Animation: To cheat time, move really, really fast

First elaborated one hundred years ago, the Twin Paradox is an outgrowth of special relativity, and one of those counterintuitive conclusions so typical of recent physics. Using atomic clocks and sophisticated measurements, several experiments have since proven that time dilation is a real phenomenon.

It goes to show that the nature accessible to our senses is but the merest fraction of reality.

Here, via Curiosity Counts, is one of the better explanations of time dilation that I've seen.

A Tale of Two Twins from Yuanjian Luo on Vimeo.