The universe really is as surprising as scientists have come
to suspect it is, according to a discovery that University of
Chicago astrophysicists will announce Thursday, Sept. 19, at
the COSMO-02 conference at Adler Planetarium and Astronomy
Museum. The discovery, which astrophysicists have pursued with
increasingly sensitive instruments for more than two decades,
verifies the framework that supports modern cosmological theory.

Using a radio telescope called the Degree Angular Scale
Interferometer (DASI) at the National Science Foundation’s
Amundsen-Scott South Pole Station, the Chicago scientists
measured a minute polarization of the cosmic microwave
background, the sky-pervading afterglow of the big bang.

Most light is unpolarized, its many individual waves jumbled
together, each wave flickering up and down in a different
plane as it speeds toward Earth. Unpolarized light becomes
polarized whenever it is reflected or scattered. This is the
principle behind polarizing sunglasses that remove the glare
from the hood of a car or the surface of a pool. In both
cases the sunglasses only permit waves that tend to flicker
up and down in the same plane to pass.

The polarization of the cosmic microwave background was
produced by the scattering of cosmic light when it last
interacted with matter, nearly 14 billion years ago. If no
polarization had been found, astrophysicists would have to
reject all their interpretations of the remarkable data they
have compiled in recent years, said John Carlstrom, the S.
Chandrasekhar Distinguished Service Professor in Astronomy &
Astrophysics at the University of Chicago.

“Instead of stating that we think we really understand the
origin and evolution of the universe with high confidence,
we would be saying that we just don’t know,” said Carlstrom,
who will announce the discovery. “Polarization is predicted.
It’s been detected and it’s in line with theoretical
predictions. We’re stuck with this preposterous universe.”

It’s a universe in which ordinary matter, the stuff of which
humans, stars and galaxies are made, accounts for less than
five percent of the universe’s total mass and energy. The
vast majority of the universe, meanwhile, is made of a
mysterious force that astronomers call “dark energy.” This
vague name reflects the fact that scientists simply do not
know what it is. They only know that it acts in opposition
to gravity, accelerating the expansion of the universe.

In addition to the dark energy theory, cosmic inflation
theory improbably proposes that the universe underwent a
gigantic growth spurt in a fraction of a second just moments
after the big bang.

“This beautiful framework of contemporary cosmology has many
things in it we don’t understand, but we believe in the
framework,” said Clem Pryke, Assistant Professor in
Astronomy & Astrophysics at the University of Chicago and
a member of the DASI team. “This new result was a crucial
test for the framework to pass.”

Carlstrom’s other collaborators on the polarization discovery
were John Kovac and Erik Leitch, University of Chicago; and
Nils Halverson and Bill Holzapfel, University of California,

The discovery follows in the wake of another important DASI
finding. Last year Carlstrom’s team precisely measured
temperature differences in the cosmic microwave background,
further supporting for the cosmic inflation theory.

The polarization signal is more than 10 times fainter than
the temperature differences that DASI detected earlier.
DASI’s first discovery came after it collected data for 92
days from 32 spots in the sky. But DASI needed to watch
two spots in the sky for more than 200 days to detect the

The discovery opens a new era in cosmic microwave background
experiments, said the Chicago astrophysicists. They predict
that increasingly sensitive detections of polarization will
yield many more discoveries. “It’s going to triple the
amount of information that we get from the cosmic microwave
background,” said Kovac, a Ph.D. student in Physics. “It’s
like going from the picture on a black-and-white TV to

The polarization is a signpost from when the universe was
only 400,000 years old, when matter and light were only just
beginning to separate from one another. “What’s unique about
polarization is that it directly measures the dynamics in
the early universe,” Carlstrom said.

Temperature differences revealed patterns of lumpy matter
frozen in the early universe, but by measuring polarization,
astronomers can actually see how the early universe was

In the coming years, astronomers will attempt to use the CMB
polarization to measure gravity waves, a form of radiation
predicted by general relativity that corresponds to ripples
in the fabric of space-time, said Michael Turner, the Bruce
and Diana Rauner Distinguished Service Professor in
Astronomy & Astrophysics at the University of Chicago.

“Detection of the polarization opens a new door to exploring
the earliest moments and answering the deep questions before
us,” Turner said.

The web page for experts contacted by the press to form an
opinion on the DASI polarization results can be found at:

Print-quality photos are available at