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A common picture of someone floating on the Dead Sea or Great Salt Lake, shows how high you float.

lMan Floating

If you had that water in a bath tub, I don't think you would sink to the bottom, you would just awkwardly float in the tub. Bathing in small tub where your body does not rest on the bottom would be impractical/impossible. Imagine bobbing around in the tub trying to wash without tipping over and banging your head against the side of the tub.

With the gravity on Mars being much less than Earth, would you float in the bath water?

James Jenkins
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    Related: http://space.stackexchange.com/questions/6607/how-would-swimming-on-mars-feel-given-the-lower-gravity – called2voyage Aug 17 '16 at 14:00
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    That 'floating on water' is nothing to do with gravitational pull (so long as it is not 0), and everything to do with the relative density of the floater and fluid! The density of the water in those places is higher because the water is laden with dissolved salt. – Andrew Thompson Aug 17 '16 at 14:10
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    Lunar Pool by XKCD: https://what-if.xkcd.com/124/ – Dohn Joe Aug 17 '16 at 15:48
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    Also related: http://physics.stackexchange.com/questions/272918/does-an-object-float-more-or-less-with-more-or-less-gravity – hobbs Aug 17 '16 at 20:09

1 Answers1

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Short answer, No different from Earth in floating.

Buoyancy in water or any fluid is based on the weight of water displaced. Floating is based on the weight of the item displacing water. This is ultimately ends up in comparing densities. If the density of the displacing object is greater than the density of the fluid it will weigh more and sink, if it's density is less it will weigh less than the water displaced and float. On Earth people float higher on very salty water because the water is denser than fresh water, so less fluid must be displaced to support the weight of the person.

In a lower gravity field like on mars, your body and the water would both weigh less by the same amount (local gravity), but your densities would compare the same way, so floating or sinking would be unchanged.

Josh King
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    There is something missing here though. It is true that while at rest your buoyancy will remain unchanged, but as pointed out in the linked question regarding swimming, it is easier to push yourself to the surface because of lower gravity. This may be relatively unnoticeable in a bathtub--I'm not sure--but it is possible that moving around in a full tub might feel a little different. – called2voyage Aug 17 '16 at 14:49
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    @called2voyage So what you're saying is.. Humans swimming on Mars may be able to frolic around like dolphins, leaping from the water? Sounds fun. – Saiboogu Aug 17 '16 at 17:02
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    @Saiboogu Well, Mars gravity isn't quite as low as the moon, but something like that, yes. – called2voyage Aug 17 '16 at 17:03
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    If your pool on Mars was an outdoor pool, you'd sink straight to the bottom (because the water evaporated away) – Cody Aug 17 '16 at 17:27
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    @Saiboogu Can't wait for the pool party. ;) – Kevin Aug 17 '16 at 19:50
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    @Saiboogu https://what-if.xkcd.com/124/ – kasperd Aug 17 '16 at 20:53
  • @called2voyage The Martian bathtub would be a lot more splashy. Move your whole body in the tub and you could get quite a splash out of it. – Loren Pechtel Aug 18 '16 at 04:20
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    @Cody You mean boil. Violently. To the point of an epic explosion. There would be very little left of you to "sink". Although I'd doubt the pink mist would gain escape velocity. But you would be spread out in such a large area, again the word "sink" would be moot. – Aron Aug 18 '16 at 04:42
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    @Aron: Epic explosions, as well as boiling water in general, take a lot of energy -- where would that come from? A pool at room temperature on Mars would start boiling, but most of the water would have to freeze for the remainder to be able to boil off, leaving a pool more than half full of slowly sublimating ice. And the lowest points on the Martian surface actually have enough pressure for liquid water to exist up to something like 10 °C. – hmakholm left over Monica Aug 18 '16 at 08:57
  • @HenningMakholm Sorry I was assuming magical teleportation of a swimming pool of STP water to the martian surface. – Aron Aug 18 '16 at 09:14
  • @Aron: Even so -- cooling a kilogram of water from 30°C to the freezing point will only supply some 125 kJ, and it takes at least 2400 kJ to turn it to vapor -- so most of the pool's content will still end up frozen. – hmakholm left over Monica Aug 18 '16 at 09:24
  • @Aron: Note also that even with vacuum above, the weight of the water under Martian gravity will raise the pressure at a depth of just 115 cm high enough for the boiling point to be above 30 °C, so a magically transported pool would not instantly start making bubbles for its entire depth. – hmakholm left over Monica Aug 18 '16 at 09:33
  • Related Boiling ponds and pools on Mars? – James Jenkins Aug 18 '16 at 15:48