The solar eclipse that will shadow a great swath of the United States on August 21, 2017, has caused great excitement among millions, most of whom have never had the opportunity to witness such a celestial event. Most folks have seen a lunar eclipse, which can occur up to twenty times in as many years in any given spot on the planet. By contrast, even though a solar eclipse occurs about every eighteen months somewhere on the globe, the same spot will see a solar eclipse only