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  They found that it did not work—for instance, Aristotle's theory could not account for the changes in brightness of the planets over time, changes that Ptolemy understood to be due to the fact that each planet is not always at the same distance from Earth. Because of the prestige of Aristotle's philosophy, some philosophers and physicians (but few working astronomers) continued through the ancient world and the Middle Ages to adhere to his theory of the solar system, but by the time of Galileo it was no longer taken seriously. When Galileo wrote his Dialogue Concerning the Two Chief Systems of the World, the two systems that Galileo considered were those of Ptolemy and Copernicus, not Aristotle's.

  There was one more reason that the usefulness of astronomy was important to the advance of science: it promoted government support of scientific research. The first great example was the Museum of Alexandria, established by the Greek kings of Egypt early in the Hellenistic era, around 300 BC. This was not a museum in the modern sense, a place where visitors can come to look at fossils and pictures, but a research institution, devoted to the Muses, including Urania, the muse of astronomy. The kings of Egypt supported studies in Alexandria, probably at the museum, of the construction of catapults and other artillery and of the flights of projectiles, but the museum also provided salaries to Aristarchus, who measured the distances and sizes of the sun and moon, and to Eratosthenes, who measured the circumference of Earth.

  The museum was the first of a succession of government-supported centers of research, including the House of Wisdom, established around 830 AD by the caliph al-Mamun in Baghdad, and Tycho Brahe's observatory Uraniborg, on an island given to Brahe by the Danish king Frederick II in 1576. The tradition of government-supported research continues in our day, at particle physics laboratories like CERN and Fermilab and on unmanned observatories like Hubble and WMAP and Planck, put into space by NASA and the European Space Agency.

  In fact, in the past astronomy benefited from an overestimate of its usefulness. The legacies of the Babylonians to the Hellenistic world included not only a large body of accurate astronomical observations (and perhaps the gnomon) but also the pseudoscience of astrology. Ptolemy was the author not only of a great astronomical treatise, the Almagest, but also of a book on astrology, the Tetrabiblos. Much of the royal support for compiling tables of astronomical data in the medieval and early modern periods was motivated by the use of these tables by astrologers. This appears to contradict what I said about the importance in applications of getting the science right, but the astrologers did generally get the astronomy right, at least as to the apparent motions of the planets and stars, and they could hide their failure to account for human affairs in the obscurity of their predictions.

  Not everyone has been enthusiastic about the utilitarian side of astronomy. In Plato's Republic there is a discussion of the education to be provided for future philosopher kings. Socrates suggests that astronomy ought to be included, and his stooge Glaucon hastily agrees, because "it's not only farmers and others who need to be sensitive to the seasons, months, and phases of the year; it's just as important for military commanders as well." Poor Glaucon—Socrates calls him naive and explains that the real reason to study astronomy is that it forces the mind to look upward and think of things that are nobler than our everyday world.

  Although surprises are always possible, my own main research area, elementary particle physics, has no direct applications that anyone can foresee,5 so it gives me little joy to note the importance of utility to the historical development of science. By now pure sciences like particle physics have developed standards of verification that make applications unnecessary in keeping us honest (or so we like to think), and their intellectual excitement incites the efforts of scientists without any thought of practical use. But research in pure science still has to compete for government support with more immediately useful sciences, like chemistry and biology.

  Unfortunately for the ability of astronomy to compete for support, the uses of astronomy that I have discussed so far have largely become obsolete. We now use atomic clocks to tell time so accurately that we can measure tiny changes in the length of the day and year. We can look up today's date on our watches or computer screens. And recently the stars have even lost their importance for navigation.

