Five Billion Years of Solitude (35 page)

Sagan called Earth’s image a “pale blue dot,” and went on to use the phrase as the title for one of his many bestselling books. In the decades since the Green Bank meeting, he had ascended to the pinnacle of practicing and popularizing space science, performing crucial work on planetary atmospheres and producing the wildly successful television miniseries
Cosmos
. With Frank Drake and other collaborators, Sagan had designed and curated a long-playing phonograph record to be sent to the stars with the Voyagers. Crafted from copper, aluminum, and gold, a copy of the record was bolted to the side of each spacecraft, ready for playback, complete with a magnetic cartridge, stylus, and pictogram instructions. In the emptiness of interstellar space each record should persist for untold eons, outlasting the Sun and the Earth alike. Any eventual encounter with another planetary system is improbable—if ever found at all, the records will most likely be recovered by some wildly advanced civilization traveling between the stars. Maybe even by our distant descendants, if we are so lucky. The Voyager records were vaingloriously utopian, and excluded references to such entropic human failings as crime, war, famine, disease, and death. Each contained recorded messages from President Jimmy Carter and United Nations diplomats, greetings in fifty-four languages, and 118 joyful photographs of life on Earth. Each would share the sounds of wind and rain, heartbeats and laughter, kisses and rocket launches, electroencephalograms and whale songs. Each would play the music of Bach and Beethoven, Mozart and Stravinsky, Peruvian panpipes, Javanese gamelans, and Chuck Berry performing “Johnny B. Goode” on his electric guitar. Each would be a murmur from the departed Earth, a golden memory of beings either sublimed into some unknowable future form or long fallen from their ancient flaws.

To many humbled and earthbound souls living in a universe revealed year by year as increasingly aloof and uncaring, Voyager’s glimpse
of far-off Earth and its messages to the stars became beacons of hope, perseverance, and wisdom, pure and noble expressions of the better angels of our nature. Meditating on the pale blue dot in an essay, Sagan poetically called it a “mote of dust suspended in a sunbeam.” It was “the aggregate of our joy and suffering” upon which “everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” To Sagan, the image was a symbol of the cosmic folly of human divisions and geopolitical conflicts. “In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves,” he wrote. “The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. . . . [T]he Earth is where we make our stand.”

Earlier in the same essay, Sagan touched on the difficulties of finding any plausible future planetary home for humanity. He thought that the pale blue dot approximated the view of Earth as seen from a starship arriving after a long interstellar voyage. He did not mention that it also replicated how our planet would appear through a first-generation TPF-style space telescope, though the thought perhaps crossed his mind. We would know from experience that our home planet’s pale blue came from its life-giving seas of water and clouds of water vapor, Sagan wrote, but he doubted whether an alien observer could surmise so much from Voyager’s single, spectrum-free image. More detailed inspection would be required.

That inspection arrived ten months after
Voyager 1
’s historic image—on December 8, 1990, when Sagan masterminded a suite of Earth observations using the Galileo spacecraft, which was flying by our planet on a roundabout voyage to Jupiter. Examining the Earth as if it were a newly discovered alien world, Sagan and the Galileo team successfully confirmed Earth’s habitability, then detected its biosphere and technology, all from the depths of space and purely from first principles. They took the planet’s temperature in infrared light, and confirmed its polar caps, seas, and clouds were made of water.
They found evidence of life in the oxygen-soaked, methane-tinged atmosphere, far out of thermodynamic equilibrium, as well as in the vegetation-filled continents, which reflected the spectral sign of light-absorbing chlorophyll, of photosynthesis, out into space. Powerful pulses of narrowband modulated radio waves from the planet’s surface hinted at technological civilization. The collective verdict was indisputable: much of the planet was literally covered with life, and something down there had been smart enough to build a global telecommunications network. Later, Sagan and his team turned Galileo’s instruments toward Earth’s Moon, finding to no surprise that, unlike our living planet, it was a desolate, dead rock. As pat and prosaic as Sagan’s Galileo observations may first appear, they constituted a potent control experiment, a standard of proof that could be applied to any planet, whether investigated via close-flying probe or by telescopes gathering light over interstellar distances.

