For all its poetry, and in some cases because of it, Sagan's message lacked convincing substance for many in the scientific community. Among his many colleagues, Sagan's vision was fundamentally undercut by one fact: in 1980, we knew of only nine planets (including the since-demoted dwarf-planet Pluto) not just in our Solar System but in the entire cosmos. Extraterrestrial life needed more than the molecules of life; it needed somewhere to live. As far as we could tell, however, the other planets of our Solar System lacked a heartbeat. They were lifeless orbs of rock and gas. But in December 1996, fifteen months before Sagan's death, the extraordinary discovery of planet 51 Pegasi b (commonly referred to as “51 Peg b”) broke a scientific spell—the discovery of the first exoplanet, a planet around a distant Sun-like star. For half a century, almost all astronomers believed that if there were planets around other stars (and many doubted this), they would be impossible to detect, let alone study. It took thousands of hours of telescope searching, technical innovation, personal and professional heartbreak and disappointment, and endless errors to discover this first planet orbiting a star other than our Sun.
The discovery of exoplanets did more than launch the greatest search of all time. It was the breaking down of the Berlin Wall of the Stardust Revolution. Change had come. And with it, a new way of thinking took hold—that the cosmos’ biological nature is knowable. For decades, astronomers, including Carl Sagan, who talked about the study of life in the universe, were derided by scientific colleagues for pursuing a topic without a subject matter. Beyond Earth, in our Solar System there was no other life, and, more importantly, there was no way of studying the question of life in the universe or its cosmic origins. End of discussion. But the discovery of exoplanets was the tipping point in a decades-long buildup of evidence—from the discovery that the elements are forged in stars, to the discovery of interstellar water and organic molecules and of amino acids in meteorites—that is the foundation of the Stardust Revolution. The biological universe could now also be described by Einstein's statement of astonishment: “The most incomprehensible thing about the universe is that it is comprehensible.”
NEW WAYS OF SEEING
In the Stardust Revolution, this growing comprehension is driven by new ways of seeing the cosmos. The history of science is the history of resolution, and this is no more so than with stardust science. With each advance in telescopes, we don't just see better and more, we see differently. The more detail we can see, whether in a cell or in the cosmos, the more we know. Until Galileo looked through his telescope, there was no way of seeing Jupiter's moons, no way of seeing that the milkiness of the Milky Way is in fact the light of countless individual stars. The lenses in Galileo's telescope, crafted with what was then the world's finest glass, made by Venetian glassmakers, provided only about thirty times magnification, but the impact on human consciousness was tremendous and far reaching.
The Stardust Revolution involves not just greater resolution but different ways of seeing. Prior to World War II, humanity had explored the heavens only in light visible to the human eye, but today optical telescopes are only part of an armada of observatories, many of which don't see in visible light. Stardust scientists are exploring the cosmos in almost every wavelength of the electromagnetic spectrum, from gamma rays to x-rays, ultraviolet to infrared, and microwaves to radio waves. Each wavelength reveals different aspects of cosmic nature that are often impossible to observe in other wavelengths. It took the serendipitous 1940s development of radio astronomy—of using not visible light but radio waves and microwaves—to explore the heavens and reveal the previously invisible molecular universe. Space-based infrared telescopes, such as NASA's Spitzer Space Telescope, reveal the dusty origins of distant stars and planets. Future ground- and space-based telescopes will probe the atmospheres of Earth-like planets around distant suns.
