Chapter One
Foggy Vision
The sky was dark, the air clear. It was an excellent night for astronomical photography.
On March 7, 1945, Enrique Gaviola of the Cordoba Observatory of Cordoba, Argentina, carefully positioned the observatory''s 61-inch telescope for an evening of research. Painstakingly, methodically, Gaviola aimed the telescope at one of the more spectacular spots in the southern sky, the Keyhole Nebula in the constellation Carina.
First observed by John Herschel in the mid-1830s while in South Africa doing a survey of the southern sky, it had been given its name by Herschel because of its distinctive keyhole-shaped dark patch. What made this particular place in the sky even more intriguing was that on December 16, 1837, Herschel had been surprised to see a new star shining brightly there. "[The star] had come on suddenly," he wrote that night in a letter to Thomas Maclear, the astronomer at the Royal Observatory at Cape Town.
At first Herschel thought the star might be what was then called a bright nova, similar to those discovered in 1572 and 1604, and now dubbed supernovae. After some careful measurement, however, he realized that the gleaming, unexpected spark above him was not a new star suddenly bursting into visibility, but the star Eta Carinae, shining three times brighter than he had ever seen it before, and approaching 1st magnitude.
For several hours into the wee hours of the morning Herschel stared at this inexplicable object. For years it had remained unchanged to him, shimmering at about 2nd magnitude just off the edge of the Keyhole itself. In fact, only a week earlier he had noted the star''s annual arrival in the December evening sky, and had commented to his chief assistant that "We must soon begin [studying] him again."
Before Herschel could "begin," however, the star had suddenly become one of the brightest in the sky. Unable to contain his excitement, he called his wife, his assistant, and his personal butler all out of bed to have them look and confirm what he saw.
As he wrote that night to Maclear, "How big will it grow?"
In the thirty years that followed Eta Carinae faded in fits and starts from 1st to 7th magnitude, while the darker parts of the much larger Keyhole Nebula slowly brightened so that it no longer stood out so distinctly.
In the twentieth century astronomers returned to this star periodically, trying to figure out what had happened in 1837 as well as afterward. Though some thought the nebulosity surrounding the star was slowly growing, in 1932 astronomer Bart Bok of Harvard concluded decisively that this was an imaginary effect. In fact, most observers in the early twentieth century assumed that the faint collection of bright hazy spots surrounding Eta Carinae were actually a handful of individual stars, embedded in a gas cloud.
Now, more than a hundred years after Herschel, Enrique Gaviola was back, taking another careful look at Eta Carinae. For several hours he took two sets of nine images, beginning each set with a one-second exposure and doubling the exposure duration each time until the exposure for his last picture was over four minutes long.
Once developed, these images from 1945 were considered by many the best ever taken of this strange star. They showed what Gaviola humorously dubbed the Homunculus, Latin for "little man," a kind of Pills-bury Doughboy "with its head pointing northwest, legs opposite and arms folded over a fat body."
As good as Gaviola''s photographs were, they were generally fuzzy and revealed little detail. The best that Gaviola''s images could do was to show that the hazy bright spots surrounding Eta Carinae were probably not multiple stars but several gas shells and clouds enveloping the star and illuminated by it. Moreover, he was able to extrapolate backward and conclude that the nebula was formed "by clouds ejected by the star around 1843," about the time of a second outburst following Herschel''s initial 1837 discovery.
Why the expansion happened, how it was unfolding in detail, and where it was going to end up, however, was utterly impossible for Gaviola to deduce from his nebulous images. Gaviola''s photographs, as groundbreaking as they were, were typical of all astronomical images since the invention of the camera. The atmosphere that we breathe and that makes life possible also acts as an annoying translucent curtain, blurring our vision of the sky. Just as a prism will bend the light that passes through it, so does the atmosphere. The atmosphere, however, is in constant flux, causing the path of that light to shift and jiggle. When we look up at a star, this shifting makes it appear to twinkle. On a photographic plate this twinkling in turn causes the accumulated light to spread out so that a truly sharp image is just not possible.
The result: before the advent of space flight astronomers, both professional and amateur, were left thwarted and unsure about what they saw. For someone like myself, who has poor vision and requires glasses, this situation is self-evident. Though the metaphor is not technically correct, for me to understand the limited view of the heavens from the beneath the atmosphere, all I have to do it is to take off my glasses. Everything becomes fuzzy, unclear, and indistinct.
