"A long time ago, in a galaxy far, far away..." so begins the epic Star Wars saga--the timeless tale of the struggle between light and dark, good and evil. George Lucas' film trilogy and the world he created have become part of the collective consciousness of our times. Videos, books, toys, calendars, comics and other spin-offs continue to perpetuate the saga, which has assumed mythic proportions since it was first launched 20 years ago. The key to the trilogy's enduring magic, according to a new exhibition at the National Air and Space Museum, was its success in fashioning a modern-day myth a story that inspires and instructs, that reflects contemporary concerns, yet embodies a universal and timeless wisdom. "Star Wars: The Magic of Myth," on view from October 31, 1997, through November 1, 1998, showcases 200 original props, models, costumes, characters and artworks used in making the films. The artifacts are on loan from the archives of Lucasfilm Ltd., whose Star Wars universe captured the imaginations of millions of viewers by juxtaposing elements of classic myth aprinces and ogres, enchantment and chivalry awith a galaxy of androids and starships to create a space-age "hero's journey." The show, which was made possible by Bantam Books, examines these mythological roots and celebrates the trilogy as a cultural artifact. Admission is free, but timed tickets are required. A companion book by exhibition curator Mary Henderson, with images by Smithsonian photographers Eric Long and Mark Avino, is also due out from Bantam. "Underneath the flash and dazzle of special effects," writes Henderson, "is the magic of myth, a shape-shifting realm where heroes, monsters, wizards and magic talismans dwell in labyrinths of discovery. It is a story that will endure into the next millennium."