Five Billion Years of Solitude

by Lee Billings

  No matter how many holes Laughlin tried to poke in his thinking, deeper scrutiny deflected each of his criticisms, and the idea of a Centauri-centric RV survey stood unscathed. The more he turned it over in his head, the more ideal and fortuitous the situation seemed. Though most stars appear immobile in the sky on human timescales, the Sun’s 250-million-year orbit about the Milky Way’s center ensures that every few hundred thousand years our solar system has entirely new neighbors. “If we were plopped down at some random point in the galaxy, there’s only a 1 percent chance we’d find ourselves near stars so optimal for detecting small rocky planets like our own,” Laughlin told me during an interview in late 2008. “The hand of fate has dealt us a very interesting situation that has not existed for at least 99.9 percent of Earth’s history. It’s remarkable that Alpha Centauri is right next door just as humans emerge and develop the ability to make these measurements. I’m enamored with that coincidence.”

  A survey seemed worth the risk of coming up empty-handed, Laughlin told himself as he sat at his kitchen table on that summer night in 2006. Finding any planets at all around the stars of Alpha Centauri would be a historic discovery. By virtue of their close proximity they would be prime targets for subsequent study, and regardless of their characteristics would likely garner large amounts of in funding for further research.

  For a moment he allowed his thoughts to drift far away, into hazy realms of possibility. Detecting potentially habitable worlds around Earth’s nearest neighboring stars would be a truly revolutionary development, one that could stimulate major investments and advances in the quest to learn about our place in the universe. Without actually seeing any terrestrial planets that orbited in the stars’ habitable zones, no one could know whether they were places like Venus, Mars, Earth, or something else entirely outside of expectations. In comparison with the prospect of confirming other living worlds right on our galactic doorstep, the cost of building a direct-imaging space telescope to study such planets would seem to shrink. If, by happy chance, those nearby worlds looked particularly inviting when viewed through new telescopes, they would lure generations of scientists, explorers, and dreamers just as the planets of our own solar system did during astronomy’s earlier, more romantic eras. Alpha Centauri would call across that briefest interstellar gulf, and someone would surely strive to answer. The first emissary would undoubtedly be robotic, maybe something the size of a Coca-Cola can somehow sent voyaging at 10 percent of the speed of light. And if, nearly a half century after its launch, the probe against all odds beamed back to Earth high-resolution images of another clement planet replete with oceans, clouds, continents, and . . .

  Laughlin blinked and reined in his mind’s free roaming, which had suddenly slipped beyond the stars. Too much extrapolation was dangerous. He closed his laptop, rose from his kitchen table, and went to bed.

  Within months of his kitchen-table reverie, Laughlin had performed numerical simulations of planetary assembly in Alpha Centauri with a graduate student, Javiera Guedes. They began with Moon-size planetary “embryos,” and watched as the embryos gravitationally clustered into small, rocky planets in stable, habitable orbits around each star. Laughlin next approached Debra Fischer, Marcy and Butler’s former collaborator, to propose a search. With funding from the NSF and help from many colleagues, including Laughlin, Butler, and her own students, Fischer began an intensive survey of Alpha Centauri in 2009, using a small 1.5-meter telescope at the Cerro Tololo Inter-American Observatory in Chile. Sixty kilometers to the north, at Cerro Paranal, the Swiss had been monitoring Alpha Centauri B since 2003, but soon after Fischer’s program began, they drastically upped the cadence of their observations. They could not focus as intently on the stars as Fischer and her collaborators—HARPS was simply too valuable a resource to be monopolized by a single star system. In 2011, a third team officially joined the search, obtaining funding to perform a high-cadence survey using a 1-meter telescope at Mount John University Observatory in New Zealand.