I, however, can buy eyeglasses. Until the late twentieth-century astronomers had no such option. Trapped on the Earth within its unsteady and hazy atmosphere, astronomers were condemned to look at the heavens as though they had bad vision and were forbidden from using glasses.
The consequences of this hazy situation have been both frustrating and profound. Consider for example the efforts of Giovanni Schiaparelli and Percival Lovell to map the surface of Mars in the late nineteenth and early twentieth centuries. Beginning in 1877 Schiaparelli studied Mars nightly, using an 8.6-inch telescope at the Brera Observatory in Milan. After more than a decade of work he finally published his map, outlining a wide range of vague shapes and streaks on the Martian surface. Of greatest interest were what he called "canali" (which means "grooves" in Italian).
Though Schiaparelli was convinced the canali were real, he found that their
... aspect is very variable.... Their appearance and their degree of visibility vary greatly, for all of them, from one opposition to another, and even from one week to another.... often one or more become indistinct, or even wholly invisible, whilst others in their vicinity increase to the point of becoming conspicuous even in telescopes of moderate power.
Percival Lowell followed Schiaparelli with decades of more work, studying Mars''s surface and making endless sketches of what he thought he saw there.
From Lowell''s perspective, the complex series of straight lines that crisscrossed Mars strongly suggested what could only be artificial constructs, which he labeled more bluntly as canals. As he wrote in 1895, "There is an apparent dearth of water upon the planet''s surface, and therefore, if beings of sufficient intelligence inhabited it, they would have to resort to irrigation to support life." To Lowell, the canals appeared to be built by the inhabitants of the red planet as a vast irrigation system to stave off the consequences of an increasingly arid planet.
For the next seventy years the human race debated the possibility of life on Mars. Lowell''s thoughts inspired such classic works of fiction as H. G. Wells''s War of the Worlds as well as a plethora of science fiction books and movies.
Then, in the mid-1960s the United States sent a series of unmanned probes to Mars to take the first close-up images-and burst Lowell''s bubble. Mars has no canals, no intelligent life. The canals were an optical illusion created by the Earth''s varying atmosphere.
The atmosphere causes similar problems across the entire field of astronomical research. Worse, not only does it distort optical light, it entirely blocks large portions of the rest of the electromagnetic spectrum. Except for radio wavelengths and a few select infrared wavelengths, the majority of the infrared and all of the ultraviolet, x-ray, and gamma ray regions of the spectrum are inaccessible to astronomers working from the surface of the Earth. This fact is especially crippling because the bulk of astronomical research is done through spectroscopy, and much of the most interesting and informative spectroscopy needs to be done in these unavailable wavelengths.
For example, by observing the spectrum of light coming from a star, astronomers can gather information about that star''s chemical makeup. Each element when heated emits light at a specific wavelength. If you see a spike of light at that specific wavelength you know that element is present in a star''s atmosphere. Similarly, if there is a dip of light at that wavelength you know that that element is standing somewhere between you and the star, either in the star''s surrounding nebula or in some intervening gas in interstellar space, absorbing that light. Unfortunately, the spectral signature of a large percentage of the most interesting elements occurs at wavelengths outside visible light in parts of the electromagnetic spectrum that are blocked by the atmosphere.
In the visual wavelengths, meanwhile, the atmosphere''s blurring action makes the interpretation of the astronomical data more challenging. Our brains are tightly wired to our eyesight. Very roughly speaking, if we cannot see a clear image of something, it is difficult for us to fully grasp what is going on, no matter how much other information is available. Conversely, if we have a good image to look at, we can more easily interpret all the other data and understand how they fit into that visual image.
Consider for example what astronomers call planetary nebulae. These objects were given that name because at first glance they seemed to resemble planets, but by the 1800s scientists had realized that the nebulae were not planets at all but distant stars surrounded by large and beautiful cloud structures.
By the early 1960s astronomers were reasonably sure they understood their origin. When a star like the Sun has used up most of its hydrogen fuel and begins burning helium, it becomes unstable, starts to pulse, and ejects mass in a series of expanding shells. After some ten to fifty thousand years these shells form a planetary nebula, which surrounds a slowly dying and cooling white dwarf star.
This theory, however, did little to explain the complex but hard-tosee structure of the encircling clouds visible in pre-Hubble astronomical photographs. In most cases the nebula looked like one or several rings. For example, in long photographic exposures the Ring Nebula in the constellation Lyra resembled a bluish-green oval with horizontal wreathlike veils cutting across its central regions. Similarly, the Helical Nebula in Aquarius looked like two overlapping rings, though the best photographs also showed strange spokelike features pointing inward toward the central star. Other planetary nebulae, such as the Dumbbell Nebula in the constellation Vulpecula, looked as if we were viewing the ring edge-on so that it resembled a barrel on its side.
