One wonders what Melloni's detector was. Very sensitive was Edison's tasimeter, which from what I've read could detect radiation from individual stars at the prime focus of a telescope.
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Monday, January 17th, 2022 at 2:47 PM, H LV <hveeder...@gmail.com> wrote: > The first person credited with detecting heat from moonlight was > > Macedonio Melloni in 1846. Below is a brief description of the > > experiment from "Infrared metaphysics: the elusive ontology of > > radiation. Part 1" by Hasok Chang , Sabina Leonelli. > > (Btw, I have read elsewhere that the experiment was performed on top > > of Mount Vesuvius rather than on his apartment balcony. Scientific > > folklore perhaps?) > > There is a link below of a video described as a reconstruction of > > Melloni's experiment. However it is only a laboratory demonstration > > using an electric burner as a source of infrared radiation, but it > > does use Melloni's large fresnel lens which is worth seeing. If the > > temperature change observed by Melloni was the same as in the video, > > then he observed an increase of only about 0.25 degrees. > > begin quote: > > <<On a clear moonlit night in 1846, Macedonio Melloni (1798–1854) took > > a magnificent lens out to the balcony of his apartment in Naples. He > > had just received the lens, one meter in diameter and the finest he > > had acquired so far for the Osservatorio Metereologico then under his > > direction. Melloni expectantly trained the powerfully focused > > moonlight on his 'thermomultiplier', the most sensitive thermometer > > yet known to science. To his delight, the thermomultiplier needle > > swung immediately on receiving the light. Over the ages moonlight had > > been considered the archetype of 'cold light', famously listed under > > the heading of 'negative instances of heat' in Francis Bacon's > > analysis of thermal phenomena designed to illustrate the methods of > > the new inductive science in the seventeenth century. Marc-Auguste > > Pictet in the late eighteenth century focused moonbeams into a bright > > light, but still detected no heat. Now Melloni had finally shown the > > fallacy of the old opinion. Only moments later, however, Melloni's > > delight turned into puzzlement as he noticed that the direction of the > > needle-swing indicated a cooling of the thermometer by the moonlight. > > That would not do. Melloni considered possible sources of error, made > > calculations, and cajoled the instruments, repeating the trials until > > he managed to produce a repeatable detection of a positive heating > > effect. > > This was not a frivolous experiment. Melloni was at the height of a > > productive research career that earned him the epithet of 'the founder > > of the science' of radiant heat, even 'the Newton of heat'. He made > > the moonlight experiment with a very specific purpose in mind: Melloni > > needed moonlight to have heat, in order to uphold his recent > > conversion to the view that illumination and radiant heat were both > > effects of one and the same cause. The radiation of heat (unmediated, > > near instantaneous transfer of heat) had been the subject of active > > research at least since about 1790, but the nature of radiant heat had > > still not been elucidated thoroughly. Melloni's importance in the > > history of science now rests mostly on his contributions toward the > > identification of radiant heat as long-wavelength light, but curiously > > he had spent the 1830s piling up experiment after experiment that went > > against the idea that 'obscure radiant heat' was 'invisible light'. > > His experimental arguments had convinced many others to turn away from > > the apparently absurd notion of non-illuminating light.>> > > end quote > > a reconstruction of a historical experiment > > https://youtu.be/iDcy21D6LLc > > Harry
