This is just a filler to say I aten't dead yet. I'm just fairly busy.
Macedonio Melloni (1798 - 1854) is
little-known, which is why this is a brief account. Still, what there is seems
quite interesting, and it sets the scene for several other stories, so I will
share it with you.
First, some background. William Herschel did many things in
astronomy. Among other things, he took the temperature of different parts of
the spectrum, and found that the hottest part of the Sun’s spectrum was beyond
the visible range. Using a thermometer, he discovered the infrared part of the
spectrum.
Now back to Melloni: if you heat a junction
between two different metals, you generate a very small current. In order to be
able to measure the current, you need to multiply it by linking a number of
these junctions together, to make a battery of them, like the pile of cell units that Alessandro Volta
made. This is why we call Melloni’s invention a thermopile.
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| Source: https://muxindia.wordpress.com/2014/11/06/passive-infrared-sensor-pir-sensor/ |
As well, Melloni developed ways of
concentrating the heat from distant sources, and he found out how to use rock
salt to make lenses to focus the heat rays, in the same way we use glass lenses
to focus light rays. He established that the infrared rays were in every way
like light: they could be refracted, reflected, polarised and made to interfere
with each other, exactly like light.
Melloni really deserves to be better known,
for while Herschel’s discovery of the infrared is a commonplace, few people
realise that Melloni’s investigations laid a practical framework within which
James Clerk Maxwell could propose the existence of a continuous electromagnetic
spectrum.
Everything in science is connected, which is why we can usually spot fraudulent science at a glance. It doesn't connect with all the other bits...
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