I've conducted a test with two fans connected to each other. The top fan was setup to spin counterclockwise and the larger fan spun clockwise. In my test, it showed that once the two fans reached the same rotational speed, the beads where in a rest state (well, if it was perfectly centered and didn't have a wobble that shook the beads about) and were no longer being affected by centripetal forces. You can see my simple test here that I built in an afternoon: Opposing Centripetal Force: Two-fan TEST YouTube Video

After doing this test, I have two questions:

  1. Will conducting a similar test up in space result in the same outcome?
  2. In theory, is there a way to have a space station that is using centripetal force to mimic earth's gravity AND also rotating in the opposite direction at the same speed so that someone inside the space station could look out a window and objects outside the space station (earth, moon, sun, stars) would appear stationary and not rotating around the station hundreds of times per day?

The main goal here is trying to create (only in theory) a space station that has gravity simulated via centripetal force yet ALSO having it appear as if you're not rotating while inside the space station so that objects aren't moving past the window numerous times per day. Is that even remotely possible (again, only in theory and NOT actually building a real space station that does this in real life)?

  • $\begingroup$ " rotating around the station hundreds of times per day?" A low Earth orbit at about 400 km has a period of about 90 minutes, that are only 16 revolutions per day. $\endgroup$
    – Uwe
    Nov 10, 2021 at 2:00
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    $\begingroup$ @Uwe, I'm not referring to orbits around the earth, I'm referring to how many times the space station would complete a full ring-rotation. In order to maintain 1G of centripetal force and the space station ring had a radius about 10,000 meters (a little over 6 miles radius) it would need to have a velocity of 700.51 mph which would be 430 revolutions per day. Smaller the diameter, more revolutions $\endgroup$
    – rpoduska
    Nov 10, 2021 at 4:16
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    $\begingroup$ Simply put, you seem to have a massive misconception of what constitutes "centripetal force". Please correct this deficiency, and then look at your question (and video) again. It should be enlightening. $\endgroup$ Nov 10, 2021 at 7:40
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    $\begingroup$ Ah... at simple standard approach, this is a very simple "No" - not in regular conditions like occurring between "anywhere within this supercluster of galaxies" up to "anywhere within our universe". But it becomes a very, very interesting question if you take more general cosmology, e.g. the idea of a Newton's Bucket in an empty universe, and start mucking around with engineering a specific pseudo-special frame of reference instead of taking whichever the universe threw at you. Can we generate a local pseudo-special frame of reference which is spinning relative to the more global one? $\endgroup$
    – SF.
    Nov 10, 2021 at 10:47
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    $\begingroup$ I’m voting to close this question because it just doesn't make any sense. The OP needs to understand some basic physics concepts. $\endgroup$
    – Rory Alsop
    Nov 10, 2021 at 11:07

1 Answer 1


Your own experiment answers your question.

When immobile, the beads hang on pieces of string dangling from the fan which you'd consider that "special interior" of the space station. Once you start that fan and the blades start spinning, the strings extend outwards, the beads hanging outwards towards the chassis of the fan. Then you apply spin of the other fan, spinning the chassis of the first one in opposite direction, until you reach such speed that the fan blades are mostly immobile relative to the room around. Observe the state of the strings and the beads in the slo-mo part at the end: they hang down towards the floor again, shaken around by vibrations but no longer pulled straight outwards.

That outwards pull is the centrifugal acceleration, opposed by centripetal force of the tension of the strings, the "artificial gravity" of a spinning space station - and it vanishes once the fan stops relative to "the outside universe". So, no - in your situation, and in any situation we can practically achieve, being gravitationally bound to the universe, there is a pseudo-special frame of reference where centripetal forces don't occur, and whichever means you choose to make an object non-rotating within that frame of reference (like in your case counter-rotate the source of rotation of this object) it will cause it to behave the same - no rotation = no "artificial gravity".

This becomes much less clear and obvious if we replace the universe your "station" is in with one with no, or very little matter / sources of gravity, which would essentially "undefine" the pseudo-special frame of reference. But that's cosmology of a higher order, the essential step of "replace the universe" being a rather hard threshold to meet.

  • $\begingroup$ Thank you for taking the time to help answer my questions. It really helped and I really appreciate it! $\endgroup$
    – rpoduska
    Nov 10, 2021 at 13:56

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