[Xplo]

I'm a little fuzzy on what would happen if you literally tried to jump to light speed - relativistic physics isn't something I'm well-schooled on - but I suppose that as you accelerated to a significant fraction you would find it much more difficult to continue accelerating, and also your perception of time would change drastically.

Also, doing this in an atmosphere would presumably result in a giant explosion as you impart insane quantities of kinetic energy to the air around you.