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T
he discovery of the
universe’s “first light”
is one of the most
fundamental scientific findings
of all time. A full 99.9 percent of
all photons (light particles) arriving
at Earth are associated with this
cosmic microwave background
(CMB). It has been traveling for
more than 13 billion years, reaching
us from a time near the very dawn
of the universe. The CMB is the
thermal radiation emitted when
the universe was at a temperature
of about 4,000 K.
The scientist who usually takes
the credit for the prediction of the
CMB is physicist George Gamow
(pp.196–97). An expanding universe
implied a point at which it was once
squeezed into a tiny volume. Gamow
saw that this in turn implied a hot
beginning, and realized that such
a hot “Big Bang” would have left
its signature in the sky. In 1948,
his doctoral students Ralph Alpher
and Robert Herman worked out
the details of this “fireball radiation.”
Cooled by the expansion of the
universe, over 13 billion years, they
deduced that it should take the form
today of radio-frequency radiation as
if emitted by an object at 3 K—justSEARCHING FOR THE BIG BANG
above absolute zero. Seemingly
unaware of Alpher’s and Herman’s
work, Robert H. Dicke, working
at the Princeton University “Rad
Lab,” independently predicted the
CMB in the early 1960s. Dicke
asked his team of postgraduates
to find it. David Wilkinson and
Peter Roll were to build a machine
to detect it, while James Peebles
was to “think about the theory.”Echoes of the Big Bang
Gamow had assumed that the
faint signal of the CMB would be
indistinguishable from radio waves
flooding in from other astronomical
objects, but Alpher and HermanIN CONTEXT
KEY ASTRONOMERS
Robert H. Dicke (1916–1997)
James Peebles (1935 –)BEFORE
1927 Georges Lemaître
proposes his “hypothesis
of the primeval atom.”1948 Ralph Alpher and Robert
Herman predict that radiation
from the Big Bang would now
have a temperature of 5 K.1957 Soviet astronomer
Tigran Shmaonov reports a
“radioemission background”
of 4 +/- 3 K, but does not connect
this finding with the Big Bang.AFTER
1992 The COBE results confirm
black-body curve and anisotropy
(tiny variations) of the CMB.2010 WMAP measures tiny
temperature variations of
0.00002 K in the CMB.2013 The Planck team releases
a detailed map of the CMB.The Big Bang is a disputed theory.One of the predictions of the Big
Bang theory is a cosmic microwave
background radiation at a temperature
of about 3 K, with a spectrum very
nearly that of a black body.The Big Bang is no longer a disputed scientific theory.There is no point in attempting
a half-hearted experiment with
an inadequate apparatus.
Robert H. DickeThe background radiation is discovered
at about 3 K. Further studies show that
it has a spectrum that is almost
exactly that of a black body.