Quantum Leap 
Discovery 
The Final Frontier
To solve the mystery of dark energy—a phenomenon that could reveal the origins of the universe—Texas astronomers need a $34 million telescope and a little bit of luck. There are only two problems: it may not be dark, and it may not be energy. In fact, it may not exist at all.
Related Multimedia
(Page 2 of 3)
Meanwhile, a decade before Hubble, Einstein had revised Newton’s idea of gravity—an attractive force between massive objects—with his theory of general relativity, in which gravity depends on the curvature of four-dimensional space-time. The twentieth century saw the Newtonian model of a fixed, orderly universe supplanted by that of a warping, expanding space with unimaginably chaotic origins. This universe had a beginning and would perhaps come to an end as well: If the expansion of space was indeed due to the propulsion from the big bang, then it stood to reason that because the gravitational pull of all the matter in the universe would be retarding that outward growth, one of three things would ultimately happen: Gravity would win out and the universe would collapse, the initial propulsion from the big bang would win and the universe would expand forever, or—and this is the most accepted case—the two would be perfectly balanced.
But in 1998, two groups of researchers independently arrived at a surprising result, so surprising that members of each originally believed that they had made a mistake. Both teams had been studying a class of exploding stars called type 1a supernovae, measuring their distances and speeds. What each team found was that the most distant supernovae were fainter than expected, fainter than they would have appeared in a decelerating or even a coasting universe. The expansion of the universe, this meant, seemed not to be slowing down but rather speeding up. And no one had a good explanation for it. What phenomenon could possibly be pushing space outward?
“Theorists have been guiding observers for ten thousand years,” said Edward “Rocky” Kolb, a professor of astronomy and astrophysics at the University of Chicago. “Now they’ve observed something that we don’t understand. We desperately need a better idea of what’s going on.” The notion that some form of mass energy might pervade all of space dates back to Einstein, but it gained widespread acceptance only in response to the observed acceleration of the universe. But what sort of energy? Has it changed over time? Or could it be that there really is no such thing as dark energy and that our understanding of gravity is actually wrong? These questions demanded new experiments, which in turn would require new telescopes or modifications to existing ones.
Karl Gebhardt arrived at the University of Texas in 2000, an expert on nearby galaxies and black holes. But in 2004 he attended a meeting on the future of U.S. telescopes, where much of the talk was about dark energy.
“It really hit home: Everyone is pushing on this,” he told me when I visited him in his office. “All the dark energy missions were beginning to take root, and I said, ‘Hey, look, I think we can do this at Texas.’ I came back from the meeting all excited. So one day in the hall I was talking to Gary Hill about it, and I said, ‘Can we do this? Can we study dark energy?’ It turned out he was working on an instrument design with Phillip [MacQueen, the observatory’s chief scientist and a senior researcher at UT-Austin], and we decided we can make a really nice instrument to look at the problem.”
For the next few weeks, Gebhardt and Hill traded ideas about how to proceed, and MacQueen and Hill consulted about whether the instrument they’d conceived would be up to the task. “We went back and forth for a few months until we came up with a nice design,” Gebhardt said. “But it’s easy to come up with designs. The hard part is finding the money and the telescope to do it on.” Here, though, the team had two advantages: the Hobby-Eberly Telescope and a recent grant from the Air Force.
Not long afterward, they began trying to raise the $34 million, more than the cost of the original telescope. The financial end was both a burden and a potential edge: The Texas scientists would not be bound by the same sort of bureaucratic limitations that they might have encountered using a federally administered facility or depending heavily on government grants. “The National Science Foundation won’t go off the beaten path until they’ve beaten the path,” said Gary Bernstein, a professor of physics and astronomy at the University of Pennsylvania. “If you have your own facility and can do what you want to do, you have more freedom.” Or as Hill said to me, “In Texas, if you have the idea and you have the money, you can do it.” And the $34 million, while hardly a small sum, was much lower than the costs of other proposed dark-energy experiments.
