DISPATCHES FROM PLANET 3
Also by Marcia Bartusiak
Thursday’s Universe
Through a Universe Darkly
Einstein’s Unfinished Symphony
Archives of the Universe
The Day We Found the Universe
Black Hole
Published with assistance from the foundation established in memory of Philip Hamilton McMillan of the Class of 1894, Yale College.
Copyright © 2018 by Marcia Bartusiak.
All rights reserved.
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Illustration courtesy of Barbara Schoeberl, Animated Earth, LLC, for the cutaway of a massive star in Chapter 15.
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Library of Congress Control Number: 2018933935
ISBN 978-0-300-23574-6 (hardcover: alk. paper)
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10 9 8 7 6 5 4 3 2 1
For Steve, my polestar
Contents
Preface
ONE. Earth Is but a Speck
Celestial Neighborhood
TWO. Bedazzled by a Comet
THREE. To Be . . . or Not to Be a Planet
FOUR. The Watery Allure of Mars
FIVE. Rings, Rings, Rings
SIX. The Baffling White Dwarf Star
SEVEN. The Star No Bigger Than a City
EIGHT. Ye Old Black Hole
NINE. As Though No Other Name Ever Existed
TEN. Like This World of Ours
Realm of the Galaxies
ELEVEN. Our Spiraling Home
TWELVE. The Woman Who Chased Galaxies
THIRTEEN. Stuff of the Heavens
FOURTEEN. Recipe for the Stars
FIFTEEN. Find a Way Around It
SIXTEEN. Dark Matters
SEVENTEEN. Cosmic Funhouse
EIGHTEEN. Rivers of Galaxies
NINETEEN. The Big Dipper Is Crying
TWENTY. Einstein’s Symphony
TWENTY-ONE. Underground Astronomy
TWENTY-TWO. Eavesdropping on the Universe
TWENTY-THREE. The Once and Future Quasar
To the Big Bang and Beyond
TWENTY-FOUR. Finding a Cosmic Yardstick
TWENTY-FIVE. The Cosmologist Left Behind
TWENTY-SIX. The Primeval Atom
TWENTY-SEVEN. Proving the Big Bang
TWENTY-EIGHT. It’s Now Einstein’s Universe
TWENTY-NINE. The Big Burp
THIRTY. The Great Escape
THIRTY-ONE. Meet the Multiverse
THIRTY-TWO. When the Universe Began, What Time Was It?
Notes
Bibliography
Acknowledgments
Index
Preface
Almost no discovery in astronomy is a total surprise. Not really. Sifting through the histories of unexpected findings, one frequently encounters early hints, precursors, a sense of something in the air. As Isaac Newton famously noted in the seventeenth century, “If I have seen further, it is by standing upon the shoulders of giants.” In other words, predecessors often pave the way, which makes the journey toward a new scientific vision possible.
My mission over the past several years, when writing the essays contained in this book, was to provide the back story for many recent astronomical discoveries. These explorations have included events in our nearby celestial neighborhood and out to the farthest reaches of the universe. Even beyond space-time to the multiverse.
I had no determined path in the course of my inquiries. Upon coming across a specific news item that piqued my interest, I headed to the archives to uncover a richer context. The controversial demotion of Pluto to dwarf planet, for example, reminded me when another solar-system member was similarly downgraded in the nineteenth century. And the discovery of an amino acid within a stream of interstellar dust is only the latest confirmation of our intimate connection to the cosmos, knowledge that is surprisingly recent. For most of history, astronomers were not at all sure that the stuff of the heavens was the same as the stuff on Earth. And when news stories kept referring to Edwin Hubble as the “discoverer of the expanding universe,” I couldn’t help but let readers know that a humble Belgian cleric, Georges Lemaître, and a former Midwest farmboy, Vesto Slipher, were equally responsible for revealing this astounding cosmic property.
My armchair investigations whisked me off in spirit to exotic locales: to ancient Mars, when liquid water once flowed freely on its surface; to an ensemble of galaxies that to our eyes resembles Alice in Wonderland’s Cheshire Cat; to the collision of two massive black holes a billion light-years away, an event that released fifty times more energy than all the stars in the universe were radiating at that moment; and finally down to the limit of the smallest quantum grain, where space and time allegedly come unglued and start to wink in and out of existence in a probabilistic froth.
While assembling these articles into book form, I was pleasantly reminded: I hadn’t kept track of how many women I had portrayed over the years. I always let the news set my agenda and, lo and behold, there they were. Vera Rubin brings dark matter to the forefront of astronomical concerns; Jocelyn Bell keenly spots a bizarre new star; Henrietta Leavitt ingeniously devises a revolutionary cosmic yardstick; Jane Luu co-discovers the first solar-system object beyond Neptune and Pluto; Beatrice Tinsley proves that galaxies evolve; Cecilia Payne tries to reveal the universe’s major elemental ingredient (until told to ignore it); and Margaret Burbidge contributes the observational proof that the calcium in our bones, the iron in our blood, and the oxygen we breathe came from the ashes of ancient stars. Many of these names are not found in astronomy textbooks, so it was gratifying to bring them into the spotlight.
