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In 1936, the glass disc arrived at the Pasadena optical shop of the California Institute of Technology to be ground and polished. The 20-ton blank was placed face up on a turntable. As it revolved slowly, a 48-inch disc set with blocks of abrasive was stroked mechanically back & forth from its edge across its center. The whole process was maddeningly tedious.
The telescope frame progressed faster, but both it and the mirror were still unfinished when Pearl Harbor Day scattered the astronomers to those odd, essential posts that scientists fill in wartime. Hubble tried to get back his old job in the infantry, but was made Chief Ballistician at Aberdeen Proving Ground, Md.
Astronomer-Ballistician Hubble came back from his second war with the Medal of Merit, and settled down. With his wife, the former Grace Burke, he lives in a charming mission-style house in San Marino, near Pasadena, on the edge of a steep geological fault which he thinks may be incubating an earthquake.
His brother astronomers straggled back too. The massive telescope frame was completed quickly. At the optical shop, work went more slowly; the incredibly delicate task of polishing the mirror could not be hurried. The mirror had to be a paraboloid (a slightly deeper curve than a hollow sphere), accurate to two-millionths of an inch. Each grinding and polishing was done with fanatical watchfulness. Visitors were asked to remove their shoes, like pious worshipers at the door of a mosque; a single grain of tracked-in sand might scratch up the glass and spoil months of work.
By August of last year, the worst was over. Dr. John A. Anderson, who had supervised the polishing, knew that he had succeeded. He set the great disc on edge for the final tests, which it passed with flying colors* (TIME, Oct. 13). Seven weeks later, it was crated and trucked up Palomar Mountain.
Hair Oil & Aluminum. The polished surface of the mirror was transparent glass, still to be covered with a reflecting film of aluminum. Before this could be done, the glass had to be cleaned perfectly. The trick was to cover the surface with a "monomolecular layer" (one molecule thick) of a fatty acid to keep dust off the glass. This process sounds formidably scientific, but in practice the glass was covered with a well-advertised brand of hair oil (essentially an emulsion of lanolin), and the excess wiped off carefully with special wool flannel.
After the hair oil was removed by an electric blast of "ions," the great disc was "silvered" with vaporized aluminum. At last, the big eye was finished.
The Pleasant Science. Long before this stage, Hubble and his colleagues had been driving up & down Palomar Mountain to admire their still blind telescope and its lovely setting. Of all the sciences, astronomy is in many respects the pleasantest. There are no dead animals (as in biology) or horrible smells (as in chemistry). Astronomers work on clear-aired mountaintops with clean and beautiful instruments. Their experimental material—light—filters down unbidden out of the cold, dark sky.