What do you do when you've described the nature of the universe?

In the late 1920s Einstein was working on a grand unified theory of the universe, having given us E=mc2, space-time and the fourth dimension. He was also working on a fridge.

Perhaps motivated by a story in the Berlin newspapers about a family who died when toxic fumes leaked from their state-of the-art refrigerator, Einstein teamed up with another physicist Leo Szilard and designed a new, safer refrigerating technology. And so it was that in 1930, the man who had once famously worked in the patent office in Bern was granted a patent of his own. Number: 1, 781, 541. Title: refrigeration.

Phillip Ball explores this little known period of Einstein's life to try and find out why he turned his extraordinary mind to making fridges safer.

Despite considerable commercial interest in the patent, Einstein's fridge didn't get built in his lifetime.The Great Depression forced AEG and others to close down their refrigeration research. But in 2008 a team of British scientists decided to give it a go.Their verdict : Einstein's fridge doesn't work.

Producer: Anna Buckley