These are among the thirty-two stories in this collection, which I have loosely arranged, starting with our solar system and working outward in space-time to the Big Bang . . . and beyond. There is no need, however, to read them in this particular order. For the most part, each chapter stands alone, so you are welcome to wander, as I have, along your own desired path among the stars.
DISPATCHES FROM PLANET 3
CHAPTER ONE
Earth Is but a Speck
Our cosmic address keeps getting longer
WALK into an open field on a clear, moonless night. Overhead, sparkling stars are sprinkled across the sky. All of them seem equidistant from you—and no one else—and you are lulled into imagining yourself at the center of the universe.
For nearly five hundred years, astronomers have struggled to break that illusion. Our petty standing in the cosmos is a scientific fact, if not a visceral experience. Earth zips at nearly 67,000 miles (108,000 kilometers) an hour around the Sun, which in turn completes one lap around the Milky Way every 220 million years, meaning that the last time we were in this neck of the galaxy, dinosaurs were getting ready to rule the planet. Still, as you look skyward in that pitch-black field, Earth seems to be at the heart of all creation.
We should blame Aristotle for initiating that perspective. So authoritative was his pronouncement of an Earth-centered universe in the fourth century BC that
few challenged the idea for nearly two millennia. But over time, the urge to better explain the universe’s behavior gave rise to new concepts of Earth’s celestial position. In 1543, Nicolaus Copernicus reintroduced a hypothesis first posited by the ancient Greek Aristarchus of Samos some eighteen centuries earlier. His model boldly placed the Sun at the center of the universe, shoving the Earth into motion. The radiant Sun was at last in its proper perch, “as if resting on a kingly throne,” wrote Copernicus.
Copernicus was not disturbed at all by a moving Earth, frightening as that might seem at first. More disturbing to him was the rotating sky in an Earth-centered universe. The farther out one moves from a stationary Earth, the faster and faster the sky must move to stay in place. But the Polish mathematician and astronomer knew quite well the consequences of challenging conventional notions. In the preface to his great work De revolutionibus orbium coelestium (On the revolutions of the heavenly spheres), he predicted that “as soon as certain people learn that in these books of mine . . . I attribute certain motions to the terrestrial globe, they will immediately shout to have me and my opinion hooted off the stage.”
That misfortunate fate fell upon Galileo, who starting in 1609 gathered the crucial evidence supporting Copernicus’s heliocentric vision. In 1633 he was brought before the Inquisition and eventually put under house arrest for daring to oppose an Earth relaxing at the universe’s center.
By the time of Newton decades later, though, such hostility had finally faded. For one, Sir Isaac’s physics could at last explain why we aren’t thrown off the planet as the Earth rotates and orbits the Sun. Yet even though Copernicus moved Earth from the hub of the solar system, its inhabitants remained confident that they retained a privileged place at the center of the Milky Way, then thought of as the sole galaxy. Homo sapiens is an egotistical species; we resist being kicked out of a prime spot in the cosmic scheme of things.
Earth as seen from Apollo 11 in 1969.
(NASA)
That confidence, though, withered as astronomy underwent a spectacular transformation starting in the nineteenth century, an era teeming with technological innovation. Prominent industrialists, enriched by the Gilded Age, provided the money that allowed dreamers to construct the powerful telescopes they had long desired.
With one of those new instruments atop California’s Mount Wilson, Harlow Shapley resized the Milky Way. He discovered in 1918 that it was ten times larger than previously thought, and along the way, he relocated the Sun and its planets into the galaxy’s suburbs. The Sun resides roughly 30,000 light-years from the galactic center, more than halfway to the Milky Way’s edge. “The solar system is off center, and consequently, man is too,” Shapley liked to say.
But Shapley did not take the next step; he, too, fell victim to cosmic pride. Despite the growing circumstantial evidence that the Milky Way was not alone in the universe, he held fast to his beloved “Big Galaxy” model. In this scheme our galaxy remained at center stage, meaning we lived in a solitary, star-filled oasis suspended in a darkness of unknown depth.
Shapley’s vision was demolished in 1924, when Edwin Hubble at last proved that the cosmos is populated with myriad galaxies as far as the telescopic eye can see. The Milky Way suddenly became a bit player in a much larger drama.
As you can see, the history of astronomy is a continuing extension of the Copernican principle, moving us farther and farther from a front-row seat. It’s a principle of irrelevance that involves not only our position in space and time but also the contents of the universe. In recent decades, astronomers have learned that a hidden ocean of cosmic matter—comprising about 85 percent of the universe’s mass—surrounds us, possibly elementary particles yet to be discovered. The stuff of stars, planets, and us is but the flotsam in this enveloping sea.
More startling—and taking the Copernican principle of displacement to its ultimate end—our universe may not be the only cosmos. As physicists attempt to construct a theory that unifies all the forces of nature, one theme repeatedly arises: that additional cosmic realms may be lurking in other dimensions. We could be part of the multiverse; the Big Bang might have occurred when universes outside our dimensional borders bumped into one another.
