Odd this day
On this day, mathematician Urbain Le Verrier announced to the Académie des Sciences in Paris that a new planet had been identified: Vulcan.
It orbited the Sun, apparently, closer than Mercury, its transit having been observed by doctor and amateur astronomer Edmond Modeste Lescarbault in his homemade observatory.
(Le Verrier, the established Parisian academician, got to announce it, but the doctor did get a Légion d’honneur, and a road named after him in his hometown, which is still there.)
This was terribly exciting, because astronomers had been looking for planets inside Mercury’s orbit since the 17th century, when they’d spotted that it moves in a mysterious way. Its orbit is elliptical, not circular, so sometimes it’s 29 million miles from the Sun, and sometimes 43m miles away.
A planet’s closest point to the Sun is its perihelion, its furthest the aphelion, and for Mercury, the difference between the two varies more than any other planet’s. Also, when it’s further away, it travels faster. The extra planet which could explain all this had been named Vulcan after the Roman god of fire, because it would, of course, have been absurdly bloody hot there.
Le Verrier put Mercury’s eccentricity down to the gravitational woo of a nearby celestial body, and said Vulcan orbited — in a neater, more circular fashion — about 13 million miles from the Sun.
People were ready to listen to him because he’d used the same kind of maths to examine the orbit of Uranus and predict (correctly) the position of Neptune in 1846.
He’d published a paper in September 1859 giving his analysis sufggesting that Vulcan was definitely there on the grounds that Newtonian physics couldn’t fully explain Mercury’s orbit. This had prompted Lescarbault to write to him, because the previous March, Lescarbault had seen a black spot in transit across the face of the Sun.
Le Verrier, according to the Spectator of 15 March 1879, took data from
several other accounts of round spots, and by combining them together, deduced several orbits which could be reconciled with these observations.
Another French astronomer, working in Rio, said he’d been looking at the Sun at exactly the same time as Lescarbault, through a much better telescope, and hadn’t seen anything answering its description. With nothing definite, people kept looking, with no success at all until a total eclipse in 1878 when two American astronomers saw Vulcan, separately. None of the sightings’ coordinates matched, though, so the searching went on — especially during seven further solar eclipses between 1883 and 1908.
Not a sausage.
It eventually turned out that calculations like Le Verrier’s based on Newtonian mechanics couldn’t explain everything — because Einstein, the bloody spoilsport, came up with the theory of relativity, and showed that there didn’t need to be a Vulcan for Mercury to be all weird.
Photos (during a solar eclipse) in 1919 show starlight bending around the Sun because spacetime is curved. You may well have as much chance of getting your head round that as I do, but essentially this meant that gravity was explained by a different equation, and that meant no Vulcan. (Until 1965, when Gene Roddenberry made things all better again.)
Black blobs, incidentally, had been seen in front of the Sun since at least 800BCE, and were eventually explained as sunspots — dark patches, slightly cooler than the rest of the Sun, caused by magnetic flux.
Some sources if you want to know more:
