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For example, Galileo's breathtaking discovery of the moons of Jupiter, new worlds that refused to orbit the sun, challenged the whole doctrine of the earth being the center of the universe. With the start of the 20th century, Shapley pushed back the envelope that had been opened by Galileo by proving that the center of our galaxy is very far beyond our own sun. And Hubble showed that even our galaxy is but a tiny part of a universe that is rapidly expanding. In describing these milestones of science, Levy reveals his own spirited conversations with such luminaries of the imagination as the discoverer of the planet Pluto, Clyde Tombaugh, and one of the world's greatest science fiction writers, Sir Arthur C. Clarke.
Through Levy's unique perspective on cosmic discovery, he is able to connect his own personal life story with that of astronomers of the past and by extension with the history of the whole universe. As the codiscoverer of the spectacular comet that crashed into Jupiter, Levy formulated a whole new range of exciting questions about the universe: Do comets serve to transport the elements of life from one planet to the next? What is the evidence that a large comet once hit the earth? Will the earth someday be in danger of colliding with another such comet and will we have the technology to stop it?
This fascinating book will excite any of us who have stared at the night sky in awe and amazement.
TO SAIL BEYOND
Portraits of Discovery
Come, my friends,
'Tis not too late to seek a newer world.
Push off, and sitting well in order smite
The sounding furrows; for my purpose holds
To sail beyond the sunset, and the baths
Of all the western stars, until I die.
It may be that the gulfs will wash us down;
It may be we shall touch the Happy Isles,
And see the great Achilles, whom we knew.
Tho' much is taken, much abides; and tho'
We are not now that strength which in old days
Moved earth and heaven; that which we are, we are;
One equal temper of heroic hearts,
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.
—Alfred, Lord Tennyson, Ulysses, 1842
There it was that I found and visited the famous Galileo, grown old, a prisoner to the Inquisition for thinking in Astronomy otherwise than the Franciscan and Dominican licensers of thought.
—John Milton,Areopagitica, 1644
The Shoemaker-Levy Double Cometograph is a complex name for a simple and beautiful instrument of discovery. It is the result of a dream that began one night as Gene and Carolyn Shoemaker and I were partaking in our comet and asteroid search program at Palomar Observatory, California. This program, which had resulted in the discoveries of many new worlds, including the great Comet Shoemaker-Levy 9 that extinguished its life in a spectacular collision with Jupiter, was about to end. Late in 1994, during one of our last observing sessions with that project, Gene and I were taking a photograph of the star fields, while Carolyn, one floor below, was scanning the films that we had taken earlier.
"We need to find a way for Carolyn to keep finding comets," Gene began as we marked time for a photographic exposure that would last eight minutes. By the end of the exposure, we had agreed on a plan for a new program using two wide-field telescopes known as Schmidt cameras. Gene called them cometographs, in honor of their intended purpose to record comets.
Within a year, our new two-camera program was already being tested. Like any search program, Gene was delighted that this new project was getting off the ground and producing consistent searches of the night sky for comets. In the years to come, the Shoemaker-Levy Double Cometograph project would continue to build on Gene's prescription: Cover as much sky as you can, keep good records and statistics, take advantage of breaks in the clouds, and never, never give up.
As I write this, Tennyson's adage of "To strive, to seek, to find, and not to yield" seems true in all except the "find" part. Though Gene is no longer with us, his hope and dream is very much alive in our program each evening as Carolyn, my wife, Wendee, and I begin our photographic search. Our films show regions of the sky, taken over and over again, but no new comets have been captured by them as yet. We have expanded the program recently with a wonderful new twelve-inch Schmidt camera from Meade Instruments Corporation. Also, we have joined forces with Carol Neese and Gil Esquedero of the Planetary Science Institute in Tucson to add an electronic component to our search. An electronic camera—a CCD, or charge-coupled-device—has been attached to one of our telescopes, and we hope that this novel technique will aid our search for comets in the near-Sun areas through which I have looked for so many years.
