What Is the Solution to the Twin Paradox?
This paradox, also called the clock paradox and the twin paradox, is an argument about time dilation that uses the theory of relativity to produce a contradiction. The argument considers two twins at rest with their clocks synchronized. One twin climbs into a spaceship and flies far away at a constant speed, then reverses course and flies back at the same speed. When they reunite, will the twins still be the same age? No. Relativity theory implies that the twin on the spaceship will return and be younger than the Earth-based twin. The elapsed proper time of the twin who returns is less than the elapsed proper time of the Earth-based twin. However, it’s all relative, isn’t it? That is, we could have considered the spaceship to be stationary. Wouldn’t relativity theory then imply that the Earth-based twin would race off (along with the Earth), then return and be the younger of the two? If so, we have a contradiction: when the twins reunite, each will be younger than the other. Einstein w
