Crookes Radiometer

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A great learning tool that helps your students understand how the thermodynamics.
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Nancy B's Science Club MoonScope

Nancy B's Science Club MoonScope
Calling all budding astronomers! Take your star-gazing to a whole new level with this kid-friendly telescope and accompanying journal packed with facts and fun activity prompts.

How does the sun make it spin!? This question has had scientists scratching their heads since 1873 when the radiometer was first invented by chemist William Crook. The prevailing theory is one based on thermodynamics. What we do know is that the radiometers vanes rotate faster when exposed to more intense light. The instrument provides a quantitative measure of energy from light sources such as the sun, artificial globes, or infrared radiation - even the heat of a hand nearby can be enough to get the vanes moving. A great learning tool for any science classroom.

Ages: 10 +, under adult supervision

What you get

Crookes Radiometer. This is not a toy, the glass is fragile.

How does it work?

The airtight glass bulb has had much of the air removed creating a partial vaccum. Inside are a set of vanes which are mounted on a spindle and rotate when exposed to light (no batteries or electrical energy needed here to generate movement). It is thought that the radiometer, also known as a light mill, works like a heat engine when exposed to a radiant energy source like sunlight. Meaning it converts a temperature difference to mechanical output. In this case, the temperature difference is created by the black side of the vane becoming hotter than the other white side. Cooling the radiometer causes rotation in the opposite direction.


  • Heat Engine (the radiometer effectively becomes a heat engine when a light energy is directed at it).
  • Sustainable and solar energy.
  • Thermodynamics.
  • Black-body absorption the black vanes inside the radiometer heat up quickly because they absorb all radiation falling on them. This contrasts to the other white side of the vanes.
  • Light energy and electromagnetic radiation.

WARNING: CHOKING HAZARD - Small Parts. Not for children under 3 years.

More Information
Length (cm) 16
Width (cm) 9
Height (cm) 9
UPC 043067018007
Age Group 7-8 Years, 9-10 Years, 11-12 Years
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