Space Chronicles: Facing the Ultimate Frontier (15 page)

What is the cumulative influence of all this technology and cosmic discovery on society, aside from creating more effective instruments of destruction and further excuses to wage war? The nineteenth and early twentieth centuries saw the development of transportation that did not rely on energy from domestic animals—including the bicycle, the railroad, the automobile, and the airplane. The twentieth century also saw the introduction of liquid fuel rockets (thanks in part to Robert Goddard) and spaceships (thanks in part to Wernher von Braun). The discovery of improved means of transportation was especially crucial to geographically large but habitable nations such as the United States. So important is transportation to Americans that the disruption of traffic by any means, even if it occurs in another country, can make headlines. On August 7, 1945, for example, the day after America killed some seventy thousand Japanese in the city of Hiroshima, with tens of thousands more deaths following soon afterward, the front page of the
New York Times
announced, “FIRST ATOMIC BOMB DROPPED ON JAPAN.” A smaller headline, also on the front page, read, “T
RAINS
C
ANCELED
IN
S
TRICKEN
A
REA
; Traffic Around Hiroshima Is Disrupted.” I don’t know for sure, but I would bet that day’s Japanese newspapers did not consider traffic jams to be a top news item.

Technological change affected not only destruction, of course, but also domesticity. With electricity available in every domicile, it became worthwhile to invent appliances and machines that would consume this new source of energy. Among anthropologists, one of the broad measures of the advancement of society is its per-capita consumption of energy. Old traditions die hard, though. Lightbulbs were a substitute for candles, but we still light candles at special dinners; we even buy electric chandeliers studded with lightbulbs in the shape of candle flames. And of course car engines are measured in “horse” power.

The dependence on electricity, especially among urban Americans, has reached irreversible levels. Consider New York City during the blackouts of November 1965, July 1977, and August 2003, when this decidedly twentieth-century luxury temporarily became unavailable. In 1965, many people thought the world was going to end, and in 1977 there was widespread looting. (Each blackout allegedly produced “blackout babies,” conceived in the absence of television and other technological distractions.) Apparently, our discoveries and inventions have gone from making life easier to becoming a requirement for survival.

Throughout history, discovery held risks and dangers for the discoverers themselves. Neither Magellan nor most of his crew remained alive to complete the round-the-world voyage in 1522. Most died of disease and starvation, and Magellan himself was killed by indigenous Filipinos who were not impressed with his attempts to Christianize them. Modern-day risks can be no less devastating. At the end of the nineteenth century, investigating high-energy radiation, Wilhelm Röntgen explored the properties of X-rays and Marie Curie explored the properties of radium. Both died of cancer. The three crew members of Apollo 1 burned to death on the launchpad in 1967. The space shuttle Challenger exploded shortly after launch in 1986, while space shuttle Columbia broke up on reentry in 2003, in both cases killing all seven crew members.

Sometimes the risks extend far beyond the discoverers. In 1905 Albert Einstein introduced the equation
E = mc
²
, the unprecedented recipe that interchanged matter with energy and ultimately begat the atomic bomb. Coincidentally, just two years before the first appearance of Einstein’s famous equation, Orville Wright made the first successful flight in an airplane, the vehicle that would one day deliver the first atomic bombs in warfare. Shortly after the invention of the airplane, there appeared in one of the widely distributed magazines of the day a letter to the editor expressing concern over possible misuse of the new flying machine, noting that if an evil person took command of a plane, he might fly it over villages filled with innocent, defenseless people and toss canisters of nitroglycerin on them.

Wilbur and Orville Wright are, of course, no more to blame for the deaths resulting from military application of the airplane than Albert Einstein is to blame for deaths resulting from atomic bombs. For better or for worse, discoveries take their place in the public domain and are thus subject to patterns of human behavior that seem deeply embedded and quite ancient.

Discovery and the Human Ego

The history of human ideas about our place in the universe has been a long series of letdowns for everybody who likes to believe we’re special. Unfortunately, first impressions have consistently fooled us—the daily motions of the Sun, Moon, and stars all conspire to make it look as though we are the center of everything. But over the centuries we have learned this is not so. There is no center of Earth’s surface, so no culture can claim to be geometrically in the middle of things. Earth is not the center of the solar system; it is just one of multiple planets in orbit around the Sun, a revelation first proposed by Aristarchus in the third century
B.C.
, argued by Nicolaus Copernicus in the sixteenth century, and consolidated by Galileo in the seventeenth. The Sun is about 25,000 light-years from the center of the Milky Way galaxy, and it revolves anonymously around the galactic center along with hundreds of billions of other stars. And the Milky Way is just one of a hundred billion galaxies in a universe that actually has no center at all. Finally, of course, owing to Charles Darwin’s
Origin of Species
and
Descent of Man
, it is no longer necessary to invoke a creative act of divinity to explain human origins.

Scientific discovery is rarely the consequence of an instantaneous act of brilliance, and the revelation that our galaxy is neither special nor unique was no exception. The turning point in human understanding of our place in the cosmos occurred not centuries ago but in the spring of 1920, during a now-famous debate on the extent of the known universe, held at a meeting of the National Academy of Sciences in Washington, DC, at which fundamental questions were addressed: Was the Milky Way galaxy—with all its stars, star clusters, gas clouds, and fuzzy spiral things—all there was to the universe? Or were those fuzzy spiral things galaxies unto themselves, just like the Milky Way, dotting the unimaginable vastness of space like “island universes”?

Scientific discovery, unlike political conflict or public policy, does not normally emerge from party-line politics, democratic vote, or public debate. In this case, however, two leading scientists of the day, each armed with some good data, some bad data, and some sharpened arguments, went head to head at the Smithsonian’s National Museum of Natural History. Harlow Shapley argued that the Milky Way constitutes the full extent of the universe, while Heber D. Curtis defended the opposing view.

