Trouble in the Heavens
Astronomers determined that Uranus's orbit around
the Sun took 84 years. But after tracking Uranus for several years, astronomers
realized something was amiss with their calculations.
According
to Newton's Law of Gravity, Uranus should move about the Sun in a certain
orbit, whose ellipticity would be determined by its mass, distance from
the Sun, and small gravitational effects of Jupiter and Saturn. In other
words, Uranus should behave in a predictable manner, if it had any respect
for science. It didn't, and scientists were duly perplexed. Was Newton's
Law wrong?
In 1824, the German mathematician Friedrich Bessel suggested that the
errors in Uranus's motion would be explained by the discovery of another
planet farther out. Of course, some argued that Newton's Law was not universal,
as previously advertised, but was only valid out to Saturn--beyond that
it required modification.
This was deemed a rather compromising solution to an elegant law of
physics, and by the end of the 1830s astronomers generally acknowledged
that there was an undiscovered planet whose gravitational attraction caused
Uranus's troubled motion.
Next: A Discovery and a Scandal
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