How scientists predict the path of the 2017 total solar eclipse

(During a total solar eclipse, the moon completely obscures the sun for parts of the Earth. Careful calculations help researchers and the public determine where to go to see the total blackout. Credit: Miloslav Druckmüller, Peter Aniol, Martin Dietzel, Vojtech Rusin)

Millions of people intend to watch the 2017 total solar eclipse, which will cross the continental U.S. on Aug. 21. Here's how NASA scientists figure out exactly where the moon's shadow will fall on the surface of the Earth, down to the city block.

Space.com talked with NASA's Ernie Wright, who has been producing NASA's visualizations of the celestial event, to learn how satellites mapping the surface of the moon and advances in computing power have made it possible for scientists to predict precisely where on Earth the eclipse will be visible and for exactly how long — with a precision of about 100 meters (330 feet, or about the length of a city block).

Knowing where to watch the eclipse means the difference between seeing totality — when the sun is fully concealed by the moon — and just a partial eclipse, where the moon covers part of the sun but the sky doesn't fully darken. If you're outside the path of totality, the moon's crossing will be just a glancing blow.