Excitement about the August 21, 2017, eclipse is as hot as a star, but solar eclipses happen at least twice a year, when the orbits of the moon and Earth align with the sun. What is unusual this time is that the moon will totally block the sun, instead of doing so partially, and that the strip of darkness cast on Earth will fall on millions of people rather than plankton out at sea or polar bears or penguins at the poles. Forty-six solar eclipses of various types will occur over the next 30 years. Grab a friend and go.