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"Earth loses angular momentum because the high tide closest to the Moon is trying to get back directly underneath the Moon, while the high tide farthest from the Moon is trying to get as far away from the Moon as possible. Consequently, the high tides flow westward, and in so doing, they encounter continents and islands. The water pushes against these land masses, which, because of rotation, are moving eastward. The net result is that the eastward rotation is retarded by the westward motion of the tides -- slowing down the rotation. The day is getting longer by about 0.002 seconds per century. It doesn't sound like much, but over billions of years it adds up.

If Earth is slowing down, it must have been rotating more rapidly in the past. By counting the growth rings in 400-million-year-old coral fossils and in 3-billion-year-old stromatolites, geologists calculate that Earth was rotating four times faster when it formed than it is today. The tidal effects of the Moon and, to a much lesser degree, the Sun have lengthened the day from six hours to 24 hours.

We can also work backwards in time for the Moon. Since the Moon is moving away, it must once have been closer. The closest the Moon could have been was about 7,300 miles above Earth's surface, 1/20th its present distance -- any closer, and the tides created on it by Earth would have ripped the Moon apart, turning it into a ring. This limit on the Moon's distance is consistent with the theory of how our satellite formed.

The Moon did not form with Earth. The chemistry of the Moon's rocks and other evidence indicate that the Moon was once part of Earth."

http://www.astrosociety.org/education/publications/tnl/33/33.html

Imagine a full moon 20 times its present size looming in the night sky. The atlantean tides produced by the moon of ancient times must have been staggering and awesome.

How protected is the moon from cosmic impacts, such as comets and asteroids.. does this affect our abilities and decisions to place permanent human bases on the moon?

"Humans could be living on the Moon within 20 years, says a leading lunar scientist. According to Bernard Foing of the European Space Agency, the technology will soon exist to set up an outpost for visiting astronauts.. However, political will is needed to inspire the public to support the initiative." ..and...

"However, under current policy, the UK would not be included in any manned mission because it does not support human space exploration." Wonder why.

http://news.bbc.co.uk/2/hi/science/nature/3161695.stm

Sincerely,


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Quote:
Originally posted by Mung:
"However, under current policy, the UK would not be included in any manned mission because it does not support human space exploration."

Wonder why.
Very interesting post Mung, I also wonder why, perhaps Mike Kremer knows.

Mike, can you help us?

Other UK'ers?

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Nice non sequitur there, Mung.


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Quote:
he closest the Moon could have been was about 7,300 miles above Earth's surface, 1/20th its present distance
Tides are a quadrupole distortion of gravitation. A sphere of liquid orbiting in a divergent gravitational field will be periodically distorted so that it elongates in the radial direction and pinches its waist in the tangential direction. This is how you get an ocean high tide on the opposite side of the Earth to the moon and why there is an offset between complete full moon and maximum high tide.

Free tides are typically (+/-) a few feet of water. The stiffer rock also slightly distorts. The interior of the Earth and Moon are heated by the tides in their bodies, just as a paper clip is heated by constant bending.

Now bring the moon in by a factor of 20 and 1/r^2 by a factor of 400.

http://csep10.phys.utk.edu/astr161/lect/moon/tidal.html
http://www.cartage.org.lb/en/themes/sciences/astronomy/Solarsystem/TheSolarsystem/theearth\'smoon/TidesandGravitationalLocking/TidesandGravitationalLocking.htm

The land will be moving up and down by feet! HUGE ocean tides! Massive energy dissipation leading to serious internal heating, vulcanism, and earthquakes. Somebody call an Enviro-whiner.

Quote:
How protected is the moon from cosmic impacts, such as comets and asteroids.. does this affect our abilities and decisions to place permanent human bases on the moon?
How protected is the EArth from cosmic impacts, such as comets and asteroids? Does this affect our abilities and decisions to place permanent human bases on the Earth? Barringer crater, boys...


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Mung finds moon stuff.

"Earth loses angular momentum because the high tide closest to the Moon is trying to get back directly underneath the Moon, while the high tide farthest from the Moon is trying to get as far away from the Moon as possible. Consequently, the high tides flow westward, and in so doing, they encounter continents and islands. The water pushes against these land masses, which, because of rotation, are moving eastward. The net result is that the eastward rotation is retarded by the westward motion of the tides -- slowing down the rotation. The day is getting longer by about 0.002 seconds per century. It doesn't sound like much, but over billions of years it adds up.?

?If Earth is slowing down, it must have been rotating more rapidly in the past. By counting the growth rings in 400-million-year-old coral fossils and in 3-billion-year-old stromatolites, geologists calculate that Earth was rotating four times faster when it formed than it is today. The tidal effects of the Moon and, to a much lesser degree, the Sun have lengthened the day from six hours to 24 hours.?

JW: Nice stuff. Currently they measure our day at 23 hours 56 minutes. That translates to 86,160 seconds a day. Assuming accurate measures in the past we had a popular time schedule of 86,400 seconds in a day which could have been more symbolic than precise AND intended to equate to a Sun diameter size of 864,000 miles. Forgetting that speculation and looking at the numbers Mung offers we can look backwards as if there really was 86,400 seconds in a day and try to work out when that was. We have a difference of 240 seconds. We lost .002 seconds per century they tell us. Is this 240/.002 or 120,000 centuries times 100 for 12,000,000 years? If so it means that there were number cognizant observers at least that long ago and our historical conclusions need attention. Else, it simply means we generalize too much and fit some things in by desire rather than my careful attention to detail.