This book, however, is a direct result of the Shoemaker-Levy Cometograph program. Our search program involves taking two exposures of each field of sky each night. To accomplish this, we take a series of several photographs of different fields of sky. When the series is complete, we repeat it. The films are then prepared for scanning and finally they are placed into a device called a stereomicroscope.
A few months ago, I placed two films into the stereomicroscope and began searching them for comets. The two films were of an identical area of the sky, but were taken the previous evening about forty-five minutes apart. As the stars passed before my eyes, I felt myself taking my place in line with other men and women who had done the same thing, either with their own eyes, by watching through a telescope, looking carefully at pictures, or in modern times scanning an electronic image. It was at that moment that I got the idea to write this book.
Why do people search the sky? What's in it for them? And more important, what's in it for the rest of us? Of these questions, the answer to the last one is easiest. Were it not for those who, like Ulysses, sailed beyond the sunset, our knowledge and understanding of the universe would not be anywhere near where it is today. We might still be wandering the halls of ancient universities, proud of our ability to weave a perfect argument, and oblivious of whether that argument really explains how the universe works. We are indebted to the great discoverers of history, for they have forced us to look not at the universe as it seemed, but as their new findings show it to be.
There is no unique and simple answer to the question of why people search the sky. Here we will explore the discoveries and lives of some of the people who made them in an effort to shed light on this question. One of the most remarkable discoverers was Galileo Galilei. He spent the early part of his professional life doing experiments that included dropping objects of different weights from the Leaning Tower of Pisa, and creating the first liquid thermometer by showing that the density of a fluid varies inversely with its temperature. Had he done only these things, he would be remembered as one of a number of important scientists of the Renaissance. Until 1595, for example, he was one of many who accepted Ptolemy's view that the Earth was the center of the universe, despite Copernicus's alternate idea, that the Sun was the center, which had been proposed decades before. In that year, however, the thirty-one-year-old scientist determined that the Earth's rotation on its own axis, plus its revolution around the Sun, offered a better explanation of the tides than did Ptolemy's view.
Galileo's fertile mind, combined with a confluence of historical events, pushed him to go far beyond the tides. His great contribution arose from his building a telescope, looking through it, measuring with it, and thinking carefully about the results he obtained with it. The change came in 1609, when Galileo heard of the invention of a new device that could magnify distant objects. By 1610 Galileo had recognized the awesome potential of this "spyglass." Increasing its power, he turned it toward the sky, and discovered that Jupiter had four moons that clearly revolved about the giant planet. He knew that Jupiter's moons were strong evidence, but not proof, that the Earth was not the center of the universe. When Venus appeared in the sky later that year, he used his telescope to discover that it had phases that simply would not be seen in that way if Venus orbited Earth. Galileo could explain his own observations of the changing phases of Venus only if Venus orbited the Sun.
Two years later, Galileo developed a means of predicting the times when Jupiter's moons would pass behind Jupiter. Again, these predictions were accurate only when he took into account the changing position of his observing site on Earth as it orbited the Sun. Over a two-year period of observation, Galileo's telescope provided him with incontrovertible proof that the planets orbit the Sun, not the Earth. With the combination of telescope and mind, Galileo left humanity a new vision of the Earth's place, the first one in about two thousand years.
MILTON'S VISIT WITH GALILEO
Now we move forward from 1612 to 1638. Almost thirty years had passed since Galileo first lifted his telescope to the sky, and much had changed. In the spring of 1633 he had faced the Inquisition in Rome, and was forced to retract his statements about the Earth orbiting the Sun, even though they had been confirmed by his telescope. Now near seventy years of age and blind, he was sentenced to life imprisonment even though he had been led to believe that a far lighter sentence was in store. Galileo was so stunned by this harsh sentence that he nearly died. Subsequently the sentence was lightened; Galileo was forced to remain for the rest of his life in his villa in Florence, under guard by the Office of the Inquisition.
