I know this has been asked tons of times on here. But I never seem to understand the answers. So I challenge all you smart people to explain it as simple as possible. How does time slow down for a person who is traveling at a hihg speed and not for someone standing still? The person standing still is still moving around the solor system, that is traveling around the solor system. There is no universal time frame. So if someone is traveling very fast away from me why would he age slower and not me, how could time now who is traveling and who is not. Please make the answer as easy as possible.