Suppose engineers built a large circular room in a rotating space station where if one looked directly up from any location, one could see the floor.

If one used a ladder to reach the center of the room, could they balance an object in the center of the room's rotation, such that the object floated unsupported? Would it be easy to place the object there or quite difficult?


1 Answer 1


Assuming the whole space station was moving inertially, whatever gravity field it is in is essentially flat (tidal effects insignificant), you let the object go exactly on the axis of rotation of the space station, and you released it with 0 apparent speed as you observe it inside the room, then yes, the object would would float in place once released.

If the object is small and released not only on the space station's axis of rotation but also its center of gravity, then even tidal effects cancel out.

  • $\begingroup$ As an add-up, it's just the same as if you released the object into the center of Earth, or Sun or whatever ;-) $\endgroup$ Mar 31, 2013 at 15:33
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    $\begingroup$ @Crazy: With one big difference which is that the gravity of the earth or sun would be significant, whereas the gravity of the space station itself would be considered insignificant. That's why you could release the small object anwhere on its axis of rotation, but with massive objects (like a planet), it would have to be additionally released at the center of mass for it to appear to float. $\endgroup$ Apr 1, 2013 at 23:03
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    $\begingroup$ Would it be rather easy for someone to place the object there or would it be rather challenging and likely fall in one direction if not placed precisely in the correct spot? $\endgroup$
    – Village
    Apr 10, 2013 at 12:20
  • $\begingroup$ @Village it could be challenging to get the exact center, but it wouldn't drift off very quickly if you missed. It would make small orbits around the center if it weren't centered. If these small orbits made significant air drag, it would drift off farther and faster. $\endgroup$
    – EL_DON
    Aug 19, 2016 at 20:12

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