What would happen if you moved at the speed of light?

First, let's assume that it is possible — though it is not — for a human to move at the speed of light, which is 299,792,458 meters per second (983,571,056 feet per second), or about 186,000 miles per second. There's no issue, per se, with a person moving at a very fast constant speed. Humans can't feel constant velocity, so you wouldn't even necessarily notice you were moving that fast.

Your biggest issue would be acceleration — actually reaching that speed. Too much acceleration force can hurt, and even kill, us. At high accelerations, "your blood will have a hard time pumping to your extremities," said Michael Pravica, a professor of physics at the University of Nevada, Las Vegas.