First Light: The Search for the Edge of the Universe (8 page)

When McCauley opened the cold oven, he saw that he had made the world’s largest monolithic piece of glass. It had a hole in the center, like a doughnut. Corning engineers encased the disk in a steel shell and stood it upright on a flatcar, to be drawn by a steam locomotive to California. For more than two weeks the telescope train crossed the United States, often at speeds of five miles an hour. Every time the train stopped, armed guards dived underneath it, looking for hobos trying to ride under the disk, for this was the Depression. Huge crowds turned out. Ten thousand people in Indianapolis watched the telescope train pass. Afraid that someone might try to take a potshot at the disk, Hale and Anderson felt it necessary to armor the disk with steel plates. If a bullet had broken the glass, that certainly would have killed Hale. At night the train was parked on a siding, illuminated with floodlamps, and patrolled by guards carrying loaded rifles, who had orders to let nobody approach within shooting distance. The train passed through St. Louis, Kansas City, Clovis, Needles, and San Bernardino, and arrived in Pasadena on Good Friday, April 10, 1936, witnessed by crowds. The disk was unloaded and lifted into the Caltech optical shop. A Pasadena newspaper reported: “There has not been such excitement since Ambler’s Feed Mill burned.”

The excitement was too much for George Ellery Hale. Too ill, physically and psychologically, to watch the triumphal entry of his glass into Pasadena, he had withdrawn from the world, broken on the wheel of whirligus. He spent his last years with his instruments in the underground chamber of his solar laboratory, looking into the sun. Day by day a heliostat mirror (a sun-tracker) turned slowly at the top of the building, throwing a shaft of sunlight into the basement, where Hale, staring through an eyepiece just two millimeters across, watched prominences heaving and lapsing around a ball of hydrogen as old as the world but never the same from one minute to the next. His grandchildren would visit him and listen to his stories, and perhaps the elf listened too. He maintained contact with the Palomar project through long letters to a few friends. In 1938, at the Las Encinas sanatorium in Pasadena, he said to his daughter, Margaret Hale, “It is a beautiful day. The sun is shining, and they are working on Palomar.” He died a few days later. Hale had not returned to Palomar Mountain since the day he chose the fern meadow. He never saw his greatest telescope.

Marcus Brown, Caltech’s chief optician, directed the grinding of the mirror. Brown hired twenty-one unemployed men (mostly right off the street) to operate a polishing machine. Brown’s men wore white suits and white sneakers—clothing that never left the shop. The glass disk sat on a turntable. While the turntable rotated, an arm pressed a rotating circular polishing tool against the glass; the arm moved the tool in differing directions across the glass, thus tracing overlapping cycles of movement known as Lissajous figures.

I drove up into the Verdugo Hills, near Pasadena, one afternoon in spring, along an unmarked dirt road, until I found a sunny house where lived Melvin Johnson, who as far as I could tell was the only master optician still alive who had worked on the two-hundred-inch mirror. We sat and drank coffee, and Johnson said that it had been so long since he had talked about that mirror that he might have a little trouble finding the right words, but then his words began to move in Lissajous figures around a giant disk of flame Pyrex with a hole in the middle. The opticians inserted a Pyrex plug into the hole before they started to polish the disk. The polishing tool was covered with a layer of black pitch, which rubbed
and sleeked against the glass. The formula for the pitch changed now and then, Mel Johnson said, and the method of cooking the pitch in a pot was essentially a black art. “We tested all kinds of mixtures. I threw out a garbage can full of formulas,” he said. The pitch, he said, contained amber rosin from Alabama pines, pine-tar oil, and beeswax. Hoping to get a smoother polishing action on the glass, the opticians experimented with pitches adulterated with paraffin wax, automobile motor oil, and a powder made from ground walnut shells, “which was like flour,” Johnson said. Every few minutes the opticians poured across the glass a slurry of water and Carborundum grit. They used finer and finer grades of Carborundum and then switched to red jeweler’s rouge. By 1941, they had polished away five and a quarter tons of glass, had used up thirty-four tons of abrasives and jeweler’s rouge, and had brought the surface of the Pyrex disk down to a hollow sphere. From there they had to deepen the glass slightly into a paraboloid. A paraboloid is a saucer that focuses light to a point. The layer of glass that they had to remove in order to parabolize the mirror equaled the thickness of half a human hair. This work required eight more years of polishing, interrupted by World War II, when Caltech halted work on the telescope.

