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island universe hypothesis, and that was the work of the great cosmologist Harlow Shapley on the size of the Milky Way. Shapley began by gathering data on globular clusters from the one-hundred-inch Hooker telescope recently unveiled as the world’s largest atop Mount Wilson. By 1920 Shapley concluded that these stellar globes circle about the center of the Milky Way like wasps swarming about a nest. Since it had by now been determined that the sun is nowhere near the center of the Milky Way, Shapley increased the estimated size of the Milky Way by an order of magnitude, from 30,000 light-years to 300,000 light-years across. He called it his “big galaxy” hypothesis, and it was a galaxy easily large enough to accommodate all celestial objects—including those pesky nebulae—into the known universe. If Shapley was right, there is only one island universe and we’re in it, along with the nebulae. To test his hypothesis, Shapley returned to the data on whether or not nebulae rotate. If they do, then they cannot be that far away, because an object whose rotational motion was detectable over a course of only a few years at that distance would mean that it was rotating faster than the speed of light, which is not possible. Because some astronomers thought that they had detected just such motion in Andromeda, Shapley concluded that it could be no farther away than about 20,000 light-years.

Measurement of the rotational speeds of the nebulae began in earnest by the Dutch astronomer Adriaan van Maanen on the sixty-inch Hale telescope at Mount Wilson in 1915. Using a stereoscopic viewfinder that alternated two identical photographic plates shot at different times, Van Maanen compared photographs of spiral nebulae taken in 1899, 1908, and 1914 to his most recent photographs. Scanning the images for anything that moved or any rotational change from one year to the next, Van Maanen thought he saw motion in M101—the Pinwheel nebula—which he estimated was completing one full revolution every 85,000 years. If M101 was an island universe at a vast distance, this would mean that the stars on the nebula’s edge would be rotating faster than the speed of light, which Einstein had recently proven was impossible. Ergo, M101—and by extension the other spiral nebulae—were nearby and well within Shapley’s newly reconstituted 300,000-light-years-across Milky Way. Shapley wrote Van Maanen: “Congratulations on the nebulous results! Between us we have put a crimp in the island universes, it seems,—you by bringing the spirals in and I by pushing the Galaxy out.”18

Since the theories were in conflict, the rub was in the data, which Heber Curtis at the Lick challenged. He attempted to measure nebular rotational motion himself but couldn’t. Where Van Maanen thought he saw rotational periods of 160,000 years for M33, 45,000 years for M51, and 58,000 years for M81, Curtis saw no motion at all. How can this be? Either nebula are rotating or they are not, right? Herein lies a problem in patternicity and how the mind fills in the details when the data do not speak for themselves, which they rarely do. Measuring nebular rotation was incredibly tedious work in which error measurement could easily exceed the measurement of motion itself, leading to a completely erroneous conclusion. It would be like estimating the speed of a car at 30 mph, ± 30 mph. This, it would seem, was what happened. As improvements in measuring quality increased, motion of the nebula decreased … until it disappeared entirely.

“VAR!”

Enter Edwin Hubble, one of the grandest characters in the long and colorful history of astronomy, who cultivated a British air of aristocracy even though he was from Missouri. Hubble arrived at Mount Wilson shortly after the magnificent new one-hundred-inch Hooker telescope (see figure 20) came online, with a capacity to discern a candle at a distance of five thousand miles. Hubble’s considerable intellect and ambition were afforded the technology to adjudicate once and for all the great debate between the nebular hypothesis and the island universe theory.

Figure