Assume the following scenario:

-two objects in constant velocity free fall side by side to each other (imagine two astronauts in orbit)

-one of the two astronauts is inside a non rotating ring structure (imagine space station in orbit) but not connected to the structure in any way

-space station is also moving at constant velocity so that there is no relative motion between the three objects

-only thing separating the two astronauts is the wall of the ring structure

If the ring begins to spin about its axis without otherwise changing its constant velocity or relative motion to the two astronauts, will the astronaut inside the ring nonetheless experience centripetal forces and thus "artificial gravity" and be forced toward the outer wall of the ring whereas the other astronaut does not experience any relative force?

From reading and seeing this basic premise in science materials (and in science fiction films no less like Interstellar, Martian, 2001), this should be the expected outcome, but this seems like "spooky action at a distance" as well.

How does the spinning of the ring suddenly create a force that acts on the astronaut in free fall inside the ring whereas the astronaut immediately adjacent to but just outside the ring wall not feel any force?


1 Answer 1


No, the spinning of the ring itself does not suddenly create a force on the astronaut. It is the tangential velocity of the astronaut that makes him hit the ring, as he can not continue traveling straight due to the ring being in front of him, which ultimately leads to a change in direction and a corresponding force to make that change.

In short, astronaut will experience a force only if he is connected to the rotating ring. And to simplify even more, their rotational speeds should mach.


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