William Herschel, A Blue Sky Hero

There are some people in the sphere of science that stand out as simply spectacular contributors. One such is Sir William Herschel. Not only was he a gifted composer, writing 24 symphonies, but he also discovered infra red light,  the planet Uranus, and four moons (two each of Saturn and Uranus), he coined the term asteroid, pioneered astronomical spectrophotometry and discovered that Mars’ polar caps varied with the season. Achieving just one of those would normally be ample legacy for one lifetime.

Herschel was born in Germany (his birth name was Wilhelm) in 1738 but emigrated to England in his late teens along with his sister, Caroline, who would herself go on to be an accomplished astronomer that would discover numerous comets. The first part of his life was dominated by music, it wasn’t until his late thirties when a chance encounter with an amateur violinist, who happened to be a leading mathematician with an interest in astronomy, that he turned his gaze upon the heavens. The Herschel siblings became famous for constructing the best telescopes in the land and for grinding and polishing their own extremely high quality lenses – they would spend up to 16 hours per day working on them.

In 1781 Herschel was working on his catalogue of stars when he noticed that one of them appeared as more like a disc and moved in a most unusual fashion. Closer observations led him to the discovery of Uranus, the first time a planet had been discovered since ancient times. The finding made him famous and he was especially favoured by King George III who knighted him (only an honorary title as he wasn’t British), made him the King’s Astronomer (not to be confused with the Astronomer Royal) and made sure that he was well funded.

For me it was his discovery of infra red light that I find most interesting. It was the year 1800 and at that point no one knew that the light we see was just a tiny fraction of the electromagnetic spectrum, no one had heard of ultra violet light, radio or microwaves, x-rays or gamma rays. No one was even looking for them, not even Herschel himself. Just like his planetary discovery his electromagnetic one was born out of nothing more than an insatiable curiosity and the desire to observe, categorise and record.

By this point it was well established that sunlight could be split into the colours of the rainbow using a prism. When I was a kid the mnemonic was Richard Of York Gave Battle In Vain. Herschel was at home in Slough when he pulled his curtains closed leaving only a little chink for light to get through. He carefully placed a prism so the the spectrum of visible light, red through blue, was spread across his table. He had a series of thermometers all laid out in a row each with their ends in a different colour, he also laid out a couple just past the red end to measure the ambient temperature of the room and act as controls.

As suspected, each colour in the spectrum registered a different temperature starting with the coolest at the blue end and getting steadily hotter as it transitioned towards the red. He was certainly surprised, however, when he noted that the hottest temperature of all was measured on the control thermometers out past the rainbow where no light could be seen to be falling. He carried out further experiments on what he initially termed ‘calorific rays’ and found that their properties were very similar to that of visible light in that they could be reflected, refracted and absorbed.

This was the first time that anyone had ever demonstrated there was a type of light beyond what we could simply observe with our eyes and, in a stroke, he breathed life into an entirely new field of science.

For me, Herschel is a wonderful example of why a big chunk of science needs to be curiosity driven. Now doubt there is also a need for very focussed, goal orientated science too, like developing new vaccines and antibiotics, making nuclear fusion work on an industrial scale or improving safety in vehicles of all kinds. But, alongside that, an essential part of a healthy science ecosystem must be the people who are simply allowed to go where their curiosity takes them. From the discovery of penicillin and DNA fingerprinting to the Higgs boson and the world wide web, many of the most significant discoveries of all time were down purely to nerds being allowed to be nerds for nerds sake.

As the inimitable Isaac Asimov said:

The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ but ‘That’s funny…’

Sir William Herschel, by Lemuel Francis Abbott, 1785

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