00:00 Total eclipses occur when the moon passes directly between the Earth and the Sun, blocking
00:10 solar light.
00:12 Since 1900, only 12 have touched the U.S. mainland, most of them only glancingly.
00:19 On average, a total solar eclipse will happen where you live only once every 375 years.
00:27 Why are they so rare?
00:28 Well, the Sun is about 400 times larger than the moon, but the Sun is also 400 times farther
00:35 away, so the two bodies appear about the same size to us on Earth.
00:41 The moon orbits the Earth once each month, so why doesn't its shadow touch the Earth,
00:47 causing an eclipse with each pass?
00:51 Partly because the moon's orbit is tilted slightly, which causes its shadow to miss
00:55 the Earth most of the time.
00:59 But it's also because the moon's orbit is elliptical.
01:02 For much of its path, the moon is farther away from Earth and appears too small to block
01:07 out the Sun completely.
01:09 Those eclipses are called annular.
01:13 Only when the eclipse occurs at the moon's closest approach is a total eclipse possible.
01:19 Even then, the narrow band of totality usually tracks over water or away from population
01:25 centers.
01:27 That's why this eclipse on April 8th is so special.
01:31 As it crosses the Texas border at about 1.27 p.m. local time, cities closest to the center
01:38 of the path, like Waco, Cleveland, and Buffalo, could witness up to four minutes or more of
01:44 darkness.
01:45 In all, 31 million U.S. residents live in the path of the eclipse.
01:51 Even if you don't live in the path of totality, most of the U.S. will experience some level
01:56 of darkness.
02:00 It's a two-hour spectacle that you don't want to miss, because the next total solar eclipse
02:05 to hit the U.S. mainland won't be until 2044.
02:09 [MUSIC PLAYING]
Comments