the theories on how the moon was created, ive read books and heres what ive come up with:
1.accretion theory- that a meteor hit earth and knocked a big part off and it later grew larger and formed the moon, because they have found numers particles on the moon iddentical to the earth...
2.fission theory-that the moon was spun off the earth because the earth was spinning so fast.
3. the gravity(or pull-in) theory-that the moon was a small minor planet that was orbiting the sun and somehow the earths gravity pulled it into its orbit and it started orbing the earth.
ive narrowed it down to 2 number one and number 3. which one do you believe happened or any other theories.
There are several theories as to how the moon was created. The dominant theory, though, is that when Earth was young, a planet about the same size as mars crashed into the earth. It hit with such an impact that most of the iron from the planet went into Earth's core. This impact created a splash which sent debris into the earth's orbit. These fragments eventually formed the moon. This would also explain why the moon has very little iron.
I concur - I think this theory is now widely accepted amongst cosmologists and planetary scientists.
| Afaceinthematrix wrote: |
| There are several theories as to how the moon was created. The dominant theory, though, is that when Earth was young, a planet about the same size as mars crashed into the earth. It hit with such an impact that most of the iron from the planet went into Earth's core. This impact created a splash which sent debris into the earth's orbit. These fragments eventually formed the moon. This would also explain why the moon has very little iron. |
yah i stated that in my first post... but is that the one you believe?Actually you didn't state this theory in your first post...
The question is wrong. It's not a case of belief, it's a case of the hypothesis which has the most evidential/logical support. If new evidence arises then a new theory might arise also. At the moment the collision theory seems to fit all available data and provides a logically coherent account - therefore it is accepted as the best theory. I (and I suspect afaceinthematrix) therefore accept that theory until such a time as a better one comes along, if ever.
'Believe' is often a loaded word. It can imply that you think something is true despite good evidence to the contrary. Words like 'belief' and 'faith' are not really useful in science.
Just to play devils advocate...you did manage to forget to include another theory.
That theory being that the earth and moon were "created" in nearly the same state as they exist now. It is widely known that the moon is slowly spiraling away from the earth, hence the use of the term "nearly."
Anyway, I don't necessarily "believe" any of these theories. I think that there are too many flaws in them all to say that any of them are completely correct. I also think Bikerman has a very good point about the difference between "belief" and "acceptance."
As for your thoughts about narrowing it down to #s 2 and 3:
2. This seems pretty preposterous to me as far as the physics involved. Suggesting this is how the moon formed implies that the Earth spun up and flung a huge portion of itself away. If the Earth didn't spin up, how did it stay together before flinging off a huge chunk of itself? If the Earth spun fast enough to fling a chunk of itself off, I find it hard to believe that this chunk would end up orbiting in the Earth as the moon currently does. I also find it hard to believe that the separational forces involved would resolve into the 2 bodies we currently observe. So assuming this all happened despite the aforementioned aggrievences, what then caused the earth to slow to its current speed? Because of the observed rate at which the moon is currently spiraling away from the Earth, we can make an educated guess as to when this theoretical split took place. I believe most estimates give less than 2 million years (though I'm not bothering to look up figures.) How could the Earth slow down so quickly?
Anyway...because of all this and more, #2 is out in my opinion.
3. Again, something I find ridiculous based on the physics involved. Have you ever done any research on the forces needed to pull two bodies in space together into orbit? The likelihood of such an occurrence happening is so far beyond slim that the odds are ridiculously, astronomically small. The only way that the odds are increased is when the two bodies are traveling in the exact same direction at nearly the same speed. Do a little research on "spheres of influence." This may help you to understand how and why it is so ridiculous to think that the earth could "capture" an incoming object such as the moon.
#3 is also out in my opinion.
This leaves only #1 and my aforementioned "forgotten" theory. I would argue that the two are the most popular theories that exist. Both have flaws, but despite such flaws, they also have the most supporting evidence compared to other less popular theories. I find them both a little hard to swallow, mainly because neither of them can describe completely the formation of the earth and moon without "holes" in their description.
Without further evidence for either (or patching of the substantial "holes") I'm content to say "I don't know, and I may never know how the moon and earth came to be." Because what's more important to me is that I am currently enjoying the benefits of them both being in existence 
What about other planets with a moon? or multiple moons?
you'd have to assume that however our moon was formed
would be simillar to how their moons were - which would mean
that all of the planets with moons were struck by large objects
that caused simillar effects.....seems a lil far fetched.
However I can't think of any better theories.....
I think when all else fails on this subject,
you have to solicate an expert opinion....
which is why i suggest asking the moon monkeys:
http://www.rathergood.com/moon_song/
There are so many 'balls' of material flying about the place, it's a wonder i can't find a link to an article on the moons of moons of moons i read some time back... 
However, i did find a couple of interesting articles anent:
| Quote: |
from: http://www.cbc.ca/quirks/
To: Bob McDonald re moons of moons.
Dear Bob
I have three questions that have intrigued me for a while. You interested?
(1) Re: movement of satellites around celestial bodies, we know that stars revolve around the centre of galaxies, planets revolve around stars, and moons revolve around planets. But are there any natural bodies that revolve around moons?
…snip (2 other Qs)…
Warren Harbeck, Calgary
Hi Warren, thanks for the interesting questions.
Regarding moons of moons, it doesn't usually happen because the gravity of the parent planet is normally too strong to allow a secondary orbit around a moon to form. However, there is one case I know of where two tiny moons embedded within the rings of Saturn share the same orbit and perform a kind of dance with each other.
