Why are eclipses rare?

Solar scientist Lucie Green explores the four different types of solar eclipse and why seeing one is such a rare opportunity. read more

The solar eclipse that will cross the continental U.S. this Aug. 21 will attract a huge audience — and rightly so. The millions of people who are expected to witness the astronomical event won’t show up just because solar eclipses are exceedingly beautiful — they’re also exceedingly rare. read more

Solar eclipses are rare because even though the moon orbits the Earth once a month, it requires a very exact alignment between the Earth, sun and moon to create a solar eclipse. Even when the alignment occurs, the eclipse is limited to a small portion of Earth's surface. read more

Although there's a total solar eclipse somewhere on Earth about once every 18 months, many people never witness one. read more