BEYOND THE IMPOSSIBLE
The Stardust Revolution is also the story of what it's like to live in revolutionary scientific times. It is a revolution in the sense of what science historian Thomas Kuhn called a “paradigm shift,” in which there is a gradual building of evidence against the predominant worldview until one day, while that view still seems strong, the scientific old guard lays down its arms and the wall comes down. Revolutions in science involve all the elements of political revolutions, at least bloodless ones. Sir Fred Hoyle, the British astrophysicist who in many ways was the great twentieth-century prophet of stardust science, noted in his autobiography that “I grew up with the erroneous notion that the scientific establishment welcomes progress, which is the opposite of what is generally true. Progress is equivalent to revolution.” There are opposing camps: one entrenched in the bastions of power, the other claiming that the emperor has no clothes. It might seem like a tempest in a teapot, and at times it is, but there's something much larger at play—our understanding of ourselves, the universe, and our place in it. In science, the revolutionaries fight to get funding, to get published, to get telescope time, and more. Their scientific papers are often rejected and even ridiculed by anonymous reviewers. Stardust revolutionaries have faced an establishment that has dissuaded and ridiculed their research; that has denied, dismissed, or simply ignored findings.
Scientists have long had their own way of describing the painful and frustrating experience of a paradigm shift. Fred Hoyle's colleague, the Cambridge University physicist Ray Lyttleton, said that there are three stages in the acceptance of upstart scientific ideas: first, the idea is nonsense; then, somebody else thought of it before you did; and finally, we believed it all the time. The Stardust Revolution has been a centuries-long dance between what seemed reasonable at the time and what observation actually revealed, between elaborate theories of how the cosmos worked and singular theory-shattering discoveries.
In retrospect, we see a single narrative. In many cases, there's a stardust science pedigree of scientists trained and inspired by stardust mentors who in turn go on to train and enthuse a next generation. It's not, however, lived as a single narrative but rather as a maelstrom of uncertainty in which there are countless possible endings to the story. For all its messiness, though, science gropes and stumbles toward observable truth. Many of the establishment's leaders became converts over time. Though resistant at first, they are drawn to a vision because they refuse to deny the truth of their own scientific intuition and observations. The stardust story is possible because of the strength of their personal convictions, their wide-ranging curiosity, and their vivid imaginations. Because a universe seeking to know itself urged them to speak their truth.
The modern space age began in 1957 with the successful launch and orbiting of the Soviet Union's Sputnik 1, the world's first satellite. Sputnik sparked the frantic creation of NASA a year later and also the US National Research Council's Space Studies Board, which Lucy Ziurys would later join. But 1957 was also the year that Fred Hoyle and three colleagues wrote a seminal paper, one of the landmarks in the history of science, describing how stars fuse hydrogen and helium to create all the other elements in a process called stellar nucleosynthesis. Thus, they showed that with every atom of carbon, oxygen, iron, and calcium in our bodies, we are truly the stuff of stars. While the world's attention was occupied by its fear of intercontinental missiles and the race to the Moon, the Stardust Revolution had begun.
Today, after millennia of stargazing speculation and nearly a century of space-age science fiction, the search for extraterrestrial life is real. When humans next voyage to the Moon, we might do so with the knowledge that light-years away is another living world; that on a distant exoplanet—under the light of a full moon, or two—other beings experience lives of mystery; that not only are we not alone, but these beings are our relatives, made from the same materials and as a result of similar biological processes; and that just with every atom of our bodies, we are joined with a living cosmos.
Stardust science raises profound questions about previously staunch intellectual boundaries between living and nonliving, be
tween us and everything else. How did life begin before the Earth took shape? What's our living relationship with the rest of the universe? Who and what are we, in a cosmic sense? What is life? Are there abundant Earth-like exoplanets, as is argued by many astrobiologists, or are we an exquisitely “rare Earth,” a singular blossom in an otherwise utterly barren cosmos? At its core is one question: Is life a fundamental emergent property of the universe?
To tell the story of the Stardust Revolution, it's necessary to start at the beginning, at a time when astronomers and physicists were struggling to explain the basic nature of stars. As so often happens when we travel, in seeking to understand something else, what is most profound is what we discover about ourselves.
The tiny, twinkling stars of the night sky, shining with feeble and fluctuating beams, appear so minute and unsubstantial that an inexperienced beholder might expect one after another to vanish from its place…. Instead of infinitesimal points of light…[the astronomer] visualizes them as giant globes of incandescent matter pouring forth energy at so terrific a rate as to stagger the imagination. The contrast between the apparent and the real is the most stupendous in all human experience.
