Why does the path of a solar eclipse travel west to east?

We are now about a year away from a total solar eclipse in North America, the first one on American soil since 1991. You’ll have to drive south to experience it, however.

The path of the August 21, 2017 eclipse, during which the moon blocks the sun, will take it across a small sliver of Iowa as it zips to the South Carolina/Georgia area.

Like so:

Ira Flatow, of Science Friday, posted that video on his Facebook page today.

But why, when the earth rotates in the opposite direction, is the path moving from west to east?

Astronomer Barbara Becker provides the answer:

Good question! This happens because of the Earth’s motion in its orbit around the Sun. If you could look down at the Earth in orbit from a place high above the Sun’s north pole, you would see it moving very fast in a counter-clockwise direction.

Earth’s leading (western) edge will intercept the Moon’s shadow first. Our planetary spaceship has only 365.24… days to make its yearly journey around the Sun. With a radius of 93 million miles, that makes Earth’s orbit nearly 600 million miles long (c= 2R x pi)! So we really have to hustle to cover about 1.6 million miles each day!

A solar eclipse gives us a rare opportunity to witness and really “feel” the immense speed at which we are all whizzing through space. By comparison, the Earth’s rotation goes on at a rather leisurely pace.

Although the Twin Cities will not experience a total eclipse, people will be able to see a partial eclipse starting at 11:43 a.m., reaching maximum coverage at 1:06 p.m.