> Now if you have reached the speed of light, doubling the speed will never make you go back in time, it will just halve the time it takes you yet again. It ac

> Now if you have reached the speed of light, doubling the speed will never make you go back in time, it will just halve the time it takes you yet again. It actually makes sense in that regard, because while accelerating, you will shrink along the acceleration vector. Let's say you are 6 feet tall and fly Superman-style at 0.9c. You will then, from the outside, be 2.6 feet (or so). This means that if you from your timeframe accelerate by 1 km/s, to the outside you will accelerate by 0.4 km/s. This acceleration in turn cause you to shrink even further, and as you approach the speed of light your external length will approach 0. So any further acceleration in your frame of reference, no matter how immense, would approach 0 from the outside.