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DIRECTIONS: Reаd the pаssаge and answer the questiоns.Cоsmic VisiоnA History of TelescopesA 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.B Galileo, who first trained a telescope on the night sky 400 years ago, 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 them 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. He charted four bright satellites as they revolved around Jupiter like planets in a miniature solar system, something that critics of the sun-centered cosmology had dismissed as physically impossible. Evidently the Earth was a small part of a big universe, not a big part of a small one.C 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. Subsequent observers took the design of glass-lensed, refracting telescopes to great lengths. In Danzig, Johannes Hevelius deployed a telescope 150 feet long; hung by ropes from a pole, it swayed 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 offered fleeting glimpses of planets and stars that only aroused a burning desire to see more.D 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. The GiantsE Some of the largest telescopes have mirrors up to some ten meters (33 feet) in diameter, with quadruple the light-gathering power of the legendary five-meter Hale Telescope at Palomar Observatory in southern California. Looming large as office buildings, some of these giants are so highly automated that they can dust off their optics at sundown, open the dome, carry out observations throughout the night, and shut down if threatening weather arrives, all with little or no human intervention. F 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 hinders infrared wavelengths— that astronomers like to study—from passing through.GeminiG The 8.1-meter Gemini telescope is housed in an onion-shaped silver dome ringed by a set of shutters. 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 panorama1 of the blue Pacific all the way to Maui and beyond. Gemini’s four main digital detectors—cameras and spectrometers, heavy as cars and costing around five million dollars 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. SubaruH The Subaru telescope’s instruments are housed in alcoves. 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.KeckI Keck consists of two identical telescopes. Both have ten-meter mirrors made of 36 segments; with its support structure, each segment weighs close to a thousand pounds, costs close to a million dollars, and would suffice to create a fine, university-grade telescope on its own. The telescopes’ “tubes” are thin steel skeletons that look as delicate as spiders’ webs but are very precisely configured. “We use the telescope’s mission to motivate ourselves,” one Keck astronomer told me. “If a little wire or something is found intruding into the optical path, we think, “If the light has been traveling through space for 90 percent of the history of the universe, and it got this close to the telescope, we’d better make sure it gets the rest of the way.”Telescopes of the FutureJ What’s next? Even bigger telescopes, of course, with the capability to shoot cosmic pictures faster, wider, and in even greater detail. Among the behemoths2 due to come on line within a decade are the Giant Magellan Telescope, the Thirty Meter Telescope, and the 42-meter European Extremely Large Telescope.K Particularly innovative is the Large Synoptic Survey Telescope, or LSST, whose 8.4-meter primary mirror was cast last August in a spinning furnace under the stands of the University of Arizona Wildcats’ football stadium in Tucson. Conventional telescopes have narrow fields of view, typically spanning no more than half a degree on a side—much too narrow to take in the enormous patterns that grew out of the big bang. The LSST will have a field of view covering ten square degrees, the area of 50 full moons. From its site in the Chilean Andes, it will be able to image galaxies far across the universe in exposures of just 15 seconds each, capturing fleeting events to distances of over ten billion light-years, 70 percent of the way across the observable universe. “Since we’ll have a big field of view, we can take a whole lot of short exposures and—bang, bang, bang, bang—cover the entire visible sky every several nights, and then repeat,” says LSST Director Tony Tyson. “If you keep doing that for ten years, you have a movie—the first movie of the universe.”L Tomorrow’s enormous telescopes will do as much in one night as today’s do in a year, but that will not necessarily render the older telescopes obsolete. When the giants come on line, says Gemini astronomer Scott Fisher, “the Geminis of today will become the telescopes that get to go out and do the surveys,” finding interesting phenomena for the largest scopes to investigate in detail. “It’s like a pyramid, and it feeds both ways: When a really big telescope finds something exciting that we can’t spend every night observing, the astronomers can apply for time on a smaller telescope to, say, check it out every clear night for a year and see how it changes over time.”1 A panorama is a view in which you can see a long way over a wide area of land.2 A behemoth is something that is very huge and/or powerful.Source: Adapted from “Cosmic Vision,” by Timothy Ferris: NGM July 2009 Choose the best answer.In the time of Galileo, why did people make such long telescopes?
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