When it comes to inflation, cosmologists are pondering a future that probably would leave even Alan Greenspan scratching his head. Of course, the Federal Reserve chairman is merely concerned with economic policy and hasn't had to stare down the complexities of how the universe pumped up after the Big Bang.
And now, new research tools promise tantalizing glimpses of characteristics in the universe that until now have gone unseen.
"We might, in a technical sense, soon observe the beginning of time," University of Washington cosmologist Craig Hogan writes in the March 22 edition of the journal Science.
It was just a decade ago that a National Aeronautics and Space Administration project called the Cosmic Background Explorer, or COBE, began returning data aimed at mapping the universe's background radiation, which was first observed in 1965. That radiation is residual heat from the Big Bang, the event that sparked the beginning of the universe some 13 billion years ago.
COBE produced a map that included ripples, or amplitude fluctuations, in the structure of space-time across billions of light years. Those ripples are the largest structures humans ever will be able to see, Hogan said. But they also are greatly magnified images of the smallest structures ever visible – the same fluctuations that started out smaller than a subatomic particle at the Big Bang, then were frozen into the fabric of space-time and stretched as inflation expanded the universe to its current size.
Upcoming projects promise even more-detailed information, said Hogan, a UW physics and astronomy professor.
In a Perspective article for Science, he discusses the possibility that new experiments will shed clues about subatomic particles called gravitons and perhaps bring enough information to unite quantum mechanics and relativity, the two great theories rooted in the work of Albert Einstein. These new experiments include a NASA mission called Microwave Anisotropy Probe, or MAP, that was launched last year with a mission to collect information to chart the microwave light left over from the Big Bang.
Unlike subatomic particles that make up matter and energy as we know them, gravitons are elementary particles that compose the fabric of space and time.
"No one has ever seen a graviton, but with these new efforts we might," Hogan said. "If you can see gravitons in these maps, then you'll start to see the essence of space and time and matter."
Hogan also believes the next generation of research might shed light on other cosmological puzzles. One of these involves the holographic principle, which states that everything that happens three-dimensionally can actually be specified by the amount of information it would take to project it two-dimensionally, like a hologram. If that turns out to be true, Hogan speculates that all the information needed to show the entire universe during early inflation, shortly after the Big Bang, could have fit on a compact disc.
Whatever is learned from the new research, Hogan said, will lend to the basic scientific understanding of time, space, matter and energy. And while that might sound terribly esoteric, he said, it could turn out to have very practical applications.
He noted that Einstein's theory of space-time and gravity, called general relativity, was long regarded as something of an elegant ornament for the science of physics, but nothing with any realistic usefulness. However, it turns out there are practical applications. For instance, without relativity, backcountry hikers, drivers and pilots – let alone smart bombs – couldn't use global positioning technology.
"If you want to hit a cave in Afghanistan, you need general relativity," Hogan said. "And why is that? It's all based on light traveling through space, and precisely timing the pulses of light."
For more information, contact Hogan at 206-616-4475 or hogan@u.washington.edu
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Science