Theater Of The Stars

Natural History, Feb, 2000 by James B. Sweitzer

Planetariums have come a long way in the past 300 years.

Within the globe of the new Hayden Planetarium, advanced projectors are fed by some of the most powerful computers ever used to advance the public understanding of science. This cutting-edge technology makes it easy to forget that the planetarium descends from a lineage that is more than 300 years old.

In the mid-1600s, Adam Olearius, court mathematician and librarian to the duke of Holstein-Schleswig-Gottorp, designed a hollow, ten-foot-diameter, water-powered rotating sphere into which people could climb to see gilded constellations illuminated by centrally placed oil lamps. At best, the Gottorp globe was a crude depiction of the celestial sphere, but it could not adequately represent the planets of our Solar System.

For that, one would have to wait for the mechanical tabletop orreries of the eighteenth century. Orreries were simulation devices based on one of the most advanced technologies of the time, that of the gear-driven clock. They allowed students of astronomy to move miniature planets round and round a small brass ball that represented the Sun. The orrery was ideal for displaying the Copernican model of the planets in our Solar System, but, like the Gottorp globe, it failed to provide an integrated view of the universe.

The next leap did not come until the 1920s, when the firm of Carl Zeiss in Jena, Germany, invented an electro-optical projector that cast images of the stars, Sun, Moon, and planets onto a large hemispheric screen. The positions and motions of these celestial bodies could be realistically recreated from any perspective on Earth and for any date up to 26,000 years in the past or the future.

From the time it opened in 1935, the old Hayden Plan-the electro-optical planetarium was, however, its perspective remained geocentric. To offset this limitation, the Hayden installed a large overhead orrery (with a lightbulb as the Sun and motorized planets circling around it on electrified orbit rails) that operated until the early 1980s in a gallery below the Sky Theater.

But even the best mechanically driven projectors and orreries are incapable of depicting the universe as we now understand it. Astrophysicists of the twentieth century demonstrated that far from living in the center of a gently rotating, unvarying clockwork world, we humans inhabit instead an expanding, constantly evolving universe. The stars and galaxies are organized in hundred-million-light-year structures that extend as far as telescopes can see. To represent this universe, new technologies and devices are required, and the data fed into them must be constantly updated. This is precisely what happens in the new Hayden Planetarium.

With two projection systems, the new Space Theater simulates a vehicle that can fly to any place in the universe. The most modern star and planet projector in existence--a Zeiss Mark IX, special Hayden edition--depicts the night sky as seen from Earth. Nine thousand stars are projected fiber-optically, which lends them a new sharpness and subtle distinctions of color. The Sun, Moon, and planets course through the sky, steered by special computers, and the sky can be displayed not just from Earth but from any planet in the Solar System.

For deep space travel, the task falls to the digital-dome simulator, a one-of-a-kind system integrated by SEOS Trimension of Great Britain. Seven powerful video projectors blend together to display on the huge dome a single image of more than 7.2 million pixels. Fed by a Silicon GraphicsOnyx 2 Infinite-Reality Engine computer, the system is similar to those used by the film industry for special effects. But the Space Theater's effects are based on data from NASA and the European Space Agency, as well as on supercomputer models of the universe. The result is a digital model of the galaxy, featuring billions of stars.

In the Space Theater's signature program, the audience will take a grand tour from Earth into deep space. Voyaging through the Milky Way, they will stop off at a fantastic nebular region. Shifting to a higher speed, they will--in one continuous movement--take a turn, head out the southern side of the disk of the galaxy, fly past Earth's nearest extra-galactic neighbors, and then hurtle a billion light-years from home, journeying trillions of times farther than NASA's most remote space probe.

The new planetarium also treats an aspect of cosmic history that was all but unknown in the 1930s. The Big Bang Theater, located in the bottom of the planetarium orb, is, in effect, a giant time machine. As though suspended over the abyss of the early universe, visitors will stand on a doughnut-shaped glass floor lying over a deep, wide projection screen. A high-powered laser beam and dozens of other computer-controlled lights will immerse viewers in an accurate re-creation of the most important epoch of the early cosmos.

Unique in the universe of planetariums, the new Hayden, with its capacity to accurately simulate the universe in extraordinary three-dimensional detail, will launch visitors on one-of-a-kind expeditions into deep space and time.