From: Alex Michael Bonnici (albonnici_at_vol.net.mt)
Date: Sun Sep 11 2005 - 04:41:44 UTC
Hello Gang this just came in over the Skeptics Forum Mailing List.
Alex
A new analysis of 'cool' spots in the cosmic microwave
background may
cast new doubts on a key piece of evidence supporting the
big bang
theory of how the universe was formed.
Two scientists at The University of Alabama in Huntsville
(UAH) looked
for, but couldn't find, evidence of gravitational "lensing"
where you
might expect to find it, in the most distant light source
in the
universe -- the cosmic microwave background.
Results of this research by Dr. Richard Lieu, a UAH physics
professor,
and Dr. Jonathan Mittaz, a UAH research associate, were
published
Monday in the "Astrophysical Journal."
In the same paper, Albert Einstein's 1917 theory that at a
certain
"critical" density the counteracting forces of gravity and
expanding
space can result in a "flat" universe no matter how
irregular the
distribution of matter might be, is proven mathematically
for the
first time.
Proving Einstein right might become a problem for the
standard
cosmological model of how the universe was formed because
Einstein's
theory also predicts that the cosmic microwave background
shouldn't
look the way it does, according to Lieu.
The problem, he says, is that cool spots in the microwave
background
are too uniform in size to have traveled across almost 14
billion
light years from the edges of the universe to Earth.
"Einstein's theory of how gravity attracts light, coupled
with the
uneven distribution of matter in the near universe, says
you should
have a spread of sizes around the average, with some of
these cool
spots noticeably larger and others noticeably smaller," he
said. "But
this dispersion of sizes is not seen in the data. When we
look at
them, too many cool spots are the same size."
The cosmic microwave background is believed to be the
afterglow of hot
gases that filled the fledgling universe immediately
following the big
bang. These microwaves permeate the sky, coming to Earth
from every
direction in a nearly homogeneous blanket of weak
radiation.
Nearly homogeneous because some spots are slightly cooler
than the
average "temperature" of less than three Kelvin -- three
degrees
Celsius above absolute zero.
Cosmologists have theorized that these cool regions in the
microwave
blanket are the birthmarks of galaxies and clusters of
galaxies that
condensed out of the primordial plasma a few eons after the
big bang.
Based on theories about disturbances in gases that existed
for
millennia after the big bang, cosmologists developed
detailed
estimates of how big these cool spots should have been when
they
emitted the radiation reaching us as microwaves today.
These cool spots were studied in detail by the Wilkinson
Microwave
Anisotropy Probe (WMAP), which found that the average spot
is about
the size that had been forecast for a flat, smooth
universe.
The problem, says Lieu, is that not only is the average
about right,
but far too many of the spots themselves are "just right"
with too
little variation in sizes. Given the uneven distribution of
matter in
an expanding universe, he says, we should see a broader
size
distribution among the cool spots by the time that
radiation reaches
Earth.
The distribution of matter and the expanding universe are
important
because they have opposite effects on the "shape" of space
and the
paths taken by light, microwaves and other radiation as
they zip
through the cosmos.
An expanding universe would tend to "stretch" space,
causing radiation
to disperse as it flies through. That dispersion would make
objects
appear to an observer to be smaller than they really are,
as if the
light went through a concave lens.
"As far as we know," said Lieu, "the expansion takes place
smoothly
everywhere. When the universe reaches a certain age all
points in
space at this moment expand in the same way."
Matter -- or more specifically gravity -- tends to
constrain space.
And because matter is distributed unevenly across the
universe, so are
its gravitational effects.
If you have enough matter in one small place, such as a
galaxy or
cluster of galaxies, that super concentration of gravity
can act like
a convex lens, bending inward both space and any light
traveling
through it. When light from a distant galaxy is bent by
gravity as it
passes another galaxy or galaxy cluster, these distortions
can appear
as Einstein rings or weak lensing shear effects.
If the object emitting light is like a cool spot in the
microwave
background, the focusing effect of galaxy clusters or
groups of
galaxies between those spots and Earth might make the spots
appear to
be larger than they really were.
