GENERAL ARTICLES

The Big Eye

Howard W. Blakeslee May 15 1947
GENERAL ARTICLES

The Big Eye

Howard W. Blakeslee May 15 1947

The Big Eye

Can Mars support life? Is the universe exploding? When was creation? Palomar’s giant telescope may provide the answers

Howard W. Blakeslee

Associated Press Science Editor

THE GREAT 10-ton blob of glass shimmered with heat. It was already hard to the touch of a crowbar, but still nearly as hot as molten iron. It glowed red and yellow, separated by white bands.

It had been poured that morning, Dec. 2, 1934, at the Corning Glass Works in Corning, N.Y., the first step in making the 200-inch diameter mirror which would be the heart of the world’s largest telescope. Now it was time to set it away carefully to cool for months, so that it would emerge (lawless, and strong.

Today, after almost a year in an annealing oven, after five years in which more than five tons of its circular face has been ground away by carborundum in Pasadena, Calif., and polished by 50 pounds of cosmetic rouge an hour, and after seven years’

delay of a world war, this great eye of the future is ready to peer into the unknown. Atop Mount Palomar, 125 miles from Pasadena, a great new observatory has been raised to house it. When the big eye -twice the size of any previous telescope mirror -first sweeps across the sky this coming fall or winter it will see twice as far as any other telescope, will penetrate eight times more space than has previously been revealed to man.

Trained on the moon, this telescope will give the observer a close-up as if he were a mere 300 miles from the earth’s satellite—perhaps even bring it as close as 25 miles, under ideal atmospheric conditions. It will permit the planet Mars to be magnified to a diameter of several inches—to astronomers, a thrilling possibility. It will add testimony to the growing evidence of the existence of other worlds outside the sun’s family, and to the creation and death of stars, both now apparently going on in the Milky Way.

But all this will be incidental to the real tasks set for the 200-inch eye, whose scope can’t be measured in terms of such close-range targets. Rather, the Palomar telescope is designed to catch the light of celestial families of stars, called nebulae, so far off in space that their rays have taken a billion years to get here though flashing earthward at 186,000 miles a second.

The newinstrument has been built to reach out fo the possible fringes of the universe in the hope of finding the answers to such scientific brain stoppers as whether or not our universe is expanding —or, as the astronomers

say, “exploding.” It Continued on page 63

One man will hove the seeing power of 200000 human eyes when he peers at the heavens with the Palomar telescope, shown here in diagram form.

Heart of ths cos mk spyglass is the I 5-ton mkror, rest ing in a 500-ton cradle. It catches faint star glimmers a billion years old.

Continued from page 8

may reveal instead that space is curved —that light, does not always travel in a straight line. It may help strip away the mechanical mysteries of creation itself—how our own and other worlds were fashioned, how the very atoms of which all matter is composed originated.

The Palomar project was initiated 19 years ago by the late George Ellery Hale with a $6 millions grant of the

General Education board of the Rockefeller Institute, made to the California Institute of Technology and the Carnegie Institute of Washington. These two organizations will jointly operate the observatory on the 5,500foot peak of Mount Palomar.

There is almost complete public misunderstanding of how the 200-inch telescope will see. The most familiar type of telescope—the collapsible brass instrument that the sailor holds to his eye—consists of a series of lenses mounted within a hollow tube; when

the tube is adjusted to bring the lenses into focus the light passes directly down the tube to the observer’s eye, and the object is “brought nearer” or enlarged by the lenses.

The Palomar telescope, like other large astral instruments, operates on an entirely different principle, and is actually much simpler in design. It has no lenses; it does not magnify. Basically it consists simply of the great mirror, 17 feet in diameter, mounted at the bottom of a large telescope tube, the upper end of which is open to the sky.

The mirror’s job is to collect the light of the stars that passes down the tube and—thanks to its highly polished slightly concave surface—reflect and focus this light back up the tube to where the observer sits in a little cage slung inside the top of the telescope itself. So much light floods down the open end of the tube that the observation cage does not interfere with the mirror’s view.

Actually, the Palomar astronomers will do little of their work by looking into the telescope. Instead, what the big eye sees will be recorded in photographs which will show far more than the human eye could ever see, no matter how long anyone peered into the instrument. For this reason Dr. Ira Sprague Bowen, director of the Palomar observatory as well as the nearby Mount Wilson observatory, has said that the new instrument should really be called the 200-inch camera.

200,000 Eye Power

No matter how long the human eye gazes at a section of the sky it will continue to see the same number of stars. But expose a camera for an hour, then two hours, and the second picture will show a greater number of stars because the camera has had more time to collect light from fainter objects and build up an image on the film.

