SANTA CRUZ, Calif. — You can imagine it in a episode of “The Jetsons,” as one of that show’s famous sight gags, or as the main prop if someone were to make a Willy Wonka movie for bookworms. Or maybe you can picture Jules Verne or H.G. Wells a century ago enthralling some Victorian-era audience of amateur futurists speculating on its arrival sometime in the distant 21st century.