Ok, so I read about a thought experiment pertaining to special relativity in a book somewhere and the experiment was that of chasing a light beam, which im sure everyone here has heard of. For those who havent heard of such an "experiment" here is how it goes: Bart has just bought himself a new nuclear powered skateboard able to reach a speed of 260,000km/s, he decides to have a race against a beam of light using his skateboard. His sister Lisa has a laser beam and stands at rest on a flat never ending plane. Both have sychronized atomic clocks, before Bart starts moving. So Lisa starts the countdown and then they're off! From Lisa's perspective, Bart is being outrun by the light beam by only 40,000km/s, but from Bart's perspective he is being untrun by the speed of light, 300,000km/s. Now, i can't seem to make sense of this, if you look at the equations explaining time dilationand length contraction, the gamma factor is cancelled out when you divide length by time in any reference frame. So if i were to say that from Bart's perspective the light beam is 300,000km ahead of him after he measures 1 second on his clock, and from Lisa's persepective the light beam (using time dilation and length contraction equations) would be 600,000km ahead of him after 2 seconds (I used 260,000km/s for a reason), meaning Bart is being outrun by the speed of light in her reference frame as well. This is where im lost and can't make sense of that statement above where Lisa's persepective shows Bart being outrun by only 40,000km/s. I'm obviously not looking at it the right way. Anyone have an idea?