Five years later, a young English poet named John Milton was traveling through Switzerland and Italy. In September 1638 Milton visited Galileo. Milton's brief sentence about the visit, quoted at the start of this chapter, was written in his 1643 treatise Areopagitica: A Speech for the Liberty of Unlicensed Printing to the Parliament of England. Milton's treatise was political, but the poet was so moved by the strength of mind he perceived in the aged scientist in Florence that he never forgot that day. Twenty-three years after Galileo's death in 1642, John Milton completed his own great contribution to humanity, his epic poem Paradise Lost. In it he mentions Galileo twice, once even by name:
The broad circumference
Hung on his shoulders like the moon, whose orb
Through optic glass the Tuscan artist views
At evening, from the top of Fesolé,
Or in Valdarno, to descry new lands,
Rivers, or mountains, in her spotty globe.
In another example, Milton compares the lens of Galileo to the eye of the "Eternal Father," who sees everything clearly; Galileo is "less assured" as he uses his telescope to study the Moon:
... as when by night the glass
Of Galileo, less assured, observes
Imagined lands and regions in the Moon;
Or pilot from amidst the Cyclades Delos or Samos first appearing kens,
A cloudy spot.
Can it be said that the discoveries of a scientist were of such magnitude to stimulate the mind of one of the greatest English poets? Milton left his meeting with Galileo troubled that such a man would lie imprisoned in his home merely because of his ideas. That meeting is an important symbol of the compelling influence of science on literature, and of the great power of astronomical discovery that affects all of us. The nineteenth-century English writer Walter Savage Landor guessed at what their conversation might have entailed. "Let us talk of something else," Galileo says when Milton brings up the subject of torture at the hands of the Inquisition. To which Milton said angrily, "Italy, Italy, Italy! Drive thy poets into exile, into prison, into madness. Spare thy one philosopher! What track can the mind pursue, in her elevations or her plains or her recesses, without the dogging and prowling of the priesthood?"
THE MIND OF THE DISCOVERER
In one of his early books, The Exploration of Space, Arthur C. Clarke told the story of Pheidias, the sculptor who spent years creating the frieze on the Parthenon. Would someone have asked him, Clarke wrote, "why he was not engaged in something useful like rebuilding the Athenian slums[?] If he had kept his temper, the artist would probably have answered that he was doing the only job that interested him. So it is, in the ultimate analysis, with those who want to cross space." People who discover, I contend, do it because it is the one job that interests them, and they cross space without even leaving the Earth.
"You have to have the imagination," Clyde Tombaugh told me, "to recognize a discovery when you see one." As the discoverer of Pluto, the solar system's most distant major planet, Tombaugh was in a good position to know this. "When they examined Voyager images," he went on about the intrepid spacecraft traveling through the outer solar system, "and saw for the first time the volcanic eruptions on Io, that called for some intuitive imagination."
"I would suggest," Tombaugh continued, "that above everything else, in observing you have to be very alert to everything. You have to be able to recognize a discovery as such. There are so many people who don't seem to have that talent. A research astronomer cannot afford to be in such a rut. I might say that different types of personalities in astronomy make certain types of discoveries that are in line with their personalities."
