If I am wrong, which I think that I'm not, please correct my statement.
I am trying a clean slate thing here, so don't judge this based on past comments. Time travel is based on time dilation by a greater velocity than the stationary viewpoint, gravitational field stuff, or both. Velocity time dilation is t=t1/(sqrt(1-(v^2-c^2))). Gravitational is T=T1/(sqrt(1-(2GM/(Rc^2)))). t is stationary frame's time. t1 is moving frame's time. v is velocity, c is speed of light, G is gravitational constant, M is mass, R is radius.
So, explosive, you might reconsider being a douche because you know everything. You don't. You seem like much of a dumbass, typing in such ugly way.
It's the fact that photons bump into particles when travelling through matter, and the denser the matter is, the less straight is their path. Because the path isn't straight, it's longer, and it takes more time for a photon to get from one point to another (if you treat light like a wave though, which it also is, then it's simple, the wave changes the enviroment and slows down...)
Well, @explosivepowder, you still didn't learn to type well and use correct grammar. It's true thatt light travels slower in different enviroments, however it is not due to the common resistance forces.
I know its cool... I know its a great concept... but just like every other save... it deserves to be obliterated in a nuclear maelstrom. +1 +fav
Also, being eleven today, i had a working knolage of black holes when i was F-I-V-E! NO UR NOT GOING CRAZY, IM NOT LIEING EITHER
@warhampster thats not true, they trsvel slower in air (air resistance) and even slower in water (water resistance)
The time doesn't get slower near you god damnit. Time isn't an absolute value, it's relative to an observer. There is no big "timespeed field" or something that determines the speed of time at some point, thats nonsense... TIME IS RELATIVE. It's different for someone that moves fast and different for another one that moves slower. Jeez