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CMB had the black-body signature
of a system in thermal equilibrium,
with no heat flowing from one part
to another. This astounding—and
often overlooked—result verified
that the signal was thermal in origin.
Unfortunately, the rocket’s hot
exhaust gases often marred Gush’s
measurements, preventing him
from producing a definitive result.
Edged out
By 1989, Gush had finally developed
an instrument that could compare
the CMB spectrum with that of an
onboard radiator that approximated
a black body. However, problems
with a malfunctioning vibrator
delayed the launch until early
- The results were immediate
and striking, but Gush had missed
his opportunity for a scoop by a few
weeks. NASA’s Cosmic Background
Explorer (COBE) satellite, launched
in late 1989, already had the shape
of the spectrum with a temperature
near 2.7 K. In the end, Gush’s
rocket data confirmed COBE’s
results and not the other way
around. Peebles was later to state
that Gush had deserved a Nobel
Prize for his work.
COBE’s results returned a near-
perfect match with the theoretical
black-body spectrum and revealed,
for the first time, a faint unevennessNEW WINDOWS ON THE UNIVERSE
James Peebles Phillip James Edwin Peebles^
was born in 1935 in Winnipeg,
Canada. After graduating from
the University of Manitoba, he
earned a doctorate at Princeton
University, where he found himself
“surrounded by all these people
who knew so much more than I.”
Working under Robert H. Dicke,
Peebles found he was retreading
old paths. He began to focus on the
constraints that the CMB put onto
the early universe—specifically
on the creation of atomic nuclei
in the Big Bang and on how small
temperature differences affect
models of structure formationin the universe. Peebles also
made important contributions to
theories of dark matter and dark
energy. With typical modesty,
he says that his cold dark matter
model became popular because
it was easy to analyze. He
is currently Albert Einstein
professor of science at Princeton.Key works1971 Physical Cosmology
1980 Large Scale Structure
of the Universe
1993 Principles of Physical
Cosmologyin the background radiation.
Subsequent missions—such as
NASA’s Wilkinson Microwave
Anisotropy Probe (WMAP),
launched in 2001, and ESA’s Planck
spacecraft, launched in 2009—have
mapped the CMB’s “lumpiness”
in greater detail. ■The CMB represents the outer shell
of the observable universe. Just beyond
it lies the moment of the Big Bang,
shown here as a series of flashes.