Monday November 9, 2015

The Slinky, which first appeared in the Gimbels department store in Philadelphia 70 years ago this month, didn't start out as a toy. A mechanical engineer at a shipyard in Philadelphia, Richard James, was trying to come up with an anti-vibration device for ship instruments. He knocked some springs off a desk and was startled when they took slinking steps, almost as if they were strolling away. He saw their potential as a plaything.

The simplicity of a Slinky belies its scientific complexity. Each ring of a slinking Slinky is pulled up by another and pulled down by gravity in equal amounts. Try holding the top of a Slinky, while letting the bottom dangle over a step. The bottom of a Slinky doesn't move until you let go and the top of the Slinky comes down and is completely compressed. Astronauts on the shuttle Discovery in 1985 found that the Slinky did not behave in weightlessness the way it does on Earth. One astronaut said: "It sort of droops." More than 300 million Slinkys have been sold since Mr. James and his wife, Betty, demonstrated the toy at Gimbels.