**AAS 197, January 2001**

*Session 1. HAD I: Boners of the Century*

Special Session Oral, Sunday, January 7, 2001, pm, SDSU, Zinner Collection
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## [1.01] J. B. Biot and Refraction Calculations

*A. T. Young (SDSU)*

The Auer-Standish (AJ **119**, 2472, 2000) algorithm,
recommended in the revised Explanatory Supplement for
calculating refraction in an arbitrary model atmosphere, was
derived and used by J.~B.~Biot (Conn.\ des Tems pour l'An
1839) a century and a half earlier, using Newton's (wrong)
emission theory, and the clumsy notation of Laplace's *
Mécanique Céleste*, which Biot had proof-read.
Newton, Laplace, and Biot all describe refraction in terms
of the trajectories of ``luminous molecules'' attracted by a
central force exerted by the atmosphere; this explains why
Laplace considered refraction a topic in celestial
mechanics. Fortunately for these authors, the only optics
required is Snel's law of refraction, which was discovered
before Newton's birth, and which Newton's corpuscular optics
was rigged to reproduce. Thus Biot's ``derivation'' of the
refractive invariant nr \sin z by Laplace's method is a
circular and unnecessary argument.

While Auer & Standish were reinventing Biot's method, the
historian D.~T.~Whiteside (Centaurus **24**, 288, 1980)
noticed the mathematical similarity of the refraction
theories of Newton and Biot to modern ones, and rashly
concluded that ``working astronomers still find
computational advantage in maintaining the fiction of a
Newtonian emission theory'' --- which is absurd nonsense!

Despite being an emissionist, Biot understood atmospheric
refraction much better than most astronomers do today: he
knew why refraction is almost independent of atmospheric
structure, except within a few degrees of the horizon, and
that refraction at the horizon depends mostly on the local
temperature gradient. His work --- together with that of
Lord Rayleigh, who derived his eponymous scattering law from
the elastic-solid theory of the luminiferous æther ---
reminds us that a theory's correct results do not make it
true.

This work was supported by NSF grant ATM-9714357.

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