Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Anomalous precession of Mercury (was Re: Ice Age)



At 5:04 PM -0700 7/22/02, Roger Haar wrote:

I am amazed that in the 1910's the large Newtonian contribution to
the precession was calculated so well that a 10% disagreement was
well known and accepted.

It's much more amazing than that. As I understand it Leverrier
observed the anomalous (non-Newtonian) precession to be something
like 35" of arc per century in 1845. (Let's be clear that this
implies a period of some 10,000 years for the accumulation of just 1
degree of residual error!) His confidence in the significance of
this discrepancy (which is at least superficially justified by its
reasonable agreement with the modern figure) was sufficient to cause
him to seriously propose the existence of an as yet undiscovered
planet--"Vulcan." And *well* before the turn of the century, the
problem of Mercury's anomalous precession had risen to the stature of
a crisis in Newtonian physics.

I use this as a great example emphasizing to students the necessity
for careful error analysis in scientific work. Most wouldn't blink
an eye before attributing that astonishingly minuscule 35" of arc per
century to "human error."

--
John Mallinckrodt mailto:ajm@csupomona.edu
Cal Poly Pomona http://www.csupomona.edu/~ajm

Visit my Interactive Physics[TM] page at
http://www.csupomona.edu/~ajm/ip.html
(featuring new "Molecular Interaction" modules)

... and get FREE MUSIC (worth every penny) at
http://www.csupomona.edu/~ajm/personal.html#music