Examining the breadth of Sagan’s later work, it is hard to escape the conclusion that he was methodically preparing for any observational studies of potentially habitable exoplanets that might occur during his lifetime. We will never know for certain. His life was cut short in December 1996 at the age of sixty-two, after a two-year battle with bone marrow disease, only months after NASA’s administrator, Dan Goldin, had announced plans to build TPF. Even at the end, by all accounts Sagan was just as sharp and limber-minded as he had been in all the earlier decades of his scientific career. If Goldin’s initial projections for TPF’s launch in 2006 had held, Sagan would have been seventy-two when the telescope began uncovering any pale blue dots around nearby stars. Had he lived longer, he could have served as an authoritative elder statesman to guide and promote the next giant leap in humanity’s understanding of the universe. Instead, with Sagan’s passing and the eventual demotion of TPF to NASA’s technology-development dustbin, his Voyager and Galileo observations of Earth were quite possibly the closest astronomers would get to investigating a living, alien world for many generations to come.

•   •   •

I
n 1990, while Sagan was scrutinizing Earth from afar, Sara Seager was beginning her freshman year at the University of Toronto, tearing through her introductory coursework in math and science. She had convinced her father, a doctor who had left medicine to start a small hair-transplant business, that she would pursue a premed track. He encouraged her to specialize in something lucrative, dependable, and relatively stress-free, like dermatology. Instead, to her father’s chagrin, Seager soon switched her focus to physics and astronomy. She had been curious about the night sky ever since she was a young girl, when on nighttime family car rides she would wonder why the Moon always seemed to follow overhead no matter where they went. Soon after, Seager’s father took her to a “star party,” where an amateur astronomer explained the Moon’s orbit and let her gaze at it through a telescope. When she was ten, on a camping trip into the Canadian backwoods, Seager’s view of the world had drastically expanded as she stepped out of her tent at night beneath a clear sky suddenly free of city lights. Looking up at so many stars, she for the first time sensed the continuum that began with the Earth beneath her feet and extended out into the endless heavenly depths above. At sixteen, while attending a university open house, she learned that some privileged people actually studied stars, planets, and all else beyond Earth for a living.

“It was one of the most exciting days of my entire life,” Seager later recalled to me. “You can do this as a job? I rushed home and told my dad. He was so hard on me, and discouraged me with the harshest lecture he ever gave. He said, ‘You have these natural skills, but you need to be able to support yourself and not rely on any man!’ He wanted me to be independent, and just didn’t think it was a good career choice.” Seager’s father valued practicality, but time and time again, he told her she must think big, set goals, and visualize herself reaching them. Otherwise, she should not expect success.

Despite that advice, Seager often described her early path toward astronomy as an unfocused “random walk,” like that of a photon bouncing chaotically around the seething heart of a star. She appeased her father by first concentrating on physics, reasoning that would boost her chances of employment both within and outside of academia, but the more she learned, the less interest she could muster. “I believed you could perfectly describe everything with equations,” she said. “Then I learned that approximations were rampant. I was working so hard for three, four years, why should I suffer my whole life and work so hard for something that’s not enjoyable?”

Approaching graduation, she took a risk and tried her luck applying to astronomy programs at graduate schools. She decided to think big, and submitted an application to Harvard in the fall of 1994. She was twenty-two. To her astonishment, Harvard replied in February of 1995, offering her a grad-school spot as well as a modicum of funding. Seager received the news while cross-country skiing with friends in Ontario. She accepted, and set about planning her move from Toronto to matriculate at Harvard in the fall. That summer, she had little to do other than wait. She decided to travel north and go camping, but she didn’t want to journey alone. Seager reached out to an occasional canoeing partner, Mike Wevrick, a robust thirty-year-old who loved cars and the outdoors. Wevrick looked rather like a grizzled Marine, blue-eyed and broad-shouldered, with long, powerful legs and biceps as big as Seager’s thighs. He sported a crew cut and a constant few days’ growth of stubble on his lean face, and had a reputation for quiet intelligence and kindness. They had first met skiing in Ontario, on the very day Seager learned of her Harvard acceptance. For both reasons, she would later call it the luckiest day of her life.

