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How can there be gravitational pull in space but no gravity?
Question Date: 2014-10-03
Answer 1:

Well, that depends on what you mean by "gravitational pull" and "gravity". "Gravity" and "gravitational pull" usually mean the same thing - they just refer to the force between two masses. And both of those definitely exist in space. I think what you mean is "weightlessness" - that is, that when people go into space, they float and have no weight.

So what causes things in space to be weightless? Well, let's ask a different question: what causes you to feel like you have weight? When you're standing (or sitting) on the surface of the Earth, the force of gravity is pulling you towards the center of the Earth. So why aren't you falling down? Well, it's because the ground you're standing on is also pushing back on you and holding you up. It's that upward push from the ground that you actually feel as your weight.

Now, what about when you're falling freely (say, while skydiving)? Well, with no ground below you to push up on you, you don't feel like you have any weight, so you feel like there's no gravity. There really is gravity, of course - that's what's making you fall - but you can't feel it. This is exactly what happens in space - you're always falling under the pull of gravity, but because there's no ground below you to hold you up, you feel weightless.

Answer 2:

There is gravity in space, it is just weaker because of the distance away. Objects with mass have a gravitational pull, even you and I do. The Earth has a large pull, so it can exert that on large objects farther away. But still, its individual gravity isn't very strong at long distances. In low earth orbit (LEO), like the international space station, gravity is still fairly strong, so why are astronauts weightless?

You would have to be deep in space to escape Earth's gravity fully. The reason has to do with being in orbit. Think of being inside a plane in freefall. You and your environment would be moving downward so rapidly it would appear that you were weightless click here to see.

The space station is falling in the same way. But, it is falling at an angle so that it continues to fall in circles around the Earth, if that makes sense, like the rock in this picture would click here.

It continues to "fall" around the Earth as it orbits, making the astronauts appear weightless.

Answer 3:

Gravity is force between two objects. Gravity, FG is defined as


Where m1 and m2 are the mass of the two objects attracting each other and r is the distance between the two objects; G is a constant that depends on the units specified for m1, m2, r, and F. What most people think of when they hear the word gravity is weight, which is a force preventing someone from accelerating towards the center of a mass.

In space one doesn’t feel the weight of gravity, because there is no surface, such as the surface of the earth push against them. It is the same effect as free fall.

Note: gravity falls off as 1/r2. Try plugging in different values for r in the equation and see how quickly it can change the force of gravity.

Answer 4:

Actually, there IS gravity in space -- there is gravity everywhere! Perhaps the question you would like to ask is why astronauts feel weightless in space.

Consider for instance that the gravity experienced at the altitude of the space station is 90% of the gravity experienced at the Earth's surface (so a person who weighs 100lb at the surface of the Earth and climbs a ladder to the altitude of the space station would weight 90lb). Trippy, right? So why do astronauts at the space station feel weightless? The weightless sensation that astronauts experience in space is a consequence of the fact that there are no objects in contact with their bodies to exert a push or pull ("contact forces"). In other words, the only force they experience is a "non-contact" force (gravity).

It is through contact forces that people perceive weight. When a person stands on the ground on earth, there is a downward force being exerted on him or her (the person's mass times the gravitational constant). The ground in turn exerts a "normal force" (upward on the person's feet) that balances the the downward force (if it didn't, the person would fall through the ground).

To clarify this idea, let's consider putting this person in an elevator. Now, the person is falling at the same rate as the Earth is, so the person has some inertia, which can be stated as the tendency of an object to continue moving in the same direction it is already moving. Thus, the person's inertia would prefer if the person remains stationary. In order to move the person up in the elevator, the elevator must exert more normal force on the person's feet than the person would feel on ground that isn't accelerating upward. Thus, the person's perceived weight is higher. If the elevator is accelerating downward, the normal force pushing on the person's feet is less than the person's weight on the ground (hence accelerating downward), so the person's perceived weight is less than their perceived weight on the ground.

So how does this relate to why astronauts feel weightless?
Astronauts in a space station that is orbiting Earth are accelerating ("falling") toward Earth at the same rate that the space station is (since space is a vacuum, the mass of the object does not affect its acceleration -- all objects accelerate at the same rate). Because of this, astronauts do not experience the contact forces necessary for them to perceive weight. I hope that helps!

Answer 5:

There is gravity in space.

If everything around you is subjected to the exact same gravity as everything else, then it will create the illusion that there is no gravity. So, standing on Earth, the ground underneath you is supported by the rocks underneath it, thus resisting the force of gravity, so you stand on the surface of the Earth, recognizing fully that gravity exists. In orbit, or even on amusement park rides where you are (briefly) falling, you and everything else orbiting/falling with you will seem weightless, because you are all orbiting/falling in the same direction at the same rate.

As I said, this is an illusion. The International Space Station experiences *most* of the same gravity that we do down at the surface, but since it is all orbiting/falling together, an astronaut on the space station will not notice that there is any gravity because there set of the space station experiences the same acceleration.

Answer 6:

So there is gravity in space, it is just very weak. Gravitational pull between 2 objects is proportional to how large the objects are. It is also proportional to how far the two objects are apart from each other. For a very large object like the Earth and a very small object like a ball that are close together, the gravity can be pretty strong. However, for a relatively small object such as a space craft that isn’t really close to any large object, the gravity isn’t that strong. As soon as the space craft gets near a planet or a moon though, the distance becomes small enough that gravity becomes significant and it is pulled towards the large body. Technically speaking, there is gravity in space, it just exerts such a small force that it doesn’t move anything and therefore seems like it doesn’t exist.

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