[dominic horath]

dominic horath  asked the Naked Scientists:

Hello guys.

I have a question regarding the way a beer bottle (or any similar shaped bottle) behaves in water. Why is it that if the bottle is submerged right side up water will flow in immediately but if the bottle is submerged upside down the air stays in the bottle perfectly well?

Thank you,
Dominic. from California

What do you think?

[Madidus_Scientia]

Because the air floats, so it can't go down.

[lyner]

If the bottle is upside down, the air has nowhere to go- the water pushes it up to the top (i.e. the 'bottom' of the bottle).

[syhprum]

what would happen if the bottle was submerged to such a depth that the air that normally has a density 1/800th that of water was compressed by the virtually uncompressable water so that its density was greater than the water ?

[lyner]

Ah well - that's a typical TNS response!
I guess it would have dissolved long before that situation?
The answer can't just be that it would flow out of the neck of the bottle, can it?

[LeeE]

I believe that the compressability of air, when used to provide bouyancy, is an issue in the design of deep-sea diving bathyscapes and instead, petrol is used.

http://en.wikipedia.org/wiki/Bathyscape

[syhprum]

Simple calculation shows that one would have to descend 8000 meters for the air to become as dense as water assuming the water maintains its normal density.
I believe there are parts of the ocean this deep but it would be interesting to perform the experiment in a pressure chamber if one was available.

[qazibasit]

it remains inside the bottle only till the inlet of the bottle is downwards towards the base of the water table and the base of the container is directed towards the surface of the water table. it is because of the movement of air molecules directed upward in the container and not getting anywhere to escape.