Is gravity elastic....?

Question

For example, the gravity of the Earth "tethers" the moon and the gravity of the sun "tethers" the Earth. The root of my question is what keeps the moon from being pulled away from the Earth when it travels to the sun side of the Earth.

Is this what causes the elliptical orbit of the moon, and if so does this mean gravity has some sort of elasticity like a rubber band.

Answer 1

Gravity is not elastic. Note that a rubber band's pull actually _increases_ the farther it is stretched. In contrast, the pull of gravity _decreases_ as the two objects get farther away.

> what keeps the moon from being pulled away from the Earth when it travels to the sun side of the Earth[?]

That's an excellent question. In fact if you do the math, you will find that indeed the sun's pull on the moon is _greater_ than the earth's pull on the moon!

But this doesn't mean that the moon will get "sucked in" to the sun. Just as with all the planets, the moon's "sideways" momentum is enough to keep it from getting too close to the sun.

What it _does_ mean, though, is that if you track the path of the moon while it's between the earth & sun, you should find that the moon's path curves slightly sunward. And in fact, you DO find just that.

So why doesn't the moon "curve away" from the earth at that time? It's because the EARTH'S path is _also_ curving sunward at the same time; and in fact is curved more sharply than the moon's path. In essence, the earth "catches up" with the moon. The net effect is that the moon stays nearby the earth.

> Is this what causes the elliptical orbit of the moon[?]

No. If this were the case, you would expect the moon's orbit to be lined up somehow with the sun, so that the long axis of the moon's orbit would always "point to" the sun. But this is not the case. It turns out that when two "small" things (moon & earth) are orbiting a far-away "big" thing (sun), then the interaction between the two small things is almost as if the big thing weren't there.

Answer 2

Every month the moon does pass beyond the point where the Sun's gravity has more effect.
It is not ripped from orbit because momentum carries it back into orbit.
I once read somewhere that if the Moon were to disappear the loss of its mass in the Earth-Moon system would cause the Earth's orbit to expand out to somewhere between Mars and Jupiter.
The Moon's orbit is elliptical because all orbits are elliptical.
A circle is a very special case of an ellipse.
Tidal forces (gravity) will soon cause a perfectly circular orbit to degenerate to elliptical.
The Moon may have started with an elliptical orbit.
That such a complex system could be stable is an interesting artifact of the scale of this.

Answer 3

First, you have to realize that a body in orbit around another body is in a state of equilibrium between being pulled in and flying away from the object. Its speed is just fast enough that it avoids being pulled towards the object, but not fast enough to break orbit.

Gravity is not elastic. Its force is a function of the mass of the body and your distance away from that body. Although the sun is much more massive than the Earth, the moon is much more closer to Earth than the Sun.

The Earth's gravity field is stronger than the Sun's gravity field, so the Moon orbits the Earth rather than maintaining its own orbit around the Sun. The moon feels the same gravitational pull from the Sun that the Earth does (and the difference in distance when the moon is closer to/farther from the sun is negligible.

What keeps the moon from being "pulled" by the Sun is this: The Earth and moon experience the same gravitational pull from the Sun and are traveling at essentially the same speed around the sun as each other. But the Earth also exerts a stronger gravitational field on the moon causing the moon to orbit Earth while BOTH bodies orbit the Sun. The Sun IS pulling the moon towards it, just as it is pulling the Earth towards it, but the speed of both bodies keeps it in orbit AROUND the sun.

Answer 4

Simply put:
Gravity is a force, not an object.
It decreases as the square of the distance
over which it acts.
Even in that sense it is not elastic.
In an elastic the force would increase.

Answer 5

Not elastic but varies in strength inversely with distance. The further you go, the less the force.

Answer 6

no elasticity, but it decreases with the square of the distance.

It does not get pulled away significantly because of the proximity of the earth.

Answer 7

Do you mean like a bouncing ball? I don`t know the answer sorry.

Answer 8

no

Answer 9

NO