The opticians were afraid that their machines would drop a metal filing on the glass. A grain of metal or grit trapped between the polishing tool and the glass would have cut a helical scratch in the glass that would have delayed the project for six months, or perhaps for years. They swept the room with vacuums and electromagnets. Then they looked at the dust they had collected under a microscope, classified the particles, and saved them in envelopes. If they saw a dust particle of a type they did not recognize, they stopped all their machines until they could trace the particle to its source. Toward the end of the polishing, the opticians spent more time testing the glass than rubbing it, fearful that they might polish too deeply in places, especially around the outer edge of the glass, in which case they might never be able to resurrect a true optical surface. Their testing apparatus was keen enough so that an optician could place his hand on the glass for a minute until the glass warmed, take his hand off it, and see a swelling in the shape of a hand persist on the glass. Before they looked at the
glass through the testing apparatus, they had to turn off all fans and prevent people from walking around the room, “because a current of air coming through the room made the air look like a smoke screen,” Mel Johnson said. He remembered seeing waves twitching along the surface of the glass, as if the glass were restless, gently pulsing with life. The waves mystified the opticians, until they discovered that the mirror was picking up harmonic vibrations from traffic on California Boulevard, near the optical shop. After that the opticians scheduled precision testing of the glass for early Saturday mornings.

When the surface of the glass had reached a fairly acceptable paraboloid, the opticians removed the plug from the hole in the center of the glass. In November 1947, they mounted the glass in a steel mirror cell (it would never leave the mirror cell again) and put it in a box and carried it in a flatbed truck up Palomar Mountain. The purpose of the superstructure of the telescope is to move the glass around and to keep it pointed at one spot in the sky. The purpose of the glass is merely to support five grams of reflective aluminum in a perfect paraboloid, in order to focus starlight into a camera. John Strong, a physicist, had invented a technique for depositing aluminum on glass. Strong had taught the Caltech opticians his trick and then moved on. He eventually wrote a textbook on physics. When I asked around Caltech about John Strong, people seemed to think that he was dead. I made some telephone calls to various parts of the United States and turned up John Strong in Amherst, Massachusetts, nowhere near dead, because he was working on a new edition of his textbook. “I never saw the mirror again,” Strong said over the telephone. He explained that he had had to clean the glass in order to make the aluminum atoms stick to it, for he had learned that oil from the human skin, which inevitably got on the glass from the opticians’ hands, caused aluminum to crinkle off. Strong had tried washing astronomical glass with chemical solvents, but no solvent seemed powerful enough to remove skin oil. Then Strong discovered Wildroot Cream for the hair. “I never used it on my own hair,” he said, “but it was one of those things you just knew about.” He mixed powdered chalk with Wildroot Cream and rubbed it all over the two-hundred-inch glass, which terrified the opticians. “In order to get glass clean,”
Strong told them, “you first have to get it properly dirty.” He wiped the sludge off with wads of felt, leaving a molecular film of Wildroot Cream on the glass. He placed the glass in a vacuum chamber, then fired hot electrodes over the glass, which burned off the Wildroot Cream along with the fingerprints, leaving virgin glass. “Wildroot Cream was one of those little black arts,” Strong explained to me. “It has Peruvian lanolin in it.” While the glass was still sitting inside the vacuum chamber, Strong vaporized aluminum wires in the chamber, and aluminum fell in a dew over the glass.

The opticians opened the tank; the glass had become a mirror. Three nights before Christmas, 1947, a crowd of astronomers and engineers gathered in the dome for first light. They rolled the mirror cell under the butt of the telescope. They raised a hydraulic jack and inserted the mirror into the telescope. Byron Hill’s workmen began tightening a circle of bolts around the mirror.

A bang and a hideous squeal filled the dome. It sounded like a pig being clubbed to death—the unmistakable screech of a crack fingering through sixteen feet of Pyrex. Many eyes turned toward John Anderson, who had been waiting twenty years for this moment and who had a heart condition. After a silence during which Anderson did not collapse, a workman said, “You ever seen a one-million-dollar bolt snap?” The bolt had not snapped off, anyway; it had only creaked. A few minutes later, John Anderson sat in a lift chair, which raised him fifteen feet until he could peer into an eyepiece mounted at the base of the Big Eye. He gazed for a while into the Milky Way, in silence. When he came down, somebody asked him, “What did you see?”

