Explore the spectacular cosmic phenomenon of a total solar eclipse. On April 8, a lunar shadow 115 miles wide will move across Mexico, 15 U.S. states, and northeastern Canada, sending locations in its path of totality into darkness for more than four minutes. Learn how to watch the eclipse safely and follow scientists as they prepare experiments to help unlock the secrets of our sun.

Watch NOVA: Great American Eclipse here or tonight at 8pm on GBH 2