Measuring Distance, Light and Curved Space-Time

On Sep 1, 7:14 pm, wrote in
sci.physics.relativity:
jeffp wrote:
A quick question (or series of related questions) thats been bugging
me for years for the physics gurus out there.
Given that space-time warps based on its proximity to massive objects
(including unobservable black holes, and theoretically, unobserved-to-
date dark matter) and that light travels over that warped medium, how
do scientists know whether or not light from a distant object has been
significantly bent/slowed down for some part of the journey on the way
to earth?

In general, the effect of bending is quite small. A light ray grazing
the Sun, for example, is deflected less than two arcseconds, about
1/1000 of the angle subtended by the Moon. A light ray passing
even slightly farther from the Sun is deflected less -- the deflection
angle is inversely proportional to the "impact parameter," the distance
of closest passage. Bigger masses can give bigger deflections, but only
if the light happens to pass very close to their centers.

There is, in fact, a major effort to measure this deflection, since it
can be used to map the matter in the Universe, including dark matter.
The measurements are possible because gravitational lensing, in
addition to deflecting light, also distorts images. If you look at http://www.cita.utoronto.ca/~hoekstra/lensing.html you'll see some
nice illustrations and photos. The deflection is almost always small
enough, though, that it takes a huge amount of data to extract it from
random noise. (This will be one of the main missions of the LSST, the
Large Synoptic Survey Telescope.)

Astronomers also look for deflection by black holes and other forms of
concentrated matter. This is possible, in part, because light deflected
by a gravitational field is also focused, so an image becomes brighter.
Since a black hole, say, is unlikely to be exactly at rest relative to a
background star, we can look for sudden brightening -- in a particular,
predictable pattern -- to search for a black hole (or a planet, or a
brown dwarf, or a lump of dark matter) passing in front of a star.

This search for "microlensing" events was pioneered by the MACHO
project, http://wwwmacho.mcmaster.ca/. (A MACHO is a "massive compact
halo object," a possible form of dark matter; a competing form is a WIMP,
a "weakly interacting massive particle.") Looking at 18 million stars,
they've found 53 likely microlensing events -- it is, again, not a very
common event.

There is also a time delay (the Shapiro time delay) from gravitational
fields, but this is again small. For example, there was a famous
supernova, SN1987A -- I guess "famous" depends on the circles you
travel in -- in 1987, and physicists did a reasonable careful calculation
of the time delay (see Longo, Phys. Rev. Lett. 60 (1988) 173. The total
time delay comes out to about five months. This seems large, but it's
over a travel time of some 160,000 years. So again it's a very small
error -- astronomers would be thrilled if they could measure distances
to anywhere near that accuracy.

Steve Carlip

The last active teacher in Einsteiniana, Steve Carlip, stopping short,
as though by instinct, at the threshold of the dangerous thought:
"Arthur Eddington was simply unable to measure the deflection, let
alone to discriminate between the prediction given by Newton's
emission theory of light and that given by Einstein's "theory", and
therefore the 1919 experiment "catapulting Einstein into fame" was a
complete fraud":

http://www.liferesearchuniversal.com...html#seventeen
George Orwell: "Crimestop means the faculty of stopping short, as
though by instinct, at the threshold of any dangerous thought. It
includes the power of not grasping analogies, of failing to perceive
logical errors, of misunderstanding the simplest arguments if they are
inimical to Ingsoc, and of being bored or repelled by any train of
thought which is capable of leading in a heretical direction.
Crimestop, in short, means protective stupidity."

http://vaghelasv.com/Documents/Steph...ry.Of.Time.pdf
Stephen Hawking: "Einsteins prediction of light deflection could not
be tested immediately in 1915, because the First World War was in
progress, and it was not until 1919 that a British expedition,
observing an eclipse from West Africa, showed that light was indeed
deflected by the sun, just as predicted by the theory. This proof of a
German theory by British scientists was hailed as a great act of
reconciliation between the two countries after the war. It is ionic,
therefore, that later examination of the photographs taken on that
expedition showed the errors were as great as the effect they were
trying to measure. Their measurement had been sheer luck, or a case of
knowing the result they wanted to get, not an uncommon occurrence in
science."

