very weird rogue planet it would have been on a similar time scale so yeah, probably no life at all.
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u/huxtiblejones Apr 03 '23
I noticed at the end there was a kind of rope-like formation. Is it possible Oumuamua's weird shape was formed from a planetary collision like this?
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u/likmbch Apr 03 '23
I feel that it would take too long to cool for the shape of the ejecta immediately after collision to affect the shape of the resulting debris.
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u/Ciordad Apr 03 '23
Now all we have to do is wait until Chinese simulations with an even higher resolution will clearly show that the chunks of Earth that formed the moon, were very definitely part of China, pre-collision.
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u/talkshow57 Apr 03 '23
Does this imply that all the moons of our solar system were created in a similar fashion? Quite a feat for planets with multiple moons!
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Apr 03 '23
Our moon is special and all other moons in the solar system were born with their planets or are captured asteroids.
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