The Perfect Machine (71 page)

Max Mason, back in Pasadena, waited until he heard that the mirror was safely in the dome to call Warren Weaver at the Rockefeller Foundation. Mason passed on the reports he heard, letting Weaver share the good news. Only then did Mason break the bad news: The telescope project was broke.

34
Finishing Touches

The final journey of the mirror was front-page news.
Collier’s, Life,
and
Time
all planned features on the telescope and, discovering that it was far from operation, sent their reporters to George Hall, in charge of publicity at Caltech, for material. Hall had been on the job long enough to know the weeklies loved nothing as much as a colorful personality, so he set up interviews with Fritz Zwicky and Edwin Hubble. Zwicky’s thickly accented explanations that he would use the telescope to search for neutron stars and gravitational lenses sounded wacky, but Edwin Hubble was a reporter’s dream.

Hubble had returned from his wartime service as chief ballistician at the Aberdeen Proving Ground with the Medal of Merit. He enthusiastically posed for pictures at the two-hundred-inch and at the forty-eight-inch Schmidt camera, and explained to the reporters, in his acquired English accent, that when the telescope was ready, he would extend his measurements of red shifts and counts of nebulae out to the “one-billion light years range of the 200-inch,” and test the cosmology of an expanding universe and Einstein’s geometry of space. Tantalizing quotes like, “Mathematical physicists believe (from Einstein’s ubiquitous Relativity) that space is curved back upon itself, in a four-dimensional way,” and photographs of the tweedy, handsome astronomer with his pipe, a bold adventurer preparing to solve the mysteries of the universe, sold magazines.

“It will be a historic night,”
Time
wrote, “an extra-clear night, with the sky velvety black and the stars, though bright, twinkling hardly at all. Hubble will go into the observatory after dusk, rise to the big round telescope chamber in a push button elevator.” Along with the interviews Hubble also gave speeches on the problems the two-hundred-inch telescope might solve. Mostly the problems he described were his own cosmological program, but he added that the telescope would determine, once and for all, whether there were canals on Mars.

The new wave of publicity raised hackles at Mount Wilson and
Caltech. Astronomers and engineers on the project had learned to live with minor inaccuracies. The “big round telescope chamber” was the prime-focus cage, six feet in diameter, cramped inside for a six-footer like Hubble. The telescope would never be used for observation of Mars, and the issue of canals had long been dismissed by most astronomers. What galled most of all was that Hubble had hoodwinked the press. Walter Adams, a quiet, gentlemanly sort who avoided publicity and nastiness, sent a handwritten complaint to Bowen, “because it is not material I should want to give to a stenographer.”

Adams was troubled that the new round of news stories was so one-sided, that there was no mention of men like Max Mason, and instead it seemed to be

a kind of glorification of two men, Hubble and Zwicky, the first of whom has done little work of the first order for twenty years, and the second hardly anything at any time.

It’s clear that Hubble cannot be relied upon to provide a fair or adequate description of the work of a large modern observatory to a journalist seeking information. He knows little about spectroscopy and what it is doing, and at the age of practically sixty is still eager for notoriety and has his press agent continuously at work. I judge he will never be able “to put away childish things.”

The short shrift given to other astronomers was improper and just plain wrong to a fair-minded man like Adams. He was even more troubled by the impression Hubble had publicized that the two-hundred-inch telescope would
answer
the important questions of cosmology. “It is just possible,” Adams wrote, “that the Hale telescope will not meet all our hopes in its penetration of space, or that even if it does, the gain will not be sufficient to answer many of the important cosmological questions.” If the public was led to believe that “answers” about the size and shape of the universe were the sole purpose for the telescope, it might be considered a failure if it did not answer those questions—while the considerable contributions the telescope might make in dozens of other fields of astronomy were ignored.

Propriety wasn’t the only reason for the confidentiality of Adams’s letter. Harlow Shapley had begun another round of skeptical comments about the telescope, and the first tests of the completed telescope hadn’t produced any good news to quash the rumors he started.

