What is another name for a lava lamp?

lava lamps by Yvonne Bernal

The unique lamps were created by a British inventor and former World War II pilot, Edward Craven-Walker, who reportedly thought up the idea after seeing a homemade, liquid-filled egg timer at a pub.

In September of 1963, Craven-Walker started a company to research and develop his invention. But his widow, Christine Baehr, told BBC News they had a rough time, at first, trying to find investors.

But Baehr said that, after the couple took their product around the British countryside in a van, word of the wildly original illumination spread. Pretty soon lava lamps could be seen in science fiction movies and television shows like "Dr. Who," and became extremely trendy. By the mid-1960s, according to an MIT report, lava lamps "had exceeded 7 million units worldwide."

Baehr told The Associated Press that she knew the lava lamp had "made it" as a product when she heard that Beatles drummer Ringo Starr had purchased one.