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How did Earths Moon come to be?


LukeSkywatcher
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49 minutes ago, Thalestris24 said:

The theory is that it was created out of a collision between another planet and the Earth during the early history of Earth and before the Late Heavy Bombardment which pockmarked the Moon.

Louise

I agree with this as being the idea that currently best  fits the evidence we have available.

The least persuasive theory I've heard is that the moon was made in the big cheese factory in the sky. ?

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Although i pretty much agree with the above statements, i also heard several other theories.  Like it was a captured moon from the planet that was destroyed ( asteroid belt ) to aliens towed it into place to stabilise the wobble of the planet before they seeded it for life. Would be nice if it was the latter :) 

 

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I read that all the asteroids in the asteroid belt are the supposed remnants of 5 planets destroyed during the development of the early solar system when the current planetary orbits were much different than today, so with that might the moon be some sort of captured remnant or possibly a product of many remnants as the destruction of 5 planets must have had far reaching consequences. Entertaining an alternate formation theory is interesting.

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The planet that may have collided with Earth is called Thea. A week or so ago I heard something about it on the radio. A paper was published that argues that the Moon's composition is too much like the Earth's. It is not impossible that Thea had a composition very much like the Earth, but that is unlikely. The Earth has a rather characteristic composition.

I was thinking that Thea may have plunged into the proto Earth, getting under the mantle more or less completely, and that from the other side of the Earth a peace of Earth's own mantle was ejected into space. (Like a Newton's cradle.)

Not sure if that could work at all. I don't think we can ever know for sure what happened.

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I think I heard that the collision pretty much caused the earth+object to fragment and our current setup is a result of the subsequent coalescence around the two biggest chunks. So the surface layers are bits from each of the original objects - hence the similarity in composition.

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I had heard it was likely from a collision during the Earth's formation where it hit just right (not so hard that the Earth was blown to bits, and not so soft that they combined into one).  The pretty cool thing about our moon today is that it is huge (especially compared to most moons out there - it's half the size of Mars if that puts it into perspective), almost to the point that the moon and the Earth make a binary planet orbiting the sun, so it makes sense that it would be the product of a protoplanet collision.  I'd guess we are fairly lucky to have it in our sky.  It also means with that size that close that we get some pretty spectacular views, without the need for a telescope. ;) 

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One of the whacky theories I’ve heard is that the moon is a giant alien base, and is in fact hollow, and was placed there to watch over the earth. The aliens (along with their ships, stay underneath the lunar surface.

But back to reality Louise stated the current scientific favourite for how the moon came to be created. Whether correct or not time will tell. 

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The Thea theory is most accepted, and simulations suggest that a grazing collision with an object in the order of the size of Mars is what best fits the current situation. Originally the moon was much closer, but tidal friction slowly reduces the rotational energy, and means the moon has slowly receded from Earth. The process is ongoing, with the moon moving away at a rate of a few cm per annum.

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I rather like the cheese theory myself, but then you cannot beat a nice piece of Wensleydale in my opinion.

On a more serious note, I go with captured remnants of asteroid belt debris, the same material earth was formed or forming from. As to the big impact theory, possible but it does not sit well with me for some reason.

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I accept the (current?) conventional scientific ideas. Why do we
have to WAIT for some sort of "ambush" idea on this one? lol ?
Under such circumstances I tend to say nothing (incriminating).

Edited by Macavity
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I listened to an interesting documentary recently which described another theory, further to the Thea impact one which it cited as the widely accepted one.  Will see if I can find & link it.

Edited by niallk
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So we are mainly all in agreement that the Moon was created by a collision between Earth and another body way back when the planets were forming.

I was talking to an astrophysicist lecturer (no older than me) from my local Uni the other night (as you do) and he rubbished/hands down dismissed this idea. He said that the Moon was a planet in its infancy and because it was so close to Earth (4 times bigger), that the Earths gravitational pull "captured" the Moon and stopped it from forming into a planet.

 

Edited by LukeSkywatcher
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13 minutes ago, SIDO said:

Something I read this morning among others but this one spiked my interest...

https://www.sciencedaily.com/releases/2018/02/180228103238.htm

"The moon is almost chemically the same as the Earth".

I put this fact to the astrophysicist and he brushed it off as "coincidence".

Seriously, if this guy is the type of person that Uni's are employing to teach................i worry about future generations.

Anyways............we went on to other stuff and he was throwing out questions and most of the group of people were scratching their heads because they didnt know the answers.

I stood my ground and gave him the answers he was looking for. He said "You know your stuff".

Not sure if that is a compliment or an insult considering who it came from.

LOL.

The local Uni must be teaching "Astrophysics for dummies", because ive never studied it and i could answer his question.

 

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3 minutes ago, LukeSkywatcher said:

The Moon is chemically almost the same as the Earth

Aren't alot of comets, planets asteroids and dwarfs planets of similar geologic makup as earth and as well origin. If the whole asteroid belt was once 5 Rocky planets they must have had similar geological makups/origins as well/questions?

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10 minutes ago, SIDO said:

Aren't alot of comets, planets asteroids and dwarfs planets of similar geologic makup as earth and as well origin. If the whole asteroid belt was once 5 Rocky planets they must have had similar geological makups/origins as well/questions?

I'm not disputing that the earth and moon are or are not chemically similar, merely only pointing out they are not the only two inner solar system objects that are so, the article I posted you must not have read as its theory complies with the earth and moon being chemically the same.

Edited by SIDO
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The possible formation from a synestia is interesting but it doesn't make sense since the density of the Moon is much lower than that of the Earth on account of our metallic core. The Moon is maybe similar to the Earth's mantle which is why a glancing blow from another planet seems to fit. But the truth just may be a bit more complicated. Maybe someone will come up with something better in the future. If that's not in my lifetime - well, I won't lose sleep over it!

"The green earth, say you? That is a mighty matter of legend, though you tread it under the light of day!"

Louise

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3 minutes ago, Thalestris24 said:

The possible formation from a synestia is interesting but it doesn't make sense since the density of the Moon is much lower than that of the Earth on account of our metallic core. The Moon is maybe similar to the Earth's mantle which is why a glancing blow from another planet seems to fit. But the truth just may be a bit more complicated. Maybe someone will come up with something better in the future. If that's not in my lifetime - well, I won't lose sleep over it!

"The green earth, say you? That is a mighty matter of legend, though you tread it under the light of day!"

Louise

I do like it in the fact that earth was obliterated and robbed of part of it's iron core then the two cores gravity captured the remaining material but size then should be equal to mass for both objects but again during such an event the larger heavier core would have more gravity and thus collect more of the heavier matter so I may be only slightly more sold on this theory than you but still just as unconvinced.

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15 minutes ago, DAVE AMENDALL said:

Surely the answer to this one is to ask the man in the moon.Super Don talks to him all the time?...............Dave

Possible...the White Rabbit may also have the digs on this ?

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