  Analyzing the RV data proved harder than anticipated, partially due to difficulties with precisely removing the binary orbits—Alpha Centauri A and B orbit each other in a roughly 80-year period, at an average separation somewhat greater than the distance between our Sun and Uranus. The orbit is significantly “eccentric” (non-circular), but its fine details were not known down to the level of centimeters-per-second, making RV signals of small planets in either star’s habitable zone harder to see. That eccentric orbit posed further problems, according to another round of numerical simulations performed by the theoretician Philippe Thébault of Paris Observatory and a few collaborators. In run after run, gravitational perturbations driven by the orbit’s eccentricity disrupted the formation of structure well before any Moon-size building blocks could coalesce. Thébault’s simulations suggested nothing larger than sand grains and pebbles would orbit either star.

  Laughlin could find no potential oversights or errors in the newer simulations, save for one: Thébault had assumed that the stars were born at their current distances from each other, with each sporting a protoplanetary disk approximately the same size as the one astronomers think formed our own solar system’s planets long ago. Laughlin believed Alpha Centauri’s stars had begun with very different initial conditions, at wider separations, perhaps with stubbier, smaller protoplanetary disks—any of which could prevent Thébault’s subsequent eccentric disruptions. The presence of the red dwarf Proxima was a potential piece of forensic evidence, Laughlin thought. “Had Alpha Centauri formed in a very dense stellar cluster, like what we see in the Orion Nebula today, then in all likelihood Proxima would have been stripped from its orbit by a passing star,” he explained to me. “Of course Proxima may have been only captured much later on, but I would bet its presence means Alpha Centauri formed in a more open, less cluttered environment, where the stars were further apart. . . . If you start with [Thébault’s] initial conditions, you’ll end with no planets. I just believe the initial conditions were quite different than what he uses.”

  In October of 2012, a discovery was finally made. Using more than 450 combined HARPS measurements, the Swiss had detected what looked to be an Earth-mass planet around Alpha Centauri B. It resided in an inhospitable three-day orbit, so close to the star that its surface would be broiled at temperatures exceeding 650 degrees Celsius, yet it was universally acclaimed as a promise of great things to come, of a life-friendly cosmos. Somehow, even in uninviting circumstances, small, rocky planets still found ways to form and persist. Alpha Centauri Bb, as the new world was called, is so light it only creates a wobble of some 50 centimeters per second upon its star—a bit faster than the average speed of a crawling baby. If HARPS could detect that faint signal, the Swiss said, then any undiscovered rocky planets in Alpha Centauri B’s habitable zone were also likely within reach. And more planets were almost certainly there—statistics from the Kepler mission strongly suggested that where one small, close-in planet was detected, several more would lurk farther out, as yet unseen. Astronomers began to murmur that, in all likelihood, all three of Alpha Centauri’s stars possessed planets, and that quiescent, placid B would again be the first to yield additional discoveries. It was only a matter of time.

  Once, years before its first planet was detected, I asked Laughlin via e-mail if he had ever dreamed about the environment of Alpha Centauri. Did he ever try to visualize what a habitable world might look like around one of Alpha Centauri’s stars? His reply contained only a passage from The Martian Chronicles by Ray Bradbury:

  The old Martian names were names of water and air and hills. They were the names of snows that emptied south in stone canals to fill the empty seas. And the names of sealed and buried sorcerers and towers and obelisks. And the rockets struck at the names like hammers, breaking away the marble into shale, shattering the crockery milestones that named the old towns, in the rubble of which great pylons were plunged with new names: IRON TOWN, STEEL TOWN, ALUMINUM CITY, ELECTRIC VILLAGE, CORN TOWN, GRAI
N VILLA, DETROIT II, all the mechanical names and the metal names from Earth.

  Laughlin declined to elaborate, but the quotation suggested we would unavoidably filter any alien world’s mysteries through our familiarities, reshaping all we found into our own image, our initial conditions from Earth.

  Months later, out of curiosity I sought Laughlin’s opinions on SETI. Would it ever be successful? He laughed coolly, then began thinking aloud. “Heh. Maybe. Ahh . . . Well. Eventually. Though not how most people think. If you get a radio signal, that’s great, you can get right down to work. That’s a nice dream. That works well for some fraction of our galaxy. A big space telescope could look for some signs of life on planets in the habitable zones of some very nearby stars, but distinguishing signs of intelligence would be tough. I think if a SETI detection ever comes, it will probably be extragalactic.”