The 200-inch mirror of the Palomar camera-telescope collects as much light as 200,000 human eyes. Twice the diameter of the next largest telescope (Mount Wilson’s 100-inch mirror), it has four times the area and four times the light-gathering power.

While Palomar marks an amazing advance in the science of astronomy, the men who conceived, designed and built the new telescope and the observatory in which it is housed have also achieved something of an engineering wonder.

The 15-ton mirror is shaped like a slice of canned pineapple, having a 40inch hole at its centre. It was cast as a huge ribbed disc of pyrex glass, 30 inches thick. Unlike the familiar type of mirror that hangs on your wall, and which is silvered on the back, the 200inch has a dazzling aluminum coating on its slightly concave front or upper surface. It was the precision grinding and polishing of this concave surface which took so many years. The degree of curve had to be figured within one or two millionths of an inch.

The telescope tube, at the base of which is mounted the upward-facing mirror, weighs 125 tons, is 60 feet long and 25 feet in diameter. Its walls are an openwork structure of steel girders. The light rays reflected by the mirror focus on the photographic plate held in a special camera mounting 5514 feet above the surface of the mirror. This is the focal length of the mirror—exactly as the focal length of your camera is the distance between its lens and the film.

The telescope tube must be able to scan the sky in all directions, so it is pivoted between the twin steel arms of a giant cradle, and the combined motions of telescope and cradle enable the big eye to see any part of the heavens except the most southern part

of the southern hemisphere—its only blind spot.

Mirror, telescope and cradle together weigh more than 500 tons. The whole assembly floats on oil so that despite its size the great telescope is a precision instrument, so finely balanced in all directions that it is moved accurately, and in pace with the stars, by a clockcontrolled motor of only half a horsepower.

The 1,000-ton dome also revolves with ease despite its weight, riding on trucks which follow a circular track around the top of the wall, so that a vertical window in the dome can be moved with the telescope as it swings across the sky.

The visual observer or camera operator working in the cage at the top of the telescope tube, 55 Y feet above the mirror’s surface, will study the mirror’s image at its primary focus. But three sets of mirrors which may be swung into position within the observer’s cage will make it possible for the image to be viewed at three other points, one at one side of the tube, another under the mirror itself (the light reaches this one through the 40-inch hole at the centre of the big reflector), and another in an air-conditioned room at the lower end of the cradle on which the telescope is mounted. Here observations are made which require constant ' temperature to enhance accuracy.

Don’t Twinkle, Little Star

While the telescope itself does not magnify, the view of the heavens it provides can be observed (or photographed) through a microscope which will enlarge the object studied. Since it gathers far more light than any other telescope, its brighter image permits of far greater enlargement. This is why it will be possible to view the moon through the Palomar instrument at a 300to 25-mile range, depending on the constantly changing turbulence of the sea of air which surrounds the earth to a depth of 200 miles.

It is this turbulence which makes the stars seem to twinkle when you look at them with the naked eye; in a telescope it causes a vibrating image. Small magnification brings out details, but great magnification usually produces only a blur. Yet there may be some lucky moments, while the air is least turbulent, when some dramatic magnifying of the moon and planets may be possible. At 25-mile range, for instance, keen eyes might be able to discover objects the size of buildings on the moon. Some astronomers have said that two lights, 150 yards apart on the moon, could be discerned as separate by the Palomar telescope; others think that two lights only 30 feet apart could be distinguished. These are, of course, only theoretical examples, for it’s known that anything approaching human life is impossible on the moon.

The handicap of the vibrating image can be overcome by such recent devices as the photoelectric cell, which changes light to electric current, and the infrared cell which picks up heat and changes it to electric current. These electronic cells, undreamed of 19 years ago when the 200-inch was first projected, have actually increased the effectiveness of the instrument five times beyond original expectations.

Actually, enlargement of what is seen is unessential to most of the long-range work for which the Palomar telescope has been designed. The great astronomical discoveries are made by analyzing the light of stars and nebulae. The most important method calls for use of a prism to break down the light of a star into the spectrum of its component colors. By studying this rainbow of color, scientists can

I iuentiiy the atoms in stars, in nebulae I and in clouds of stellar dust and gas.

The spectrum of a star tells how hot its atoms are, what pressures they are under, the speeds at which they are moving. There is a different color, or line in the spectrum for each kind of atom, and for each different state of the atom. More than 500 of these lines are known. These celestial colors never duplicate, and never get mixed up'.

Thanks to one of the most exciting of the new aids, the peanut-sized infra-red electronic cell the spectra of the stars can now be taken in infra-red providing an infra-red rainbow made of heat rays, colors invisible to human eyes.

Plant Life on Mars?

