# A submarine problem

1. Nov 5, 2006

### raul_l

Suppose with have two objects underwater: a scuba diver and a submarine that travels close to the speed of light. For the scuba diver is seems that the submarine is getting heavier and from the submarine it seems as if everything else is getting heavier.
So which is it - will the submarine rise to the surface or sink to the bottom?

I kinda get the feeling that I'm missing a lot of factors here so any help would be welcome. :)

2. Nov 5, 2006

### pervect

Staff Emeritus
This is known as Supplee's paradox. It's been discussed here before (look for Supplee), it's also discussed in the wikipedia http://en.wikipedia.org/wiki/Supplee's_paradox and at this physical review focus article http://focus.aps.org/story/v12/st4, which has a link to a physical review letters paper (which you'll need to access from a library, unfortunately).

There are several different ways of explaining the results from various viewpoints, but everyone agrees that the submare was at neutral buoyancy at rest, if it moves at relativistic velocities it sinks, assuming that it generates no lift forces, i.e. assuming that it imparts no upward or downward momentum to the fluid via its passage.

3. Nov 6, 2006

### raul_l

Thanks.
I feel kinda stupid for posting this before searching the web.