Neptune - The "Intentional" Planet

When William Herschel found Uranus in 1781, other [jealous?] astronomers said it was "accidental", a claim Herschel disputes with substantial reason. The discovery of Neptune on the other hand was certainly no accident but the result of a carefully determined analysis of the orbit of Uranus. After you add up the gravitational influences of the Sun and all the planets, the direction Uranus was heading was slightly off course. Not only was Uranus heading slightly off course but the course deviation was becoming greater as time passed. Only by supposing that another planet farther out existed could the deviation be explained.

Two mathematically inclined astronomers, John Couch Adams in England and Urbain Jean Joseph Leverier in France using the ever more precise orbital information for Uranus were able to predict that a large planet would appear in a certain part of the sky. Neither astronomer knew of the others work. In the spring of 1846 Adams had troubles getting the English Astronomer Royal to use the Greenwich telescope to find this predicted planet because of a series of unfortunate miscommunications. Leverier was luckier even through he started later. He easily convinced Johann Gottfried Galle at the Berlin Observatory to look for the planet. Although Galle spotted the planet first, Adams shares the title of discover with Leverier because of their mathematical predictions.

Not only were the predictions significant in themselves but they were a stunning proof of the accuracy and power of Newton's Laws. This prediction demonstrated the power of mathematical astronomy and physics in a way which would not be surpassed until an eclipse in 1919 provided proof that star light bent in the intense gravity of the Sun, thus verifying Einstein's Theory of Relativity.

Both Adams and Leverier made large mistakes in the assumed mass of Neptune. The planets from Mercury to Uranus are in a mathematical ratio called "Bode's Law". "Bode's Law" predicted the next planet would be 20% farther out than Neptune. Since both men assumed "Bode's Law" would apply to Neptune's distance, they made a second mistake which cancelled the first mistake! It helps in science, as in life, to be lucky.

Other eager astronomers tried to extend this technique to find additional planets. There seemed to be small deviations in the heading of Neptune. This seemed borne out when Pluto was found in 1930, even through Pluto was not were predictions indicated. In fact, the small deviations turned out to be slight errors in measurements in the position of Neptune. These tiny errors became apparent after enough time passed and new observations were made of Neptune's orbit.

The deity Neptune modeled after their earlier Greek deity Poseidon was in turn the merger of two earlier middle eastern gods - the god of the sea (Posei) and the god of earthquakes (Dan). What these two gods had in common was their love of horses and the realization by middle eastern people's that earthquakes followed the shorelines of the Mediterranean Sea. Neptune was deemed as powerful in the sea as Jupiter was on the land. Together with their third brother who ruled the Underworld [Pluto] they were paramount. The three greatest epics of the Greeks and the Romans [The Iliad, the Odyssey, by Homer and the Aeneid by Virgil] essentially deal with the wrath of Neptune at the Trojan war. His disagreements with the other gods, aided by a trio of angry goddesses who participated in an ill conceived beauty contest provided the impetuous for these epics. The entire Odyssey consists of a series incidents where Neptune/Poseidon interferes with the homecoming trip of Ulysses/Odysseus.

Leslie Coleman
Leslie Coleman
Entry Date:
Jun 1, 2002
Published Under:
Leslie Coleman's Columns
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