Picture the two moons following each other around Saturn with the rear moon moving a little faster, so it's catching up to the lead moon. When they get very close, and it looks like they are going to collide, they change places, so the lead moon speeds ahead, and the chase moon now lags behind. You have to think about how objects behave in orbit to understand how it works. In space, you speed up to slow down, and put on the brakes to speed up. That's because the higher you go, the longer it takes to go around the planet. The lower your orbit, the less time it takes. Astronauts aboard the space shuttle have to deal with this when attempting to rendezvous with the Mir space station.
When the faster moon of Saturn catches up with the slower one, they are attracted to each other by their mutual gravity. This causes the rear moon to speed up just a bit and the leading moon to slow down slightly. Since the rear moon is now moving faster, it rises a little higher in it's orbit. The lead moon loses some energy and falls a little lower. That means the rear moon that was catching up, will now take a little longer to complete it's orbit around Saturn. The leading moon, even though it has lost energy, is now on a lower and therefore shorter orbit, so it pulls ahead. Months later, when new lead moon has lapped the slower one, they change lead again. So they are not exactly in orbit around each other, but it's as close as you can get.
There was also the discovery a few years ago of a tiny moon going around an asteroid. It's called Dactyl, and it has a very close orbit around the asteroid Ida. It's probably a chip off the asteroid from an earlier collision.
EOS
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|
Also, more stuff about moons in our Solar System here: http://en.wikipedia.org/wiki/Natural_satellite | KronikSindrome wrote: |
What about other planets with a moon? or multiple moons?
you'd have to assume that however our moon was formed
would be simillar to how their moons were - which would mean
that all of the planets with moons were struck by large objects
that caused simillar effects.....seems a lil far fetched.
However I can't think of any better theories.....
I think when all else fails on this subject,
you have to solicate an expert opinion....
which is why i suggest asking the moon monkeys:
http://www.rathergood.com/moon_song/
|
Our Moon is unique in that it is so large compared to the size of the Earth. Jupiter and Saturn have numerous moons and as far as I remember they are indeed captured asteroids and the like. But this does not work nearly so well with the Earth-Moon system and so the Big-Splash theory is the currently accepted one albeit with some details still to be agreed upon.
Also the Moon is believed to have formed about 4.5billion years ago just after the rest of the Solar System (well 30million years or so).
David.powers1983 - your reply is not strictly accurate. Titan (1 of Saturn's moons) is 50% larger than the Earth. If it was not orbiting Saturn, it would be classed as a planet in its own right.
KronikSindrome raises an interesting point, although it is somewhat specious. Just because our moon was formed as the result of an impact (maybe), that doesn't mean that other moons must necessarily have been formed the same way. In fact, in the case of the gas giants, it is extremely improbable.
Collisions involving gas giants would not cause rock or metal to be ejected as there is no rock or metal to begin with. It is more likely that the gravity of the outer planets attracted space debris that coalesced into their moons.
My reasoning being this - the inner planets are composed of rock as, during the era of planetary formation, lighter substances such as hydrogen and helium were pushed further away from the sun by the cosmic wind. As you get further away from the sun, its gravity has less effect. Therefore any rocks or metal that far away would more likely be drawn towards large gravitational masses in their vicinity - those large masses being the outer planets. Some of the rock and metal would go into orbit around the planets and gradually accrete into the moons.
very true.......
so it's like the ultimate question: 'just how many licks does it take to
get to the center of a tootsie roll tootsie pop?' the world may never know.
I'd rather know how the moon monkeys were created and where I can buy one....
hell yeuz.
anyway. very interesting topic, thank you all for the good read eh.
| KronikSindrome wrote: |
very true.......
so it's like the ultimate question: 'just how many licks does it take to
get to the center of a tootsie roll tootsie pop?' |
That would depend on tongue size. A giraffe could probably manage it faster than a mouse | DoctorBeaver wrote: |
powers1983 - your reply is not strictly accurate. Titan (1 of Saturn's moons) is 50% larger than the Earth. If it was not orbiting Saturn, it would be classed as a planet in its own right.
KronikSindrome raises an interesting point, although it is somewhat specious. Just because our moon was formed as the result of an impact (maybe), that doesn't mean that other moons must necessarily have been formed the same way. In fact, in the case of the gas giants, it is extremely improbable.
Collisions involving gas giants would not cause rock or metal to be ejected as there is no rock or metal to begin with. It is more likely that the gravity of the outer planets attracted space debris that coalesced into their moons.
My reasoning being this - the inner planets are composed of rock as, during the era of planetary formation, lighter substances such as hydrogen and helium were pushed further away from the sun by the cosmic wind. As you get further away from the sun, its gravity has less effect. Therefore any rocks or metal that far away would more likely be drawn towards large gravitational masses in their vicinity - those large masses being the outer planets. Some of the rock and metal would go into orbit around the planets and gradually accrete into the moons. |
I did not say it is because the Moon was big - just that it is big when compared to the Earth. A planet the mass of Saturn is perfectly capable of capturing massive bodies whilst a much smaller planet such as ours would not be able to capture the Moon with the result that it orbits us in the way that it does.
And all the theories presented are possible ways of 'creating/capturing' moons, and all can happen, but it depends on the starting conditions and on the relative sizes/orbits etc (well maybe not the licking of the moon by the space monkeys - not sure on that one).
