In answer to our solar eclipse question, in theory a total solar eclipse viewed from the surface of the Earth can never be longer than 7 minutes, 32 seconds long. A total solar eclipse occurs when a new moon passes directly in front of the Sun, casting a shadow on part of the Earth. Consequently, geometry and the motion of the Earth, Moon and Sun are the time-limiting factors.
The next total solar eclipse will take place on Monday, August 21, 2017, following a path across the United States from Oregon to South Carolina. People directly within the approximately 70 mile wide path the moon’s shadow will take, will see the sun disappear, will see daylight turn to twilight and will feel the temperature drop. Outside that band, others will see a partial eclipse of the Sun.
You should never look directly at the sun, but if you learn how to view the eclipse properly, anyone directly in the shadow will see the Sun’s corona – appearing to have streamers of light surrounding the silhouette of the moon. NASA has information that can help you understand how to protect your eyes: Eye Safety During a Total Solar Eclipse.