If the moon were destroyed

[GrahamT]

What would be the effect on the earth if, say,an asteriod hit and destroyed the moon?

[hopalong]

Its the moon that keeping the earth in an orbit so without the moon the earth would spin out of control and be destroyed

[hopalong]

http://curious.astro.cornell.edu/question.php?number=104

[CT]

I would suggest that your first post is inaccurate. The link in the second one, pretty accurate.

[RogerWilco]

We would need more street lamps

[RogerWilco]

BTW, I'm assuming the first answer (about the moon keeping the earth in orbit) was a joke

[bernardo]

If it were smashed into lots of little bits, then the bits would mostly coalesce again to re-form a Moon, and/or stay in the Moon's orbit as debris. Some chunks would fall to Earth, and cause widespread devastation and flooding etc.

[gamsy]

if moon is destroy then without it also the earth will remain stable and last for long as there are some planet without moon still existing on this universe. the effect of without moon will that there is totally dark in the night time.

[KebabMeister]

The link posted by hopalong mentions that the rotation of the Earth would increase and therefore causing a shorter day. If that's the case would we notice the increase in rotation and would that increase gravity?

[xrayspecs]

Gamsy... are you an alien??

[qapmoc]

The link does not say that the earth will rotate faster, what it does say is that the effect of the moon is slowing the earth down over time, this effect would stop and the earth would then not slow down but would remain at its present rotation speed for ever or at least for the time it takes ''deep thought'' to finish its program.
Another effect is that the seven barrier and other tidal power generations system would not work as there would be no more lunar tides, there would be a very small solar tide but this would be so small that it would be almost nothing at the beach.

[hopalong]

no roger it was not a joke but I now it's wrong

[KebabMeister]

qapmoc, we viewing the same link? Where does it say it will slow down?

In response to your question about not having a Moon, won't the Earth spin faster if there was no moon?

Lynn: Yes, this is true, thanks for bringing it up! The Earth's rotation is being slowed through tidal interactions with the Moon. If the Moon had never existed the Earth would be spinning much faster. In fact, our day would probably only be about 6 hours long! The fast rotation rate would lead to faster winds and stronger storms. The fast rotation speed would also have implications for plant photosynthesis, and animal hunting and sleeping cycles.

So, it doesn't mention if the Earth spun faster would that increase gravity a la centrifuge?

[Robert G]

The cow would have to find something else to jump over.

We wouldn't be able to sing "I see the moon, the moon sees me", "Moonlight becomes you", and countless other daft moon songs.

Or say "I'm over the moon".

We'd have to abandon plans to launch space missions from a moon base.

There'd be no more eclipes of the moon or of the sun.

[Gnisy]

We'd have no tides, which would affect beach areas in the world. No surfs. Pitch black at night. No werewolves. And I'd thought that the debris coming from the moon plus the impact from the 'impact' would have affected the earth as well.

[qapmoc]

OK, lets put this simply

Present situation - The moon is slowing the Earth's rotation speed down.

Situation if the moon vanished today - The Earth will rotate at its present speed forever (almost)

Situation if the moon had never existed - The Earth would be rotating much faster than it is now.

[MrPahoehoe]

I'm not entirely sure, but if the loss of the Moon had any effect on gravity it would be to decrease it....I think. Or rather, the effects of gravity would be reduced.

There are a couple of factors to consider. In the present system the Moon's gravity is added to that of the Earth and the Sun (& everything else although they are essentially negligable). So when the Moon is on one side of the Earth, people on that side would feel slightly less gravity (as the Moon's gravity is apposed to the Earth's gravity) and whilst people on the other side to the Moon would have increased gravity. As I cannot feel this difference throughout a Lunar month I'm prepared to guess that this an irrelevant change.

However, I also believe that the rotation of the speed of the Earth would increase, which would reduce the effect of the Earth's gravity. Centrifugal force will drive objects away from the centre and so its effect would be to lessen the acceleration under gravity. However, that only applies if you assume that the rotation speed of the Earth would increase, which I do: as the removal of the Moon's mass would reduce the drag on the Earth and "the conservation of momentum" dictates the rotation speed increases (i have tested this extensively on a spinning chair with my feet stuck out, then if you draw them in whilst spinning you will speed up;-) ).

For the same reason I think the years would also become shorter as the rotation around the Sun got faster.

There are other things to consider though as this would require the complete removal of the Moon, not just its destruction.