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LE SAGE GRAVITYbyRobert NemiroffMichigan Tech
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Physics X: About This CourseOfficially "Extraordinary Concepts
in Physics"Being taught for credit at Michigan TechLight on math,
heavy on concepts Anyone anywhere is welcome No textbook
requiredWikipedia, web links, and lectures onlyFind all the
lectures with Google at:"Starship Asterisk" then "Physics X"
http://bb.nightskylive.net/asterisk/viewforum.php?f=39
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GRAVITYIs the mechanism for gravity known?
1. Yes, it is the changing geometry of spacetime.2. No, gravity
still requires "action at a distance".3. Maybe and sometimes.
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LE SAGE GRAVITY"There is no model of the theory of gravitation
today, other than the mathematical form."- Richard Feynman (The
Character of Physical Law 1965) Le Sage gravity
was an early attempt to provide a mechanism for gravity.was
discussed in detail in the mid-1700s by Le Sage.was preceded by
several similar theories, most notably one by Newton's contemporary
Fatio.shares some attributes with virtual quantum forces.
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LE SAGE GRAVITY
has problems -- no classical formulation works.was never
accepted as a serious mechanism for gravity.is occasionally
reinvented today by people who don't know its history or
flaws.remains useful today asa toy model."mock gravity" in some
physical situations.
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LE SAGE GRAVITYBasics:A sea of unseen particles moves in all
directions.A single body experiences no net force as it is impinged
from all directions.Interestingly, this does not depend on the
object's shape.Two bodies will create "shadows" in this sea of
particles that will cause mutual attraction.
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LE SAGE GRAVITYBasics:Objects are mostly empty space, so
interaction cross-section scales not as area but volume (assuming
constant density).Correctly shows proportionality to object mass.
Scattering is somehow unimportant.Le Sage gravity correctly yields
an inverse square law in these approximations.
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LE SAGE GRAVITY: PROBLEMSBasics problems:Masses must be (almost)
completely transparent to these "ultramundane corpuscles".or Le
Sage gravity will not be proportional to mass.Reflected corpuscles
cannot create force.or Le Sage gravitational force will not drop as
inverse square.Absorbed corpuscles would heat any object to
explosion quickly.Drag force expected for motion through the sea.
No external evidence for these corpuscles.
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LE SAGE GRAVITY: PROBLEMSBasics problems (continued):Range:
corpuscular interactions would limit the range of this
force.Aberration: orbital aberration of Le Sage gravity would cause
spiraling out, unless corpuscles moved much faster than light.Lunar
Theory: doesn't match Moon's motion.Relativistic effects
unaccounted for.Binding energy effects unaccounted for.
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LE SAGE GRAVITY:USEFUL VISUALIZATION TOOLSometimes useful for
visualizing force directionality.
For example, using Le Sage gravity, it is easy to picture that
everywhere inside a massive spherical shell there is no net
gravitational acceleration. This is because the shell blocks Le
Sage particles the same in all directions.
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LE SAGE GRAVITY: MOCK GRAVITYMock gravity, a distant cousin of
Le Sage gravity is actually useful in some astrophysical
situations.
One such situation is two opaque dust grains in a photon
field.
The dust grains attract because they create shadows in this
field.
The force is only proportional to the area of the grain,
however, andnot the mass of the grain.
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GEORGES-LOUIS LE SAGEDeveloped an early version of the electric
telegraph in 1774predecessor of the Internethad 26 wires strung
between two roomsone for every letter
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