Will a fluid loose it's bouyancy in zero-gravity. What would happen if an object is immersed in a liquid in space (if the liquid is still very much together and not spilling as big bubbles or droplets).

Example Scenarios

1 if water is put in an enclosed container (e.g. a glass jar filled to the brim) on a table (or held in a constant orientation) and a small rubber ball (which floats back on earth when in it) is put in the jar would the ball rise to the lid of the jar or sink to the bottom?

2 if a jar containing a helium balloon and oxygen gas in it is taken to space and held straight at a specific orientation would the helium balloon still rise above the oxygen in the jar or if two gases helium and oxygen are in the jar only, will helium gas always stay separated and above the oxygen gas in the jar?

  • $\begingroup$ "Rise?" That word means, "go up," and "sink" means "go down," but which way is "up?" which way is "down?" $\endgroup$ – Solomon Slow Jan 14 at 17:22
  • $\begingroup$ up would be as on earth and down alike, I am aware space has no up and down however you want to interpret it(your discretion). the main thing is what would happen to the ball in the first jar and the helium balloon in the other jar $\endgroup$ – LiNKeR Jan 14 at 17:57
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    $\begingroup$ If "space has no up and down...," then I do not understand what you mean when you say, "up would be as on earth..." You asked, "...would the ball rise to the lid...or sink to the bottom?" But how can a ball know which end of the jar is the "lid" and how can it know which is the "bottom." A ball that sinks in a Jar on Earth doesn't sink toward the bottom of the jar: It sinks toward the center of the Earth. $\endgroup$ – Solomon Slow Jan 14 at 18:13
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    $\begingroup$ P.S.: The reason why an astronaut feels weightless is not because she/he is in "space," It's because he/she is in free fall. $\endgroup$ – Solomon Slow Jan 14 at 18:18
  • $\begingroup$ the top of the jar(as up), the bottom of the jar(as bottom). It's concerning the behaviour of the ball in the fluid that I ask. The top and bottom in the question only talk about what part of the bottle we know on earth as top or bottom $\endgroup$ – LiNKeR Jan 14 at 18:19

If there is no gravity there is no buoyancy. If there is weak gravity then buoyancy force will be proportionally weaker.

If there is no gravity then in both the scenarios you stated there will be neither sinking nor rising, despite density differences. If there is gravity then (when placed inside a fluid) less dense object will move opposite to gravity and more dense object will move along gravity (just as on earth); if the gravity is weak then the corresponding motion will be slower.


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