The Day We Found the Universe - Marcia Bartusiak [124]
With NGC 7619's speed record in hand, Humason was able to put a further gold star in Hubble's rising constellation by noting that his measurement meshed exactly with the relation that Hubble had just found between a galaxy's distance and its velocity. “The high velocity for N. G. C. 7619 derived from these plates,” Humason was able to report, “falls on the extrapolated line.” With that triumphant pronouncement, Humason was extending Hubble's findings even farther into space, out to 20 million light-years.
It seemed inevitable that the only astronomer to voice immediate doubts about Hubble's new law was his long-standing adversary, Harlow Shapley, who was concerned that distances could only be certain for the nearest galaxies. He was perhaps envious, “in part regretting a lost opportunity to pursue such a relation himself,” suggests historian Robert Smith. Shapley wrote a quick and pointed response to Hubble's paper, where he rightly argued that at a great distance a cluster of stars would be mistaken for a single star, making it a bad “standard candle.” But on the opening page of this article, he didn't miss the opportunity to steal away a bit of Hubble's thunder and proclaim that ten years earlier he had published a notice that “the speed of spiral nebulae is dependent to some extent upon apparent brightness, indicating the relation of speed to distance.” Shapley failed to disclose that in 1919 he still believed that the spiral nebulae were minor members of the Milky Way. So his claim, in the end, was meaningless.
Within two years, Hubble and Humason examined forty more galaxies beyond the several dozen that Slipher had earlier measured. They proceeded outward from what was then measured as 6 million light-years to as far out as 100 million light-years, a tremendous vault into the cosmos over such a short time. “Humason's adventures were spectacular,” recalled Hubble many years later. “When he was sure of his techniques, and confident of his results, he set forth. From cluster to cluster he marched with great strides right out to the limit of the 100-inch.” At one point Humason spent an entire week, night after night, gathering the light from just one faint galaxy in the Leo cluster to determine its redshift. Nicholas Mayall, a graduate student from Berkeley who was then assisting Hubble on a galaxy-counting project, was there as Humason developed the photograph at the end of the run. Holding the small plate up in front of the light box, Humason declared, “My God, Nick, this is a big shift!” The spectral lines, recalled Mayall, “were shifted way over to hell-and-gone from where they should have been. This proved to be a red shift of 20,000 kilometers per second, and it was probably more than twice the biggest one he had ever obtained before. He was simply jubilant.” This galaxy was racing outward at more than a twentieth the speed of light. Caught up in the moment, Humason announced it was time to celebrate and promptly went down to his room, swung open his closet door, and took out a bottle of his mysterious “panther juice,” an illicit alcoholic brew. After their toast at dawn and a brief nap, the two colleagues went for breakfast at the Monastery and called up Hubble on the phone with the news of the record-breaking redshift. “Milt,” replied Hubble, “you are now using the 100-inch telescope the way it should be used.” The link between a galaxy's velocity and its distance had been made even stronger. “You can't imagine how electric the atmosphere was,” said Mayall. “So many things were happening in astronomy and physics—they all came to focus at that time and place.”
Humason's velocities were so astounding that some astronomers were finding it difficult to believe that he could measure them at all. But Humason had the benefit of experience. By first pegging redshifts at relatively low velocities, he became