C&B Notes

Seeing in the Dark

Armed with a 570 megapixel digital camera — the world’s most powerful — installed on a telescope on the outskirts of La Serena, Chile, scientists are trying to understand why galaxies seem to be moving apart at increasingly faster rates on the outer edges of the universe.  The discovery could have implications for Einstein’s theory of relativity, which has so far withstood all challenges effectively unscathed. Fifteen years ago, the world of science was rocked by the discovery that, contrary to our notions of gravity, distant galaxies appeared to be flying apart at an ever-accelerating rate.  The observation implied that space itself was stretching apart faster and faster.  It was akin to watching a dropped ball reverse course, speed upward and disappear into the sky… Now, after years of planning and construction, four new projects at telescopes in Chile, Hawaii and the South Pole are getting a handle on what, exactly, is doing this unseemly pushing.

Leading the way is the world’s most powerful digital camera, constructed at Fermilab, the Energy Department facility in Illinois.  The $50 million Dark Energy Camera took a decade to plan and build, and it sports a resolution of 570 megapixels — about a hundredfold more pixels than a smartphone camera.  Technicians installed it atop a telescope in Chile last year, and after initial jitters — the camera was so heavy it made the telescope jiggle — the camera has been “tested, tweaked and fine-tuned,” said Joshua Frieman, the Fermilab scientist leading the project, which has enlisted 120 scientists from 23 countries.

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Each click captures light from nearly 100,000 distant galaxies.  Over the next five years, the project, called the Dark Energy Survey, will catalog some 300 million galaxies and thousands of exploding stars flung across distant space and time, in what Frieman called “the biggest galactic survey yet.”  Every night, scientists will beam 400 gigabytes of camera data to a supercomputing center at the University of Illinois at Urbana-Champaign, where machines will build a giant time-lapse map of the universe going back some 8 billion years — or more than half way to the Big Bang that started it all.

Frieman calls it “a movie of cosmic history.”  Scrutinizing this movie will narrow down the possibilities for what’s causing cosmic acceleration.  Because this acceleration can’t be measured directly, its nature can only be divined indirectly, by measuring, for instance, how clumps of galaxies coalesce across space and time.

One possibility: Our understanding of gravity, explained by Einstein’s general theory of relativity, breaks down across huge distances.  The theory marked the culmination of Einstein’s hardest thinking, and since its inception in 1916 it has withstood every test thrown at it.  But general relativity may be incomplete.

Another possibility: A mysterious repulsive force permeates every point in the universe.  This dark energy, if revealed, would be instant Nobel Prize fodder, Kamionkowski said.  “This is the one a lot of people would bet on,” said David Spergel, an astrophysicist at Princeton University.  “It’s where I’d put most of my money.”