Will the Moon Crash Into Earth?

soup wrote:
wrote:

( when the Sun was in the Lion hence the Sphinx symbol made by the
Antediluvian meaning that anticipation of that event )

WTF?

He means he doesn't know!

On 9 Feb 2007 01:43:09 -0800, wrote:

On 9 fév, 03:47, wrote:
I asked a science prof if the moon will eventually move away or into
the earth.

He said neither, it will remain revolving the earth for eternity.

I'm told the moon moves further away from the Earth by 2 inches per
year, apparently due to the loss of energy due to the tides on Earth.

However, wouldn't it take an energy GAIN in order to move a body
further away? Ideas?

Stan

On Sat, 10 Feb 2007 17:45:16 GMT, wrote:


On 9 Feb 2007 01:43:09 -0800, wrote:

On 9 fév, 03:47, wrote:
I asked a science prof if the moon will eventually move away or into
the earth.

He said neither, it will remain revolving the earth for eternity.

I'm told the moon moves further away from the Earth by 2 inches per
year, apparently due to the loss of energy due to the tides on Earth.

However, wouldn't it take an energy GAIN in order to move a body
further away? Ideas?

The Moon is gaining part of the energy that the Earth loses.

Bud
--
The night is just the shadow of the Earth.

wrote in message
...
On 9 Feb 2007 01:43:09 -0800, wrote:
On 9 fév, 03:47, wrote:

I asked a science prof if the moon will eventually move away or into
the earth.

He said neither, it will remain revolving the earth for eternity.

I'm told the moon moves further away from the Earth by 2 inches per
year, apparently due to the loss of energy due to the tides on Earth.

However, wouldn't it take an energy GAIN in order to move a body
further away? Ideas?

Yes, as the radius increases, the kinetic energy actually
decreases but the gravitational potential energy increases
at twice the rate. The energy comes from the spin of the
Earth so the day gets slightly longer.

The answer to the original question is that the Moon
is slowly moving away but the Earth's rotation will
slow until it becomes tidally locked at which point
the Moon's orbit would cease to increase. However,
the Sun will swell into a giant before that happens.

George

Thanks George. If we could figure out how much energy was in the
Earth's spin, then would it be possible to figure out hypthetically
how much further away the moon could go? Assuming circular orbit, no
effects of other bodies, etc.

Would I be wrong to say that the Earth would only slow down to the
point that it equals the moon's period around us?

Stan

On Sat, 10 Feb 2007 20:58:25 -0000, "George Dishman"
wrote:


wrote in message
.. .
On 9 Feb 2007 01:43:09 -0800, wrote:
On 9 fév, 03:47, wrote:
I'm told the moon moves further away from the Earth by 2 inches per
year, apparently due to the loss of energy due to the tides on Earth.

However, wouldn't it take an energy GAIN in order to move a body
further away? Ideas?

Yes, as the radius increases, the kinetic energy actually
decreases but the gravitational potential energy increases
at twice the rate. The energy comes from the spin of the
Earth so the day gets slightly longer.

wrote in message
...
On Sat, 10 Feb 2007 20:58:25 -0000, "George Dishman"
wrote:
wrote in message
. ..
On 9 Feb 2007 01:43:09 -0800, wrote:
On 9 fév, 03:47, wrote:
I'm told the moon moves further away from the Earth by 2 inches per
year, apparently due to the loss of energy due to the tides on Earth.

However, wouldn't it take an energy GAIN in order to move a body
further away? Ideas?

Yes, as the radius increases, the kinetic energy actually
decreases but the gravitational potential energy increases
at twice the rate. The energy comes from the spin of the
Earth so the day gets slightly longer.

The answer to the original question is that the Moon
is slowly moving away but the Earth's rotation will
slow until it becomes tidally locked at which point
the Moon's orbit would cease to increase. ...

Thanks George. If we could figure out how much energy was in the
Earth's spin, then would it be possible to figure out hypthetically
how much further away the moon could go? Assuming circular orbit, no
effects of other bodies, etc.

Roughly, yes.

Would I be wrong to say that the Earth would only slow down to the
point that it equals the moon's period around us?

Yes, that's what I meant by "tidally locked" in the second
paragraph (restored above).

There are three components to the total angular momentum of
the system, that of the Earth due to its spin, that of the
Moon around the Earth (by far the largest) and a small
contribution from the Moon which is rotating once a month
as it is already locked to the Earth.

Angular momentum is conserved and the final orbital period
can be determined by finding value when both bodies are
locked to each other. Once you know the period, the radius
follows and hence energy.

George

On Feb 9, 1:43 am, wrote:
It has already happened 3 times and all Orogenesis are consecutive toMooncrashon thisEarth!
( Caledonian, Hercynian & Alpine orogenesis 120 centuries ago )

LOL The moon maybe round, but a giant beach ball .. only three bounces
to date?
Only 12000 years ago too!

The Roche Limit. The closest distance at which a natural satellite can orbit
a planet without being broken up by the planet's gravitational field, i.e.
tidal forces. Look it up on Google.

"Ian Smith" wrote in message
...
The Roche Limit. The closest distance at which a natural satellite can
orbit a planet without being broken up by the planet's gravitational
field, i.e. tidal forces. Look it up on Google.


Nothing to do with it.

The moon is moving further away from the earth, as the earth transfers
angular momentum (and energy) to the moon via tidal forces. The earth-moon
distance increases, as does the length of a day.

Its pretyy easy to work out exactly where it will end up - the final
position is where the earth and moon keep the same face to each other (ie
where a day equals a month). This is easy to calculate through conservation
of angular momentum, this allows the final distance from the earth to the
moon to be calculated, though working out how long it takes is way harder.

"Peter Webb" wrote in message u...

"Ian Smith" wrote in message
...
The Roche Limit. The closest distance at which a natural satellite can
orbit a planet without being broken up by the planet's gravitational
field, i.e. tidal forces. Look it up on Google.


Nothing to do with it.

The moon is moving further away from the earth, as the earth transfers
angular momentum (and energy) to the moon via tidal forces. The earth-moon
distance increases, as does the length of a day.

Its pretyy easy to work out exactly where it will end up - the final
position is where the earth and moon keep the same face to each other (ie
where a day equals a month). This is easy to calculate through conservation
of angular momentum, this allows the final distance from the earth to the
moon to be calculated, though working out how long it takes is way harder.


It's pretty easy to guess where it will end up, and your guess isn't
a good one.
http://antwrp.gsfc.nasa.gov/apod/ap051113.html
This is easy to calculate through conservation of angular momentum,
this allows the final distance from the earth to the moon to be
calculated, though working out the eccentricity of the orbit is
beyond your guess.