Earlier in the century, both scientists had participated in a wave of discoveries derived primarily from classification schemes for cosmic objects and phenomena. With the help of a spectrograph (which breaks up starlight into its component colors the way raindrops break up sunlight into a rainbow), astrophysicists were able to classify objects not simply by their shape or outward appearance but by the detailed features revealed in their spectra. Even in the absence of full understanding of the cause or origin of a phenomenon, a well-designed classification scheme makes substantive deductions possible.

The nighttime sky displays a grab bag of objects whose classifications were not subject to much disagreement in 1920. Three kinds were especially relevant to the debate: the stars that are quite concentrated along the narrow band of light called the Milky Way, correctly interpreted by 1920 as the flattened plane of our own galaxy; the hundred or so titanic, roughly spherical globular star clusters that appear more frequently in just one direction of the sky; and third (or perhaps third and fourth), the inventory of fuzzy nebulae near the plane and spiral nebulae nowhere near the plane. Whatever else Shapley and Curtis intended to argue, they knew that those basic observed features of the sky could not be reasoned away. And although the data were scant, if Curtis could show that the spiral nebulae were distant island universes, then humanity would be handed the next chapter in its long series of ego-busting discoveries.

In a casual look at the night sky, stars appear uniformly spread in all directions along the Milky Way. But in fact, the Milky Way contains a mixture of stars and obscuring dust clouds that compromise lines of sight so that it becomes impossible to see the entire galaxy from within. In other words, you can’t identify where you are in the Milky Way because the Milky Way is in the way. Nothing unusual there: the moment you enter a dense forest, you have no idea where you are within it (unless you carved your initials into a tree during a previous visit). The full extent of the forest is impossible to determine because the trees are in the way.

Astronomers of the day were fairly clueless as to how far away things are, and Shapley’s estimates of distance tended to be quite generous, indeed excessive. Through various calculations and assumptions, he ended up with a galactic system more than 300,000 light-years in extent—by far the largest estimate ever made before (or since) for the size of the Milky Way. Curtis was unable to fault Shapley’s reasoning but remained skeptical nonetheless, calling the assumption “rather drastic.” Though based on the work of two leading theorists of the day, it was indeed rather drastic—and those theorists’ relevant ideas would soon be discredited, leaving Shapley with overestimates in stellar luminosities and, as a result, overestimates in the distances to his favorite objects, the globular clusters.

Curtis remained convinced that the Milky Way galaxy was much smaller than suggested by Shapley, proposing that in the absence of definitive evidence to the contrary, “the postulated diameter of 300,000 light-years must quite certainly be divided by five, and perhaps by ten.”

Who was right?

Along most paths from scientific ignorance to scientific discovery, the correct answer lies somewhere between the extreme estimates collected along the way. Such was the case here, too. Today, the generally accepted extent of the Milky Way galaxy is about 100,000 light-years—about three times Curtis’s 30,000 light-years, and one-third Shapley’s 300,000 light-years.

But that wasn’t the end of it. The two debaters had now to reconcile the extent of the Milky Way with the existence of high-velocity spiral nebulae, whose distances were even more highly uncertain, and which seemed to avoid the galactic plane altogether, earning the Milky Way the spooky alternative name “Zone of Avoidance.”

Shapley suggested that the spiral nebulae had somehow been created within the Milky Way and then forcibly ejected from their birthplace. Curtis was convinced that the spiral nebulae belonged to the same class of objects as the Milky Way itself, and proposed that a ring of “occulting matter” surrounded our galaxy—as is true of so many other spiral galaxies—and might be obliterating distant spirals from view.

At that point, if I were the moderator, I might have ended the debate, declared Curtis the winner, and sent everybody home. But there was further evidence at hand: the “novae,” tremendously bright stars that occasionally, and very briefly, appear out of nowhere. Curtis contended that the novae formed a homogeneous class of objects that suggested “distances ranging from perhaps 500,000 light-years in the case of the Nebula in Andromeda, to 10,000,000 or more light-years for the more remote spirals.” Given those distances, those island universes would be “of the same order of size as our own galaxy.” Bravo.

Even though Shapley discounted the concept of the spiral nebulae as island universes, he no doubt wanted to appear open-minded. In his summary, which reads like a disclaimer, he entertained the possibility of other worlds:

But even if spirals fail as galactic systems, there may be elsewhere in space stellar systems equal to or greater than ours—as yet unrecognized and possibly quite beyond the power of existing optical devices and present measuring scales. The modern telescope, however, with such accessories as high-power spectroscopes and photographic intensifiers, is destined to extend the inquiries relative to the size of the universe much deeper into space.

How right he was. Meanwhile, Curtis openly conceded that Shapley might be on to something with his hypothesis concerning the ejection of spiral nebulae, and in the course of that concession, Curtis unwittingly managed to reveal that we live in an expanding universe: “The repulsion theory, it is true, is given some support by the fact that most of the spirals observed to date are receding from us.”

By 1925, a mere half decade later, Edwin Hubble had discovered that nearly all galaxies recede from the Milky Way at speeds in direct proportion to their distances. But it was self-evident that our galaxy, the Milky Way, was in the center of the expansion of the universe. Having been an attorney before becoming an astronomer, Hubble probably would have won any debate he might have had with other scientists, no matter what he argued, but he clearly could muster the evidence for an expanding universe with us at the center. In the context of Albert Einstein’s general theory of relativity, however, the appearance of being at the center was a natural consequence of a universe that expands in four dimensions, with time as number four. Given that description of the universe, every galaxy would observe all other galaxies to be receding, leading inescapably to the conclusion that we are not alone, and we are not special.