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 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:
>
> <
> 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
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> 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