  Somewhere out there, Laughlin said, perhaps beyond our present observable horizon, perhaps in another universe entirely, there would be galaxies containing civilizations very much like ours, except with much more fortunate initial conditions. Maybe they had emerged, as we had, on a planet like Earth, with a moon close and tempting in the sky. Maybe their star had not one, but two or even three habitable Earth-like planets, and their nearest neighboring star had held habitable worlds as well. Maybe they had originated in a binary or trinary star system, with each sun blessed by multiple habitable worlds. If a civilization somewhat like ours got lucky enough, he said, and took advantage of its good fortune with the kind of “mid-twentieth-century-style Space Age expansion” that had flashed and faded here in our own solar system, it would reasonably have a chance of spreading out to grasp and shape its entire galaxy. Evidence for such galactic empires could be lurking latent in any number of the thousands of unnamed galaxies contained in a typical long-exposure “deep field” image from current space telescopes.

  I wondered what that evidence might look like. Laughlin laughed again and said that was something he couldn’t predict.

  • • •

  On July 13, 1963, just off the Cabrillo Freeway in San Diego, a time capsule was sealed in a small subterranean concrete vault beneath what was then the west entry ramp into the General Dynamics Astronautics plant, where the company built Atlas rockets for the U.S. government. General Dynamics was bought out in the 1990s, and much of its Atlas-manufacturing infrastructure was dismantled to make room for easier money from industrial parks and office buildings. The capsule, meant to be unearthed a hundred years after its burial, was instead dug up and relocated to storage at the San Diego Air & Space Museum in Balboa Park. If you were to open the capsule today, you would find a slim, aged volume entitled 2063 A.D. The book had been commissioned to commemorate General Dynamics’s fifth anniversary, and contained hopeful prophecies from experts—generals, politicians, scientists, and astronauts—about humanity’s conquest of space a century hence. Someone at the company thought to print a few hundred extra copies, which is how we know about the book’s contents today.

  Mercury astronaut John Glenn, the first American to orbit the planet, predicted that within a century we would have linked atomic power plants to “anti-gravity devices,” fundamentally rewriting the laws of physics and revolutionizing life and transportation on Earth and in the heavens alike. Another Mercury astronaut, Scott Carpenter, expressed his hope that the anti-gravity “scheme” would help humans colonize the Moon, the Martian moon Phobos, and Mars. The prominent astronomer Fred Whipple suggested that Earth’s population would have stabilized at 100 billion, and that planetary-scale engineering of Mars would have altered the Red Planet’s climate to allow its 700,000 inhabitants to be self-sufficient. The director of NASA’s Office of Manned Space Flight, Dyer Brainerd Holmes, suggested that in 2063 crewed vehicles would be reaching “velocities approaching the speed of light,” and that society would be debating whether to send humans to nearby stars.

  A majority of the twenty-nine respondents predicted a peaceful world, harmoniously unified under a democratic world government and freed from resource scarcity. Each entry had its optimistic idiosyncrasies. Edward Teller, one of the masterminds behind the hydrogen bomb, hoped that ballistic missiles would no longer be used to loft nuclear-tipped warheads, but would instead be turned to transporting passengers anywhere in the world in less than an hour. He doubted, however, that it would ever be “a comfortable way to travel.” Vice President Lyndon B. Johnson opined that we might use satellites to control Earth’s weather. The Republican California congressman James B. Utt thought that society would master the science and technology of human teleportation, though he didn’t “look forward to this with any sense of enjoyment.” Another California congressman, the Democrat George P. Miller, offered his curious opinion that by 2063 we would “have found humans living elsewhere in the universe besides Earth.”

  The strangest entry of all was the long, decidedly pessimistic response of Harold Urey, the Nobel-laureate chemist. Where few other contributors had filled more than a single page, Urey took up roughly a third of the entire book. His thoughts may well have been inspired by his participation in Frank Drake’s Green Bank meeting two years earlier.

