The core principle of the Crookes radiometer's optical drive is the momentum difference of gas molecules caused by photothermal conversion: 1. The black side of the blade absorbs light and heats up (20-50°C higher than the white side), heating the remaining gas molecules (optimal conditions are a vacuum of 1-10 Pa). 2. The heated gas molecules violently collide with the black side, generating thrust that causes the blade to rotate (a complete vacuum or high-pressure environment cannot drive the blade). 3. Experimental results confirm that the direction of rotation is opposite to that of light pressure theory, confirming that thermodynamic effects dominate.
