I tried to find an answer to this one during the time of the 1999 eclipse, but nothing came of my enquiries. Time to try again through the Answer Bank.
The Moon is apparently receding from the Earth at approximately 2cm per year. This means that there must eventually come a time when the residents of the far-future Earth will sadly never again experience the fabulous sight of a total solar eclipse, as the Moon will no longer come close enough to exactly cover the sun's disc. Does anybody have any idea how long this will take?
Also, the occurrence of eclipses would appear to be quite rare, as it requires a very specific set of parameters to be in place - size of bodies, relative distances from each other, orbital concurrence, and of course the actual existence of a moon in the first place, etc.
Are there any other planets in the Solar System which can enjoy such magnificent sights, or is the Earth unique in this respect?
AndiFlatland Thurs 29/05/08 17:51
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This is sadly absolutely true, indeed some solar eclipses are already "sub total" or annular where the moon is too far away from the earth to produce a complete coverage of the sun's disk, the effect is a ring or "annulus" of sunlight around a black central disk.
However the last total eclipse is still many millions of years away, so we can still enjoy a marvel of nature for a while yet.
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Isn’t it a strange coincidence that the moon is just large enough to cover the sun almost exactly from our viewpoint?
Another is that it takes exactly a year for the earth to complete an orbit of the sun ... and a day for it to rotate once on its axis. Amazing!
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It's kinda similar to the way that legs are always the right length to reach from your waist to the ground, isn't it?
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Yeah and has anyone noticed how it always rains after a dry spell? What curious worls we live in.
Yes as Azalian says as the moon receded all eclipses that would otherwise have been total will be annular:
http://sci.esa.int/science-e-media/img/c0/Mvc- 680f-410.jpg
Still a few million years yet though.
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It really is a coincidence that the moon is 400 times smaller than the Sun and also 400 times closer to Earth. Unlike the other “coincidences” comically referred to, there is no reason why this should be so.
Indeed, as has been mentioned, this will not always be so in the future. The moon exerts a gravitational effect on the earth which produces “bulges” in its shape (which manifest themselves as the daily tides in the sea). As a result, some of the Earth's rotational momentum is gradually being transferred to the Moon's orbital momentum, and this causes the Moon to slowly recede from Earth. The rate of recession is currently about 3.8cm per year.
The reason some eclipses are not total at present has little to do with this relatively small movement. The moon’s distance from the earth varies as it follows an elliptical orbit and this variation is as great as 26,000 miles (42,000km). It is when the moon is at its farther distances in its monthly orbit that “annular” eclipses occur. It is estimated that the Moon will have to recede from the Earth by about 10,000km before total eclipses are no longer a possibility and at the present rate of recession this will take more than 250 million years.
For the same reason that the moon is receding from the Earth, the Earth’s rate of rotation is gradually slowing. In theory this will continue until the Earth’s “day” and the lunar month coincide. (This has already happened to the moon. It takes 28 days to orbit the Earth and 28 days to revolve on its axis, which is why we only see one side of the moon facing towards Earth). However, this process is continuing at such a small rate that the Sun is expected to die and engulf the inner planets before then.
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I think the real point is there are millions of other non-coincidences.
If we had a ring rather than Saturn we might remark how is it the we alone of all the planets have such a beautifull ring and seek to use it as proof of our special status.
The list is endless I'm sure you can come up with better ones than that
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weggie, if i can just pick up on something you mentioned. the Earth does take a year to orbit the sun, but the year is not ONLY 365 days. its roughly 365 and a quater days long. this being the reason we get a leap year every four years.
i find the leap year amazing. i just cant get my head around the extra 6 hours or so we get each year !!!!
in saying that, its a dream of mine to see a total solar eclipse. apparently you can see the darkness coming towards you if you are on high ground !!
:-)
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I saw a total eclipse on the south coast in the 1950s – I think it might have been 1954. I don’t remember a lot about it (I was only 7)!
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The amount of junk floating around our planet will surely lead us to having rings of our own in the far future.
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