I have a question concerning this article. It says, “As the sun rotates, its polar regions make a complete circle in about 34 days, compared with the 25 days required by its equator.” I was wondering how it’s possible to have two points on a rotating body take different amounts of time to make a complete revolution.

Mike Crawford
Snohomish, Wash.

The sun is a giant ball of gas, not a solid like a planet. Different points rotate at different rates, in a process called differential rotation. —R. Cowen