New look at microwave background may cast doubts on big bang theory(Forwarded)

University of Alabama in Huntsville

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8/2/2005

New look at microwave background may cast doubts on big bang theory

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.