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.
Quantum LeapOne evening last October, a University of Texas at Austin astronomer named Gary Hill stood behind a lectern at Miss Hattie’s Café and Saloon, which occupies a restored nineteenth- century bank building in downtown San Angelo, and cheerfully proclaimed his ignorance. “We really don’t understand the universe,” he said. “We thought we did, but it turns out we only understand about four percent of it.”
A dozen or so people, among them businessmen, the editor of the local newspaper, a school librarian, and a couple of college professors, had assembled at Miss Hattie’s, where the lace curtains and rose-print wallpaper harked back to a time when the universe was no larger than our own galaxy and Newton’s laws seemed to explain it and a tunnel linked the building where we sat to a nearby bordello. There was something old-fashioned too about the fact that a bespectacled, British-born scientist had traveled from the state capital to give a talk to the curious and that the curious had turned out to hear what he had to say. His subject, on the other hand, was the very future of cosmology and physics and how they might be affected by one telescope in particular, located 212 miles farther west.
Galileo stuck lenses onto either end of an organ pipe; today’s research telescopes, while considerably more elaborate, still perform the same fundamental task of collecting and focusing light. It’s all astronomers have to go on: electromagnetic radiation from distant objects, whether it arrives in the form of X-rays or visible light or radio waves. “We’re detectives, but we can only use what light will give us,” Hill had said to me earlier that day. “So we get fairly ingenious in the ways we analyze light to look for clues.” They rely, for instance, on spectroscopy, the process of separating light emitted by an object in space into its component wavelengths, as a prism does, then analyzing those components. And they invent new tools to analyze the light. To probe deeper and deeper into space, scientists must design better and better detectors, sensitive to the faintest of emissions.
Such instruments don’t come cheaply, which is why Hill and his colleague Karl Gebhardt have periodically taken to the road over the past three and a half years: They’ve been promoting an ambitious $34 million overhaul of a telescope at UT’s McDonald Observatory, in the Davis Mountains of West Texas. Speaking to potential donors in Houston or a luncheon group in Abilene, they’ve been publicizing an endeavor called HETDEX, or the Hobby-Eberly Telescope Dark Energy Experiment, the aim of which is to help attack what some have labeled one of the most important problems in science.
Hill grew up in England but left to go to where the telescopes were, first as a graduate student in Hawaii, then as a postdoctoral researcher in West Texas, in 1988. Finding that certain instruments at the observatory weren’t sensitive enough, he designed and built a new spectrograph on the cheap, still in use today. He is now the observatory’s chief astronomer. At Miss Hattie’s he applied his knack for innovative thinking to the problem of business attire—he wore a striped green shirt and a pink tie—and as he spoke, he grinned and nodded infectiously. “We have a huge opportunity to lay the groundwork in Texas for understanding how the universe has changed through time,” he said. He outlined the goals of the experiment: to conduct the largest survey of other galaxies ever completed and to use that information to measure how the scale of the universe has evolved—and to reinvent the telescope in the process. By doing so, Hill, Gebhardt, and their collaborators hope to better understand what astronomers call dark energy, though no one really knows what the term means: “Dark energy” is a label for a mystery. “The thing is,” Hill told his audience, “it may not be dark and it may not be energy.”
After the presentation had ended and most of the audience had departed, Hill was subjected to a more rigorous interrogation at dinner from Ken Gunter, a tall, poker-faced San Angelo businessman and a member of the McDonald’s Board of Visitors, a statewide group of observatory supporters. This turned into a debate between the gruff West Texan and the polite but impassioned British scientist, while half a dozen others at the table looked on. Though he supports the experiment, Gunter was skeptical as to whether he could raise funds for it. “What is the pragmatic end product, except exciting a bunch of astronomy Ph.D.’s in Austin? Give me something I can identify with. If you want to raise some honest-to-God money, you better start raising some honest-to-God tie back to medical or energy.” That, said Hill, wasn’t the point. The most practical argument he could make for the telescope was that it might excite students in a country where science education was failing and draw better faculty to the university. Gunter seemed unconvinced. “My sense is that most people don’t give two hoots in hell whether the universe is expanding or contracting or moving sideways!” he said, and drew out a cigar.
Earlier that day I’d ridden in a rented suburban with Hill; David Lambert, the director of the observatory; and Joel Barna, its development director, from Midland to Abilene to San Angelo. The flat landscape was staked by the technology of energy production: Near Midland the pump jacks kowtowed to the brush, while farther south a line of soaring silver windmills receded toward the horizon. (One question often posed by lay audiences in Texas, Hill told me, is “How can we harness dark energy for human use?”) It was a warm, hazy morning, and as we’d all risen early to catch a seven o’clock flight from Austin to Midland, a soporific air had fallen over the car, leaving me in a state of sleepy wonderment at one of astronomy’s fundamental principles, that light can ripple for billions of years through the vast universe and collide with nothing else during that unfathomably long journey, reaching our planet with information about its place of origin. How can that be, I asked. “There’s a lot of empty space out there,” Hill said. “The fraction of the area of the sky with stuff is not very great, so the chances of a photon of light hitting anything along its route other than your telescope are actually very small.”
I fell silent. All that void. A little while later I asked something else, then mulled over the answer, and that’s pretty much how the ride went, as I surfaced every so often with another question for the patient professors, then let my head spin for a while. It’s humbling to stumble up against the edifice of astronomy, the massive and intricate body of knowledge humans have built up over the millennia, and then all the more humbling—if somehow also reassuring—to contemplate how much more we don’t know. And how much we can’t possibly see, since only 4 percent of the stuff in the universe is thought to be visible matter. That includes you and me and microorganisms and other galaxies, at least 100 billion of them. As one scientist put it recently, “we’re just a bit of pollution,” while most of the universe is made of something else.
“Nature and nature’s laws lay hid in night” goes the famous epitaph Alexander Pope composed for Isaac Newton. “God said, ‘Let Newton be!’ and all was light.” But as it turns out, almost all is, in fact, dark, and a crucial portion of those laws remain hidden. Theorists first ventured into the “dark” to resolve a problem concerning the motions of galaxies and the stars within them. The trouble was, there just weren’t enough visible stars out there. Matter far away from the center of a galaxy tended to move much faster than could be explained by the net gravitational attraction of all the visible matter. So in order to save Newton’s laws of gravity, astronomers invented a new type of matter that was dark but plentiful: dark matter. The universe is littered with it, they concluded. Which might seem like cheating—the invisible check is in the mail—yet the theory has helped explain the motions of other cosmic entities, and there are high hopes that dark matter will be detected in experiments this year at CERN, the particle physics laboratory in Geneva, Switzerland.
Then scientists discovered another anomaly, this one not limited to objects like galaxies but pertaining to the entire cosmos. And they came up with something even stranger to explain it. The problem was the way in which the universe was growing. Until the twentieth century, the universe was generally thought to be static, neither expanding nor contracting. But along came Edwin Hubble (who, late bloomers take note, taught high school and coached basketball in Indiana before returning to school for his Ph.D.). In the twenties he made measurements of how far away galaxies were and how fast they were moving, and he discovered that the farther away they were, the faster they were receding. The universe, this implied, was expanding, everything moving away from everything else. (Albeit with negligible impact locally. In Annie Hall, Alvy Singer’s mother is basically correct when she tells her existentially morose son that “Brooklyn is not expanding.”) The concept of an expanding universe in turn suggested that at one time, everything was closer together. Thus Hubble’s discoveries were a prod to the subsequent development of the big bang theory.
