Moon Colliding With Earth

Is it possible that an impact of an object into the moon could change its trajectory just enough to send it on a collision course with earth?

How fragile is the moons orbit?

As fragile as any orbit. An orbit is the speed at wich centripetal force equals gravity. So it doesnt fly away, and doesnt fly down. (you could have something orbit earth at 1 meter height it would just have to be pretty darn fast (And some folks keeping the way clear))

In fact the moon is a little bit too fast for it's orbit, it is spiraling away from us.

So you would have to slow it down. The energy you need to do that is funny enough mainly depending on the mass, and the moon is a pretty big mass.

How much force would be needed to engage a revolution from the moon?

How hard would an object have to collide with the moon in order for the moon to start revolving?

If possible how would this change its orbital pattern?

To actually do the math i would have to look stuff up.
And i know there are people on here who would not have to

Also: the moon does rotate. You only see one side because it rotates at the right speed to always turn the same side towards earth. I actually don't think rotation matters.

Ok: here is how you would calculate it:
Calculate the speed required to orbit earth at the distance of the moon (don't recall that formula, something M1+M2/r^2 but that has been a while)

Find the speed the moon is actually orbiting at.

Find the minimun delta V to push the moon below that required speed. (Vm-Vr)

F=M*V
There is the force you need to do it

I would imagine they could use multiple wave/beam technology to create a bedding to stop the moons orbit from decending then perhaps build a ship or satallites to tow or push the moon using gravity wave projections.

bam from the spice weasel

Originally posted by debunky
To actually do the math i would have to look stuff up.
And i know there are people on here who would not have to

Also: the moon does rotate. You only see one side because it rotates at the right speed to always turn the same side towards earth. I actually don't think rotation matters.

Ok: here is how you would calculate it:
Calculate the speed required to orbit earth at the distance of the moon (don't recall that formula, something M1+M2/r^2 but that has been a while)

Find the speed the moon is actually orbiting at.

Find the minimun delta V to push the moon below that required speed. (Vm-Vr)

F=M*V
There is the force you need to do it

Thats odd, I always thought the law of inertia was causing the moon to rotate with each revolution, like spinning yourself holding a bucket full of water.
How is it possible that the moon just happens to rotate at the same rate that it revolves?
And it just so happens that the visual diameter of the moon from the earth is exactly equal to the visual diameter of the sun from the earth. Ie: Lunar and Solar eclipses.

How come there are craters all over the moon, and not the earth?

The moon may block some impacts, but what about objects with a polar trajectory? ie: an asteroid hits the north pole, never coming close to the moon, as the moon, revolves horizontally, and a pole impact would be a verticle impact?

Originally posted by raj9721
Is it possible that an impact of an object into the moon could change its trajectory just enough to send it on a collision course with earth?

How fragile is the moons orbit?

The orbit of the moon is actually getting larger.

Sure it's possible that a MASSIVE impact could change the orbit of the moon but any object large enough to change that orbit would also most likely wipe out all life on earth anyway.

The moon has taken many impacts in the past, thus the craters so I wouldn't worry too much.

Consider this analogy:
Try playing pool (billiards) by rolling a bb pellet at the pool balls.

Originally posted by jfj123

Originally posted by raj9721
Is it possible that an impact of an object into the moon could change its trajectory just enough to send it on a collision course with earth?

How fragile is the moons orbit?

The orbit of the moon is actually getting larger.

Sure it's possible that a MASSIVE impact could change the orbit of the moon but any object large enough to change that orbit would also most likely wipe out all life on earth anyway.

The moon has taken many impacts in the past, thus the craters so I wouldn't worry too much.

Consider this analogy:
Try playing pool (billiards) by rolling a bb pellet at the pool balls.

Could there by a magnetic repulsion between the earth and the moon? and could the moon be attracting potential impacts through gravity and magnetism?

What about the moons core?

PS: The moon takes 27 days to revolve and.... you guessed it, 27 days to rotate as well.

Originally posted by raj9721


Could there by a magnetic repulsion between the earth and the moon? and could the moon be attracting potential impacts through gravity and magnetism?

What about the moons core?

PS: The moon takes 27 days to revolve and.... you guessed it, 27 days to rotate as well.

There is no magnetic repulsion between Earth and Luna. It doesn't attract impacts either. Most the craters you see are really, really, really old. As the moon has no atmosphere there is nothing to prevent asteroids from hitting it's surface- nor is there anything to erode evidence of previous impacts.

