Ive wanted a Crookes radiometer for some time, but I wanted something attractive and well made enough to have on display, where most on the market are poorly made or tacky in their design. However, this one is a very pretty simple design, and is also excellently made. Its bearing is so free moving that it even goes around slowly under overcast skies if the radiated heat is still stronger than the ambient temperature. There is no sign of the paint flaking off the paddles (often seen on less well made versions). It has been spinning happily in bright sun for a week and a half without any issues. Given these are intended to be put on window sills in the sun, it is important the materials are UV proof, so as well as looking good the wooden base is far better than a plastic base that will become brittle. The wooden base has a ridged plastic insert to grip the glass bulb which does so very well, avoiding need for any unsightly glue found on inferior versions. Im utterly happy with my purchase, and even have a colleague whos decided to get the same model.

A Crookes' radiometer has four vanes suspended inside a glass bulb. Inside the bulb, there is a good vacuum. When you shine a light on the vanes in the radiometer, they spin -- in bright sunlight, they can spin at several thousand rotations per minute! The vacuum is important to the radiometer's success. If there is no vacuum (that is, if the bulb is full of air), the vanes do not spin because there is too much drag. If there is a near-perfect vacuum, the vanes do not spin unless they are held in a frictionless way. If the vanes have a frictionless support and the vacuum is complete, then photons bouncing off the silver side of the vanes push the vanes, causing them to rotate. However, this force is exceedingly small. If there is a good but incomplete vacuum, then a different effect called thermal transpiration occurs along the edges of the vanes, as described on this page. The effect looks as though the light is pushing against the black faces. The black side of the vane moves away from the light.

Per quanto possa essere interessante dal punto di vista scientifico, questo strumento non funziona.
Ho provato a metterlo alla luce diretta del sole, sia dentro casa che all'esterno, ma non funziona.
Sto considerando di restituirlo

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