Gazing up at the sky on a clear, dark night, you can readily convince yourself that the stars are tantalizingly close—close enough, if not to touch, then at least to visit with a spacecraft. A small dose of astronomy, however, quickly dispels the hope of interstellar travel: the stars are impossibly distant, separated by trillions of miles, and the distances we humans have traveled vanishingly small. With that in mind, you could be forgiven for revising your first reaction to the night sky and becoming convinced that any journeys our species makes to the stars will take place only in our imaginations.
But imagination thrives on ideas. Stirring people’s imaginations with an accurate and dynamic representation of our place in the universe is well worth engaging the best minds and methods. After all, the first maps of the New World, and the first reasonably accurate globes of Earth, created a powerful sense of wonder, widening our perspective of humanity’s place in the world.
Similar flat maps and globes, as elaborately decorated as fantasy could inspire, have for centuries portrayed the stars and constellations of the night sky. But unlike a globe of the Earth, a celestial globe has little practical use today. No one believes anymore, as scholars did in the Middle Ages, that the stars are lights on a uniformly distant sphere. Tracing a path from star to star on such a surface, as if it were the outline of a constellation, reveals next to nothing about the shifting perspective that a true stellar voyager might experience, or what our Sun might look like from another star. No flat map, no globe painted with stars, can accurately render the true three-dimensional spatial relations among the objects scattered across the sky. No flat map, no globe painted with stars, can accurately render the true three-dimensional spatial relations among the objects scattered across the sky.
Imagine that you could travel to the Big Dipper in a faster-than-light spaceship that could take you there in less than a minute. At the beginning of your journey, the small group of seven bright stars takes its familiar shape: three stars for the handle, four stars for the bowl of the dipper. Some of those stars, of course, are actually closer than others. So as you leave our solar system and approach the Dipper, its outlines become distorted. You pass the nearest star, then the second-nearest, the third, and now, with the seven stars all around you, it hardly makes sense to think of them as a dipper at all. They have become just a collection of stars.
Until recently, a trip to the Big Dipper could take place only in one’s imagination. But now, powerful new tools have been created that enable you to experience such an interstellar journey in a planetarium or even on a laptop computer, with an accuracy as pinpoint as modern astrophysics can provide.
The possibility of taking such a virtual tour of the universe in three dimensions has been realized by the NASA-supported Digital Universe atlas, developed by the Hayden Planetarium of the American Museum of Natural History. Depending on your taste and the time you devote to your tour, the Digital Universe can carry you anywhere—from the orbits of the innermost planets, to the stars that form the constellations, to the galactic neighborhood of our own Milky Way, to the most distant known objects in the universe.