A large portion of the mass in the nearby universe is
concentrated in
small volumes of space. These are galaxies and massive
galaxy
clusters, which are surrounded by vast empty voids of
intergalactic
space. If the standard big bang model is correct, that
means the
microwave radiation from some cool spots would travel
through mostly
empty space, would be dispersed by the expanding universe
and would
look small by the time that radiation reached Earth.
Radiation from other cool spots, however, would pass around
or near
massive gravity lenses. These focused spots would appear to
be larger
than the average cool spot.
"But you don't see this fluctuation," said Lieu. "There
appear to be
no lensing effects whatsoever. This lack of variation is a
serious
problem."
In his "Cosmological Considerations of the General Theory
of
Relativity," Einstein theorized that the net effect of the
counteracting forces of expansion and gravity should remain
the same
if the amount of matter in the universe stays the same.
While Einstein developed this theorem based on a universe
where the
distribution of matter is "smooth," the UAH mathematical
work shows
for the first time that the net effect on the propagation
of light
doesn't change even if the universe is "clumpy."
If the cool spots are too uniform to have traveled to Earth
from near
the beginning of time, Lieu says cosmologists are left with
several
alternative explanations.
The first is that the cosmological parameters (including
the Hubble
constant, the amount of dark matter, etc.) used to predict
the
original, pre-lensed sizes of the cool and hot spots in the
microwave
background might be wrong. These parameters could be
adjusted to
predict a narrower range of sizes on either side of the
"pre-lensed"
average.
Then, after the effect of gravitational lensing is folded
in, the
resulting average size and size dispersion would agree with
what WMAP
actually saw, said Lieu. "This approach is the most
conservative, but
would still result in an overhaul of the standard model."
"Or, could it be that although the radiation itself is from
far away,
some of these cool spot structures are caused by nearby
physical
processes and aren't really remnants of the universe's
creation?" Lieu
asked. "Could they have been imprinted locally and aren't
cosmological
at all? Given that we find no lensing, that might be one
possibility.
"Or is it possible that as light goes through the vast
areas of space
there is some other, unknown factor damping the effects of
dispersion
and focusing? There is certainly plenty of room for
unknowns."
The most contentious possibility is that the background
radiation
itself isn't a remnant of the big bang but was created by a
different
process, a "local" process so close to Earth that the
radiation
wouldn't go near any gravitational lenses before reaching
our
telescopes.
Although widely accepted by astrophysicists and
cosmologists as the
best theory for the creation of the universe, the big bang
model has
come under increasingly vocal criticism from scientists
concerned
about inconsistencies between the theory and astronomical
observations, or by concepts that have been used to "fix"
the theory
so it agrees with those observations.
These fixes include theories which say the nascent universe
expanded
at speeds faster than the speed of light for an unknown
period of time
after the big bang; dark matter, which was used to explain
how
galaxies and clusters of galaxies keep from flying apart
even though
there seems to be too little matter to provide the gravity
needed to
hold them together; and dark energy, an unseen, unmeasured
and
unexplained force that is apparently causing the universe
not only to
expand, but to accelerate as it goes.
In research published April 10 in the "Astrophysical
Journal,
Letters," Lieu and Mittaz found that evidence provided by
WMAP point
to a slightly "super critical" universe, where there is
more matter
(and gravity) than what the standard interpretation of the
WMAP data
says. This posed serious problems to the inflationary
paradigm.
Recent observations by NASA's new Spitzer space telescope
found "old"
stars and galaxies so far away that the light we are seeing
now left
those stars when (according to big bang theory) the
universe was
between 600 million and one billion years old -- much too
young to
have galaxies with red giant stars that have burned off all
of their
hydrogen.
Other observations found clusters and super clusters of
galaxies at
those great distances, when the universe was supposed to
have been so
young that there had not been enough time for those
monstrous
intergalactic structures to form.
University of Alabama in Huntsville
For more information: Phil Gentry, (256) 824-6420
8/2/2005
-- Regards, Joe Needham
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