Sluneční radiometr

The vanes start spinning within seconds of even indirect sunlight hitting the glass bulb. It's a mesmerizing little science piece that needs no batteries, just a bright windowsill.

Pleasantly surprised at how quickly the vanes start spinning once you set it in a sunny window. The glass bulb feels sturdy, and it's mesmerizing to watch the light energy at work without any plugs or batteries.

My kids dragged this onto the kitchen windowsill first thing this morning, and the pinwheels were spinning before our coffee was done. It's such a simple, clever way to see light energy doing its thing—no batteries, just sunlight, and it's oddly mesmerizing to watch.