Earth is JUST as cratered as the moon is when it comes to larger impact craters, but natural growth and weather erosion hides it much better.

In short: The moon is not shielding us from all impacts, we're both being hit about equally. It is actually the atmosphere of Earth that makes the difference.


Yes the moon does rotate, but it's rotation is the same as it's orbit so the same face is nearly constant towards us. However that doesn't mean the face we see can not be impacted. Asteroids can come in from our end too, skip the atmosphere or swing in close...then impact the surface we see. Simple as such, no magic.

How to force the moon into a collision with Earth: when it is exactly at that point along its orbit when it is travelling perpendicular to the line of Earth's own orbit round the sun, hit it head on with something large, travelling very, very fast.

This will reduce the moon's orbital velocity. Hit hard enough, with a big enough hammer, and the moon will lose so much orbital velocity it will begin spiralling in towards Earth. Eventually the two will collide.

Easy peasy.

Originally posted by raj9721
How is it possible that the moon just happens to rotate at the same rate that it revolves?

Because it is "tidally locked", which is not at all unusual for a moon to be tidally locked -- in fact the orbits of most major moons behave in the same way our moon does. The two moons of Mars are tidally locked to their planet. Jupiter has 8 moons that orbit like that. Saturn has 15 moons that are in tidal lock.

There are over 30 moons in our solar system that act this way, and they are about 25 more that scientists THINK act that way. It's possible for whole planets to be locked to their stars. The planet Gliese 581C may only put one face towrds its star at all times.

And it just so happens that the visual diameter of the moon from the earth is exactly equal to the visual diameter of the sun from the earth. Ie: Lunar and Solar eclipses.

It is now. Several short million years ago it was closer (thus bigger) and in several million years it will be further away (thus smaller).

How come there are craters all over the moon, and not the earth?

Two reasons:
1. As you said, the Moon has served to "block" many meteors/asteroids from hitting the Earth, and (more importantly)

2. The Earth HAS been struck countless times by meteors and asteroids -- more that the Moon has been struck, but the since the Earth's geology and weather makes it a very active planet, most of the craters have been "erased" over the past 4 Billion years, either through geology (volcanoes and plate tectonics) or erosion due to weathering.

There are craters on the moon 50 times older than the dinosaurs. The Moon is not geologically active nor has any practical weather to speak of. Craters don't get erased on the Moon like they do on Earth.



[edit on 6/6/2009 by Soylent Green Is People]

reply to post by raj9721

PS: The moon takes 27 days to revolve and.... you guessed it, 27 days to rotate as well.

Yea, that's why we have a 'dark side' on the Moon.

Originally posted by raj9721
Could there by a magnetic repulsion between the earth and the moon? and could the moon be attracting potential impacts through gravity and magnetism?

What about the moons core?

PS: The moon takes 27 days to revolve and.... you guessed it, 27 days to rotate as well.

The fact that the Moon's orbital period and its period of revolution is equal is not due to magnetics.

As I said in my post above, it's due to gravity and orbital mechanics, which results in "tidal locking". There are at least 30 other moons in the solar system whose orbital period matches its period of revolution -- and all of these moons are that way because of gravity + orbital mechanics, not magnetism.


[edit on 6/7/2009 by Soylent Green Is People]

reply to post by jkrog08

Yea, that's why we have a 'dark side' on the Moon.

Sorry, jk....I just can't let that one get through.

These members are asking legitimate questions, and want factual information.

Once and for all...There is no "dark side" of the Moon!

It cannot be said any more plainly. Or, it could be said that every side of the Moon has a 'dark' time, just as we do here on Earth.

Think about it....imagine, for a moment, you can place yourself at the Sun. Now, move 'up', perpendicular to the plane of the planets' orbits (well, let's just focus on Earth's, because some planets have different planes of orbit). Look down on the imagined Earth/Moon system as the whole shebang orbits the Sun. See it now?

The Moon has a day/night cycle...except each cycle of light and dark lasts about two weeks.

This is why we, from here, look up and announce a 'new Moon', and see the phases progress to 'full Moon', and then wane back to 'new'.

EDIT to add text from Wikipedia:
"The Moon makes a complete orbit around the Earth with respect to the fixed stars about once every 27.3 days[6] (its sidereal period). However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show its same phase to Earth, which is about 29.5 days[7] (its synodic period).[8] Unlike most satellites of other planets, the Moon orbits near the ecliptic and not the Earth's equatorial plane."



[edit on 6/7/0909 by weedwhacker]