Rattleback

Say what?

From the website:

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A rattleback (also known as a celt or a wobblestone) is a type of spinning top that will spin in one direction, but when you spin it the other way it will slow down until it stops, wobbling along its length, and will then spin in the opposite direction.

Originally seen as mysterious, they are now regarded as an interesting piece of physics. One of the original papers explaining how they work was presented at the Royal Society in London in 1988.

Bernhard Schoner, a skilled woodworker from Germany, has created another set of wooden rattlebacks [below] for us, made from different woods. Each one takes several hours to make and is a beautiful object, as well as having an intriguing mechanism. They vary in length from 21 to 27 cm.

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$110.60.

[via Fred]