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New glimpses of ancient light fuel cosmic debate

Cosmic microwave background\is a snapshot of the oldest light in our Universe, imprinted on the sky when the Universe was just 380,000 years old. It shows tiny temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all future structure: the stars and galaxies of today.

ESA and the Planck Collaboration

Like Don Draper, TV's unflappable ad man, the universe is smooth, really smooth – and maddeningly inscrutable about its past.

That's the underlying message from the Planck mission, a European Space Agency probe that has just delivered a stunning new view of our cosmic roots.

"It's the new gold standard," said Richard Bond, a cosmologist at the Canadian Institute for Theoretical Astrophysics in Toronto and a member of the Planck science team.

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As Dr. Bond points out, the results are impressive – a fivefold improvement that will allow scientists to speak about the basic properties of the universe with more precision than before.

But when it comes to understanding how the universe came to exist, the new data pose a thorny challenge: They portray a cosmos largely free of surprises.

"It does seem to be the case that it's a very simple picture of the universe," said Douglass Scott, a cosmologist at the University of British Columbia and also a science team member. "That is quite extraordinary."

Planck's view amounts to a map of the entire sky, spread out flat, showing the cosmic microwave background – a form of relic light that was emitted billions of years ago when the universe was still bathed in the white-hot afterglow of its own creation.

To create the map, scientists first had to carefully subtract the foreground light from stars, galaxies and dust in the universe. What remains is a direct view of a distant moment in time when the universe was only 370,000 years old. The map shows this region as a mottled patchwork of spots that represent tiny fluctuations in the temperature of the early universe. Although no single spot reveals very much, the overall pattern can be read like a bar code, revealing information about the age, contents and expansion of the universe.

The new data peg the age of the universe at 13.8 billion years, or about 100 million years older than earlier estimates. They also show that 4.9 per cent of the energy content of the universe is locked up in the form of ordinary matter, another 26.98 per cent is invisible dark matter and the remaining 68.3 per cent is dark energy, a mysterious phenomenon thought to be causing the expansion of the universe to accelerate.

The challenge is understanding the reason behind those numbers. On that point, Planck has so far been silent.

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"It is an exciting achievement, but we had hoped for some indication of new physics," said Joel Meyers, a researcher at the Canadian Institute for Theoretical Astrophysics who is not involved with the mission.

The result nevertheless represents progress of a kind. It is highly consistent with cosmic inflation, an idea first suggested by MIT physicist Alan Guth. It posits that in the first trillionth, trillionth, trillionth of a second after the Big Bang, the universe underwent a massive expansion that smoothed out its appearance.

"Not only is inflation continuing to look like a superb fit to the data, but it still looks like the simplest inflationary models are the ones that fit best," Prof. Guth said.

But not all cosmologists are satisfied. "If Planck continues to confirm a vanilla model of the early universe, the ball will be firmly in the camp of theorists … to construct a more complete and compelling theory," said Neil Turok, director of the Perimeter Institute for Theoretical Physics in Waterloo, Ont. Dr. Turok has championed alternatives to inflation that suggest the universe has formed and reformed in an endless cycle.

While the Planck data do diverge from expectations at some areas, researchers caution that this could simply be a statistical fluke. A second data release from the mission, expected in 2014, could reveal more.

Canada contributed about 1 per cent of the roughly $1-billion cost of the Planck mission, a comparatively modest sum that nevertheless allowed Canadians scientists to play a significant role in the analysis of the Planck data.

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Through the Canadian Institute for Advanced Research, Dr. Bond leads a program that includes several Canadian and international cosmologists closely connected to the Planck mission.

"It's recognized that Canadians have expertise in this area," Dr. Scott said. "We can get in and get involved with the most exciting aspects of the experiment."

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