Did Maxwell Pull a Fast One? [AP-S Turnstile]

A radiometer (also known as a light-mill, and more precisely as a Crookes radiometer) was developed by Sir William Crookes in 1873 while investigating infrared radiation and the element thallium. Crookes submitted a paper using differential radiation pressure to describe the operation of the radiometer. The paper was reviewed by Maxwell, who accepted Crookes\´s explanation, taking delight apparently in the experimental vindication of radiation pressure predicted by his electromagnetic theory. However, within a few years, it was noted that if radiation pressure were responsible for making the vanes turn, the vanes would turn in the direction opposite to what is actually observed. The brighter reflective side would have the greater radiation pressure and, therefore, the vane would be pushed towards the darker side.In 1879, Osborne Reynolds (remember the "Reynolds number" from fluid dynamics?) offered the correct qualitative explanation for the radiometer\´s rotation, based on his theory of "thermal transpiration," in a manuscript submitted to the Royal Society. In the presence of a thermal gradient, gas molecules exert tangential forces along the edges of a vane, which results in the rotation observed. Maxwell was again a reviewer for the manuscript; he bought Reynolds\´s explanation, but recommended changes to the analysis.