For people like Galileo, who discovered the moons of Jupiter, and Clyde Tombaugh, who discovered Pluto, the type of thinking that shapes their younger years is likely to produce a person with the will to sail beyond the sunset. It is incorrect to say that such people are driven by others, but it is correct to say that they drive themselves. Neither Galileo nor Tombaugh set goals to discover worlds, but they both carefully monitored the goals they did set, and they both were aware of what could lie on the road to these goals. Take Tombaugh, a man I admired for many years. Despite the fact that I wrote his biography, it was not until long after that book was out of print and Tombaugh was gone that I finally got the chance to see some of the goals he had set for himself as a young man. The list which follows was found by his wife, Patsy, when she was going through his papers a few years after his death. It is a looking glass that gives us an insight into the determination of the man. Tombaugh began the list no earlier than 1921, when he was fifteen years old, and kept it, on a double-sided sheet of lined paper, for at least five years:
THINGS TO DO
|No.||Things to do—
|1.||Make a lantern slide box
June 21, 1925
|2.||Read Pilgrim's Progress||April, 1923||Cancelled
June 9, 1925
|3.||Study part 1 of Sanitation
Aug. 10, 1925
|4.||Work the problems about star
rising in the back of
|5.||Reread "Julius Caesar"||Feb. 1924||Cancelled
June 21, 1925
|*6.||Study Spanish||Sept. 1921||college|
|7.||Read "Revelations" of the
|*8.||Print astronomical notes||1920||—|
|9.||Buy Chemistry book and
September 10, 1925
|10.||Reread "Story of the
June 21, 1925.
|11.||Measure height of east hill
from lower dam by the
June 21, 1925
|12.||Finish reading Psalms||Dec. 9, 1923||Completed
|13.||Reread my Ancient History||Sept. 1924||Canceled
June 14, 1925
|14.||Find Pickering's Station in
|15.||Make a glass vacuum tank||Oct. 1924||Canceled
May 11, 1925
|16.||Finish football field||April 1924
on July 24, 1926.
|18.||Read a Kansas History||Jan. 1925||Half read,
done with it
June 12, 192?
|*19.||Paint and draw pictures||1922|
|20.||Compare areas and volumes
|21.||Make transit instrument||March 1924||Cancelled and
Jan. 6, 1926
|22.||Make opera glass attachment
September 30, 192?
|23.||Make photographic plate
Feb. 14, 1926
|24.||Study Dad's "Zoology"||Jan. 1925||Canceled
June 14, 1925
|25.||Study Dad's "Physics"||Jan. 1925||Completed
Aug. 23, 1925
|26.||Study Dad's Chemistry||Jan. 1925||Cancelled (college)|
|27.||Make a toy steam turbine
March 26, 1926
|28.||Make a Leyden jar||Jan. 1925||Canceled
May 11, 1925
|29.||Make a static electrical
May 11, 1925
|30.||Make a water decomposing
March 26, 192?
|31.||Buy and fit a prism attachment
August 11, 1925.
|32.||Make a 10 [crossed out] 8"
|33.||Take a trip to Illinois
Dec. 28, 1925.
|34.||Take a trip to Flagstaff Arizona
to look thru the big telescope.
|35.||Finish reading "Ecclesiastes"
||Feb. 16, 1925||Completed
March 12, 1925
|36.||Study solid geometry
||Feb. 16, 1925||College|
|37.||Finish Plane geometry notebook||Dec. 1924||Cancelled|
|38.||Buy Mary E. Byrd's
"Laboratory Manual of
Astronomy" R. 9,
Box 77, Lawrence, Kans.
|March 5, 1925|
|39.||Finish Studying Phy. Geo.
|May 20, 1925||Completed
July 4, 1925
|May 20, 1925||Completed
June 14, 1925
|41.||Finish Studying Com. Law||June 9, 1925|
|42.||Study lunar craters in
"Astronomy with an opera
|June 21, 1925|
|43.||Fix generator and make use
|June 28, 1925|
|44.||Put up roof-cooling apparatus||June 28, 1925||Cancelled,
March 27, 1926
|45.||Compose a song of
to the tune of "America
|Oct. 20, 1925||Completed
Jan. 6, 1926
|46.||Buy accordion and learn to
|Dec. 26, 1925|
Clyde Tombaugh was an extremely focused man. I was delighted with this list, which says so much about Tombaugh's interests as a youth, but I wasn't surprised by it. We will read more about both Galileo and Tombaugh in later chapters. Our purpose here is to open the subject of what kind of person tends to become a discoverer. For more than twenty years after his discoveries of 1610, Galileo wrote, studied, and tried to ensure that the public understood the significance of what he had found. In that he succeeded beyond measure, but at a tremendous personal cost. No discoverer in astronomy approached the seriousness of the consequences of Galileo's findings with his telescope. In Tombaugh's case, although the discovery of Pluto opened opportunities for him, it also aroused jealousies that caused him problems in later years.
