What effect, immediate or long term, would the loss of our moon have on our planet?

Hi pathosman,

What a fascinating question. Being somewhat of an Astronomy buff (or
at least an Astronomy wanna-be-buff), I just had to answer it.

If the Earth suddenly found itself without a moon (you aren't planning
on blowing it up now, are you?), there would be some very immediate
and obvious changes and some changes that would occur over the
longterm.

For instance, probably the most immedate and noticable difference
would be that the Earth Tides, which while not disappearing entirely
(due to the force that the Sun would exert on the oceans) certainly
would experience a diminished amplitude.

Other changes would come from the lack of moon-light cast on the
planet. It certainly would be a much darker night than what we
currently have. Also, a lot of animals (nocturnal) survive based on
the light from the moon. It is possible that some nocturnal animals
couldn't adapt to the new no/low light nights and die as a result.
This decreased lack of biodiversity would manifest itself in many,
many other forms as well: mass extinctions, etc..

There are a few other more dire predicitons. For example, some
scientists argue tht the Moon acts as a "meteor shield". That if the
moon suddenly disappeared, all those massive craters on the moon would
have been all those massive craters on the earth. But, then, couldn't
you think of a place or two that just "deserves" to be flattened by a
meteor anyways?

Also, one of the serious issues in this whole question deals with the
axis, wobble, and orbit of the Earth itself. Some scientists predict
that the moon has a stabilizing effect on the Earths orbit. If
missing, Jupiters pull would cause the Earth to be less stable in it's
orbit, axis tilt and rotational speed. And, if that happened to too
great an extent, it could be either like an oven or a freezer on
Earth.

Now, luckily, the chances of the Moon suddenly vanishing is about as
likely as Dr. Evil actually making good on one of his threats, but,
just to be sure, you might want to start thinking about what part of
the world would just be better off being flattened by those killer
meteors!

I found a tongue-in-cheek look at this question called, "I plan to
destroy the moon. What effect would this have on the earth?". It's
where I got most of the information for this answer. Well worth a
read. Can be found at:
http://www.straightdope.com/columns/001027.html

Thanks for such a great question!

Legolas-ga

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Clarification of Answer by legolas-ga on 04 Dec 2002 20:07 PST

With appologies, I forgot my search terms:

moon disappeared earth
://www.google.com/search?sourceid=navclient&q=moon+disappeared+earth

loss moon effect earth
://www.google.com/search?sourceid=navclient&q=loss+moon+effect+earth

Thanks again!

I appreciate the research put into the answer.  I must admit I was
hoping someone would write a computer program to predict the answers,
but that's asking a lot for only 10 bucks.  Thanks.  When you're not
answering research questions, do you moonlight as an elf in the JRR
trilogies?

My physics teacher in high school told us that the moon, through its
effect on the water of the earth, is very slowly decreasing the speed
of rotation of the earth. In another few hundred million years or so,
the earth will rotate at the same speed that the moon orbits the
earth. Millions of years ago, a day lasted 22 hours. In the future,
this will continue to increase, though nobody alive today will know
the difference.

I wonder if we needed to go into the animal kingdom to observe changes
in the habits of living things.  Psycologically speaking, most people
go a little nuts when their car breaks down, so what effects on the
human population of this planet could we anticipate when our moon
expired.  Legolas mentioned the darkness - an in-born fear that many
of us deal with - but what effect would this have on the doomsayers of
the world, or the superstitious.  How would mom and dad explain the
loss of our satellite to their kids?  I suppose a lot of the reactions
would be mitigated by HOW the moon dissappeared.  If we had prior
knowledge of the event, what would are reaction be then?

Good answer, good comments. I think the risk of a big meteor hit would
only increase about 10% without the moon. I think most humans would
cope without a moon. We might even be a bit less looney. Pun intended.
Any mechanism I can think of for causing the non-existance of the moon
would impact Earth severly. The present arrangement is quite stable
and has a good chance of modifing only slightly over the next billion
years.   Neil

I think it'll take more than a few hundred million years for the Moon
to tidally lock the Earth so that the lunar period and the day are the
same length.  The day (and "month") will be almost 7 weeks long by
that time, and as funkywizard pointed out, the change over the last
few hundred million years has only been 2 hours.  Tidal forces are
proportional to the inverse cube of the distance, so as the Moon
spirals away, it is less able to slow the Earth's rotation.

As far as blocking meteors, the gravitational effect of the Moon on
them is probably quite hard to estimate (3-body problem), but as far
as physical shielding, the Moon blocks about 5 millionths of Earth's
view of space.  Obviously, the stuff that hit the Moon and made
craters didn't hit the Earth, but that doesn't mean the Earth didn't
take a beating.  The Earth has life, weather, and plate tectonics all
hard at work removing the evidence of big impacts.

Please note that Earth and Moon are very unlikely to have the same
periods, ever. Although it is true that the gravitational effects of
Moon is slowing down the rotation of Earth, the time it will take to
'lock' to each other is longer than it is needed for Sun to become a
Red Giant and destroy both Earth and Moon. This have been previously
discussed and related to Pluto-Charon in this topic as a comment: 
https://answers.google.com/answers/main?cmd=threadview&id=98625

regards.