OK - What happens to time if part of the the universe does not exist in a vacuum?

Question

Einstein arrived at some of his ideas by picturing himself riding on a beam of light. What if that beam were slower due to passing through a medium? Would that affect simultaneity across the boundary of the medium? Wouldn't distant stars be seen in the more distant past? We know that time runs slower on the outside of a rotating disk than it does on the inside. Does time run at a slightly different rate underwater? This has no effect on relativity - in fact, I am trying to live within the confines of relativity.

Excuse me -

I was basing Einstein's statement regarding riding on a beam of light on The Ascent of Man, which was written by Jacob Bronowski (who knew Einstein personally I believe) and Cosmos by Carl Sagan, who used to work in pretty much the same job Dr Zikzak held. I guess you gentlemen know more than they do.

I have taken a class in relativity, and during that class I found that the professor was much easier to talk to and ask similar questions of than you gentlemen, who seem so over-impressed by your own admittedly superior knowledge that you respond by intimidation.

I understand that c is a fixed speed. I have understood that for decades. What I do not understand so well is how time works and how it is perceived. Thanks anyway.

Answer 1

>Einstein arrived at some of his ideas by picturing himself riding on a beam of light.

No he did not. Einstein knew very well, very early on that it is not possible to ride on a beam of light.

>What if that beam were slower due to passing through a medium?

This makes no difference. By axiom, it is the invariant speed c=3*10^5 km/s that is the fundamental quantity. It just so happens that light in vacuum travels at this speed. It is not the properties of light that are important; it is the properties of speed.

It makes no difference whatsoever that sometimes light is slowed down in media. Time does not pass at a different rate in water, because in water, the invariant velocity is still c, even though the speed of a particular light ray is slower than c.

Answer 2

Typically questions which have "Einstein said "or "Einstein arrived" are based on a total misunderstanding of physics. Please do not start a question like that. Just state what you want to know instead of putting your own faulty idea into Einstein's mouth.

Your "question" is so convoluted and far from reality that I wouldn't even know where to start correcting you.

Please take a real class on relativity, then come back with questions. As is, you are not even wrong.