A plan to put together a world-class instrument on the cheap might sound an alarm in the mind of anyone familiar with the observatory’s history, for a cost-saving design had been trumpeted once before, in building the Hobby-Eberly Telescope itself. Though less expensive than other telescopes of comparable size, the HET had suffered technical problems for several years after it was dedicated, in 1997. While it was one of the largest telescopes in the world, it had gained a reputation for poor image quality. Now, at last, it was functioning properly, and here came some upstart astronomers with a proposal to chop off its top half and replace the detector with a novel apparatus. Could grand ambitions get the better of the observatory a second time?
If the scientists themselves had such doubts, they kept them quiet. Their concerns were more concrete: Raise the money and get results before anyone else. Among the other proposed dark-energy experiments, only one will employ the same technique as HETDEX, and that’s a collaboration between scientists in Japan and the United States to build something called the Wide-Field Multi-Object Spectrograph, which would be installed on the Japanese-operated Subaru Telescope, in Hawaii. “This is a strange game, in that you don’t know exactly how much data you have to take before you can make a great discovery,” Kolb said. “Timing is of the essence. It’s sort of a race between the Japanese and Texans. This is such a hot topic that many people are interested in it. There is the potential of great discoveries to be made, and so you just can’t sit on it and wait.”
The HETDEX researchers, led by the Texas group and further supported by two universities in Germany and the consortium that operates the HET, are the mavericks of the dark-energy industry, relying on a small number of people and a relatively low-cost instrument. So far they’ve raised $20.1 million—enough to build a prototype for the elaborate new spectrograph and to rebuild the HET to give it a much wider field of view—and they’re gunning to finish their upgrade and their observations by 2013. “We are dwarfed by these other teams,” Gebhardt said. “They have the ability to go out there and barrage everybody at conferences. We can’t do that. We are working all-out just to get our instrument built. But it never hurts to be the underdog. I think people are a little scared of HETDEX because we’re going to finish soon now. We are really moving.”
If you were to look at a nighttime satellite image of Texas, you would see large splotches of light produced by Dallas—Fort Worth and Houston, smaller ones for Austin and San Antonio, and a grid of glowing points as you move west from Austin, the most prominent strand of them following Interstate 10. Gradually the lights trail away; in West Texas south of the interstate, the map goes almost completely dark. It’s one of the darkest spots in the continental United States, making it a natural place for an observatory.
The location was identified in the summer of 1932 by two astronomers who drove a Chevrolet nearly eight thousand miles—roughly one third of the earth’s circumference—all within Texas. They ranged from Galveston to El Paso and as far north as Amarillo, stopping to peer through a small telescope, make notes, and take photographs at prospective sites. An East Texas banker named William McDonald had bequeathed his fortune to the University of Texas so that it could build an astronomical observatory (for the stated purpose of “seeing closer the gates of heaven”), and the university, which had no astronomy department, contracted with scientists from the University of Chicago to supply the expertise—the first order of business being to choose a location. They selected the Davis Mountains, a choice approved by Otto Struve, the Russian émigré who became the observatory’s first director, after he spent several nights camping on Mount Locke with his wife.
Today, as you drive from the interstate to the town of Fort Davis and on to the observatory, the elevation rises, the land begins to buckle and swell, and having passed over miles of desert plains, you find yourself driving through cedar-sprinkled hills and finally up Mount Locke, where most of the observatory is located. At first you see two white domes resembling centurion helmets at the summit. They are the observatory’s older telescopes, the Struve telescope, or “the 82-inch,” after the diameter of its primary mirror, which was built in 1939, and the Harlan J. Smith 107-inch, completed in 1968. Each in its time was one of the most powerful telescopes in the world, only to be eclipsed, inevitably, by technology’s advance. (They are still in use, but they are no longer considered cutting-edge.) Higher up the hill a silver-mirrored dome resembling a giant buckyball comes into view: This, situated on an adjacent peak, is the Hobby-Eberly Telescope.
My Library