“Oh, some stars,” he said.

One by one the astronomers and engineers sat in the lift chair and went up to the eyepiece. When Byron Hill got his chance to look, as he would remember, “I had never seen so many stars in my life. It was like pollen on a fish pond.” The sight, he said, “made me feel pretty good.”

They all knew that much tweaking and polishing still remained to be done. First light on a large telescope is the beginning of a process of adjustment that may continue for years. Although glass is brittle, it is actually a supercooled liquid. Glass is physically similar to Jell-O. Glass can flop, tremble, and shudder. As a large
mirror moves through varying angles, it buckles and droops. The Hale Telescope’s mirror is rubbery. You could push down firmly on it with your thumb and throw the stars out of focus.

Today, pressure pads controlled by computers push and warp large telescope mirrors to keep them in shape. When Hale first proposed a two-hundred-inch mirror, he sensed that the problem of supporting a lake of glass to a tolerance of four millionths of an inch across two hundred and nine square feet of surface area might be impossible to achieve with existing technology. He decided to hope that the technology would come along. In the early 1930s, an engineering team designed and built thirty-six mirror-support machines, weighted with lead. When the glass disk arrived in the Caltech optical shop, the machines were plugged into pockets in the back of the disk. An engineer named Bruce Rule then tested the glass for signs of slumpage and found that the glass behaved somewhat in the manner of uncured latex rubber—when the opticians leaned the mirror at an angle, the glass would droop and not return to normal shape for quite a while. The mirror-support machines were failing to compensate for slumpage in the glass. During the summer of 1948—six months after first light—Bruce Rule extracted the mirror-support machines from their pockets in the glass and rebuilt the machines. Rule’s thirty-six mirror-support machines work passively, by means of levers and lead weights. The levers barely move, yet they exert three-dimensional forces throughout the glass, which, in places, reach stresses of up to twelve hundred pounds.

Bruce Rule was a tall, white-haired man who wore thick glasses and spoke in a soft, measured voice, and who was widely regarded around Caltech as a genius, which is a reputation not easy to get in a place like Caltech, where the geniuses do not generally refer to each other as such. I visited Bruce Rule one day at his home in Pasadena. “I wouldn’t call them machines,” Rule said. “I would call them compound support units.” Each unit, which resembles a piston inserted in the glass, contains an uncounted number of parts. Rule said, “I think that between six hundred and one thousand parts in each unit is a reasonable number.” Since there are thirty-six mirror-support units, that would mean that the Hale mirror is held up by as many as thirty-six thousand pieces of metal,
most of which move, if only slightly. Now we see why Bruce Rule was considered a genius. Rule said, “That estimate depends on how you want to count parts. If you want to count all the little parts inside ball bearings, then the number would be larger.” The support units are, in fact, mechanical computers. They react to forces in the mirror and apply corrective action. Rule said, “I never recommended that this type of system be tried again.” Virtually everybody at Caltech understands electronic computers, but nobody at Caltech understands mechanical computers, and consequently nobody dares to monkey with Bruce Rule’s support units. Since 1948, there has been one attempt to oil them. It was not much of a success. The lead weights on the units are adjustable, but nobody wants to adjust them. Once or twice a year an engineer walks around the cage at the base of the telescope and reaches up inside the mirror cell. He takes hold of the weights and wiggles each in turn, in order to give the units a bit of exercise; but the feeling around Caltech is that anybody who tries to open Rule’s units to see what is inside them will get himself fired. Rule did not worry about his units. “We didn’t give ninety-day guarantees,” he said. “We built for life.”

Once in a while these days, the stars on the video screen turn into hollow triangles—the support units have become stuck. The astronomer turns to Juan Carrasco and says, “The mirror needs exercise.” Juan then slews the telescope from horizon to horizon, from north to south, from east to west, until the stars turn back into points. The nightmare of the engineers who take care of the Hale Telescope is that one night the stars will turn into triangles, Juan will exercise the mirror, and the triangles will get bigger. In that event, the engineers would have to search the Caltech archives for microfilm of Rule’s blueprints for the support units, although no Caltecker is sure that he would understand the blueprints. During the summer of 1948, when he was designing the units, Bruce Rule liked to go to the beach for a weekend, where he would lie on the sand and hear the surf and see shapes in his mind’s eye—levers and pistons and rippling glass. “I could keep a crew of thirty draftsmen going,” Rule said.