Correctly called a Crook's Radiometer after the Victorian gentleman that is credited with inventing it. A type of perpetual motion if the sun is out. Made of glass, the four vanes are finely balanced on a pin point and revolve around inside a partial vacuum to reduce drag of air. Whilst they often will revolve (slowly) in lamp light these are one of the few items we sell that should be placed in a sunny window. The energy from the sun makes the vanes revolve fast and although of no practical use, they are an amazing piece of science. The physics behind it is still theory and hard to understand unless you're a budding scientist! Great on a window ledge. Too delicate to send - collection only, by arrangement. item is £25 Measurements: 250mm x 80mm (but do vary as handmade)
