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Thread: Space

  1. #1 Space 
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    Can anyone tell how astronauts float in space, is we say space is a vacuum without any molecule resistance. If we are falling where are we falling?


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  3. #2  
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    When they are in space there is much less gravity than on Earth. There is essentially zero gravity, because when in space the austronauts are in orbit, which means they are traveling fast enough (17,000-18,000 mph) that Earth's gravity can't pull them down. While in orbit they are falling towards Earth, but because they are traveling so fast, by the time they get "pulled down" they have moved to a new place of curvature of the Earth, keeping them at the same altitude from the surface.

    Space is a vacuum but it isn't what causes the lack of gravity or the cause of the "falling".


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  4. #3 Re: Space 
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    Quote Originally Posted by Webb
    Can anyone tell how astronauts float in space, is we say space is a vacuum without any molecule resistance. If we are falling where are we falling?
    An astronaut in space still is experiencing gravity. The effect of that gravity is a freefall condition that is equivalent to what you experience in a freefal condition near the surface of the Earth, say on a roller coaster or if you just jump off of ledge of some height.

    The difference is that the astronaut has sufficient speed to remain in a stable orbit around the earth, a trajectory that does not intersect the Earth itself.

    In terms of general relativity, the astronaut is traveling along a geodesic path in space-time, and along that trajectory "feels" no influence from an outside force. This is the general relativistic equivalent of uniform linear motion in ordinary Newtonian mechanics (just as when traveling on a train in a straight line on smooth tracks you do not sense motion).
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