Broadly speaking, the history of astronomy reads something like the story about how we humans have discovered our insignificance in the cosmos. In the last two thousand years, major discoveries about the solar system, our galaxy and the universe have shuffled the likelihood of our existence deeper and deeper into the realm of improbable chance and fortuitous coincidence. In the big picture, we're barely a pixel. I suppose it's only unsettling if you start out assuming that human beings are, quite literally, the center of the universe. Two thousand years ago, Aristotle stepped up and said the Earth sits at the center of an unchanging, infinite universe; our planet is surrounded by celestial spheres most easily observed by the movements of the Sun and planets. People believed Aristotle and moved on with their lives. In the 16th century, Copernicus stepped up to the plate, swung, and blasted the Earth out of the center. He explained the motions of the planets by invoking a heliocentric view of the cosmos. The sun, not we, sat in the middle. Earth had officially been displaced as the center of everything—at least in theory. (And Copernicus himself was displaced. Last November, archaeologists finally found his long-lost remains buried under the floor of a cathedral in Poland.) In the 17th century, Galileo improved upon the design of a Dutch engineer to build a telescope, with which he delivered good evidence in support of Copernicus. In this case, good evidence made the Dominicans mad, and Galileo was rewarded by the Catholic Church with house arrest (albeit a very comfortable house arrest) for the rest of his life.
And so on—each new discovery places humanity further from a central position. The greatest decentralizing act of our time may have occurred on New Year’s Day, 1925—the eponymous "day" in the title of science writer Marcia Bartusiak’s latest offering, The Day We Discovered the Universe. Bartusiak is an experienced and award-winning writer, a fellow of the AAAS and a former Knight fellow at MIT. (I feel fortunate to count myself among her former students.)
On that day in 1925, astronomers were gathered in Washington, D.C., for the annual meeting of the American Association for the Advancement of Science. On the third day of the meeting, someone stood up, gave a talk, and changed everything. Edwin Hubble, a 35-year-old stargazer working at the Lick Observatory atop Mount Wilson in California, had found conclusive evidence that the Milky Way—our beloved home—was not the only galaxy in the cosmos. (Hubble, fearful of sullying his reputation, didn’t even present his own findings.)
It’s easy to be blasé about the impossible-to-comprehend infinitude of the cosmos now; after all, almost everyone alive today grew up surrounded by the knowledge that the Milky Way is no loner. And we science junkies, with our varying deficits of attention, learn, marvel and move on, looking for the next big thing. Bartusiak, however, writes about that blustery day in the nation’s capital with the infectious excitement of a giddy astrophile:
In one fell swoop, the visible universe was enlarged by an inconceivable factor, eventually trillions of times over. In more familiar terms, it’s as if we had been confined to one square yard of Earth’s surface, only to suddenly realize that there were now vast oceans and continents, cities and villages, mountains and deserts, previously unexplored and unanticipated on that single plug of sod.
The Milky Way, once the universe’s lone inhabitant floating in an ocean of darkness, was suddenly joined by billions of other star-filled islands, arranged outward as far as telescopes could peer. Earth turned out to be less than a speck, the cosmic equivalent of a subatomic particle hovering within an immensity still difficult to grasp.
That’s just the beginning: In Day, Bartusiak lovingly and meticulously traces the origins and development of a big idea. Hubble’s name is familiar to most of us mainly because of recent news about the space telescope that bears his name, but he doesn’t really show up in the book until two-thirds of the way through—a structural choice that demonstrates Hubble stood on the shoulders of many, many giants. His name may be forever associated with the discovery of the universe, but his finding was no instantaneous flash of brilliance that launched him from obscurity into the annals of science.
In fact, Bartusiak calmly puts to rest the idea that scientific advancements arrive in discrete packages marked by the word “Eureka!” Despite the legend of Archimedes, scientists aren’t usually struck out of the blue by the clear light of truth: "Answers did not arrive in one eureka moment, but only after years of contentious debates over conjectures and measurements that were fiercely disputed. The avenue of science is more often filled with twists, turns, and detours than unobstructed straightaways."
Her enjoyable book is an exhaustively researched exploration of both major and minor players. She points out that Hubble wasn’t the first person to suspect the great vastness. The Roman poet Lucretius thought it ludicrous to imagine a finite universe; the polymath mystic Emanuel Swedenborg mused that there must be ‘spheres’ beyond our own; Immanuel Kant correctly discerned galactic shape and suggested galaxies were scattered throughout space.
Many unsung heroes get a nod: Vesto Slipher clocked the speeds of distant spiral-shaped nebulae (later identified as other galaxies) and found that most of them were speeding away from the Earth—“a precocious intimation of the cosmic expansion that took many more years to fully recognize.” Henrietta Leavitt’s studies of variable stars made it possible to measure the distance between us and galaxies far, far away. Leavitt, one of many women hired to be a human “computer” at the Harvard College Observatory, died in 1921—four years before the Royal Swedish Academy of Sciences tried to nominate her for a Nobel Prize in Physics. (It wasn’t to be—Nobel nominees must be living.)
The book ends with something of a cliffhanger. Hubble and his fellow giants had found that not only is the universe filled with other galaxies, but these galaxies are retreating. Further investigation revealed that these “galaxies are not rushing through space but instead are being carried along as space-time inflates without end.” No matter which way we look in the sky, we see this vast universe rushing away from us. (In a way, that does put us back at the center of things, but only because every point in the universe is the center…)
Modern astronomy continues to tell us how far we are from the center—and that we still can’t comprehend the weirdness of reality. Ninety-six percent of the stuff in the universe barely interacts with the protons, electrons and neutrons that make up our reality. (It’s most likely flowing through you right now, and there’s no way to know.) Planet-hunters are scanning the skies for the telltale spectrographic signature of distant, rocky world that may harbor life. Other astronomers are looking for the “chameleon,” a theoretical entity that adjusts its mass to its environment and may help explain dark energy, the unknown goo that fills most of space. Also unsettling is the idea that our infinite universe is just one of an infinite number of universes that together form the "multiverse.” Is there no limit to enormousness?
(PS: The International Astronomical Union and the United Nations declared this year the “International Year of Astronomy,” an initiative that invites countries and institutions to step up their education of the public in all matters regarding the universe. Bartusiak’s book would be a great way to celebrate. So would a trip to Yale’s new planetarium at the Leitner Family Observatory, which offers free shows on Tuesday nights and, on June 12, a showing of “War of the Worlds.”)