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Does time go slower underwater?

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Circlotron:
Light travels fastest in a vacuum. When it passes through water it goes slower and causes refraction. Seeing it goes slower in water, would not time also pass more slowly in water to an observer outside the water?

tom66:
Elementary physics understanding here but yes.  Water has a lot of mass, much more than air, and mass/gravity influences the passage of time.  So time will be a little slower underwater.  I am not sure by how much.

greenpossum:
I know I saw my whole life flash past my eyes when I almost drowned, so I think yes.  :-DD

Kleinstein:

--- Quote from: tom66 on July 12, 2020, 09:00:04 am ---Elementary physics understanding here but yes.  Water has a lot of mass, much more than air, and mass/gravity influences the passage of time.  So time will be a little slower underwater.  I am not sure by how much.

--- End quote ---
There is a tiny effect of gravity on how "fast" the time passes. This is a tiny effect from general relativity, but it is some tiny it need things like an atomic clock (maybe a rubidium oscillator could work) to observe it. It is the gravitational field, not the mass density close by.

For a human one may get the feeling that time slows down, as underwater is usually and unusual place to be, so one is often more excited and this can change the perception of time.

T3sl4co1l:
Heh, not like that.  You'd have to make space itself have an index of refraction -- which, along with some other crazy things, is effectively what supermassive objects do, but due to the other crazy things, you can't exactly live near them.  :)

That there are two speeds of light in a medium, like water, means you can get shockwave effects like Cerenkov radiation, when a charged particle goes faster than that speed.  This isn't possible in vacuum, where the maximum propagation velocity is equal for both matter and light.

Tim

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