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For Him / Her / Kids
Crookes Radiometer — physics that spins in the sun
DORAMI Crookes Radiometer (Glass Light Mill)
Reviewed by the WhyToBuyThis team · Updated September 2026 · How we choose
Perfect for
- Science lovers
- Desk & windowsill
- Under $25
- Curious kids too
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Price: $25.99
Price may change on Amazon. As an Amazon Associate we earn from qualifying purchases. This won't cost you anything extra.
- Great gift ideaChosen for real-world gifting
- Hand-pickedCurated, not scraped
- Honest reviewThe catch, not just the hype
Why this gift works
A Crookes radiometer is an airtight glass bulb, partly emptied of air, with a set of vanes on a spindle inside. Each vane is dark on one side and light on the other, and in sunlight or bright lamplight the vanes spin on their own - no batteries or power. This listing is DORAMI's clear glass radiometer.
The fun part is that the obvious explanation is wrong: it is not light pushing the vanes but a thermal effect in the thin gas, a puzzle that tripped up scientists for decades. It is a small, cheap desk piece that gets a scientist talking.
Who is this gift for?
Great for
- A physics teacher's desk
- A windowsill that gets morning sun
Think twice if
- Their room gets little direct light
The catch
It is fragile glass and only spins well in strong light - on a gray day or in a dim office it barely moves.
Skip for a desk with no direct sun or bright lamp.
Key specs
| Brand | DORAMI |
|---|---|
| Type | Crookes radiometer (light mill) |
| Bulb | Clear glass, partial vacuum |
| Power | Sunlight or bright light; no batteries |
| How it works | Thermal transpiration turns the vanes, dark side away from the light |
Worth knowing before you buy
- Keep it away from edges - the bulb is glass.
- It spins fastest in direct sunlight.
Why we like it
- Needs no power at all
- A real physics puzzle on a windowsill
- Cheap and eye-catching
What to look for in a radiometer
- Glass quality. Clear, even glass shows the vanes best.
- Stable base. A wide base keeps it from tipping.
- Light. It needs direct sun or a bright lamp to spin well.
Questions people ask
Light warms the dark sides of the vanes, and the thin gas in the bulb pushes on them through a thermal effect called thermal transpiration.
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