Time dilation

Time dilation is a law of nature in which, if a system is travelling at the speed of light, the biological clock and other clocks carried, will tick more slowly, whilst stationary clocks will tick at a normal rate. Particles in the accelerating reference frame will age more slowly, so a 30 year old man won't age at all, but his brother would've aged at quite an astonishing rate, in comparison to the man who went around the countryside.