Big Bang's Afterglow Fails an Intergalactic Shadow Test
In a finding sure to cause controversy, scientists at The University of Alabama
in Huntsville (UAH) found a lack of evidence of shadows from "nearby" clusters
of galaxies using new, highly accurate measurements of the cosmic microwave
A team of UAH scientists led by Dr. Richard Lieu, a professor of physics, used
data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) to scan the cosmic
microwave background for shadows caused by 31 clusters of galaxies.
"These shadows are a well-known thing that has been predicted for years," said
Lieu. "This is the only direct method of determining the distance to the origin
of the cosmic microwave background. Up to now, all the evidence that it
originated from as far back in time as the Big Bang fireball has been
"If you see a shadow, however, it means the radiation comes from behind the
cluster. If you don't see a shadow, then you have something of a problem. Among
the 31 clusters that we studied, some show a shadow effect and others do not."
Other groups have previously reported seeing this type of shadows in the
microwave background. Those studies, however, did not use data from WMAP, which
was designed and built specifically to study the cosmic microwave background.
If the standard Big Bang theory of the universe is accurate and the background
microwave radiation came to Earth from the furthest edges of the universe, then
massive X-ray emitting clusters of galaxies nearest our own Milky Way galaxy
should all cast shadows on the microwave background.
These findings are scheduled to be published in the Sept. 1, 2006, edition of
the Astrophysical Journal.
Taken together, the data shows a shadow effect about one-fourth of what was
predicted - an amount roughly equal in strength to natural variations previously
seen in the microwave background across the entire sky.
"Either it (the microwave background) isn't coming from behind the clusters,
which means the Big Bang is blown away, or ... there is something else going
on," said Lieu. "One possibility is to say the clusters themselves are microwave
emitting sources, either from an embedded point source or from a halo of
microwave-emitting material that is part of the cluster environment.
"Based on all that we know about radiation sources and halos around clusters,
however, you wouldn't expect to see this kind of emission. And it would be
implausible to suggest that several clusters could all emit microwaves at just
the right frequency and intensity to match the cosmic background radiation."
as early as 1948 and discovered in 1965, the cosmic microwave background is a
faint glow of weak radiation that apparently permeates the universe. Because it
is seen coming from every direction in nearly uniform power and frequency,
cosmologists theorized that the microwave background is afterglow radiation left
over by the Big Bang that created the universe.
If that were the case, the background microwave radiation reaching Earth today
would have traveled billions of light years through space from the furthest
edges of the universe.
Galaxy clusters are the largest organized structures in the universe. Each
cluster can contain hundreds of galaxies like the Milky Way, each with billions
of stars. The gravity created at the center of some clusters traps gas that is
hot enough to emit X-rays.
This gas is also hot enough to lose its electrons (or ionize), filling millions
of cubic light years of space inside the galactic clusters with swarming clouds
of free electrons. It is these free electrons which bump into and interact with
individual photons of microwave radiation, deflecting them away from their
original paths and creating the shadowing effect. This shadowing effect was
first predicted in 1969 by the Russian scientists Rashid Sunyaev and Yakov
Like shadow puppets on a wall, however, these shadows would only form if all
three ingredients (light, object and observer) are in the correct order. If an
object casts no shadow, it might be because the light source is closer to the
observer than the object. That might mean that the cosmic microwave background
didn't originate at the far edges of the universe, although there are no obvious
or popular alternative sources.
The WMAP dataset is available to the public and other scientists are already
testing the UAH group's results, Lieu said, although no one has yet reported
finding any flaws in their analysis.
Just over a year ago Lieu and Dr. Jonathan Mittaz, a UAH research associate,
published results of a study using WMAP data to look for evidence of "lensing"
effects which should have been seen (but weren't) if the microwave background
was a Big Bang remnant.
Lieu, Mittaz and Shuang-Nan Zhang, UAH, "The Sunyaev-Zel'dovich effect in a
sample of 31 clusters: A comparison between the X-ray predicted and WMAP
observed decrement," Astrophysical Journal, Sept. 1, 2006, Vol. 648, No. 1, p.
Source: University of Alabama Huntsville