Time Travel, effect of light speed underwater (Opera, program, scientist)

[gy2020]

I have a question? Years ago I use to SCUBA dive and I experienced the effect that when I was under water time seem to speed up. It felt like I was diving for 5 minutes. When I surfaced I found that I had been down for 20 or 30 minutes. Almost everyone I dived with felt the same thing. Over the years I just took this as being involved and having a good time and the illusion of time was different.
Yesterday I was watching the History channel and I was watching the Universe program. Dr. Mellor (or Dr. Mallett) is working on time travel using light waves as the source of energy.
The speed of light is different in air than it is in water. Light travels slower in water than it does in air.
Do you think there might be a correlation between what I took as time speeding up underwater and what it was on the surface?

[harry chickpea]

Could this be an effect of water on the brain? Movements are a little slower in the denser water than in open air. IOW, the perception of time is subjective. Either that, or all we have to do to slow time down is get a boring lecturer and have everyone have to wait for the restroom break. A couple of hours will be an eternity and we'll all live (uncomfortably and bored) forever.

The speed of light constant is by definition, within a vacuum. I think the standard vacuum is Electrolux, which allows for the charges in space as well as indicating lux or light.

[gy2020]

The speed of light might be constant in a vacuum, but on the program last night they said that light travels slower in water than in air, which means it probably travels faster in a vacuum. I know 186,000miles/sec. I taped that program, I'll have to go back and look at that segment again.

[harry chickpea]

FWIW, scientists recently "froze" light (stopped it entirely) in some ultracold thingamabob. Interesting, but not theory-breaking.

The operative idea is that the speed of light in a vacuum is the speed limit for any particle (or string, depending on your religion), not just light. Stuff can slow light down, just not speed it up past that point. I think the jury is still out on how fast "transmission" is between entangled particles, which appear to communicate through a different dimension than the four familiar ones.

[gy2020]

Which begs the question, if light slows, does it have an effect on time?

[gy2020]

Try SCUBA diving sometime and see the effect for yourself.

[jabm67]

Light travels more slowly in any medium than it does in vacuum. The factor by which it's slower is the reciprocal of the medium's index of refraction (that is, the index of refraction n = c / (velocity of light in the medium) ). For water, the index of refraction for visible light is about 1.333. That means light slows down by about 25% when it enters water. That's still a pretty high speed, of course. The path followed by the light is refracted (bent) at the surface also.

That said, it's c, the speed of light in vacuum, that matters for fundamental physics, not the speed of light in the local medium. In fact, it is possible to get particles moving faster through a medium than light does in that medium. When that happens, it gives rise to an effect called Cerenkov radiation, which is that blue glow you sometimes see pictures of around intensely radioactive objects. (It is utterly impossible for particles to reach, let alone exceed, the speed of light in vacuum.)

My guess, though, is that the effect you report is something from perception psychology, not physics of time & light.