Unlike human celebrities, equations have to prove their merit to be famous. Now Einstein's e=mc² has done just that. An experiment conducted by US researchers from the National Institute of Standards and Technology and the Massachusetts Institute of Technology, showed that e differs from mc² by at most 0.0000004, proving beyond doubt that the equation is indeed correct.

The equation, which just celebrated its 100th birthday, is part of Einstein's special theory of relativity and relates energy (e) to mass (m) and the speed of light (c). The recent experiment is the most precise and direct test of the equation ever conducted. Its results were published in the journal Nature. You can find out more about the experiment in this news release. To see special relativity in action, read Plus article What's so special about special relativity?. Another Plus article, Spinning in space, describes how the general theory of relativity is put to the test.