•   •   •

T
ogether, Wevrick and Seager devised an ambitious canoeing trip deep into Canada’s Northwest Territories, to the “Barren Lands,” the
treacherous tundra that exists past the northern limit where trees can grow, a trackless wilderness so desolate and remote that it was essentially unmapped until after World War II. They would begin by driving four and a half days from Toronto into the boreal forest of northern Saskatchewan, to where the northerly road ended at a lake. From there, for twenty days they would canoe farther north on a series of rivers before finally reaching Kasba Lake Lodge, an outpost with a small airstrip where they could replenish their supplies. From Kasba Lake, they would continue canoeing north past the tree line, into the Barren Lands, on an out-and-back journey that would take another forty days. They planned to be back at Kasba by the end of those forty days to catch a plane south. Wevrick was an expert whitewater paddler, and would guide them through the rivers and lakes. Seager would help with portages, the overland hauling of supplies and Wevrick’s red Old Town Tripper pack canoe between navigable waterways. They left Toronto on June 24, at the end of the summer thaw, planning to return in late August as northern autumn fell.

The weeks leading up to the trip had been arid, with hardly any rain. Departing Toronto, they felt optimistic the weather would hold, minimizing muddy slogs and soggy supplies. But the lack of rain also raised the risk of lightning-sparked forest and prairie fires. Arriving at the end of the road, they found the lake and surrounding forest blanketed in dense smoky haze. They paddled into the gloom and through the mouth of a river, stopping to tie wet T-shirts around their faces when they passed smoldering shorelines. They developed a routine, taking meals in the canoe and paddling through most of the twenty hours of daylight provided by the sub-Arctic summer Sun. If the wind blew at their backs, they rested and used a plastic tarp as a makeshift sail. They portaged as often as fifteen times a day to circumvent sequences of boulder-filled rapids and plunging waterfalls. When they ventured onto land, swarms of biting black flies and mosquitoes rose from the underbrush to assail them. When daylight faded, they made camp and fell into weary, dreamless sleep within their tent.

Seager and Wevrick found comfort in their quiet conversations, and
in the harsh, untrammeled beauty of the surrounding wilderness. They walked upon the Precambrian, Archean, Proterozoic rock of the Canadian Shield, the oldest exposed rock on planet Earth. They portaged over the roots of tall mountains transformed to gentle nubs by four billion years of weathering, in a country that had been compressed and scraped clean by the weight of advancing ice sheets during the last glacial advance. Sediment-clogged streams and rivers of meltwater had run like veins beneath the ice sheets, so that when the ice withdrew, it left behind eskers—sandy ridges of pink granitic gravel that followed the twisting paths of the dried-up subglacial flows. The eskers wound between and around kettle lakes, each lake a ghostly puddle from some great hunk of ice long ago calved off the retreating glaciers. The land was still slowly rising up and finding its bearings, rebounding at one centimeter per year from the heavy load of ice that had been lifted tens of millennia ago. Distant columns of smoke from incessant fires lined the horizon in all directions. During their twenty-day trek to Kasba, they saw abundant wildlife, but not another human being outside of each other.

In mid-July, Seager and Wevrick reached the Kasba Lake Lodge, perched on the west end of an island-dotted expanse of water stretching as far as they could see. They picked up supplies, hobnobbed with the lodge’s caretakers, then continued north, up through the lake and into the Barren Lands. Day by day, mile by mile, the trees became sparse, then stunted, then entirely absent, replaced by moss carpets, hardy grasses, and brightly colored lichens. Just north of the tree line, they spotted their first caribou, gazing at them as if they were visitors from another planet. Without trees, a constant wind rushed unrestrained over the sinuous hills and through the rivers and lakes in the hollows. The wind made canoeing slow going, often pressing them ashore at midday. Sometimes on a windy shore Seager would pull an astrophysics textbook from her pack. Far below the tree line, in another world, Harvard awaited. Other times, she and Wevrick would have long talks, seemingly the only people in existence, inhabiting a universe built for two.