Passage: The lava lamp turns 50

(CBS News) It happened this week . . . an anniversary that has devotees of a certain device bubbling over with excitement.

The lava lamp turned 50 this past Tuesday.

Englishman Edward Craven-Walker gets the credit (if that's the right word) for its invention . . . inspired, it is said, by some sort of liquid-filled egg timer that he saw in a pub.

The lava lamp turned 50 this week. Mathmos

His creation contains two liquids of different densities -- one waxy, the other water-based -- with a heat source at the bottom.

When the waxy liquid sinks to the bottom, the heat expands it to a lighter density, so it floats back to the top.

Once at the top, it cools, thickens, and sinks to the bottom again.

And on . . . and on . . . and on.

The mesmerizing lamp caught the imagination of swinging 1960s Britain, making guest appearances on such memorable TV series as "The Prisoner" and "Doctor Who."

The lamp caught on here in America, too, and though its popularity has waxed and waned in the decades since, it has never faded away entirely . . . or lost its capacity to captivate viewers.

As collector Anthony Voz told the Associated Press: "It kind of pulls people in, and before you know it, you've spent 15 minutes looking at it."

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