You
may not have heard of him, but in his time French mathematician
Urbain Le Verrier was famous and respected—at least among
astronomers. After all, he had just lounged about doing mathematics
and had discovered an entire planet! A big one, too!
(In
1846, Le Verrier predicted the presence and orbit of Neptune and
persuaded some astronomers to look for it at the right place. When it
was found, Le Verrier was given credit for the discovery of Neptune.)
More
than a decade later, Le Verrier announced that there was an anomaly
in Mercury's orbit—a small difference between what the mathematical
equations previously laid out by Sir Isaac Newton said Mercury should
be doing in its orbit, and what was actually observed by astronomers
watching Mercury night after night. Le Verrier said that there could
several explanations for the anomaly—one of which was another
planet that was so close to the Sun that it was very difficult to
observe.
On
this date in 1860, Le Verrier announced the discovery of such a
planet. He named the planet Vulcan, and he announced it to members of
the Académie des Sciences
with the words, “Gentlemen, I give you the planet Vulcan!”
Le
Verrier had once again used mathematics to compute where the new
planet should be, and he had consulted with amateur astronomer Edmond
Modeste Lescarbault, who had apparently spotted the planet in the
right place, making a transit across the face of the Sun.
This is a transit of Mercury. |
(We
can sometimes see the planets that are closer to the Sun than Earth,
Venus and Mercury, as they cross the face of the Sun. They look like
small black dots, and they cross the disk of the Sun in five or six
hours. These crossings are called “transits.”)
This is a sunspot. |
The
problem with this announcement is, Lescarbault was wrong—apparently
he was seeing a sunspot seem to move across the Sun as the Sun
revolved on its axis. And so that made Le Verrier's announcement
wrong, too. Many astronomers tried to confirm the so-called sightings and failed, and eventually Einstein's refinement to Newtonian physics explained the anomaly of Mercury's orbit without the need of another planet.
Also
on this date:
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