Crookes Radiometer Solar Light Windmill Glass Bulb – 14cm

Watch Science Come to Life — Crookes Radiometer

First invented in 1873 by chemist Sir William Crookes, the Crookes Radiometer is a stunning desk ornament and working physics demonstration all in one. Simply place it near a sunny window or under an incandescent bulb and watch the four lightweight vanes spin — no batteries, no motors, just the power of light.

Inside the hand-crafted glass bulb, a partial vacuum allows a low-friction rotor to spin freely. Each vane is polished on one side and dark on the other. As light energy strikes the vanes, the dark sides absorb more energy and retreat while the lighter sides advance — producing a mesmerising, seemingly effortless rotation. The brighter the light, the faster the spin!

Made in Mainland China.

Key Features

• 🌞 Powered purely by light — sunlight or incandescent light sets the vanes spinning instantly
• 🔬 Real physics in action — demonstrates how light energy can be converted into mechanical motion
• 🎁 Elegant gift idea — makes a unique, conversation-starting present for science enthusiasts, teachers, and curious minds
• 🏺 All-glass construction — clear glass globe (approx. 3.5 in / ~9 cm diameter) mounted on a glass stand, 8 in / ~20 cm tall
• ✨ Low-friction spindle — partial vacuum inside the bulb ensures near-frictionless rotation for maximum effect
• 🪟 Easy to use — just place near a light source and enjoy; no setup required

Specifications

How to Use

1. Place your radiometer on a flat surface near a window or directly under an incandescent light.
2. Watch the vanes begin to spin as light energy is absorbed.
3. The more intense the light source, the faster the rotation — try it in direct sunlight for the best effect!

Perfect For

• Science classrooms and educational demonstrations
• Desk or shelf décor for curious minds
• Unique birthday, holiday, or "just because" gifts
• Home offices, libraries, and study spaces

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Frequently Asked Questions

Q: Does the Crookes Radiometer work with LED or fluorescent light?

A: The radiometer works best with sunlight or traditional incandescent light bulbs, which emit the full spectrum of light and infrared energy needed to spin the vanes. LED and fluorescent lights emit far less infrared radiation and may not produce enough energy to rotate the vanes effectively. Placing the radiometer on a sunny windowsill is the most reliable option.

Q: Is the Crookes Radiometer fragile?

A: Yes — the bulb and stand are made entirely of glass, so it should be handled with care and placed on a stable, flat surface away from high-traffic areas. It is designed as a decorative and educational display piece, not a toy. Keep it out of reach of young children.

Q: What makes the vanes spin inside the glass bulb?

A: The vanes spin because of the difference in how the dark and light sides of each vane absorb light energy. Inside the partial vacuum, gas molecules near the dark (energy-absorbing) side become slightly warmer and push against that side, causing the rotor to turn. The greater the light intensity, the faster the rotation.

Q: What size is the Crookes Radiometer?

A: It measures 14 cm × 7.5 cm overall — the glass globe is approximately 3.5 inches (about 9 cm) in diameter, and the full piece stands about 8 inches (approximately 20 cm) tall. Please allow ±1–3 mm for manual measurement variation.

Production & Packaging Notice

To maintain high stock availability and fast shipping times, our items are sourced from multiple verified manufacturing facilities. While the core quality, materials, and product specifications remain identical, you may notice slight variations in the packaging design, manufacturing origin, or the wording of the printed instructions.