In the Museum: Centuries of Upward Gazes
In the Museum: Centuries of Upward Gazes
IN A DELIBERATELY DARK CORNER of the National Air and Space Museum's new exhibit, "Explore the Universe," a long black wooden tube sits positioned near the wall at a 45-degree angle from the floor. A man standing on a ladder peers into the top of the tube, which is mounted in a black wooden scaffold-like framework. Behind it is a dim, life-size painting of an English country cottage. In one of the windows, a woman sits writing by candlelight. Above the house, thousands of stars, illuminated from above by ceiling-mounted black lights, dot the sky.
This life-size diorama depicts a night in the life of William Herschel, a 17th-century astronomer who discovered and catalogued thousands of nebulae and star clusters, leading him to be the first to theorize that other galaxies exist beyond our Milky Way. It is just one of the scenes and scores of artifacts presented in this new permanent exhibit, which opened September 21, that paints a portrait of centuries of astronomical speculation, discovery, and advancement. Herschel's 20-foot, mahogany-tubed reflector and its 100-pound, 18.5 inch-diameter speculum mirror are both on special loan from England's National Maritime Museum. (The woman in the window? His sister, who's helping him make notes on his observations.)
"Explore the Universe" walks visitors through 400 hundred years of astronomy, illustrating how the march of technology has gradually and continually expanded our knowledge of the universe. "As our tools for observing the universe changed, our universe changed," says exhibit curator David DeVorkin. "Things started making more and more sense, but the number of questions we had also grew as we learned more."
The journey begins with a tour of astronomical instruments used to develop initial understandings of the movement of celestial objects. Islamic astrolabes and a replica of the armillary sphere and portable mural quadrant—tools painstakingly developed to calculate star and planet positions based on the date and time of day—used by Danish astronomer Tycho Brahe are coupled with three-dimensional models that show early Earth-centric notions of the universe, with the Sun floating in orbit somewhere amid Jupiter, Saturn, Mars, and Venus. The Copernican model, created by 16th century astronomer Nicolaus Copernicus, correctly placed the sun at the center of the solar system and the earth rotating on its axis, DeVorkin explains. "It took years for this to take hold, of course," he says, "so we present artifacts that depict the transition from a tentative Copernican model to a solid Copernican model."
But even with that transition, the presence of thousands of stars that were dimmer than the planets and a variety of faint patches of light stumped astronomers. But Herschel's work helped clarify the relationships—that the stars were outside of our solar system and the Sun was one of many in a neighborhood later called a galaxy. "But he was never able to positively identify the fuzzy patches as galaxies beyond our own or nebulas, the exploded remains of dead stars," says DeVorkin. "That would take better telescopes than Herschel's, and years more of study."
Around the corner from Herschel's majestic telescope is a scene representing the next quantum leap in telescope design, the Mount Wilson 100-inch observatory, shown in this exhibit with a simulated dome and the top portion of the famed telescope. Edwin Hubble sits at the eyepiece as he did in the 1920s and 1930s, when he postulated that galaxies exist are moving away from one another. This suggested to him that the universe is composed of galaxies, not stars, and is expanding.
With the Mount Wilson telescope, DeVorkin and his associates at the museum introduce photography as a critical development in astronomical study. A blink comparator, a device that allows astronomers to study stellar changes by comparing photographic images taken at different times, is a magnificent piece of technology that DeVorkin was thrilled to find. "I used one of these myself as a student," he said. "And being able to retrieve this brought back memories of an exciting time for me." Using M51, the Whirlpool galaxy near the Big Dipper, as a cornerstone for comparison, the exhibit designers proceed to walk visitors through this century's numerous rapid advances, including spectroscopic study of stellar and galactic images, which help determine stars' compositions and galaxy's movements away or toward our own—here, visitors are able to do their own comparisons of spectroscopic images—and the digital revolution, which enabled astronomers to vastly expand their knowledge.
In this final major component of the exhibit—which is introduced with a enormous three-dimensional art work that playfully integrates popular UFO mythology with a drive-in theater theme—are displays showing the many ways information is gathered with computer technology. Sensors are placed deep in mines (to gather neutrinos, ghostly particles from the Sun that pass straight through the Earth), aboard instruments floated under balloons to the upper reaches of the atmosphere, behind terrestrial telescopes, and, of course, from space. Such artifacts as the Hubble Space Telescope back-up mirror—which, incidentally, did not have the same problems as the one actually launched—and parts of the Chandra X-ray Astronomy Observatory, the Hopkins Ultraviolet Telescope, the Smithsonian Astrophysical Observatory's Z-machine, and the twin Keck Observatory interferometer are all on display to demonstrate how scientists have in the last few decades divined the large scale structure of the universe and its evolution.
And as our observational capabilities expand, DeVorkin says, so does our ability to predict what types of instruments we'll need in the future. "The majority of the Universe that we're in is something we can't see yet," he explains. "The dark universe—the matter that is not visible but which might be critical to the mechanics of the universe—is our next great unknown, and that's one of the places our next generation of instruments will be going." Thus, the final component of the exhibit is a section devoted to up-to-the-minute discoveries, as posted on a variety of continually updated bulletin boards. "I really think this is going to be a fun exhibit to maintain over the years," DeVorkin says.