Gordon D. Pusch wrote in message
...
(Starblade Darksquall) writes:
[snip]
A beam of light only exerts
"no gravitational force" on _another beam of light traveling in
the same direction_. On a massive particle, it exerts =TWICE=
the "gravitational force" one would naively calculate by Newton,
just as it experiences =TWICE= the gravitational deflection that
one would naively calculate by Newton --- and two light beams
traveling in opposite directions each experience _FOUR TIMES_
the "gravitational force" and gravitational deflection one would
naively calculate using Newton.
Wrong. In the center-of-momentum system, total energy gravitates,
nothing more nor less. Newtonian physics has nothing to say
about photons or light. In the proximity of massive bodies, photons
follow null-geodesics wherein, even in the limit of small mass and
large distance, the Newtonian gravitational potential is everywhere
"mulled-out". Unlike the Newtonian trajectories followed by massive
test particles, the deflection angle of light via space-time curvature
is independent of photon momentum. [Old Man]
-- Gordon D. Pusch