At what distance from earth is there zero gravity?

Question

And does zero gravity mean absolute zero no weight at all?

Answer 1

Einstein's principle of equivalence states that all locally intertial frames have zero gravity. This means that if you are in free-fall (for example at some amusement park rides) you are experiencing zero gravity and will have no weight at all (for a little while). Einstein wrote about a thought experiment with a freely-falling elevator.

In orbit, you can sustain a locally intertial frame indefinitely.

In all of these examples, the condition of strict freefall can apply only at a single point, and you'll see small tidal effects at small distances away from that point.

A different interpretation of your question is this: "Where is the space-time curvature due to gravity equal to zero?"
The answer to that question is probably "nowhere", although one could in principle rig up a hollow near-spherical spaceship with masses placed around the hull in such a way as to cancel out all space-time curvature over a small volume inside.

Answer 2

Points where there is zero gravity is where all of the force vectors are cancelled out. It like being pulled in opposite directions by two people with the same strength, such that you are not moving.

If you take into account just the earth alone, there is exactly one point where there is zero gravity, the exact centre of the earth. This is where the earth is pulling at you in all directions, but equally, so everything cancels out and there is zero gravity. Anywhere else, the earth will pull on you in the direction of the centre, so there is gravity.

However, when you start to take into account other celestial bodies, you can generate points outside of the earth with zero gravity. About five-sixths the way to the moon, the earth and the moon are pulling on you at the same force. (Earth is larger but farther away.) This would be a point of zero gravity.

Zero gravity necessarily means that that there is no weight, but the converse is not true. Weight is simply the amount of force that's pressing against another surface. In zero gravity, there's no force, thus no weight. However, you can be in a gravity field and have no weight by simply not pressing against anything. If you jump up, the time you are in the air is zero weight. Skydivers in freefall experience this as well.

The reason is looks like there is no gravity in a spaceship in orbit is because you are being pulled towards the earth, but the ship is being pulled at the same rate of acceleration. Hence there is no pushing on anything, and thus no weight, but there is gravity. This is replicated in NASA's "vomit comet", a plane that goes high in the sky then nose-dives as if in free-fall, giving it's passengers weightlessness for a short time.

Hope that helps.

Answer 3

Good question. We need to remember that gravity is the attraction of mass for other mass, so that when we're in a cave the mass of the rocks ABOVE us is pulling UP on us. So that even if we're closer to the center of mass of the earth, gravity will not go up much. If you are at the center of the earth, gravity is zero because all the mass around you is pulling "up" (every direction there is up!).

A few of other points concerning gravity:

If you are outside a spherical hollow "Death Star" its gravitational attraction is the same as if all its mass were concentrated at its center, but as soon as you go through the surface into the hollow interior, gravity is ZERO at all places inside the sphere.
If you are near a flat plate that stretches to infinity in all directions, its gravitational attraction is a constant and doesn't change with distance from the plate.
There are three things that cause gravity to be different between the poles of the earth and the equator. You got one of them - the fact that gravity increases as you get closer to the center of mass, because the earth is flattened at the poles. Another is the spin of the earth. The farther you are from the spin axis, the lower "gravity" is, because another force (centrifugal, or centripetal) caused by the spin pulls you in the opposite direction. If the earth were about 36,000 km in diameter with the same mass and length-of-day then the gravity at the equator would be zero. This is the altitude of geostationary orbits. The last is the fact that there is more material between you and the center of the earth when you are near the equator because of the flattening. Since there is more mass, gravity increases some. The net effect of these three factors is an increase in gravity near the poles. You'd never notice it, but its very important for space flight, since its much cheaper to launch near the equator than near the poles for most orbits.

Answer 4

Every bit of matter in the universe is under the effects of gravity. The further away you are from a planet weaker the pull, but it is never zero. Astronauts in an orbiting shuttle do not feel the effects of gravity because the centripetal force of the shuttle moving at very high speeds in a big circle exactly cancels the force of gravity. So yeah, if you could just float around in space you would have zero weight, no matter how close you were to a planet. If you think about it the only reason we "feel" gravity is that we are prevented from floating to the center of the earth, by the earth!

Answer 5

There's no definitive distance, but my guess is 100 km. This is where scientists mark the boundaries between our atmosphere and outer space. It's called the Karman line or the edge of space.

Weightlessness is not zero gravity. As other have ranted, there's no zero gravity. I'll quote an actual scientist who works for the US government for the explanation: "They (the astronauts) are going at such a speed that they fall from a straight line at the same rate as the earth beneath them curves, hence, they fall 'around' the earth. That is why they have no support force, and are weightless."

Answer 6

Theoretically, gravity exerts infinitely. That means that if I and the Earth were the only entities in the universe, and we started out 15 billion light--years apart,
then we would slowly connect and I would be "pulled back to earth", although that would take a long, long time.

But there are places in space where, depending on position, my attraction towards Earth would be balanced by the pull of the Sun, or of other planets ~en masse.

These are called LaGrange points. At those places, it is as if there is no gravity at all, and thus total weighlessness in any direction.

The most stable one is between Earth and Sol. Less stable is the point beyond Earth's orbit, between us and the Jupiter flock of planets.

Due to how infinite the Universe is, no LaGrange point can be permanently fixed for all time, because gravity constricts the Entire Cosmos, not merely two bodies that happen to be close enough to notice the gravitic attraction.

Answer 7

Gravity pervades the universe; there is no escaping it. However, the forces of gravity do vary depending on where the sources of gravity are located relative to the body it is acting on.

Zero gravity (aka, zero g) can be simulated by moving bodies with specially crafted trajectories or paths. An aircraft can fly just so; so that the effect is zero g acting on it (and everyone inside). A roller coaster going over the top can also effect zero g on its passengers. But in reality, gravity (mainly from the Earth) is still acting on these bodies in motion even though their motions have negated the effect of that gravity.

Answer 8

Gravity is considered to extend infinately, so theoretically there would never be zero gravity, however in real life when you get outside the solar system there would be little if any effect of gravity.

Answer 9

If you're overweight like Rosey O'Donnell or Kirstie Alley before five major liposuction there is no given distance for zero gravity. As a matter of fact your overbearing mass would have its own gravitational force. So, if you're looking to achieve " absolute zero no weight at all ", go see Jenny Craig.

Answer 10

There is no distance from the Earth that would result in zero gravity, as gravity is everywhere, in tiny particles of space dust, in a spaceship, even in us... all mass has gravity, albeit not much gravity in small amounts of mass, like a person or a teacup... so even in outer space, where the Earth has no pull on us, we would pull the ship to us and vice-versa, although not noticably... so wherever we are, there is gravity, hence my opinon that there is no distance that would result in ABSOLUTELY ZERO gravity... new view of your question, I hope. take care, -Rick