The children’s toy has been around for more than 75 years now and is still extremely popular. It was the creation of Richard James, a naval mechanical engineer stationed at the William Cramp & Sons shipyards in Philadelphia. In the early 1940s, he was attempting to use torsion springs to stabilize sensitive instruments aboard ships in rough seas.
James accidentally knocked one of the springs from a shelf, and watched as the spring “stepped” in a series of arcs to a stack of books, to a tabletop, and to the floor, where it re-coiled itself and stood upright. James’s wife Betty later recalled, “He came home and said, ‘I think if I got the right property of steel and the right tension; I could make it walk.'”
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Over 300 million Slinkys have been sold between 1945 and 2005, and the original Slinky is still a bestseller.
In addition to becoming a toy classic, high school teachers and college professors have used Slinkys to simulate the properties of waves, United States troops in the Vietnam War used them as mobile radio antennas (as have amateur radio operators, and NASA has used them in zero-gravity physics experiments in the Space Shuttle.
There's more at the link.
I'd never seen or heard of a Slinky until I came to the USA in the late 1990's. I guess they weren't as popular outside this country, or weren't promoted there as much. They can still make me smile. Here's a news report from several years ago on how they're still going strong.
I know that "hope springs eternal", but I didn't know that springs did, too!