  In 2005 I was on the bark Sea Cloud, cruising the Aegean Sea. One evening I fell into a discussion about navigation with the ship's captain. He showed me how to use a sextant and chronometer to find positions at sea. Measuring the angle between the horizon and the position of a given star with the sextant at a known chronometer time tells you that your ship must lie somewhere on a particular curve on the map of Earth. Doing the same with another star gives another curve, and where they intersect, there is your position. Doing the same with a third star and finding that the third curve intersects the first two at the same point tells you that you have not made a mistake. After demonstrating all this, my friend the captain of the Sea Cloud complained that the young officers coming into the merchant marine could no longer find their position with chronometer and sextant. The advent of global positioning satellites had made celestial navigation unnecessary.

  One use remains to astronomy: it continues to have a crucial part in our discovery of the laws of nature. As I mentioned, it was the problem of the motion of the planets that led Newton to the discovery of his laws of motion and gravitation. The fact that atoms emit and absorb light at only certain wavelengths, which in the twentieth century led to the development of quantum mechanics, was discovered in the early nineteenth century in observations of the spectrum of the sun. Later in the nineteenth century these solar observations revealed the existence of new elements, such as helium, that were previously unknown on Earth. Early in the twentieth century, Einstein's General Theory of Relativity was tested astronomically, at first by comparison of his theory's predictions with the observed motion of the planet Mercury and then through the successful prediction of the deflection of starlight by the gravitational field of the sun.

  After the confirmation of General Relativity, for a while the source of the data that inspired progress in fundamental physics switched away from astronomy, first toward atomic physics and then in the 1930s toward nuclear and particle physics. But progress in particle physics has slowed since the formulation of the Standard Model of elementary particles in the 1960s and 1970s, which accounted for all the data about elementary particles that was then available. The only things discovered in recent years in particle physics that go beyond the Standard Model are the tiny masses of the various kinds of neutrinos, and these first showed up in a sort of astronomy, the search for neutrinos from the sun.

  Meanwhile, we are now in what it has become trite to call a golden age of cosmology. Astronomical observation and cosmological theory have invigorated each other, to the point that we can now say with a straight face that the universe in its present phase of expansion is 13.73 billion years old, give or take 0.16 billion years. This work has revealed that only about 4.5 percent of the energy of the universe is in the form of ordinary matter—electrons and atomic nuclei. Some 23 percent of the total energy is in the masses of particles of "dark matter," particles that do not interact with ordinary matter or radiation, and whose existence is so far known only through observations of effects of the gravitational forces they exert on ordinary matter and light. The greatest part of the energy budget of the universe, about 72 percent, is a "dark energy" that does not reside in the masses of any sort of particle but in space itself, and that is causing the present expansion of the universe to accelerate. The explanation of dark energy is now the deepest problem facing elementary particle physics.

  Exciting as all this is, both astronomy and particle physics have increasingly had to struggle for government support. In 1993 Congress canceled a program to build an accelerator, the Superconducting Super Collider, that would have greatly extended the range of masses of new particles that might be created, perhaps including the particles of dark matter. The European c
onsortium CERN has picked up this task, but its new accelerator, the Large Hadron Collider, will be able to explore only about a third of the range of masses that could have been reached by the Super Collider, and support for the next accelerator after the Large Hadron Collider seems increasingly in doubt. In astronomy NASA has cut back on the Beyond Einstein and Explorer programs, major programs of astronomical research of the sort that has made possible the great progress of recent years in cosmology.

  Of course, there are many worthy calls on government funds. What particularly galls many scientists is the existence of a vastly expensive NASA program that often masquerades as science.6 I refer, of course, to the manned space flight program. In 2004 President Bush announced a "new vision" for NASA, a return of astro nauts to the moon followed by a manned mission to Mars. A few days later the NASA Office of Space Science announced cuts in its unmanned Beyond Einstein and Explorer programs, with the explanation that they did not support the president's new vision.

  Astronauts are not effective in scientific research. For the cost of taking astronauts safely to the moon or planets and bringing them back, one could send many hundreds of robots that could do far more in the way of exploration. Astronauts in orbiting astronomical observatories would create vibrations and radiate heat, which would foul up sensitive astronomical observations. All of the satellites like Hubble or COBE or WMAP or Planck that have made possible the recent progress in cosmology have been unmanned. No important science has been done at the manned International Space Station, and it is hard to imagine any significant future work that could not be done more cheaply on unmanned facilities.

