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Imagine this scenario - I'm in a space station with one of those huge torus shaped constructions, that you spin to simulate gravity through centripetal force. But it's turned off right now, so I'm floating in the air.

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When happens when they turn it on and it starts spinning? I can imagine what would happen if I was grabbing on to something. I'd be pulled around, and the angular velocity would drag me to the outer part of the torus. But if I'm just floating there, with no friction to the ground to catch me, do I stay put, with the thing just whizzing past me?

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    $\begingroup$ No. <-- answer to the title question. Yes <-- answer to the text question :-) $\endgroup$
    – Carl Witthoft
    Commented Feb 1, 2017 at 13:18
  • $\begingroup$ Yeah I could've been smarter about that Carl :) $\endgroup$
    – Hans Sjunnesson
    Commented Feb 1, 2017 at 13:32
  • $\begingroup$ In what way is that an astronomy question? $\endgroup$
    – chirlu
    Commented Feb 1, 2017 at 13:42
  • $\begingroup$ somewhat related in Space SE What happens if you jump on a “spin ship”? I suppose this question might be off-topic here in Astronomy SE but it is certainly on-topic there. If you are interested in more answers you could always propose that this question be closed and when that happens ask the mods to consider migration. $\endgroup$
    – uhoh
    Commented Jan 19, 2021 at 3:53

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Yes...

In the scenario you describe, you (and the air) will remain at rest, while the torus speeds up. One hopes there are no radial partitions, or, if there are, one comes along to pick you up fairly early in the session.

Unfortunately, the rotating torus will impart its velocity to the air in contact with all the irregularities in the wall/floor/ceiling. This would then be transferred to the rest of the air. Floating there, you would experience a very slight breeze blowing you in the direction of rotation of the station. This in turn would cause you to slowly drift radially outward, until you hit the floor and rolled along until you were at rest with respect to the floor.

Even if the station is not running up from zero rotation rate, you can experience some strange effects.

If the station is big enough, you can travel with low energy. Simply run against the rotation of the station. When you are running at the rotation speed, lift your feet, and drift in place until your destination comes along. Put down you feet, start running, and slow to a walk.

Be careful, though. If you face in the wrong direction and run at that same speed, your apparent weight will quadruple as you crash to the floor...

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  • $\begingroup$ So I guess getting safely into and out of an already spinning torus, would mean getting in at the hub of the torus, where, then floating "down" a ladder until you get heavy enough to climb down. $\endgroup$
    – Hans Sjunnesson
    Commented Feb 1, 2017 at 13:34
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    $\begingroup$ Yes, except going down the ladder you would find yourself being pressed sideways by the ladder; you're gaining tangential linear velocity as you go to a greater radius, and something has to give you that acceleration... $\endgroup$
    – DJohnM
    Commented Feb 1, 2017 at 19:25

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