![]() ![]() ![]() There is always a gradient giving rise to tidal forces. But not precisley (though it is not easy toy measure if not impossible). In the ISS gravity is nearly zero at every point. It 's a bit different from the gravity you experience in far-from-mass gravity in outer space though. It is exactly the same zero gravity as you experience in a plane paraboling to Earth. Since the 'non-artificial' kind of zero-gravity as you state in your question doesn't exist anywhere, the concept of 'artificial' zero gravity isn't an especially useful one. This is the same differential force you feel when accelerating or turning in a car, and it's because this force isn't instantaneously applied evenly through the body that we can feel it. What you do feel, while on the surface of a planet, is the ground pushing against your feet, which push against your legs, which push against your torso, which pushes against your head and vestibular system and allows you to tell which way is up. Unless you're very close to a black hole, the pull of gravity is equal on all parts of your body, and so there's no differential force that allows you to feel anything. The day to day experience of 'gravity' - the feeling of standing on the surface of a planet - isn't really the work of gravity itself. Sure, there are places such as supervoids where the influence of gravity will be very little, but there's nowhere where it is absent entirely. Gravity has infinite range, so there is nowhere in the universe where you can be free from its influence. * For completeness, if something only slightly stops you from freely following gravity, or the local gravitational field is weak anyway but some object you're pressing against stops you from following it (eg on the moon), you'll feel this as low gravity or microgravity. If something stops you doing so, you won't (or will feel it much less). If you are freely moving as gravity dictates, you will experience the sensation we call "weightlessness" or "zero gravity". "artificial", apart from simulations like floating in a water tank or other simulators. So there isn't any such thing as "artificial zero gravity", or a distinction between some kind of zero G that's "real" vs. Identical behaviour, just on different scales. ![]() And the ISS is still following Earth's gravitational pull, it's going to remain in an elliptical orbit too, if you ignore energy loss from the trace atmosphere at that altitude. If it doesn't hit anything, it will follow a path that forms a (probably highly) elliptical orbit over hundreds of millions of years, since it won't lose energy and collide. Its nearest galactic cluster, or supercluster, a few dozen megaparsecs away, perhaps, but it's still falling fast towards it. You can see that because if you zoom out your focus a bit, the spaceship "far from any object" is in fact still falling towards some object, perhaps at very high speed. There aren't 2 kinds ("artificial" vs "real"). The weightlessness you feel in a spaceship far from any object, is exactly the same weightlessness you feel on board the ISS orbiting earth. There is never any actual true "zero gravity" in the universe.īut if you're in freefall - meaning following gravity's pull rather than resisting it, or being blocked from following it (by the floor, your nearby planet, spaceship walls as it thrusts, or whatever) - you don't feel it, and that's the thing we call "weightlessness" or (wrongly) "zero gravity". ![]()
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