  It is often said that manned space flight is necessary for science because without it the public would not support any space programs,7 including unmanned missions like Hubble and WMAP that do real science. I doubt this. I think that there is an intrinsic excitement to astronomy in general and cosmology in particular, quite apart from the spectator sport of manned space flight. As illustration, I will close with a verse of Claudius Ptolemy:

  I know that I am mortal and the creature of a day; but when I search out the massed wheeling circles of the stars, my feet no longer touch the Earth, but, side by side with Zeus himself, I take my fill of ambrosia, the food of the gods.

  Notes

  1. This article is based on a talk given on September 25, 2009, at the Harry Ransom Center for Humanistic Studies of the University of Texas at Austin, to commemorate its exhibition "Other Worlds: Rare Astronomical Works," on view September 8, 2009-January 3, 2010.

  2. Of course the stars are not visible during the day, but some of them can be seen just after sunset, when the sun's position in the sky is still known.

  3. A gnomon is different from a sundial because the pole that casts a shadow on a sundial is not vertical but set at an angle chosen so that the pole's shadow follows about the same path during each day of the year. This makes the sundial more useful as a clock but less useful as a calendar.

  4. It may be wondered why Calypso did not tell Odysseus to keep the North Star on his left. The reason is that in Homer's time the star Polaris, which is now the North Star, was not at the North Pole of the sky. This is not because of any motion of Polaris itself but because of a phenomenon known as the precession of the equinoxes, discovered by Hipparchus. In modern terms, the axis of Earth's rotation does not keep a fixed direction in the sky, but precesses like the axis of a spinning top, making a full circle every 25,727 years. It is a measure of the accuracy of Greek astronomy that the data of Hipparchus indicated a period of 28,000 years.

  5. I say "direct" applications because experimental and theoretical work in particle physics that pushes technology and mathematics to their current limits occasionally spins off new technology or mathematics of great practical importance. One celebrated example is the World Wide Web. This can provide a valid argument for government support, but it is not why we do the research.

  6. I have written about this at greater length in "The Wrong Stuff," New York Review of Books, April 8, 2004.

  7. This opinion was most recently expressed by Giovanni Bignami, the head of the European Space Agency's Science Advisory Committee, in "Why We Need Space Travel," Nature, July 16, 2009.

  TIMOTHY FERRIS Cosmic Vision

  FROM National Geographic

  WHEN YOU START STARGAZING with a telescope, two experiences typically ensue. First, you are astonished by the view—Saturn's golden rings, star clusters glittering like jewelry on black velvet, galaxies aglow with gentle starlight older than the human species—and by the realization that we and our world are part of this gigantic system. Second, you soon want a bigger telescope.

  Galileo, who first trained a telescope on the night sky four hundred years ago this fall, pioneered this two-step program. First, he marveled at what he could see. Galileo's telescope revealed so many previously invisible stars that when he tried to map all of those in just one constellation, Orion, he gave up, confessing that he was "overwhelmed by the vast quantity of stars." He saw mountains on the moon—in contradiction of the prevailing orthodoxy, which declared that all celestial objects were made of an unearthly "ether." He charted four bright satellites as they bustled around Jupiter like planets in a miniature solar system, something that critics of the Copernican sun-centered cosmology had dismissed as physically impossible. Evidently Earth was a small part of a big universe, not a big part of a small one.

  And soon, sure enough, Galileo went to work making bigger and better telescopes. Large light-gathering lenses were not yet available, so he concentrated on making longer telescopes, which produced higher magnifying powers and reduced the halos of spurious colors that afflicted glass lenses in those days. Subsequent observers took the design of glass-lensed, refracting telescopes to great lengths, sometimes literally so. In Danzig, Johannes Hevelius deployed a telescope 150 feet long; hung by ropes from a pole, it undulated in the slightest breeze. In the Netherlands, the Huygens brothers unveiled lanky telescopes that had no tubes at all: the objective lens was perched on a high platform in a field, while an observer up to 200 feet away aligned a magnifying eyepiece and peered through it. Such instruments proffered fleeting glimpses of planets and stars, which, like the dance of the seven veils, only aroused a burning desire to see more.