Before they could even test the telescope, the opticians had to turn the disk into a mirror. In 1928, when the telescope project began, mirrors in astronomical telescopes were coated with a thin layer of silver. In a household mirror the silvering is applied to the back of the mirror and is seen through the glass, which protects the delicate silvered
layer. Viewing through the glass also adds distortions, intentional in an amusement park or a magnifying mirror, acceptable in a household mirror, and intolerable in a precision instrument. In an astronomical telescope the mirroring is applied to the front surface, so that nothing stands between the finely figured surface of the mirror and the light from distant objects. The reflective coating, perhaps one thousand atoms thick,
is
the telescope.

When the telescope is in use, that thin coating of the mirror is exposed to the elements, vulnerable to the corrosive effects of the atmosphere, the accumulation of dust, dripping oil from the telescope, an accidental drop of tools or equipment, rain, snow, hail, windblown debris, even a falling meteorite. The potential hazards are so great that it is tempting to never use the telescope.
^*
When the two-hundred-inch telescope is not in use, the mirror and cell are protected by a diaphragm over the mirror. Leaves, like the blades of a camera shutter, are opened and closed by motors. In case of a power failure, auxiliary power is available to close the diaphragm and protect the mirror.

Silver had long been the material of choice for telescope mirrors. It was easy to apply to the mirror chemically, and immediately after it was applied, it would reflect almost 95 percent of the visible light that struck the mirror. But, as generations of English butlers have learned, silver tarnishes on exposure to air. After a relatively short period of use, the reflectivity of a silvered telescope mirror decreases to approximately 50 percent. In the ultraviolet spectrum—which, though invisible to the naked eye, is important to the astronomer—even a freshly deposited silver film reflects only 4 percent of the light to hit the mirror. John Anderson tried some experiments, coating silvered mirrors with silica and/or fluorite, and concluded it would not protect the silver.

The problems with silver coatings prompted Francis Pease to ponder the ideal mirror material, the imaginary substance mirrorite, which would have the “reflecting power of silver, the zero coefficient of expansion of Invar, the freedom from tarnish of stainless steel, and the lightness of magnalium.” Even for the two-hundred-inch telescope, the Caltech geologists couldn’t find mirrorite.

In 1932 John Strong discovered a mirror coating almost as good. Strong was trying to deposit a protective layer on rock-salt prisms, to prevent the surfaces from deteriorating on exposure to the air. He finally succeeded in depositing a thin aluminum film on the prisms in a high vacuum, then tried the same process on glass. By 1932 he had aluminized a twelve-inch-diameter telescope mirror. The new coating was nothing short of sensational. The aluminum film didn’t need burnishing,
and instead of tarnishing on exposure to air like silver, the aluminum formed a hard, transparent oxide coating that
protected
the reflective surface. Dust could be wiped off the surface with a moist soft cloth or even washed off with soap and water—a treatment that would have removed a silver coating. The reflectivity was only 89 percent of visible light, slightly less than the initial reflectivity of silver, but the aluminum maintained its reflectivity even after continued exposure to the atmosphere and also reflected 85 percent of the ultraviolet light. Tests at the Lick Observatory showed that for stellar photography, the new coating reflected on average 50 percent more light to the photographic emulsion. It was like getting a new telescope.

The process was tricky. The aluminum had to be vaporized over the disk in a bell jar by heating it with tungsten coils. To produce a smooth, even layer on the mirror, the aluminum molecules evaporating from the coil had to travel to the surface of the disk in a straight line, which meant they could not hit another molecule. A collision-free path required that the bell jar be evacuated to a vacuum of one ten-thousandth of a millimeter of mercury, in a contained space so free of leaks that if it were evacuated and sealed off, it wouldn’t reach one-half of atmospheric pressure for fifteen years. Strong’s process required that the optician duplicate the near emptiness of outer space—no easy task in a laboratory.

George Hale, who kept his fingers on any technology that affected big telescopes, had eagerly followed Strong’s work. When Strong aluminized the mirror of the Crossley reflector at the Lick Observatory, the telescope Heber Curtis had used for his surveys of “island universes,” it improved the performance of the telescope so much that he was recruited to aluminize the mirror of the one-hundred-inch Hooker telescope on Mount Wilson. The results were spectacular. Before, the tiny companion star of the bright star Sirius had been difficult to photograph with the one-hundred-inch telescope, because the fine scratches that were inevitable on a silvered surface as it was burnished—no matter how fine the rouge used—would scatter the light. With Strong’s new aluminum coating the companion star was easily resolved in plates. There was no question that they would try for an aluminum coating on the two-hundred-inch disk.

