Echo of the Big Bang by Michael Lemonick, Princeton University Press, £17.95/$24.95, ISBN 0691102783 Reviewed by Marcus Chown
ONCE upon a time astronomers devoted whole careers to measuring the cosmological parameters that characterise our universe to an accuracy of within 10 or 20 per cent. Now they read off everything – from the Hubble constant to the amount of invisible, “dark”, matter – to a fraction of a per cent from the cosmic background radiation, a kind of cosmic Rosetta stone.
It’s been a long and hard road getting to this happy point and, in Echo of the Big Bang, Michael Lemonick describes the milestones along the way, beginning with Ralph Alpher and Robert Hermann’s 1948 prediction that a hot big bang would leave a relic “afterglow” in today’s universe, and Arno Penzias and Robert Wilson’s accidental discovery of the heat “echo of the big bang” in 1965.
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As theorist Joseph Silk first recognised three years later, the background radiation carries with it priceless information about the primordial universe in the form of tiny fluctuations in temperature from point to point across the sky. These were triumphantly detected in 1992 by NASA’s Cosmic Background Explorer (COBE) satellite. The story up to this point is told in George Smoot and Keay Davidson’s Wrinkles in Time. But Lemonick, in his authoritative book, brings the story bang up to date with COBE’s successor, the Microwave Anisotropy Probe (MAP), whose first results were released only in February.
The importance of MAP is that, unlike COBE, it is directly sensitive to the conditions in the universe at the “epoch of last scattering”, when the big bang radiation broke free of matter a mere 300,000 years after the moment of creation.
Astronomers are still digesting the MAP results but they tell us, among other things, that the universe is 13.7 billion years old and is almost certainly dominated by “dark energy”, bizarre stuff whose gravity blows rather than sucks. Even more intriguingly, the MAP results reveal that the background radiation was modified by the first generation of stars within a mere 200 million years of the birth of the universe. No one knows how they could have congealed so early out of the maelstrom of the big bang.
Lemonick tells the epic story of MAP and the dedicated band of scientists and engineers who made it happens. Sympathy goes out to David Wilkinson, who was in at the beginning of the cosmic background story in 1965 but died on the eve of his greatest triumph. Movingly, the team voted unanimously to rename the satellite, the Wilkinson Microwave Anisotropy Probe.