Quirks & Quarks

Why did the eclipse go west to east when the sun goes east to west? Quirks Question

The eclipse started on the west coast, and ended on the east coast - why?
Enthusiasts watch a total solar eclipse while standing atop Carroll Rim Trail near Mitchell, Oregon, U.S. August 21, 2017. (Adrees Latif/Reuters)

Carol Yung of Toronto asks: "The sun, from our perspective, travels from east to west across the sky. But when the eclipse happened last month, the geographic path of the eclipse was from west to east.  Why was that?"

Jielai Zhang, an astronomer and PhD candidate at the University of Toronto explains that to understand this, you need to think of how the moon orbits the earth, and how its shadow - the eclipse - is cast on the ground and then take into account the rotation of the earth.