—Paul W. Merrill,
“Stars as They Look and as They Are,” 1926
LOOKING AT THE SUN
E very workday, Steve Padilla gets up and does what mothers the world over tell their children not to do: he looks at the Sun. Atop Mount Wilson, 5,700 feet above the Los Angeles basin, from where you can only imagine its byzantine freeways snarled with traffic, Padilla leaves the modest bungalow that he's called home for the past twenty-five years and makes his daily pedestrian commute under the towering Douglas fir and the majestic canyon oak to his solitary job at the 150-Foot Solar Tower. This observatory doesn't look like the famous dome-shaped observatories Padilla passes on his way to work. The Solar Tower resembles a Texas oil rig more than it does a telescope. Its four steel-girdered legs surround a central tube, with the addition of a small dome on top. But this structure isn't mining down for crude; rather, it's looking up for sunlight. Padilla climbs into the rickety, open-bucket elevator on the tower's side (unless there's a wind over sixty miles an hour, in which case he should use the ladder, though he never has) and makes a clanking, slightly swaying ascent up to the dome. From here he gets the best view of the approximately seven million souls in the greater Los Angeles area. It's a vista that captures the contrasts of Southern California: to the west, he looks down to the San Gabriel Valley and the seemingly endless spread of the City of Angels a vertical mile below; to the east, the Sun rises over a tiered wilderness of snowcapped mountains.
Padilla opens the observatory dome and positions the primary mirror so that it aims the dawn light directly at a secondary mirror, which in turn reflects the soft morning light down into the observatory's heart. For the rest of the day, the mirror will automatically track the Sun's journey across the Southern Californian sky.
After returning to the observatory's viewing room, Padilla, monk-like, with thinning curly hair and a ripped blue windbreaker, gets a pencil and positions a fresh ten-by-twenty-inch piece of drawing paper at the light focus so that the orb of the Sun is centered in the middle of the sheet. Then, as Mount Wilson's solar observer has done for most of his life—certainly longer than any other person on Earth—Padilla draws by hand the location of sunspots. These slightly cooler, magnetized areas of the Sun's surface appear as dark blemishes on the solar face. On this day, April 14, 2011, he marks that the seeing, the term astronomers use to describe the clarity of their view, is 2.0 out of 4—a little hazy, the spring air still turbulent from a high front moving in, clearing out the previous day's clouds.
Padilla started as the solar observer in August 1976, landing the coveted post after first working as a relief night assistant on Mount Wilson's sixty- and hundred-inch telescopes. For thirty-five years he's been observing our star, recording its eleven-year cycles of dipping and peaking magnetic activity, clocking its rotational speed, and measuring its overall intensity. While for most of us the Sun is a constant, for Padilla “there's always something new.” What's new is usually the distribution of sunspots. During years of low sunspot activity, the Sun can go spot-free for months. Five years later, at the sunspot peak, the Sun's face can resemble that of an acned teenager, marked across its diameter with dozens of pairs of spots, each a north or south pole to the other.
The sunspots are like islands on the Sun's surface that appear to move across its face as the fiery orb spins on a twenty-seven-day rotation—a solar day. For the past several years, Padilla hasn't taken long with the drawings; sunspot activity has been on the wane. He's faithfully recorded the downward slope in the Sun's eleven-year sunspot cycle of activity, a process he's watched personally for a full three cycles. Today there is a smattering of sunspots along the Sun's 20° north line of latitude, and in the next eleven-year cycle the spots will mysteriously flip to the Southern Hemisphere. The largest sunspot visible today, a dimple on the solar surface, is about one and a half times the Earth's circumference. Padilla shows me the image of the largest-ever recorded sunspots from the same month in 1947, when the spots were massive, like small seas of darkness dozens of times larger than today's spots.
Padilla finishes his drawing and puts it into a binder for future reference. His drawing is the latest in an unbroken run of about thirty thousand daily Sun sketches made at the 150-Foot Solar Tower since January 4, 1917, and is now continued more as a labor of love than for science. Padilla is part of a dying breed, a ground-based solar observer. Today, most Sun observing is done with robotic telescopes or space-based satellites.
