Professional astronomers, meanwhile, had access to big West Coast telescopes like the legendary 200-inch at PalomarMountain in Southern California. Armed with the most advanced technology of the day and their own rigorous training, the professionals got results. At Mount Wilson Observatory near Pasadena, the astronomer Harlow Shapley in 1918–19 established that the Sun is located toward one edge of our galaxy, and Edwin Hubble in 1929 determined that the galaxies are being carried apart from one another with the expansion of cosmic space. Professionals like these became celebrities, lionized in the press as hawkeyed lookouts probing the mysteries of deep space.
Which, pretty much, they were: theirs was a golden age, when our long-slumbering species first opened its eyes to the universe beyond its home galaxy. But observing the professional way wasn’t usually a lot of fun. To be up there in the cold and the dark, riding in the observer’s cage and carefully guiding a long exposure on a big glass photographic plate, with icy stars shining through the dome slit above and starlight puddling below in a mirror the size of a trout pond, was indubitably romantic but also a bit nerveracking. Big-telescope observing was like making love to a glamorous movie star: you were alert to the honor of the thing, but aware that plenty of suitors were eager to take over should your performance falter.
Nor did academic territoriality, jealous referees, and the constant competition for telescope time make professional astronomy a day at the beach. As a brilliant young cosmologist once told me, “A career in astronomy is a great way to screw up a lovely hobby.”
So it went, for decades. Professionals observed big things far away, and published in the prestigious Astrophysical Journal—which, as if to rub it in, ranked papers by the distances of their subjects, with galaxies at the front of each issue, stars in the middle, and planets, on the rare occasion that they appeared in the Journal at all, relegated to the rear. Amateurs showed schoolchildren the rings of Saturn at 76 power through a tripod-mounted spyglass at the State Fair. Inevitably, a few professionals disdained the amateurs. When Clyde Tombaugh discovered Pluto, the astronomer Joel Stebbins, usually a more charitable man, dismissed him as “a sub-amateur assistant.” There were of course professionals who kept up good relationships with amateurs, and amateurs who did solid work without fretting over their status. But generally speaking, the amateurs lived in the valley of the shadow of the mountaintops. Which was odd, in a way, because for most of its long history, astronomy has been primarily an amateur pursuit.
The foundations of modern astronomy were laid largely by amateurs. Nicolaus Copernicus, who in 1543 moved the Earth from the center of the universe and put the Sun there instead (thus replacing a dead-end mistake with an open-ended mistake, one that encouraged the raising of new questions), was a Renaissance man, adept at many things, but only a sometime astronomer. Johannes Kepler, who discovered that planets orbit in ellipses rather than circles, made a living mainly by casting horoscopes, teaching grade school, and scrounging royal commissions to support the publication of his books. Edmond Halley, after whom the comet is named, was an amateur whose accomplishments— among them a year spent observing from St. Helena, a South Atlantic island so remote that Napoléon Bonaparte was sent there to serve out his second and terminal exile—got him named Astronomer Royal.
Even in the 20th century, while they were being eclipsed by the burgeoning professional class, amateurs continued to make valuable contributions to astronomical research. Arthur Stanley Williams, a lawyer, charted the differential rotation of Jupiter’s clouds and created the system of Jovian nomenclature used in Jupiter studies ever since. Milton Humason, a former watermelon farmer who worked as a muleteer at Mount Wilson, teamed up with the astronomer Edwin Hubble to chart the size and expansion rate of the universe.
The solar research conducted by the industrial engineer Robert McMath, at an observatory he built in the rear garden of his home in Detroit, so impressed astronomers that he was named to the National Academy of Sciences, served as president of the American Astronomical Society, a professional organization, and helped plan Kitt Peak National Observatory in Arizona, where the world’s largest solar telescope was named in his honor.
Why were the amateurs, having played such important roles in astronomy, eventually overshadowed by the professionals? Because astronomy, like all the sciences, is young—less than 400 years old, as a going concern—and somebody had to get it going. Its instigators could not very well hold degrees in fields that didn’t yet exist. Instead, they had to be either professionals in some related field, such as mathematics, or amateurs doing astronomy for the love of it. What counted was competence, not credentials.
Amateurs, however, were back on the playing field by about 1980. A century of professional research had greatly increased the range of observational astronomy, creating more places at the table than there were professionals to fill them. Meanwhile, the ranks of amateur astronomy had grown, too, along with the ability of the best amateurs to take on professional projects and also to pursue innovative research. “There will always remain a division of labor between professionals and amateurs,” wrote the historian of science John Lankford in 1988, but “it may be more difficult to tell the two groups apart in the future.”
The amateur astronomy revolution was incited by three technological innovations—the Dobsonian telescope, CCD light-sensing devices and the Internet. Dobsonians are reflecting telescopes constructed from cheap materials. They were invented by John Dobson, a populist proselytizer who championed the view that the worth of telescopes should be measured by the number of people who get to look through them.