Editing Crookes radiometer (section)

===Currently accepted theory===
The currently accepted theory was formulated by [[Osborne Reynolds]], who theorized that [[thermal transpiration]] was the cause of the motion.<ref>{{cite journal |first=Osborne |last=Reynolds |author-link=Osborne Reynolds |date=1 January 1879 |doi=10.1098/rstl.1879.0078 |title=On certain dimensional properties of matter in the gaseous state … |journal=Philosophical Transactions of the Royal Society of London |volume=170 |pages=727–845}}; Part 2.</ref> Reynolds found that if a porous plate is kept hotter on one side than the other, the interactions between gas molecules and the plates are such that gas will flow through from the cooler to the hotter side. The vanes of a typical Crookes radiometer are not porous, but the space past their edges behaves like the pores in Reynolds's plate. As gas moves from the cooler to the hotter side, the pressure on the hotter side increases. When the plate is fixed, the pressure on the hotter side increases until the ratio of pressures between the sides equals the square root of the ratio of absolute temperatures. Because the plates in a radiometer are not fixed, the pressure difference from cooler to hotter side causes the vane to move. The cooler (white) side moves forward, pushed by the higher pressure behind it. From a molecular point of view, the vane moves due to the tangential force of the rarefied gas colliding differently with the edges of the vane between the hot and cold sides.<ref name="Usenet Physics FAQ"/>

The Reynolds paper went unpublished for a while because it was refereed by Maxwell, who then published a paper of his own, which contained a critique of the mathematics in Reynolds's unpublished paper.<ref>{{cite journal |first=J. Clerk |last=Maxwell |author-link=James Clerk Maxwell |date=1 January 1879 |doi=10.1098/rstl.1879.0067 |title=On stresses in rarefied gases arising from inequalities of temperature |journal=Philosophical Transactions of the Royal Society of London |volume=170 |pages=231–256|url=https://zenodo.org/record/1432458 |doi-access= }}</ref> Maxwell died that year and the [[Royal Society]] refused to publish Reynolds's critique of Maxwell's rebuttal to Reynolds's unpublished paper, as it was felt that this would be an inappropriate argument when one of the people involved had already died.<ref name="Usenet Physics FAQ"/>