  Urey hardly discussed space science and exploration at all. Instead, he devoted much of his essay to summarizing the social implications of changes he had seen in his lifetime. He had been a boy at the turn of the century, growing up when steam engines, railroads, telegraphs, and telephones represented the pinnacle of technology. He was now an old man, in a world filled with automobiles, airplanes, rockets, digital computers, color televisions, and atom bombs. He lamented how technological progress had cut off his children from many of the bucolic joys of his own upbringing, such as riding “in a sleigh behind a matched team of blacks, on a clear night with stars above and white snow around . . . nestled warm and cozy beneath a buffalo robe.”

  For every decade of Urey’s life, human society had experienced a relatively constant factor of growth in technological capability and economic capacity. The expectation of continued growth—indeed, endless growth—was what underpinned capital investment in the ongoing research and development that was transforming the globe. But that exponential profusion, he wrote, was not opening up magnificent new frontiers so much as it was revealing previously unappreciated limits. Looking ahead, Urey glimpsed a not-too-distant future in which things could fall apart, when the centers of the modern world could not hold, a time when growth would stagnate. He postulated no proximate causes other than already-existing cracks in civilization’s façade. Schemes for world government were unfavorable, he believed, because governments tended to grow bloated and cumbersome from “fantastic national debt” that outstripped both inflation and revenue. The ruinous deficits would be produced by “the curious psychology of politicians” paired with “the development of war machines by applied scientific methods,” and would be exacerbated by the need to provide healthcare and social security for a large, aging populace. Turning society over entirely to the whims of large, private corporations was no alternative, Urey observed, because companies would inevitably conspire to pursue short-term profits against the public interest and common good. Only through some uneasy and uncertain balance between government regulation and private enterprise could the status quo of growth be maintained. Even then, it could not be maintained indefinitely.

  Urey bemoaned the fact that most ordinary people were trapped in the present, scarcely able to consider a past predating the lives of their grandparents, unable to plan for a future beyond the lives of their grandchildren. Worse yet, he saw a public increasingly hostile to any scientific research and technological development that did not directly contribute to greater comfort and convenience in their daily lives. In developed nations, more effort than ever before was being channeled away from solving pressing global problems and toward making technological baubles to satisfy the cyclical desires of consumerism. Urey noted that U.S. fossil fuel consumption had increased eightfold between 1900 and 1955, much of it due
to generating electricity. Further, usage of “electrical power increased from negligible in 1900 to about five hundred watts per person” by 1963. How long could energy usage continue increasing to support economic growth? In one of the few actual predictions to be found in Urey’s response, he gently hinted such luxuries were unsustainable: well before 2063, he prophesied, we would be faced with the potentially unpleasant necessity of finding “ways to expend human energy other than by working on useful gadgets.”

  Energetic limits to economic growth are remarkably straightforward to calculate, given a few simplifying assumptions. Taking the United States as an example, data from the federal Energy Information Administration shows that the nation’s total energy usage has grown by just under 3 percent per year since the middle of the seventeenth century. As a thought experiment, a UC San Diego professor, the physicist Tom Murphy, has calculated the consequences of that continued growth out into the future, extrapolating it to the entire globe and reducing it to 2.3 percent per year, which yields a factor-of-ten increase in energy usage every century. Starting from a circa 2012 global energy use of 12 terawatts, the world of 2112 would consume 120 terawatts, and the world of 2212 would consume 1,200. By 2287, world energy consumption would be 7,000 terawatts—an amount that could in theory be delivered by covering all the land on Earth with photovoltaic solar-power arrays operating at 20 percent efficiency. From there, increasing the efficiency of the photovoltaics to a miraculous 100 percent and covering the oceans as well as the continents would allow the 2.3 percent annual growth in energy use to persist for another 125 years, taking our steadily growing civilization into A.D. 2412 before it outpaced the total amount of sunlight falling upon the Earth. Another energy source, nuclear fusion, could potentially sustain an annual 2.3 percent growth rate for some centuries beyond this, at least until the waste heat from the vast amount of power being produced evaporated the oceans and turned Earth’s crust to glowing slag. For a planet-bound civilization, the boiling point of water and the melting points of rock and metal place insurmountable limits upon the expansion of energy use.