The main response to this astounding theory has been to bury our heads in terra firma. Yet such a wider perspective can eventually offer soothing succor, allowing our earthly concerns to shed away slowly, until they dissipate completely. Hubble knew this. During a visit to the astronomer’s home, the English poet Edith Sitwell was shown slides depicting the many galaxies that cannot be seen with the naked eye. “How terrifying!” she exclaimed. To which Hubble replied: “Only at first—when you are not used to them. Afterwards, they give one comfort. For then you know that there is nothing to worry about—nothing at all.”
Granted, the hugeness of the cosmos is difficult to perceive and, as Sitwell expressed, horrifying to ponder. A character in Thomas Hardy’s nineteenth-century novel Two on a Tower gives splendid voice to this apprehension: “There is a size at which dignity begins; further on there is a size at which grandeur begins; . . . further on, a size at which ghastliness begins. That size faintly approaches the size of the stellar universe,” says astronomer Swithin St. Cleeve in the novel.
Indeed, our cosmic address is getting excruciatingly long: Planet No. 3, Solar System, Orion Spur on the Sagittarius Spiral Arm, Milky Way, Local Cluster, Virgo Supercluster, Universe, Multiverse.
It’s time for earthlings to acknowledge our minor-league status and collectively grasp the magnificent vastness that engulfs us all. While a widespread recognition of Earth’s humble station is unlikely to end conflict here, fully comprehending our planet’s infinitesimal place in the universe might be a modest step toward diminishing our hubris. Earth is but a speck, the cosmic equivalent of a subatomic particle hovering within an immensity spanning billions of light-years.
Yet, don’t despair. We can still savor our cleverness in figuring out both this and the many other cosmic mysteries in the pages ahead.
Celestial Neighborhood
Well into the nineteenth century, astronomers spent much of their time devoted to our local celestial neighborhood. They aimed their telescopes at the solar system and prominent stars in the nighttime sky. The boundaries of the known universe then encompassed only one galaxy, our beloved Milky Way. And standing like a colossus over these astronomical endeavors, even after his death, was Sir Isaac Newton, whose momentous law of gravitation enabled astronomers to predict the motions of the Moon, planets, and comets. At the same time, their mathematical and observational diligence allowed them to detect new and unexpected objects within the solar system, such as asteroids. Such discoveries inevitably led to discussions over what is and is not a planet.
Better telescopes also led to sharper seeing. Early on, observers found a ring around Saturn and canal-like features on Mars. Could that mean there is water on the red planet? Is there other life in the solar system, or even on planets circling other stars?
And what about those stars? For most of astronomical history, the stars primarily served as a backdrop in studies of the solar system, but by the twentieth century that all changed as astronomers realized that stars come in a range of sizes, from huge red giant stars to tiny white dwarf stars no bigger than the Earth. And before astronomers could even get comfortable with that fact, they were faced with even weirder possibilities: the neutron star no bigger than a city and something even smaller and more bizarre.
CHAPTER TWO
Bedazzled by a Comet
How a comet validated the laws of Sir Isaac Newton
SOME repeatedly come and go with the precision of a clock. Others arrive unexpectedly at our cosmic doorstep, providing a few days or weeks of nighttime entertainment, only to disappear into deep space and never return. And a few fizzle out altogether.
For centuries, people both feared and revered comets. For many they were harbingers of disaster, their long tails sweeping across the sky like a fiery
sword, symbol of death and destruction. But to others they were messengers of good news. Shortly after Julius Caesar’s assassination in 44 BC, a comet appeared in the sky that was so luminous it could be seen in broad daylight, a rare feat for a comet (it has only happened nine times in the past three centuries). Caesar’s successor, Augustus, wrote that this brilliant star signified “that the Soul of Caesar was received among the Divine powers of the immortal Gods.”
Humanity had to await the Age of Enlightenment for a more reasoned explanation of a comet’s nature. It appeared in the grand finale of the Principia, Isaac Newton’s masterful treatise on gravitation published in 1687. There, in his closing chapter, Newton laid out his mathematical theory of the motion of comets—an effort, he told a colleague, that was “the most difficult of the whole book.”
Newton had been inspired by the appearance of a spectacular comet in 1680, the first comet to be discovered with a telescope. In the Principia, Newton traces the path of this comet across the constellations during the months it was visible. A diagram he included in his book was the first figure in astronomical history to show a comet completely swinging around the Sun, owing to gravity. Before that, observers were not sure that a comet approaching the Sun was actually the same object seen later to fly away from it. Newton had accurately determined that “comets are a kind of planet and revolve in their orbits with a continual motion.” Their paths could be in the form of a very elongated ellipse, similar to a planet’s, or an open hyperbola. In that case, the comet would forever depart from the solar system.
Newton also concluded that the comet was “solid, compact, fixed, and durable,” just like the bodies of planets. “For if comets were nothing other than vapors or exhalations of the earth, the sun, and the planets,” he wrote, “this one ought to have dissipated at once during its passage through the vicinity of the sun.” And the tail? Hardly more mysterious than an “extremely thin vapor that the head or nucleus of the comet emits” when heated by the Sun. Comets were not omens of doom, Newton was saying. They were simply small planetoids. Nothing to be afraid of.
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