A refrigerator usually works quietly in the background, keeping food cold while electricity powers the machinery hidden behind it. But nearly a century ago, Albert Einstein and physicist Leo Szilard imagined a very different way to make cold. Their refrigerator had no electric motor, no pump and no compressor. Instead, it relied on a carefully arranged cycle involving ammonia, butane, water and heat, as per a report by Wired.
The idea was strikingly simple in principle. Heat went into one part of the system, while another part became cold. Yet despite the involvement of one of the most famous physicists in history, the refrigerator never became a commercial product.
