Astronomers tell us that we live in an expanding universe filled with myriad galaxies that are rocketing away from each other at incredibly fast speeds. Yet, they say, it's not the galaxies themselves that are doing the moving. It's actually space that's expanding, carrying the galaxies along with it.
If you find yourself as perplexed as I am by that somewhat counterintuitive concept, a new book by Chris Impey, a professor in the UA's Astronomy Department, may be just what the cosmologist ordered.
In How It Began: A Time-Traveler's Guide to the Universe, Impey says that to better understand the process of cosmic inflation, it's helpful to imagine a large balloon, with an assortment of beads attached to the surface, being blown up. The beads, like the galaxies, are expanding outward and away from each other, but it's the balloon that's doing all the work.
Cosmology, of course, has more than its share of counterintuitive concepts, but Impey's comprehensive survey of cosmic origins is brimming with nifty illustrations like that one, which help make maddeningly complex ideas easier (most of the time) to digest. Written with the wit and enthusiasm of a man who truly enjoys his work, this book is an excellent launching pad for readers who want to broaden their understanding of the cosmos.
Writing that astronomers are "armchair time travelers" who use telescopes as time machines, Impey—whose last book, How It Ends, predicts that the universe may eventually devolve into an icy porridge of subatomic particles—takes readers nearly 14 billion years into the past to the very beginnings of time. Along the way, he expounds on topics ranging from the formation of stars, planets, black holes and galaxies, to Einstein's theory of relativity, quantum physics, the paradoxical shenanigans of antimatter and the epic struggle between dark matter and dark energy, two deeply mysterious forces that appear to control the universe.
Things start to get really interesting, however, when our cosmic tour bus reaches the vicinity of the Big Bang. This stupendous event, "the instantaneous creation of all space and time, with enough mass and energy to form 100 billion galaxies and disperse them across a volume of a million billion billion billion cubic light years," is the linchpin of modern cosmogony. Impey tells us, however, that contrary to popular belief, the Big Bang doesn't refer to a time when all matter in the universe was compressed into a single point, nor was it likely an explosion. (It wasn't completely quiet, either, according to a University of Virginia astronomer who has "sonified" the microwave spectrum—residual radiation from the Big Bang—estimating that it was about as loud as a rock concert and may have sounded a bit like the resounding E chord that concludes the Beatles song "A Day in the Life.") The Big Bang also doesn't explain how the cosmos came to be. It's simply a theory, Impey says, that traces the development of the universe from a smaller, hotter and denser state.
How did the cosmos come into being? Writing that seemingly empty space is charged with a certain amount of potential energy, Impey suggests that the birth of the universe may have been a quantum event in which a tiny amount of quantum energy (a hundredth of a gram, it's approximated) was "borrowed" from a pre-existing vacuum of space-time. Quantum fluctuations (energized particle waves) were then stretched by space inflation into what would eventually become the galaxies.
The hypothesis that our cosmos emerged from an earlier universe (and may, in turn, generate still other universes) opens the door to the possibility that reality consists of an infinite array of parallel universes. The "many worlds" theory posits that in every situation where there are multiple possibilities, the cosmos divides into a separate world for each possibility.
"In each world," Impey explains, "everything is identical except for one different outcome. From then on, they each develop independently, and no communication is possible among them, so people living in those worlds are unaware that it's going on. In this way, the 'world' branches endlessly. What is 'now' to us lies in the pasts of an infinite number of possible futures. Everything that can happen, does, somewhere."
I'm beginning to understand how cosmologists can sometimes be slightly deranged.
Overflowing with fascinating but highly abstruse ideas, this book would have profited greatly from an extensive glossary. However, readers will no doubt leave Impey's erudite work with brains correspondingly crammed, a heightened sense of wonder and, hopefully, a desire to learn more about our amazing cosmic nest.