This electronic cell may settle the question of whether plant life exists on Mars. Mars, in summer, has some bluegreen patches, the size of small continents, around its equator and southern hemisphere. For many years the speculation has been that, the color may be vegetation. The temperature in the Martian summer is about 50 at midday and freezing at night. Vegetation could exist.

One way of proving the point is to analyze the blue-green light of these patches with spectroscopes. This was done by Dr. Peter Millman, formerly of the David Dunlap Observatory, Richmond Hill, Ont., and now with the Dominion Observatory at Ottawa.

First he analyzed the light of the green color of leaves, which comes from chlorophyll. But this earthly plant color was extremely strong in infra-red and Dr. Millman could not analyze the infra-red, because there was then no good method of getting the heat rainbow. The study of the other colors did not prove or disprove whether Mars colors come from chlorophyll. The infra-red spectrum, with the new electronic cell, and perhaps aided by the Palomar telescope, may settle the question of Martian life.

Peering beyond the earth’s immediate neighbors, the big eye will study the Milky Way. The Milky Way is the earth’s home, and is like an island in a universe too vast for comprehensionan island made up of a vast congregation of stars and an enormous amount of dust and gases approximately equivalent in bulk to the bulk of all these stars.

Stars That Blow Up

One of the mysteries of the Milky Way is the novae, the stars that explode. A nova would explain the star of Bethlehem. These stars flare up and then fade, usually rapidly, but they are not suicides. One is known to have exploded twice in 80 years, and all novae may be repeaters. They may be extreme forms of a great class of stars which grow alternately brighter and dimmer. A question for great telescopes to solve is why some stars explode, and others pulsate.

But to the layman the Milky Way can offer the new Palomar telescope few more fascinating tasks than the search for other worlds like our own. Astronomers are beginning to believe that other stars than the sun have planets revolving around them, and that there may be so many of these that the chances of earthly conditions being repeated elsewhere—even the evolution of life similar to our own—are not beyond possibility.

The big eye will find its most important assignments, however, beyond the boundaries of the Milky Way, which is but one of countless similar galaxies of stars which comprise the universe. Each galaxy contains about 100 million stars, possibly more, but most galaxies

as so far away that individual stars j j can’t be distinguished. These distant I galaxies are called nebulae.

Most nebulae are shaped like auto wheels, minus tires. They are rotating, inner portions travelling faster than the outer. Our Milky Way is one of these spinning nebulae. Stars near its centre travel at 190 miles a second, but out where the earth floats, three quarters of the way from the centre, the speed is only 180 miles a second, and on its outer rim the velocity is a “mere” 170 miles a second. One of the comparatively nearby nebulae, known to astronomers as Messier 33, has a speed of only 10 miles a second atitsouterrim.

Stars Without Number

One of the most incredible of all aspects of creation that the 200-inch may clarify is the fantastically great number of nebulae. Edwin Hubble, one of the Mount Wilson astronomers, basing his calculations on what he has actually seen, has estimated that there may be as many as 100 million nebulae —each about the size of the Milky Way. Calculating on theoretical grounds the late Sir Arthur Eddington said there might be 100 trillion nebulae.

But the estimates are hardly more fantastic than the cold, observed facts. The bowl of the Big Dipper—the rectangle formed by the four stars at the base of the Dipper’s handle—is a small patch of sky familiar to everyone in the northern hemisphere. Yet telescopes looking through that area alone have counted 1,760 nebulae.

One of the first major projects set for the big eye will probably be to examine something which Mount Wilsons’s 100-inch telescope discovered about nebulae ranging from 100 million to nearly half a billion light years away that, their light is always slightly red.

The farther away these nebulae, the redder becomes their light. Both the red color and its increase with distance would be fully explained if these distant star families are receding from the earth. The color shows that the farthest distant are travelling at the highest speeds. The top velocities of recession so far measured are more than 2,000 miles a second.

Does Light Slow Down?

This recession is the reason for the astronomical theory that the universe is expanding, or exploding. Such an exploding universe has no practical effect on man, because the single nebulae, or star families, definitely are neither exploding nor expanding. The expansion Is the motion of one nebula* away from another. This expansion, if verified, will furnish data on which to calculate when expansion began. And thus to know, perhaps, when creation began.

The great astronomers are in doubt whether the apparent expansion is real. For years they have waited for the 200-inch to settle this question.

There are other explanations of the reddened light. The most startling suggestion of all is that in coming so far, light might lose velocity, and that this slowdown would account for the redness.

But a slowing of light’s velocity is unthinkable in the present understanding of the nature of creation. That velocity is supposed to be absolute — j and the very highest speed possible anywhere. If Palomar’s 200-inch eye should indicate that light travelling vast distances really can slow down, then our ideas of man’s physical world would have to undergo revolutionary alterations.

These are big questions for the big eye to look into. -Ar