http://www.cieletespace.fr/evenement...taient-fausses
"Relativité: les preuves étaient fausses.....Le monde entier a cru
pendant plus de cinquante ans à une théorie non vérifiée. Car, nous le
savons aujourdhui, les premières preuves, issues notamment dune
célèbre éclipse de 1919, nen étaient pas. Elles reposaient en partie
sur des manipulations peu avouables visant à obtenir un résultat connu
à lavance, et sur des mesures entachées dincertitudes, quand il ne
sagissait pas de fraudes caractérisées."

http://www.cieletespaceradio.fr/inde...-la-relativite
"Au début du XXème siècle, des scientifiques comme le Britannique
Arthur Eddington avaient tant à coeur de vérifier la théorie de la
relativité qu'ils ont tout mis en oeuvre pour que leurs expériences
soient probantes." (ECOUTEZ!)

http://discovermagazine.com/2008/mar...out-relativity
"The eclipse experiment finally happened in 1919 (youre looking at it
on this very page). Eminent British physicist Arthur Eddington
declared general relativity a success, catapulting Einstein into fame
and onto coffee mugs. In retrospect, it seems that Eddington fudged
the results, throwing out photos that showed the wrong outcome. No
wonder nobody noticed: At the time of Einsteins death in 1955,
scientists still had almost no evidence of general relativity in
action."

http://www.newscientist.com/article/...to-albert.html
New Scientist: Ode to Albert
"Enter another piece of luck for Einstein. We now know that the light-
bending effect was actually too small for Eddington to have discerned
at that time. Had Eddington not been so receptive to Einstein's
theory, he might not have reached such strong conclusions so soon, and
the world would have had to wait for more accurate eclipse
measurements to confirm general relativity."

Pentcho Valev

On Sep 4 Steve Carlip wrote in sci.physics.relativity:
There have been efforts to see whether
high energy gamma rays from supernovae travel at a different speed
than lower energy gamma rays -- if so, this would indicate a violation
of special relativity, and perhaps give us clues about quantum gravity
-- but no real effect has been seen.

Honest Carlip your brothers Einsteinians (Lee Smolin etc.) have
extracted a lot of career and money from this so you should not be so
hostile. Instead of waiting for a "real effect", just analize the
Pound-Rebka experiment: does it confirm variable speed of light, or
does it confirm constant speed of light? Remember this:

http://math.ucr.edu/home/baez/physic..._of_light.html
Steve Carlip: "Einstein went on to discover a more general theory of
relativity which explained gravity in terms of curved spacetime, and
he talked about the speed of light changing in this new theory. In the
1920 book "Relativity: the special and general theory" he wrote:
". . . according to the general theory of relativity, the law of the
constancy of the velocity of light in vacuo, which constitutes one of
the two fundamental assumptions in the special theory of relativity
[. . .] cannot claim any unlimited validity. A curvature of rays of
light can only take place when the velocity of propagation of light
varies with position." Since Einstein talks of velocity (a vector
quantity: speed with direction) rather than speed alone, it is not
clear that he meant the speed will change, but the reference to
special relativity suggests that he did mean so. (...) In this
passage, Einstein is not talking about a freely falling frame, but
rather about a frame at rest relative to a source of gravity. In such
a frame, the speed of light can differ from c..."

Which situation are we in now? I don't know; but I don't think anyone
else does, either.

Steve Carlip

Bryan Wallace did know, Honest Carlip, but he died in oblivion while
you and your brothers Einsteinians were fiercely exploiting the money-
spinner called "theory of relativity":

http://www.ekkehard-friebe.de/wallace.htm
Bryan Wallace: "Einstein's special relativity theory with his second
postulate that the speed of light in space is constant is the linchpin
that holds the whole range of modern physics theories together.
Shatter this postulate, and modern physics becomes an elaborate
farce!....The speed of light is c+v."

Pentcho Valev