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Spin the disc on the mirrored surface and marvel at the reflections as it whirls to its finale

When you spin a coin or a lid on the table, as it falls over it will oscillate loudly for a few seconds before finally coming to rest. This is the phenomenon upon which EULER’S DISC depends, but here all has been devised to produce an unbelievably efficient and spectacular performance. The disc to be spun is metal, surprisingly heavy, 8cm in diameter, an inch thick with its rim and top decorated with highly reflective, almost holographic coating. The surface on which it is to be spun is a slightly concave framed mirror 23cm in diameter. And what happens when (“no skill required”, honest) you spin it? It spins for more than a minute, very noisily, giving off wonderful reflections when the light is right. Gradually the oscillations become faster and faster until they are no more than vibrations. And then, unimaginably suddenly, everything stops. All observers are transfixed.

How does it do it?

Magnets? A motor? When you tell them that it is only gravity they are incredulous. It’s a wonderful diversion. Every household should have one. We haven’t convinced you? Risk it! Returned goods are a huge nuisance to us, and we wouldn’t push something as hard as this unless we were sure that no-one would be disappointed by it! Incidentally, if you want to seem clever you need to know that Euler was a 18th century Swiss physicist, pronounced “Oiler”.

Features

• Metal disc, 8cm in diameter
• Concave framed mirror, 23cm
• Spins, oscillates then vibrates