Why does the moon fit almost perfectly over the sun during an eclipse?

Question

What I'm asking is, what caused it to be the right size and shape to fit like that?

Look at this picture:
http://www.flickr.com/photos/cb/49242786/

There's got to be a better explanation that chance. Please try to stick to scientific theories.

Answer 1

Well, chance *is* the correct answer... as the moon was originally MUCH close to Earth, and would regulary eclipse the sun completely; as it's moved out (and continues to move away), we now see both as about the same size. (it varies a bit, depending on where Earth is in it's orbit about the sun, and the moon in it's orbit about the Earth) In a few million years, the moon will appear smaller than the sun.

Answer 2

Sorry to disappoint you but it is sort of by chance, with very long odds on the probability scale (unless you believe in creationism by god, which I do not and which has even longer odds) and this is what makes it so amazing if you have ever seen one. You will never forget the experience.

However the Moon does not always almost perfectly fit over the Sun. Many eclipses (not including partial ones) are in fact called "annular", where the Moon does not cover the entire discof the Sun, and the Sun shows itsef as a (very) bright circle (annulus) aroubd the Moon, weather permitting of course. Most people would not notice any significant dimming of the light unless they looked at the Sun (which is not recommended under any circumstances).

This is because the Moon's orbit is not circular, it is elliptical and its' distance from Earth changes beween 356,400kn and 406,700km between its farthest point and its nearest.

There is a total eclipse in parts of China next year on 1 August 2008, go see this chance occultation if you get the opportunity.

As regards part 2 of your question the scientific evidence obtained from the Appollo missions mainly, and others, support the theory that the Moon was cleaved out of the Earth in a gigantic colision with a Mars sized planetisimal about 5 billion years ago during the solar systems formation.

Computer simulations at astronomical research units show that this explains the size of the Moon and its distance and orbit and geological composition which all fit the facts fit very accurately. I have seen nothing to suggest anything different it is now an accepted theory explained in schools.

As for its shape, all large objects such as plantets and normally stars too, naturally form into a sphere in space through their own internal gravitational attraction, unless their rotation is fast enough to ditort the shape into an oblate sphere. This is the case of the giant gas planets Jupiter and Saturn for example, or very large extreme high-rotation stars. Our own Sun is not very noticably flatter at its poles, but it is - a litlle. Some very rare ones in the galaxy do resemble cigar shapes rather than spherical so some very odd eclipses would be seen there!.

Hope that answers your question.

Answer 3

If you want a scientific explanation, then chance is the correct, mathematical answer.

For instance, if the moon could orbit in range from x thousand miles to 50x thousand miles, but it is say 7x thousand miles, you could say that it is about a 50 to 1 chance of it orbiting in just the right place, remembering that it does not fit exactly over the sun.

That's just an example of the math. The point I am making is that even if the odd are 500 to 1 of it being in the right place, that is not big odds on a universal scale.

And what about the not so good odds: for instance, if the moon's orbit was in the same plane as the Earth's orbit around the sun, we would get a spectacular eclipse every month.

So, we got good odds on the moon's distance, but bad odds on its orbital inclination. So, they sort of cancel out as far as luck goes.

Also, it is much more remarkable that the Earth is in the right place, is the right size, etc etc for life to exist on it. That may be billions to 1 chance. However, if it wasn't the case, we wouldn't be here to marvel at it. So, it is a sort of circular argument.

Answer 4

When the moon first formed billions of years ago it was only about 14,000 miles from Earth. Since then it's been moving away from us (..in this era it's recession rate is 3.8 cm/year..) By coincidence, chance, luck, happenstance, we just happen to be around when the moon is located at the precise distance from us that during a total solar eclipse it perfectly covers the disc of the sun. In the far distance future, as the moon continues moving away from us, the time will come when there will be no more perfect total solar eclipses.

The moon is receding from us due to conservation of angular momentum. Earth's rotational velocity is gradually slowing due to the friction of tides sloshing back and forth in its oceans. That slowing of rotational velocity (..angular momentum..) can't just disappear, and it doesn't. It's "transferred" to the moon, causing it to move away from Earth.

Sorry, but it just doesn't get any more scientific than that.

Answer 5

Sorry to disappoint you even though it incredibly is nearly by skill of accident, with very long odds on the risk scale (till you think in creationism by skill of god, which i do no longer and which has even longer odds) and it is what makes it so magnificent in case you have ever seen one. you will in no way forget approximately the adventure. even though the Moon does not constantly very almost completely in superb condition over the sunlight. Many eclipses (no longer alongside with partial ones) are in fact reported as "annular", the place the Moon does not cover the comprehensive discof the sunlight, and the sunlight shows itsef as a (very) surprising circle (annulus) aroubd the Moon, climate allowing needless to say. maximum individuals does not word any important dimming of the sunshine till they appeared on the sunlight (which isn't counseled under any situations). it is using the fact the Moon's orbit isn't around, it incredibly is elliptical and its' distance from Earth variations beween 356,400kn and 406,700km between its farthest element and its nearest. there is an entire eclipse in areas of China next 3 hundred and sixty 5 days on a million August 2008, bypass see this opportunity occultation in case you get the prospect. As regards area 2 of your question the medical information won from the Appollo missions specially, and others, help the thought the Moon grew to become into cleaved out of the Earth in a colossal colision with a Mars sized planetisimal approximately 5 billion years in the past in the process the photograph voltaic platforms formation. workstation simulations at astronomical examine instruments tutor that this explains the scale of the Moon and its distance and orbit and geological composition which all in superb condition the information in superb condition very wisely. I actual have seen no longer something to point something different it incredibly is now an widespread thought defined in faculties. As for its shape, all great products alongside with plantets and frequently stars too, needless to say form right into a sphere in area by using their own inner gravitational attraction, till their rotation is quickly adequate to ditort the form into an oblate sphere. it is the case of the great gasoline planets Jupiter and Saturn as an occasion, or very great intense intense-rotation stars. Our own sunlight isn't very noticably flatter at its poles, even though it incredibly is - a litlle. some very uncommon ones interior the galaxy do resemble cigar shapes extremely than around so some very unusual eclipses could be seen there!. wish that solutions your question.

Answer 6

Technically speaking, the sun is not always a perfect fit. There are annular eclipses and total eclipses (along with partial and hybrids).

In an annular eclipse the moon is not quite as 'big' as the sun in angular size.

In a total ecplise the angular size of the moon is greater than that of the sun, and for long-lasting total eclipses (i.e. 5 minutes or greater) the moon is quite a bit greater in angular size.

.

Answer 7

Actually, it's NOT a perfect fit. The moon covers the bright photosphere of the sun (the part that we perceive as light) but allows the outer portions of the sun (the corona) to be visible. Thus, the corona must have a LARGER apparent diameter than the moon, while the photosphere has a SMALLER apparent diameter than the moon.

Answer 8

It is indeed by chance.You happen to live in a time period that the moon is at the right distance to the sun,relative to it's size,that it is almost the same size to our eyes as the sun.A billion years ago,the moon would have appeared much larger than our sun,a billion years from now,it will appear much smaller

Answer 9

Its just by chance. The moon is slowing moving away from earth so in time this perfect fit will no longer be. The moon used to be closer to Earth and it would have covered the sun.

Answer 10

Coincidence.