Submitted by flipitninja t3_y90uo6 in askscience
I was just watching a video of an astronaught playing with an orb of water on the ISS and I was wondering if you had something floating that had a distinct smell, would it be in an evenly distributed sphere around the object? As opposed to the smell being stronger above the object than it is around it like on earth?
Gases are not dense enough for intermolecular interactions to affect bulk material behaviour as would be seen with liquids.
Liquids are far more dense than gases. When molecules are densely packed, as with liquids, intermolecular interactions can affect bulk behaviour.
Liquids clump up like that because of surface tension. For gases, there is not really any surface tension that would cause that.
In order for gas to stick together in a stable sphere, there needs to be enough gas in total that the mass of all the gas makes enough gravity to keep individual gas particles from achieving escape velocity at their temperature.
Smells are typically transmitted by vapors (gases), which lack the intermolecular forces that are responsible for cohesion, and cause water and other similar liquids to gather into droplets in zero-g environments. What would happen is that the gas responsible for the smell would diffuse away from the object equally in all directions.
I'm actually not sure how true it is that smells are stronger above an object than below it on Earth. It's hard to smell a mug of coffee from below because it isn't open at the bottom, for obvious reasons. And our nostrils are on the underside of our nose, so it might be a bit harder to smell scents coming from above our nose. However, if I held a piece of stinky cheese above my head and turned my nose up to sniff it, I'm pretty sure I could.
Edit: on large scales, gases do indeed gather into nebulae and sometimes even gas giants or stars (or solar systems or galaxies), but this is due to gravity rather than cohesion, and to be a significant force this requires much much more mass than the tiny amount of scent molecules that one would find radiating from an object that would fit in the ISS.
I do recall that airflow is important in accomodation areas to prevent CO2 build up around crew whilst they sleep. Am I misremembering, or is there merit to this concern, do you know?
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[deleted] t1_it3zh6d wrote
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