If the universe were ice cream, it would be vanilla. That's the take-home message from researchers working with the European Space Agency's orbiting Planck observatory, who today released the most precise measurements yet of the afterglow of the big bang—the so-called cosmic microwave background (CMB) radiation. The new data from Planck confirm cosmologists' standard model of how the universe sprang into existence and what it's made of. That may disappoint scientists who were hoping for new puzzles that would lead to a deeper understanding.
"We're always hoping to find new things," says Glenn Starkman, a theoretical physicist at Case Western Reserve University in Cleveland, Ohio, who does not work on Planck. "But we're finding that our model is really, really good—maybe disappointingly good." Max Tegmark, a cosmologist at the Massachusetts Institute of Technology (MIT) in Cambridge, agrees. "The sensational news is that there is no sensational news," he says.
Cosmology's standard model goes a bit like this. The universe sprang into existence instantaneously in the big bang as a hot, dense soup of matter and energy. Then, in the first 10-30 seconds, space itself expanded much faster than light speed. That growth spurt, known as inflation, had two main effects. First, it smoothed the universe out and rendered it geometrically "flat" on the largest scales. At the same time, it greatly magnified tiny quantum fluctuations in the density of hot matter and energy. These density fluctuations then left tiny variations in the temperature of the CMB across the sky and, much later, seeded the formation of the galaxies. Like other CMB missions before it, Planck, which was launched in 2009, studied these variations.
From studies of the CMB and other measurements, cosmologists have also deduced the composition of the universe. Planck refines those measurements, particularly those of NASA's Wilkinson Microwave Anisotropy Probe (WMAP), which collected data from 2001 to 2010. According to Planck, the universe consists of 4.9% ordinary matter, 26.8% mysterious dark matter that has revealed itself through only its gravity, and 68.3% weird, space-stretching dark energy. Those numbers amount to roughly 3% more dark energy and 3% less dark matter than WMAP's result. The Planck team also pegs the age of the universe at 13.8 billion years, 100 million years older than WMAP found.
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