The countdown to a rare celestial spectacle is on. On August 21st, people within the "path of totality," a 70-mile wide swath of land stretching from Oregon to South Carolina (14 states in all), will witness a total solar eclipse. The shadow of the moon will start in the Pacific ocean and travel at Mach 1.5 speeds across the continental U.S., creating an ethereal light show that eclipse hunters swear is unlike any other naturally occurring phenomenon. Eclipse enthusiasts describe the experience as transcendent, even life-changing. Here are five things to know about the upcoming phenomenon: 1. A total solar eclipse is the result of a remarkable cosmic coincidence. The incredible serendipity of a total solar eclipse on Earth is difficult to fathom. For the brief few minutes of a totality, the Sun and the Moon occupy the exact same space in our sky, perfectly overlapping one another. How is this possible? While the sun's diameter is 400 times the size of the