Friday, April 19, 2013

Finding Neptune

The title page for "An Explanation."
Uranus, the seventh planet, was officially discovered in 1781 by William Herschel and at that time was thought to be the farthest planet from the sun. However minor variations from its observed orbit and that predicted by computation indicated that an additional body might be present further out that was responsible for the perturbations. The challenge of calculating the hypothetical orbit of such a body and thus pinpointing its location for observation was independently taken up by Urbain Le Verrier and John Couch Adams. Unfortunately for Adams, Le Verrier published first.

Adams presented his findings to the Royal Astronomical Society on November 13, 1846, approximately two and half months after Le Verrier's calculations had been made public at a meeting of the Royal Academy of Sciences in Paris. In his paper An Explanation of the Observed Irregularities in the Motion of Uranus: On the Hypothesis of Disturbances Caused By a More Distant Planet; With a Determination of the Mass, Orbit, and Position of the Disturbing Body (London: W. Clowes & Sons, 1846) Adams discussed his own interest in the problem and attempts to resolve the issue but ultimately credited Le Verrier and Johann Galle with the discovery of what we now know as the planet Neptune.
I mention these dates merely to show that my results were arrived at independently, and previous to the publication of M. Le Verrier, and not with the intention of interfering with his just claims to honours of the discovery; for there is no doubt that his researches were first published to the world, and led to the actual discovery of the planet by Dr. Galle, so that the facts stated above cannot detract, in the slightest degree, from the credit due to M. Le Verrier.
Adams then goes into details of his attempts to calculate the orbit and the various methods that he employed. This was a tedious process of testing various hypotheses and then calculating the predicted orbit from those equations and comparing the predictions to observed data.

Rauner's copy of Adam's paper is a presentation copy from the author to a Lieutenant W. S. Swafford, R.N. Ask for Rare Book QB 681 .A32 1846.

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