If someone were traveling at lets say 99.9999% the speed of light time would go slower for them but their speed would stay the same. So lets say for every ten second we would experience here on earth they would experience they experience 1 second. so they would travel (10 seconds X 300,000 km )=3,000,000 km in 10 seconds To them though they would travel 3,000,000 km in one second (a factor of ten times the speed of light) but supposedly they shouldn't be able to travel faster than light. to them though they are. I do not understand this, can someone explain? Definition of speed of light is roughly 300,000 km a second not 3,000,000 km a second.