If you're here looking for something unusual to give as a gift for Christmas, Father's Day, Bosses' Day or his birthday this year, a Crookes radiometer definitely ticks all the boxes. It's an old timey looking device with a fascinating backstory and demonstrates scientific principles while also being quite cool to look at Put the thing in sunlight and the little vanes begin to spin on their own How does a Crookes radiometer work though? Strangely enough, even the inventor of the radiometer (a fella named Crookes, who would have thought?) didn't get it right and the debate still rages as to what exactly causes a radiometer to spin. The prevailing theory these days (according to Wikipedia and YouTube) is that thermal radiation (that's heat and light to you and I) causes the black side of the vanes to heat up faster than the light sides which creates a net exchange of heat. Sort of like a tiny heat engine. Quite fascinating really and a live action demonstration of thermodynamics The Crookes radiometer is available through LatestBuy in 18cm size or 22cm size. A Crookes radiometer is a cool sciencey gadget for teachers to keep on their desks or near a windowsill. It's also an impressive desk toy (if you're near a window ) to encourage customers and visitors to start a conversation As such this is an ideal gift for the teachers and office workers in your life. Order one today for all of your favourite science geeks Product Specifications: Dimensions: 18cm or 22cm tall This product is not a toy, keep out of the reach of young children and pets Recommended age: 14+