LAST week an international team of researchers unveiled the most detailed
image yet of the infant Universe, which shows the huge structures that would
later coalesce into the galaxies and galaxy clusters we see today. The results
of the so-called Boomerang project confirm earlier predictions that the overall
geometry of the Universe is 鈥渇lat鈥�.
鈥淐osmologists have eagerly awaited a chance to get a direct view of the early
Universe. The Boomerang data give us, indeed, our first glimpse,鈥� says co-leader
Andrew Lange of the California Institute of Technology.
The image is a map of radiation released in the big bang, known as the cosmic
microwave background. For its first few hundred thousand years, the Universe was
a fireball of elementary particles that scattered this light. When the Universe
cooled enough for atoms to form, photons could suddenly travel across the
Universe unmolested, carrying with them a snapshot of that point in time.
Fluctuations in this snapshot, first detected less than a decade ago by NASA鈥檚
COBE satellite, record density variations in the early Universe that became
galaxies and clusters.
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To get a more detailed picture of these fluctuations, the Boomerang team
suspended their improved microwave telescope from a balloon that circled high
above the Antarctic and measured the temperature of incoming microwave radiation
to the nearest one hundred millionth of a degree鈥攔oughly 35 times more
accurately than any previous instrument.
The fluctuations appear as blobs on the microwave map of the sky. Theorists
predicted that most of the blobs would be of a particular size鈥攔oughly 1
degree across. If the blobs seem any larger or smaller, physicists believe this
would mean that the Universe is curved. A curved Universe bends the path of the
microwaves as they travel through space, distorting the apparent size of the
blobs in the same way that a lens magnifies or shrinks an image.
From their initial analysis of the massive amount of data from the project,
the team concludes that the Universe is nearly flat. Flat geometry ties in with
the current consensus that the early Universe went through a period of rapid
expansion that stretched it flat. This picture is supported by recent
observations that the Universe contains enough matter and energy to maintain a
flat geometry. 鈥淭he Boomerang results fit the new cosmology like a glove,鈥� says
astrophysicist Michael Turner of the University of Chicago in Illinois.
Douglas Scott of the University of British Columbia in Vancouver, however, is
intrigued by subtle departures from the expected picture, particularly that the
blobs appear very slightly larger than 1 degree. 鈥淭here are just these hints
that things might be a little different than what you would have put your money
on before,鈥� says Scott. 鈥淭hat makes it fun.鈥