Parallel Worlds by Michio Kaku

bird
droppings) that had covered the opening of the radio telescope. The static
seemed even larger. Although they did not yet know it, they had accidentally
stumbled upon the microwave background predicted by Gamow's group back in
1948.
    Now the
cosmological history reads a little bit like the Keystone cops, with three
groups groping for an answer without any knowledge of the others. On one hand,
Gamow, Alpher, and Hermann had laid out the theory behind the microwave
background back in 1948; they had predicted the temperature of the microwave
radiation to be 5 degrees above absolute zero. They gave up trying to measure
the background radiation of space, however, because the instruments back then
were not sensitive enough to detect it. In 1965, Penzias and Wilson found this
black body radiation but didn't know it. Meanwhile, a third group, led by
Robert Dicke of Princeton University, had independently rediscovered the theory
of Gamow and his colleagues and were actively looking for the background
radiation, but their equipment was too woefully primitive to find it.
    This comical
situation ended when a mutual friend, astronomer Bernard Burke, informed
Penzias of the work of Robert Dicke. When the two groups finally connected, it
became clear that Penzias and Wilson had detected signals from the big bang
itself. For this momentous discovery, Penzias and Wilson won the Nobel Prize
in 1978.
    In hindsight,
Hoyle and Gamow, the two most visible proponents of the opposite theories, had
a fateful encounter in a Cadillac in 1956 that could have changed the course of
cosmology. "I recall George driving me around in a white Cadillac,"
recalled Hoyle. Gamow repeated his conviction to Hoyle that the big bang left
an afterglow that should be seen even today. However, Gamow's latest figures
placed the temperature of that afterglow at 50 degrees. Then Hoyle made an
astounding revelation to Gamow. Hoyle was aware of an obscure paper, written
in 1941 by Andrew McKellar, that showed that the temperature of outer space
cannot exceed 3 degrees. At higher temperatures, new reactions can occur which
would create excited carbon-hydrogen (CH) and carbon-nitrogen (CN) radicals in
outer space. By measuring the spectra of these chemicals, one could then
determine the temperature of outer space. In fact, he found that the density of
CN molecules he detected in space indicated a temperature of about 2.3 degrees
K. In other words, unknown to Gamow, the 2.7 K background radiation had already
been indirectly detected in 1941.
    Hoyle recalled,
"Whether it was the too-great comfort of the Cadillac, or because George
wanted a temperature higher than 3 K, whereas I wanted a temperature of zero
degrees, we missed the chance of spotting the discovery made nine years later
by Arno Penzias and Bob Wilson." If Gamow's group had not made a numerical
error and had come up with a lower temperature, or if Hoyle had not been so
hostile to the big bang theory, perhaps history might have been written
differently.
    PERSONAL AFTERSHOCKS OF THE BIG BANG
    The discovery of
the microwave background by Penzias and Wilson had a decided effect on the
careers of Gamow and Hoyle. To Hoyle, the work of Penzias and Wilson was a
near-death experience. Finally, in Nature magazine in 1965, Hoyle officially conceded defeat, citing
the microwave background and helium abundance as reasons for abandoning his
steady state theory. But what really disturbed him was that the steady state
theory had lost its predictive power: "It is widely believed that the
existence of the microwave background killed the 'steady state' cosmology, but
what really killed the steady-state theory was psychology . . . Here, in the
microwave background, was an important phenomenon which it had not predicted
. . . For many years, this knocked the stuffing out of me." (Hoyle later
reversed himself, trying to tinker with newer variations of the steady state
theory of the universe, but each variation became less and less