I happen to read a book on Blackholes and time travel once. A blackhole is actually a vortex - like tunnel which will suck EVERYTHING including LIGHT itself towards its other ends. Actually, you CAN time travel by doing so, since the blackhole itself have a suction speed equal to that of speed of light. However, you will DIE. Why? Because the speed is so intense and the state of "singularity" applies where everything that is being sucked in MUST exist as a single particle i.e. you will gradually lose your body, (sorta like in the
FF7 where sephiroth dies in the end).

Regarding the speed of light, Albert Einstein did illustrate it using simple math and trigonometry, yeah pretty simple. I watched it on NATGEO. When your vehicle reaches the speed of light, the light surrounding your vehicle will gradually become attracted to your vehicle, the scenery from outside your vehicle seems to bend, then, all the light will surround your vehicle until eventually you will be covered by the light itself. Then, time travel is said to occur.