Either way I like the way they worked out those numbers. Thank you Mung.
jjw

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ERROR:

"in by desire rather than my careful attention to detail." Not "my" I meant "by". sorry.
jw

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Quote:
Originally posted by Garry Denke:
Quote:
Originally posted by Mung:
"However, under current policy, the UK would not be included in any manned mission because it does not support human space exploration."

Wonder why.
Very interesting post Mung, I also wonder why, perhaps Mike Kremer knows. Other UK'ers?
Must admit this is the first I have heard of it.
Hopefully since the UK is a member of the European Space agency, things might change. Thats not to say a UK astronaught HAS to land on the Moon.
Any EuroSpace Agency's visit to the moon can only be a combined effort of the European Countrys. Only USA and probably China can go it alone.

Incidentally, if I rem correctly (It was discussed in this Forum 5 or 6 years ago) Our Earth has TWO Moons. Our other one is about 5 miles in diam: and although it has a complicated orbit, it is a true Moon, its called CRUITHNE.

With regard as to where our Moon came from, I am afraid I still prefer to believe that our Moon broke off from our Earth. Inspite of the concensus of opinion being that our Earth was struck by an unknown body in the distant past.
My personal reasons are:-
An object striking the Earth such a hard slam, would most probably produced Moonlets, or small bodies, in orbit. Where are they? Prehaps they are the moon craters and our many Earth craters. But it seems every moon including our Planets have craters. No help there.
With the Earth being given such a hearty wack.....would'nt that either slow down our rotation or even tend to speed it up?
I find it beyond comprehension that the wack the Earth got, did not upset the spin of the earth.
Yet we spin in just the SAME orientation as the rest of the Planets (or most of them anyway).
Plus, as you pointed out Mung, our Moon does have the same composition of rocks as our Earth. (Unlike Mars, its BECAUSE its composition IS so different that when we find small rocks in the Antartic, we can state they are from Mars, because they ARE different)

And why is there NO magnetic field on the Moon?
I prefer to believe that the early Earth had TWO large bulges on the equator, one was Pangea or Gwondanaland, a SINGLE large land mass from whence all the present Continents separated and formed, (still going on today)
While the other even LARGER mass opposite Pangea, was gradually thrown into the position the Moon occupies now, by the centrifugal force, of the faster spinning and hotter Earth, of that time.
That the Moon might have pulled (toffee like) out from -the huge Pacific deep basin, where indeed the crust IS a lot thinner than elsewhere.
Note that, our present continents have been drifting (roughly speaking) to fill up this deep Pacific basin, ever since. i.e America is drifting further westward away from Europe. And Asia drifting eastward.
It accounts for the fact that there is little or no iron on the Moon, and therefore no magnetic field. A land bulge centifuging away from our Earth would eventually break away, to certainly leave our heavier metal core behind. As well as constraining this new moon body to continue to rotate around us, KEEPING the same face to us , as today (being part of us, it kept our rotational speed) ....as well as receeding (faster then, much slower today)
Well thats my story, out of date and not accepted today, since as I stated above, the concensus is we were hit a heavy glancing blow. But ideas like fashion, can change. Someone might produce a computer prog, to back up this theoretical idea?

In addition the moon did once have water. I prefer to believe that some water would be the first to be centrifuged away from the Earth. Only to be attracted back slowly in the form of a thick cloud of water vapour which blocked out the Sun, back onto a much colder Earth (as a result) It might have even accounted for the Biblical account of the huge amount of extra water and flooding. That must have occurred over a long period of time, (as the Moon is not large enough to keep its water), it could well have had a vapour cloud around it, which bled off Earthwise over the millennia.
Oh well, its my pet belief, all supposition, no proof, but there is no proof as to this mysterious body that slammed into our Earth either....and went on its way, to where? smile


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"You will never find a real Human being - Even in a mirror." ....Mike Kremer.


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Thanks Mike:
I had never heard of Earth?s second ?moon?. I checked it out and note the powers that be say it is an asteroid that is not bound to the Earth but is simply in resonance with us.

Our real moon may have been pulled out of the Earth but I could never accept that view for myself. Assuming the Moon is made up of the same stuff as the Earth (all the way through) that is not all that convincing because the planets substance appears to segregate in rings as it form into planetoids and that is probably why Mars is somewhat different from Earth. If the Moon formed in a ringlet about 500,000 miles from the earth it would most logically have formed of stuff similar to that of which the Earth formed. This would be due to some force that segregated the stuff for each planets location resulting in some of the differences we find. When I think of an impact on the Earth, or some heavy object causing the Earth expel a large portion of itself, I lose attention for the concept quite quickly. Why would only a portion be expelled? If the draw was that strong why would not the entire Earth merge with the large object? The same seems logical for an impact that dispersed many parts of Earth into space, we are talking LARGE here, and why would some go and most stay?

I know I would be in the small minority with this view. It is nice to see that others enjoy these kinds of speculations.
jjw


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