On August 21, for the first time in 99 years, a total solar eclipse swept across the entire United States. Because the Moon was near its farthest point from Earth at that time in its orbit, it blocked about 94% of the Sun`s light.
Solar eclipses occur when the Moon moves between the Earth and the Sun, blocking light from the Sun.
Total solar eclipses happen because the Sun`s diameter is 400 times wider than the Moon`s, but it is also 400 times farther away.
From Earth`s perspective, this geometry makes the Sun and Moon appear to be the same size. When the two line up just right, the Moon obscures the entire Sun, and the skies go dark.
These total eclipses happen every 12 to 18 months somewhere in the world, often over the open ocean since most of the Earth is covered by water.