Both Galileo and Tombaugh, however, focused their lives in unusual ways. In Clyde Tombaugh's table, for example, lay the essence of the mind of a discoverer. Although he completed just over a quarter of the projects he started, even the completed ones show an unusually eclectic range of interests; less than a quarter of the projects are astronomy-related. The management of the projects themselves, and the maintenance of the list, seemed to be of intense interest to him as well. Each project was considered, planned, and either carried to fruition or canceled. The original sheet of paper must have been in active use for several years before Tombaugh stored it away. During the seventeen years I knew him, neither he nor Patsy ever mentioned it, and Patsy was very surprised to find it in 1999. As I went through the list, I tried to anticipate which items he cancelled (no. 24: Study Dad's Geology was one), and which he completed (no. 25: Study Dad's Physics).
Two of the items on this list have made their way into history. No. 32, which began as a ten-inch-diameter and ended up as an eight-inch reflecting telescope, was completed four years later, despite the missing date, but its quality was poor. Tombaugh followed this telescope by building a nine-inch reflector of superb optical quality. Two items later, No. 34, called for a trip to Flagstaff to "look thru the big telescope." Again, no completion date was recorded. Tombaugh sent several samples of drawings he had made using the nine-inch telescope, it turned out, to the director of the Lowell Observatory in Flagstaff, a mailing that began a chain of events that resulted in his heading for Flagstaff in 1928.
In a real sense, item No. 34 should have been marked "Completed" on February 20, 1930. On that evening, he and two members of the observatory's senior staff walked up to the dome for the twenty-four-inch refractor, took the covers off the old tube and looked "thru the big telescope." At the other end was the planet, later to be named Pluto, that Tombaugh had discovered two days before on February 18, 1930.
Excerpted from COSMIC DISCOVERIES by David H. Levy with Wendee Wallach-Levy. Copyright © 2001 by David H. Levy. Excerpted by permission. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
|Preface: Year 2000: An Ancient Comet Returns||13|
|1||1842: To Sail beyond the Sunset: Portraits of Discovery||17|
|2||1965: Passport for Discovery||26|
|3||1572: Tycho Brahe: A Swashbuckling Astronomer||37|
|4||1610: Galileo and the Interpretation of Discovery||47|
|5||1632: Galileo and the Consequence of Discovery||55|
|6||1656: Christiaan Huygens: It Is Surrounded by a Ring||63|
|7||1682: Edmond Halley: Discovery by Calculation||70|
|8||1760: Charles Messier: The Comet Hunter of Cluny||76|
|9||1781: Caroline and William Herschel||84|
|10||1846: Adams, Leverrier, and the Scandal over Neptune||94|
|11||1912: Henrietta Leavitt, Harlow Shapley, and Our Place in the Milky Way Galaxy||102|
|12||1919: Eddington, Einstein, Mercury, and an Eclipse||109|
|13||1924: Edwin Hubble: The Man Who Defined the Universe||118|
|14||1930: Clyde Tombaugh and Pluto||130|
|15||1948: Bart Bok and His Globules||142|
|16||1951: The Milky Way Is a Spiral Galaxy||151|
|17||1963: Seyfert Galaxies and Quasars||156|
|18||1979: Using a Galaxy as a Telescope: Gravitational Lenses and Einstein Rings||162|
|19||1993: Comet Shoemaker-Levy 9: Do Not Go Gentle into that Good Night||167|
|20||1999: Finding Planets around Other Stars||175|
|21||1971: Acquainted with the Night: O'Meara and Summerfield||187|
|22||1988: Jean Mueller: Of Supernovae and Songs||194|
|23||2001: To Discover an Idea: The Cosmic Vision of Arthur C. Clarke||200|