  The reflecting telescope, pioneered by Isaac Newton, made it practical to gratify such desires: mirrors required that only one surface be ground to gather and reflect starlight to a focal point, and since the mirror was supported from behind, it could be quite large without sagging under its own weight, as large lenses tended to do. William Herschel discovered the planet Uranus with a handmade reflecting telescope—he cast his metal mirrors in his garden and basement and once had to flee from a coursing river of molten metal after the horse-dung mold fractured. Spiral-armed galaxies were first glimpsed through a massive reflecting telescope with a six-foot-diameter primary mirror that Lord Rosse constructed on his estate in Ireland.

  Today's largest telescopes have mirrors up to some 10 meters (33 feet) in diameter, with quadruple the light-gathering power of the legendary 5-meter Hale Telescope at Palomar Observatory in southern California. Looming as large as office buildings, some of these giants are so highly automated that they can dust off their optics at sundown, open the dome, sequence and carry out observations throughout the night, and shut down come threatening weather, all with little or no human intervention. Yet humans, being human, still intervene a lot, if only to make sure nothing goes awry: to lose just one night's work at a big telescope these days is to squander as much as $100,000 in operating costs.

  Three of today's largest telescopes—Gemini North, Subaru, and Keck—stand within hailing distance of one another atop the nearly 14,000-foot peak of Hawaii's Mauna Kea, an inactive volcano. The altitude puts them above 40 percent of Earth's atmosphere—and most of its water vapor, which is opaque to the infrared wavelengths the astronomers like to study—but also makes it difficult for the astronomers and engineers who work th
ere to breathe and think. Many wear clear plastic oxygen tubes in their nostrils as routinely as we might wear eyeglasses. Others rely on the body's ability to adapt but worry about making what they call a CLM, or "career-limiting mistake." "At altitude, we don't improvise; that would be a disaster," says the Gemini astronomer Scott Fisher. "We're kind of trained monkeys up here. The real thinking goes on at sea level."

  These big Mauna Kea observatories are similarly smart and costly, yet each exudes a distinct personality. The 8.1-meter Gemini telescope is housed in an onion-shaped silver dome ringed by a set of shutters that, when closed during the day, make the observatory look as ungainly as a fat man in an inner tube. But the shutters open at dusk to create an enormous set of windows, three stories tall and stretching nearly three-quarters of the way around the observatory, that let in the night air and happen to afford a panorama of the blue Pacific all the way to Maui and beyond. Gemini's four main digital detectors—cameras and spectrometers, as heavy as cars and costing around $5 million each—are attached to a carousel surrounding the telescope's focal point, where they can be rotated into place in minutes. Computers run the telescope by night, shuffling requested observations to make the most of every minute. "We're all about nighttime efficiency," says Fisher.

  The Subaru telescope's instruments are housed in alcoves like jeroboams of champagne in a heavenly wine cellar. (The comparison is not entirely fanciful; one leading Japanese astronomer propitiates the gods at the start of each Subaru observing run by pouring vintage sake on the ground outside the dome at the four points of the compass.) When a particular instrument is required, a robotic yellow trolley makes its way to the alcove, picks up the detector, ferries it to the bottom of the massive telescope, and locks it in place, attaching the data cables and the plumbing for the detector's refrigeration system. Subaru happens to be one of the few giant telescopes that anybody has ever actually looked through. For its inauguration in 1999, an eyepiece was attached so that Princess Sayako of Japan could have a look through the scope, and for several nights thereafter eager Subaru staffers did the same. "Everything you can see in the Hubble Space Telescope photos—the colors, the knots in the clouds—I could see with my own eyes, in stunning Technicolor," one recalled.