In zero gravity, the vestibular system (which is responsible for feeling the balance) doesn't work since the fluids in it don't move properly in absent of significant gravitational force. Does it also mean that we can't feel dizzy when we are spinning around (either vertically or horizontally)?

Motion sickness also based on that the vestibular system signs that we are moving but we can't see it - which definitely occurs in space, where Earth and its horizon move slowly because of its size and the distance. It may mean that if we are in space and the vestibular system works, then those who are sensitive to it, they should be sick all time - or, in my theory, at least they should feel themselves like on a ship. Fix me if it's false.

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    $\begingroup$ Note the question "Do the majority of astronauts experience space sickness while adapting to micro-gravitational conditions?" space.stackexchange.com/questions/1189/… $\endgroup$
    – horsh
    Aug 13 '13 at 17:04
  • $\begingroup$ @horsh Feel free to mark it as duplicate if you think it is =) $\endgroup$ Aug 13 '13 at 18:40
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    $\begingroup$ I've voted to close this question as the duplicate of the one suggested by @horsh. I'm of opinion that your question is better written, and it did receive one nice answer so far, so having a duplicate, even when it's closed, does serve a purpose (searchability, references, more answers,...). My vote to close is in no way a critique of your question or its answers, it was merely asked later than the nearly identical one. $\endgroup$
    – TildalWave
    Aug 13 '13 at 20:33
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    $\begingroup$ @TildalWave In fact, there's not even so much things to discuss that yet wasn't in the question of horsh. My mistake because I didn't look for similar questions; I thought that with less than 400 questions, it likely wasn't asked yet. $\endgroup$ Aug 13 '13 at 20:39

To answer your question, Yes, almost everyone has motion sickness in zero gravity.

Your question has bits that are correct.

Humans rely on the vestibular system for balance and attitude, and with the lack of gravity the fluids don't move correctly. But they do still move, because inertia doesn't go away.

So if you turn your head the fluid will try to remain stationary, same as on earth. The problem is that there is no longer any 'down' so aspects of the vestibular system and eyesight that rely on correctly orienting with respect to gravity fail.

Additionally, being far away from a fixed location means the brain has trouble positioning itself.

For most astronauts (and similarly for fighter pilots) you can become accustomed to it.


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