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# Stupid gravity questions. Any answers?

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posted on Apr, 22 2005 @ 12:27 PM
If you brought the earth and moon together so that the moon is resting on the earth. Would the moon still have gravity or would its own gravity give way to the earths gravity? IE if you were standing on the moon would you still be pulled towards it center or would the gravity shift so that you would now be pulled toward earths center. Or would someting else happen to the grav.

X

Would the answer to this change if instead you brought to exact earths together were they were resting upon each other.. were then would the center of gravity be or would both Earths still pull you toward there own centers?

posted on Apr, 22 2005 @ 12:57 PM
Interesting question.

I don't really know but i would guess that their gravity would combine so there would be one center of gravity which is inbetween (not exactly inbetween) the center of Earth and the center of the moon. As the Earth has stronger gravity then it will be nearer the Earths center.

If an identical Earth joined with our Earth then the center of gravity would be exactly inbetween, where they touched.

As i said i'm not really sure, just my guess, so anyone correct me if i am wrong

posted on Apr, 22 2005 @ 01:01 PM
The gravity force you feel from any object is proportional to its mass divided by its distance to you squared. You would still feel its gravity, but if you were standing on the edge of this "moon resting on earth" thought experiment, you would still go down (i.e. fall off the side of the moon).

posted on Apr, 22 2005 @ 03:06 PM

If you brought the earth and moon together so that the moon is resting on the earth. Would the moon still have gravity or would its own gravity give way to the earths gravity? IE if you were standing on the moon would you still be pulled towards it center or would the gravity shift so that you would now be pulled toward earths center. Or would someting else happen to the grav.

Think of taking two magnets, one about 6 times more powerful than the other. Put them next to each other. That's kind of what you are talking about here, except with planets and gravitation instead of magnets and magnetic fields. Both the earth and the moon would still have their gravitational fields, and neither field would change. If you were in close proximity to both the earth and moon, you would feel the gravitational pull from both. (the moons gravity does pull on you right now but since as utrex said, the gravity force decreases with the inverse of distance squared, and the moon is really far away, its gravity doesn't affect you in any meaningful way.) No matter what, you would always be pulled towards the center of the earth and the center of the moon. The distance between you and those two objects determines the magnitude of that force.

Would the answer to this change if instead you brought to exact earths together were they were resting upon each other.. were then would the center of gravity be or would both Earths still pull you toward there own centers?

Answer doesn't change, this is the same case as above except that you've just increased the mass of one body (i.e. you now have 2 earths instead of 1 earth & 1 moon)

If you can get ahold of a basic physics text, look up the section on forces and gravity; hopefully that will help.

posted on Apr, 22 2005 @ 03:28 PM
What might help here is the concept of the barycentre

From wikipedia (above)

"Earth and Moon orbit about their barycentre, or common centre of mass, which lies about 4700 km from Earth's centre (about 3/4 of the way to the surface). Since the barycentre is located below the Earth's surface, Earth's motion is more commonly described as a "wobble". When viewed from Earth's North pole, Earth and Moon rotate counter-clockwise about their axes; the Moon orbits Earth counter-clockwise and Earth orbits the Sun counter-clockwise." (My emphasis)

So, as the Moon approached the Earth, I suspect that the common centre of gravity would get even closer to that of the Earth's and, at the condition described, the two objects centre would be essentially the same.

Of course, way before that was to happen, the Roche limit would have been reached, and tidal forces would have- presumably - broken the Moon up (the debris colliding with the Earth as well??)

posted on Apr, 22 2005 @ 10:51 PM
I agree that the center of gravity would be between the two. And the moon would still have it's own gravity. Every mass has gravity. Your own body has gravity that pulls the Earth toward you.

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