Originally Posted by
James Steele
It's been a few years since I finished my A-level physics where we covered special relativity, but I remember that as a particle or object's velocity increases, so does it's mass (and time slows down). This means that as the particle approached the speed of light, more energy would be needed due to the increase in mass, which increases exponentially and asymptotes at the speed of light. My interpretation of this is that no matter how much energy you give the particle, its increase in mass will prevent it's velocity reaching or exceeding the speed of light. It also works the other way - a photon only has mass when travelling at the speed of light. Try and slow it down, and its mass shrinks down to zero.
