Engines of Our Ingenuity

No. 1461:
TELESCOPES

by John H. Lienhard

Click here for audio of Episode 1461.

Today, we look through some really big telescopes. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The astronomer George Ellery Hale was born just after the Civil War. In 1892, as a 24-year-old professor at the University of Chicago, he organized the Yerkes Observatory.. There he built the largest telescope ever to use a conventional refractor lens. It was over three feet in diameter. But it was also doomed to become a dinosaur within a few years, because astronomers gave up conventional lenses in favor of focused mirrors after 1900.

Hale, however, was no dinosaur. By 1904 he'd convinced Andrew Carnegie to give him a hundred and fifty thousand dollars to set up the Mount Wilson observatory in California. Hale was downright greedy for high resolution, and straightaway he developed the largest mirror telescope ever built. It was five feet in diameter.

At first he joyfully cried, With this we'll record ... a billion stars! But 1918 found him back at Carnegie's doorstep asking for money to build a new mirror more than eight feet in diameter. Visit the quiet site along the Mount Wilson rim today and you'll see that telescope, along with the five-foot one, still in use.

G. E. Hale's bust in the Solar Tower, Mount Wilson Observatory. Hale was now only fifty, but his health had begun to fail him. He had to retreat from fieldwork in astronomy. But that didn't stop him from planning, writing, and organizing. In 1916 he'd founded the National Research Council, and he was now deeply involved in the task of setting America's scientific research agenda.

But one more telescope was on Hale's agenda -- a really big one this time. Andrew Carnegie was dead by now, but the Rockefellers gave Hale six million dollars for a third mirror -- one almost seventeen feet in diameter. That mirror was to become the heart of the Mount Palomar Observatory, also in California.

In 1934, the Corning Glass Company tried to make the first rough casting of this seventeen-foot mirror. They cooked a fifty-foot lake of molten glass for six days at 2700°F. When they poured it, with the press watching, the inside of the mold broke up. Nine months later they tried again and succeeded. It took eight more months to cool it down. And grinding it by hand to within a millionth of an inch took years. The story has it that the man who did that job on the eight-foot mirror ended in a mental institution.

Hale died in 1938, and the Mount Palomar telescope was finally finished ten years later. Until the Russians made a larger one in 1986, it remained the world's grandest optical telescope. Compare its five hundred foot effective focal length (ninety-one inch actual) with the eight-inch focal length of your long-distance zoom lens. It finally took the new radio telescope to improve on its resolution.

We have to be moved by Hale's unmatched vision, nerve, and determination. Just think: over a 56-year period, from the age of 24 until ten years after his death, George Ellery Hale gave us the world's largest telescope not once, but four times.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Stirling, N., Wonders of Engineering. Garden City, N.J.: Doubleday and Company, Inc., 1966, Chapt. 11.

For some wonderful images of Hale's first three major telescopes, I recommend you look at the 1911 Encyclopaedia Britannica.

This is a greatly revised version of Episode 98.


Photo by John Lienhard

Hale's 100 inch (8 foot) lens is in the blue metal housing at the bottom.


The Engines of Our Ingenuity is Copyright © 1988-1999 by John H. Lienhard.