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Imagine that a person would be put inside a vacuum sphere, just like the spheres that NASA uses for simulating space's zero gravity. That person would be hovering right in the center of the sphere. Then, the sphere would be moved quickly few meters away, quickly like a car is accelerating. When a car is accelerating the passengers inside can feel a force holding them back. And about that force I am asking here, would it occur and move the person in a sphere?

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    $\begingroup$ There are no such spheres. You can build vacuum chambers to test in, but they have normal Earth gravity. Microgravity testing is done either in airplanes performing parabolic arcs, or using neutral buoyancy in a bit pool. $\endgroup$ Commented Jul 21, 2019 at 9:49
  • $\begingroup$ Thanks Emilio. I think I was thinking about vaccum chamber. $\endgroup$
    – Prolog
    Commented Jul 21, 2019 at 10:04

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a person would be put inside a vacuum sphere, just like the spheres that NASA uses for simulating space's zero gravity

There are no such devices.

Testing for both simultaneously, while conceivable (say, as in the Bremen drop tower), is expensive and (to my knowledge) not used in practice unless it's really needed.


When a car is accelerating the passengers inside can feel a force holding them back

... because the car itself is in mechanical contact with the passengers and it's pushing them forward.

If you take an astronaut and put them in a test vacuum chamber, then gravity will pull them to the floor so that they will be standing on it. If you move the vacuum chamber, then the floor would be in mechanical contact with the astronaut and push them in its direction of movement. (If the contact isn't great, then it's like you're pulling the rug from under a person, so they might trip and fall, or they might stay stationary if the movement is sudden enough and there isn't enough friction.


That person would be hovering right in the center of the sphere

... not without additional work, they won't. Still, it's conceivable that this person is in a vacuum suit and using a jetpack which is continuously expelling propellant to counteract Earth's gravity. In this case, there is no contact at all between that person and the vacuum chamber, and moving the vacuum chamber will not affect the person.

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  • $\begingroup$ Note: some of the limits on long-range "fifth forces" come from dropping objects in evacuated columns near reservoirs, where changing the level of the water in the reservoir behind the dam changes the test mass on a scale of kilometers. $\endgroup$
    – rob
    Commented Jul 21, 2019 at 15:10
  • $\begingroup$ Great answer Emilio. Thank you. $\endgroup$
    – Prolog
    Commented Jul 21, 2019 at 19:31

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