Hypothetically, if you did go faster than light you may go back in time! This is what a previous theory in physics said, before it was replaced.
To explain using a simple method:
1. A clock strikes 12 noon, billions of beams light reflect off the clock, some go into your eye, so you can now see its 12 noon.
2. You start running really fast, at the exact speed of light. You are now running with the beams of light that "say" 12 noon, time doesn't change.
3. You run even fster and start catching up with ohter beams of light that "say" 1155, 1150, 1145 etc. You are now going back in time!
This is a simple example of how time changes relative to speed. You can't actually go faster than light and go back in time, but the general theory is true. Clocks on rockets (which travel incredabily quickly) come back several seconds out, down to the speed it was going.