Padilla's early-morning isolation belies a broader truth about the observatory's busy, central role in astronomy history: Mount Wilson is the site of the most important astronomical discoveries of the first half of the twentieth century. On the walls of the Solar Tower are pictures of some of the famous visitors who've made the pilgrimage up the mountain, including Albert Einstein in 1931, on one of several visits, and Stephen Hawking, his thumbprint marking the visitors’ book from June 2, 1990. It was here, atop Mount Wilson, that Albert Michelson accurately measured the speed of light; that Harlow Shapley determined our Solar System's position in the suburbs, rather than at the center, of the Milky Way. But what draws legions of visitors now is Mount Wilson's legendary status as the site of Edwin Hubble's astronomical insights. In 1925, using Mount Wilson's one-hundred-inch telescope—the world's most powerful at the time—Hubble discovered that distant “nebulae,” the previously mysterious smudges of light on the inky night sky, were in fact vast agglomerations of stars—galaxies. The upshot was that the Milky Way wasn't the entire universe but rather an island of stars amid millions of others. In 1929, Hubble announced that his observations showed that these galaxies are moving apart, and that the farthest ones are moving apart faster than the nearby ones. He'd shown that the universe wasn't just vaster than anyone imagined; but that it was growing.
What's often lost in this best-known version of Mount Wilson's story is that before the nighttime telescopes arrived, the observatory was established to do astronomy under the full glare of the Sun, with the goal of understanding our evolutionary connection to it.
THE GREAT SEER
Silently watching over Padilla, in the form of a ceramic bust set atop a red mechanics tool cabinet in the solar observatory, is the original Sun watcher himself, George Ellery Hale. No one has had as great an impact on modern astronomy as Hale. Without Hale, there might well not have been Hubble or the dozens of lesser-known astronomers who laid much of the foundation of twentieth-century astronomy and cosmology. Born in 1868, as the United States was still reeling from the Civil War, Hale was the son of a Chicago elevator entrepreneur who made a fortune installing “vertical railways” in the Windy City's burgeoning sky-reaching buildings following the Great Fire of 1871. But Hale Jr. lifted humanity to greater heights. He didn't just establish Mount Wilson, he also envisioned and built an astrono
my empire. Founding just the Mount Wilson Observatory would have been a life's work for any ambitious scientific visionary, but Hale was also seminal in founding the California Institute of Technology, the United States National Research Council, and the International Astronomical Union. Hale was the scientific equivalent of the legendary American industrialists, including John D. Rockefeller Sr. and Andrew Carnegie, whom he pursued and convinced to fund an unprecedented journey into the heavens.
Like the titans of industry, Hale was dedicated to the great American dictum that bigger, and technologically more advanced, is better. In astronomy, this is often the case. Like a pyramid builder, Hale could imagine projects that would take decades to complete and that would push human creativity into the realm of the seemingly impossible, but when they were completed, they would stand without equal. The observatories he built included the four biggest telescopes of the twentieth century. Each of these eyes on the universe outsized its predecessor; each finished telescope revealed ever farther and fainter glimpses of the cosmos. First came the forty-inch mirror at the University of Chicago's Yerkes Observatory in Wisconsin, then the sixty-inch telescope at Mount Wilson, followed by the observatory's hundred-inch telescope, through which Hubble made his grand discoveries. Hale's final triumph bears his name, the two-hundred-inch Hale Telescope at Mount Palomar, conceived in 1928, which saw first light in 1948. The five-hundred-ton Hale Telescope, with a curved mirror seventeen feet across, smooth to within the width of a bacterium (two-millionths of an inch), was Earth's greatest eye into the heavens until 1993, more than a half century after Hale's death in 1938. Hale's level of creative output was fueled by what today might be deemed bipolar disorder: bursts of activity interspersed with periods of profound depression and debilitating headaches that led to an early retirement.
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