Because so many of the nebulae had this ringlike morphology, it was assumed that they were really shells or bubbles, with only the outer edges visible because our line of sight was looking through the most material. Such an assumption conformed nicely to the idea that the shells were the debris from the star''s earlier helium-burning stage, when it repeatedly ejected large amounts of mass.
Other planetary nebulae, however, did not conform to this theory. Some appeared irregular, patchy disks with no discernible pattern. Others had weird shapes, making any interpretations difficult if not impossible. For example, the Owl Nebula in Ursa Major had an outer ring, but instead of an open interior its central regions looked more like an hourglass, two conelike shapes pointing inward toward the central star. And the Saturn Nebula in Aquarius was even more baffling: it had two rings, each inclined at a different angle to our view. Especially baffling were the two spikes of material at opposite ends of the nebula pointing away from the central star. For these inexplicably shaped planetary nebulae, several theories were proposed to explain their formation, including the possibility that the spikes were jets emanating from the poles, or some form of slow expansion influenced by either magnetic fields or unseen binary companions.
Because the images were so fuzzy and indistinct, however, it was difficult for scientists to reach a consensus on any specific theory. And though spectroscopy provided a great deal of information about the motion within each nebula''s surrounding gas cloud, it was often difficult to untangle this spectral velocity data into a coherent picture without a corresponding sharp visual image. Thus, few astronomers made a serious effort to explain the formation of these nebula shapes because the data were so imprecise.
The problem was the same for galactic evolutionary theories. It was impossible with ground-based telescopes to see any galaxies from the early universe, and thus get a longer view of the evolution of galaxies across time. These distant objects were simply too faint to be picked out from the blurring effects of the atmosphere. Similarly, there were a number of very strange-looking distant galaxies, such as the Antennae Galaxy in the constellation Covus, with its two long trailing tails and two warped central blobs, whose shapes ground-based telescopes could not image sharply. Though astronomers were able to put together a number of theories about galaxy mergers or collisions to explain these unusual structures, any one of these ideas could be right. Worse, until better and more precise data were available, including information from the wavelengths blocked by the atmosphere, it was also quite possible that none were correct.
In various areas of astronomy this problem repeated itself. Astronomers could put together reasonable theories to explain their data, but without clear optical images it was difficult to confirm which theories were the most accurate.
For the general public, the situation was worse. Dependent as we humans are on our eyesight, the atmosphere essentially left the human race blind to the heavens. We were like a nearsighted man before the invention of eyeglasses. We could squint and strain and maybe make a guess at what we were looking at, but to actually perceive the reality of the universe in all its glory was nigh on impossible.
* * *
Even as Gaviola was slowly developing his photographs and preparing his paper for publication-crippled as he was by being at the bottom of a 100-mile-thick fog filter-another astronomer almost half a world away was about to take the first step in what would become an epic, half-century-long odyssey to solve this centuries-long dilemma. This man was about to propose that the United States build the first optical telescope in space.
World War II had just ended. At the time Lyman Spitzer, Jr., was a thirty-one-year-old astronomer doing war work as head of a research organization called the Sonar Analysis Group. Though most of his group worked in the Empire State Building in New York, Spitzer''s headquarters and base of operations was in Washington, DC. As Spitzer explained in a 1978 interview, "My work involved talking with people who were doing [sonar] research and telling them what they were doing wrong and what they ought to be doing."
Before the war Spitzer had been a young post-graduate astronomer working at Yale University. Now that the war had ended he wanted to get back to astronomy work.
In the fall of 1945, however, Spitzer was still working in Washington, DC. Among the many scientists he ran into in DC who were part of the war effort was a geophysicist named David Griggs. During the war Griggs had been part of a group of scientific advisors working under Dr. Edward Bowles, who had been named special assistant to Secretary of War Henry Stimson. Under Bowles''s leadership, Griggs and his cohorts had been key on-site technical advisors during the D-Day invasion, the campaign in France, and later during the Battle of the Bulge. As noted by historian James Baxter, "They evacuated equipment at the last moment, they served as pinch-hit operators of gear in crucial spots, often under fire."
(Continues...)
Excerpted from The Universe in a Mirrorby Robert Zimmerman Copyright © 2008 by Princeton University Press. Excerpted by permission.
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