In connection with mt prev Q i like to know that acc to einestein light is travelling through some medium but?

Answer 1

I think I see what you're asking and where you may have gone awry here. Let me explain.

Einstein suggested that the speed of light IN VACUUM was the universal speed limit. This is a pretty important distinction because light travels at lots of different speeds, depending on what medium it's travelling through. As a matter of fact, some scientists have recently perfected a special medium that slows light down so much that it is essentially STATIONARY (which would be handy for certain types of optic computers).

Now obviously we can all travel faster than being stationary. But then that has nothing to do with relativistic effects, really.

An interesting phenomenon related to this is called 'Cherenkov radiation' - it's the weird bluish glow that is sometimes seen to surround radioactive materials. Cherenkov radiation is like a sonic boom for light, caused when particles are forced to move through a medium faster than light is able to move through it. The force of a radioactive emission is just one way to do this!

Particles that cause Cherenkov radiation are moving faster than light IN THAT PARTICULAR MEDIUM, but NOT faster the light travels when it's in a vacuum. NOTHING has ever been observed to travel that fast... though who knows? Maybe someday someone may find something that does. Maybe even you. Good luck! ( :