Handwritten example of Albert Einstein’s famous equation sold for US$1.2 million
- The 1946 letter to physicist Ludwik Silberstein set off a bidding war, bringing the price to three times what was expected
- Experts say there are only three other known samples of the world-changing E = mc² formula in the top scientist’s own hand

A letter written by Albert Einstein in which he writes out his famous E = mc² equation has sold at auction for more than US$1.2 million, about three times more than it was expected to get, Boston-based RR Auction said Friday.
Archivists at the Einstein Papers Project at the California Institute of Technology and the Hebrew University of Jerusalem say there are only three other known examples of Einstein writing the world-changing equation in his own hand.
This fourth example, the only one in a private collection, only became public recently, according to RR Auction, which had expected it to sell for about US$400,000.
“It’s an important letter from both a holographic and a physics point of view,” Bobby Livingston, executive vice-president at RR Auction said, calling the equation the most famous in the world.

The equation – energy equals mass times the speed of light squared – changed physics by showing that time was not absolute and that mass and energy were equivalent.
The one-page handwritten letter in German to Polish American physicist Ludwik Silberstein is dated October 26, 1946.