The Planck Telescope: News From the Dawn of Time

Will a new picture of the universe’s first light overturn a theory that has reigned for 30 years?

Cosmologists study the large-scale structure and evolution of the universe -- here imagined as it evolved (reading left to right) from 900 million years after the Big Bang to today. (Volker Springel / MPE)
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Tune an FM radio to one of those empty spots between one station and another and out comes the buzz of static that says: Nothing to hear here. But there is something. Deep within the static is an extraordinarily faint trace of the defining period in the history of the universe. What you’re almost hearing is a 13.8-billion-year-old signal from the Big Bang.

That signal—the oldest light of the cosmos stretched by the expansion of space into invisible, pervasive microwaves—has just been gathered and measured with greater precision than ever before. The gathering was done by a $900 million space telescope launched by the European Space Agency and named Planck, for the German physicist Max Planck, a father of quantum mechanics. Beginning in 2009, the spacecraft tagged alongside Earth in its orbit around the sun (sheltered from the sun by Earth’s shadow). Last spring, the mission’s international team of scientists released Planck’s initial results, and a somewhat puzzling picture of the universe emerged. In the new portrait, one side of the universe doesn’t quite match the other, and an odd cold spot stretches for hundreds of millions of light-years, a distance making it the largest known structure in the universe.

“These anomalies do not fit,” says Jan Tauber, ESA’s Planck project scientist. “It’s very painful because we don’t understand it and it has the potential to undermine our theories. Unless we have a theory, we don’t know what to do with it.” The theorists, he says, “are out there furiously trying to come up with something.”

But cosmology, the study of the large-scale properties of the universe, is a science of statistics and probabilities, and many cosmologists believe that a lopsided universe is not so improbable that it demands new theories to explain it. Charles Lawrence, an astrophysicist at NASA’s Jet Propulsion Laboratory and NASA’s Planck project scientist, is among them. “What is remarkable is that the large-scale structure and contents of the universe are described extremely well—not perfectly, but extremely well—by a model that has only six adjustable parameters,” he says. To describe the universe—its age, its content, its speed of expansion—cosmologists have constructed theoretical models based on the phenomena they observe. The dominant, or standard, model assumes six variables—the parameters Lawrence mentions—among them, how fast the universe is expanding and the amount of matter it contains. By slightly adjusting the values of each of the variables, and comparing the millions of permutations with the data from the telescope, researchers find the description that offers the best match.

In 2000, using measurements of the cosmic microwave background (CMB), a Princeton University team constructed this image of density variations (dark areas indicate less density) in the plasma of the very early universe. (NASA / WMAP Science Team)
The Planck space telescope, shown here in an artist's conception, took a long exposure of what the universe looked like 13.82 billion years ago. (ESA / D. Ducros)
In this Mollweide project of the whole-sky sphere, Planck’s measurements of the cosmic microwave background show the slight temperature variations present in the primordial universe. Red regions are very slightly warmer, blue regions are slightly cooler. In the southern hemisphere of the universe, there are slightly higher average temperatures, with the exception of an enormous cold spot (circled). (ESA and the Planck collaboration)
An artist’s impression of the sky at less than a billion years after the Big Bang, when galaxies (blue) were beginning to form and hydrogen fog absorbed ultraviolet light. Planck saw an even earlier time. (ESO / M. Kornmesser)

“If the universe was constructed in that statistical prescription by varying six parameters,” says Lawrence, “one out of every few hundred times, you’d get a universe where one side of the sky is as different from the other as we observe. So is that really, really so unlikely that we should lie awake at night worrying about it?”

Planck mission scientists are still extracting information from the cosmic microwave background so that physicists can offer a more complete and satisfying explanation of how the universe we see today expanded from the hot, dense speck it was 13.82 billion years ago—its age, according to Planck’s measurements. That measurement makes the cosmos 80 million years older than previously thought.

The new data from Planck offers more than twice the resolution of previous space-based instruments used to study the cosmic microwave background (CMB) and detects differences in temperature down to the 100 millionth of a degree. Planck’s first color-coded temperature maps of the CMB assemble close to a trillion observations of a billion different points in the sky. The signals are so small, so faint, and so easily obscured by stray radiation from the Milky Way and other sources that a Cray XE6 supercomputer at Lawrence Berkeley National Laboratory—capable of more than a quintillion calculations a second, one of the fastest in the world—had to spend weeks sifting the images from the satellite’s prodigious amount of data.

“Think about it a thousand years from now: This is when we first got the picture,” says Lawrence. “That would seem like a pretty exciting time.”

These more precise measurements have narrowed the range of acceptable models explaining how the universe expanded, including models for the theory of inflation: the idea that 10-35 second after the Big Bang, the universe expanded 100 trillion trillion times, from a mote far smaller than an atom to something far bigger than the Milky Way.

About Michael Milstein

Michael Milstein is a freelance writer who specializes in science. He lives in Portland, Oregon.

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