All you need is a couple of ultra-precise clocks, a mountain and a reliable kid or three to help out, and relativity, the theory that shows how time and space are woven together, is a snap to demonstrate.
The creation of Tom Van Baak, Project GREAT (for General Relativity Einsten/Essen Anniversary Test—Albert published his first paper on the theory just over 100 years ago) is a simple matter of taking one of two perfectly-synchronized atomic clocks to the top of a mountain and leaving the other one at home. Camp out for a few days, and when you get home, the minuscule gravitational difference between the two locations will have had its mysterious way with time itself: they’ll be a few nanoseconds apart.
Read Tom’s story, and get the skinny on the science, at his report in Physics Today’s website. Here’s some photos of the experiment. If you’re thinking about trying this yourself with an atomic watch, however, you’ll be disappointed: you’ll need something a little more accurate, and a little more expensive.
An adventure in relative time-keeping [PhsyicsToday.com]