Séminaire
| Résumé
: We
critically examine the evidence available
of the early ideas on the bending of light
due to a gravitational attraction, which
led to the concept of gravitational
lenses, and attempt to present an
undistorted historical perspective.
Contrary to a widespread but baseless
claim, Newton was not the precursor to the
idea, and the first Query in his Opticks
is totally unrelated to this phenomenon.
We briefly review the roles of Voltaire,
Marat, Cavendish, Soldner and Einstein in
their attempts to quantify the
gravitational deflection of light. The
first, but unpublished, calculations of
the lensing effect produced by this
deflection are found in Einstein's 1912
notebooks, where he derived the lensing
equation and the formation of images in a
gravitational lens. The brief 1924 paper
by Chwolson which presents, without
calculations, the formation of double
images and rings by a gravitational lens
passed mostly unnoticed. The unjustly
forgotten and true pioneer of the subject
is F. Link, who not only published the
first detailed lensing calculations in
1936, nine months prior to Einstein's
famous paper in Science, but also
extended the theory to include the effects
of finite-size sources and lenses, binary
sources, and limb darkening that same
year. Link correctly predicted that the
microlensing effect would be easier to
observe in crowded fields or in galaxies,
as observations confirmed five decades
later. The calculations made by Link are
far more detailed than those by Tikhov and
Bogorodsky. We discuss briefly some papers
of the early 1960s which marked the
renaissance of this theoretical subject
prior to the first detection of a
gravitational lens in 1979. An unpublished
chapter of Petrou's 1981 PhD thesis
addressed the microlensing of stars in the
Magellanic clouds by dark objects in the
Galactic halo, a topic which would be
publicised by Paczynsky five years later,
and which led to the first detections of
microlenses within the Milky Way in 1992. |
Bibliographie
- "The
conceptual origins of
gravitational lensing"
David Valls-Gabaud, in
"Albert Einstein Century
International
Conference", AIP
Conference Proceedings,
Volume 861, pp.
1163-1171 (2006), http://arxiv.org/abs/1206.1165
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