12 OCTOBER 2006
It's too bad they don't celebrate the Nobel prizes with fireworks.
This year, the prize in physics was awarded for the most important fireworks
ever, the explosion that gave birth to the universe. The colorful images and
precise graphs 
provided by the satellite known as COBE earned the Nobel for
two leaders of the scientific teams that planned the mission and analyzed the
results.
Before COBE, most experts already believed that the universe began with a bang, thanks to previous Nobel-winning work in the 1960s by Arno Penzias and Robert Wilson. Penzias and Wilson found a faint glow of microwave radiation permeating all of space, apparently left over from the genesis explosion. Initially, of course, that radiation had been ultra hot, but as space expanded over the next 13 billion years or so, it cooled down to about 3 degrees above absolute zero, colder than Alex Rodriguez in the baseball playoffs.
Because early advocates of the big bang idea had predicted such radiation to exist, its discovery convinced all but a few skeptics that the cosmos had been conceived in fire.
COBE:
Cosmic Background Explorer. Image: NASA
But nagging questions remained. How did the superhot soup, cooked up in the bang, cool into the elaborate menagerie of galaxies that decorate the cosmos today? It was almost like beginning with chicken broth and ending up with alphabet soup. Something set the stage for structure to form, and nothing about the original big bang theory hinted at where the cosmic architecture came from.
Then along came a breakthrough idea, one of those rare insights into reality that will also probably win a Nobel one day. Examining the underlying physics of the big bang, Alan Guth (now a physicist at MIT) realized in 1980 that for a tiny fraction of a second after the bang, the universe would have ballooned from a speck of nothingness into a space big enough to make a playground for subatomic particles. The universe would then continue to expand, at a more leisurely rate, after that initial brief burst of "inflation." Further work by Guth and others, notably the Russian cosmologist Andrei Linde, showed how the physics of inflation could generate tiny blips in the density of matter and energy in the baby universe. Spots of just slightly higher density could grow into blobs massive enough to form stars and galaxies, their locations tracing the patterns of the original density blips.
In other words, the brief "inflationary" epoch of the universe etched a blueprint for the future construction of galaxies and their clustering into walls surrounding vast voids. Inflation theory showed how an initial explosion could create a complex cosmos.
Of course, there was no guarantee that this idea was correct. And in fact, during the 1980s, critics often dismissed inflation as an idea whose time had neither come or was already gone. Yet, if the big-bang-birth of the universe was a correct description of nature, something had to sow the seeds of structure.
So, at the end of the 1980s, astronomers turned their eyes to COBE (pronounced like the name of that basketball player) for guidance. Launched in November 1989, it immediately began recording how bright those leftover microwaves were at various "colors" (or wavelengths). Right away COBE found that the brightness of the microwave light at different wavelengths matched expectations for an initial smooth explosion (technically, this was evidence of a "black body" spectrum, just as the big bang required). That earned the Nobel for John Mather of NASA'S Goddard Space Flight Center.
A couple of years later, a team led by George Smoot (of the University of California, Berkeley) analyzed temperatures recorded by COBE at various points on the sky, finding slight but significant variations. Those differences matched the blips in matter-energy density predicted by inflation theory. In other words, the universe's original blueprint had been recorded in the microwaves, kind of like DNA evidence preserved in a cosmic fossil. Finding that fossil earned Smoot his share of this year's Nobel.
Image: NASA
Since COBE, other experiments on balloons and satellites (notably one known as WMAP) have seen the same things more precisely, adding further weight to the already overwhelming big bang evidence. Next year another satellite, a European mission known as Planck, will be launched to dig even deeper into the cosmic details. There are always more questions to be answered.
After all, science's best feature is its capacity to produce surprises, not only about the questions science asks, but about the questions that science CAN ask (and then answer). A century ago, nobody even imagined anything so outlandish as an expanding universe burst into existence by a big explosion. The origin of space and time seemed to be a forbidden question, without any hope of ever acquiring a scientific answer. Only philosophers and poets dared to contemplate cosmic origins.
But today philosophy has given way to physics. This year's Nobel physics prize celebrates the power of human ingenuity to unveil secrets that the universe seemed determined to conceal. You could say that the fireworks inside the mind have perceived the fireworks of the heavens.
E-mail: tsiegfried@nasw.org
