I think Melloni's detector was a homemade thermocouple and probably the best one for the time. The thermalelectric effect- on which a thermocouple depends - was still pretty new at the time having been discovered in the 1820s by Seeback (who incidently helped Goethe write his book on a colour theory of light).
Harry On Mon., Jan. 17, 2022, 5:26 p.m. MSF, <foster...@protonmail.com> wrote: > 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 > >
