I received this as a gift a couple of years ago, its lovely and I would want to keep it, but its getting hard to pack and repack it. I'm afraid it'll break at some point, so its time for someone else to enjoy it!
Here's the description of it, found on another website: In a vacuum inside a free-standing globe the vanes constantly revolvein sunlight. The simplest possible demonstration of solar power.
The radiometer is made by traditional Thuringian hand-blowing in Germany, of crystal-clear Lauschaer bottle glass. In the glass body is a 4-vane drive assembly, which turns under the influence of light. One side of each vane is black, the other is silver.The Crookes radiometer was invented by the chemist Sir William Crookes as the by-product of some chemical research. In the course of very accurate quantitative chemical work, he was weighing samples in a partially evacuated chamber to reduce the effect of air currents, and noticed the weighings were disturbed when sunlight shone on the balance. Investigating this effect, he devised the device named after him, still manufactured and sold to this day as a curiosity item.