It had taken some tinkering to get Strong’s temperamental process to work on a mirror as large as the one-hundred-inch. The coating was only one thousand atoms thick, less than one-thousandth of a millimeter. For optimum effectiveness the thickness had to be uniform to within 4 or 5 percent. The slightest contamination on the surface would cause the coating to fail. Strong constantly experimented with new techniques for cleaning the surface before depositing the aluminum.

In the spring of 1947 Anderson invited Strong to return to Caltech from Johns Hopkins University to supervise the aluminization of the
two-hundred inch disk. Strong was delighted to work on the big telescope. He also had no illusions that it would be a tough job. Before he came to Pasadena he urged that whatever vacuum pumps Caltech planned to use, they should have an auxiliary pump system ready to supplement the original pumps.

The mirror cell of the two-hundred-inch disk, which held the support systems and the edge levers, complicated the plans for aluminizing the disk. The engineers had designed a wheeled platform, with screw elevators on each corner that could raise and lower the mirror and cell to the telescope. The platform served both as a carriage to remove and reinstall the disk in the telescope, and as the bottom half of the vacuum chamber. A steel bell was designed fit over the platform, with a rubber gasket fitted around the edge of the disk to isolate the high-vacuum area from the back of the mirror with its delicate support systems. Without the gasket, drawing down a vacuum to the level required by aluminizing would suck the oil and grease out of the bearings of the support assemblies, contaminating the vacuum and forcing a tricky relubrication of the mechanisms.

Strong had cleaned smaller disks by hand-burnishing with virgin chamois and extrafine rouge. The success rate was spotty. The worst contaminant, he discovered, was microscopic traces of oil from the human skin. With opticians hand-burnishing a two-hundred-inch disk, removing the traces of oil would be a Sisyphean task. So for the two-hundred-inch disk, he planned a new cleaning technique: he would first coat the surface of the disk with a “special fatty acid compound and precipitated chalk powder.” The precipitated chalk would be wiped off with virgin felt pads, leaving the fatty acid on the surface of the disk. He would then burn the residue of fatty acid off with an oxygen glow, leaving a pristine surface for the aluminizing. Strong’s procedure sounded as if it would work. The opticians eagerly awaited his arrival at Palomar with the special materials.

When Strong arrived, the “special fatty acid compound” turned out to be cases of Wildroot Cream Oil hair tonic. Radio listeners all across the United States knew what the magic ingredient was:

You’d better get Wildroot Cream Oil, Charlie;

It keeps your hair in trim,

Because its non-alcoholic, Charlie;

It’s made with soothing lanolin.

“In order to get glass clean,” Strong told the opticians and astronomers, as he unpacked cases of hair tonic, “you first have to get it properly dirty.”

Strong set to work on the two-hundred-inch disk with his Wildroot Cream Oil treatment. He and the opticians wiped the surface clean just before the overhead crane lowered the bell onto the base of the
aluminizing chamber. When it was sealed in place, Byron Hill flipped a switch, and the oxygen glow of the heating coils burned the lanolin residue off the surface of the disk, along with every trace of human body oil. Then Hill flicked another set of switches to start the big oil-diffusion pumps to evacuate the bell to a high vacuum.

The pumps ran for days. Every hour someone would check the vacuum gauges and jot figures in the notebook in which Don Hendrix was recording each step of the aluminizing process. Progress was slow. Technicians drifted off to meals, naps, other work. The staff took turns checking the gauges and jotting notes in Hendrix’s log. On the second day Ben Traxler, annoyed by the constant drone of the pumps and the funereal atmosphere of the watch over the process, wrote in the log that he had let air into the chamber to quiet the pumps. Hendrix saw the note and blew up. He had just been named optician for the two-hundred-inch mirror and wasn’t ready for jokes.