What is the difference between a rotational period and a solar day?

Answer 1

A rotational period, also called a sidereal day, is the time it takes a planet to turn 360 degrees. Sidereal means “of the stars” — it’s the time it takes for the distant stars to be in the same positions in the sky. “Ah”, you might think, “that’s twenty-four hours.”

Nope. It’s 23 hours and 56 minutes.

Remember, the Earth’s in orbit around the Sun. Eppur se muove, as Galileo said — “the Earth moves”. In that time, Earth went a little less than one degree around its own orbit — and so, after one sidereal day, the Sun is about one degree away from where it was yesterday. To get to one solar day, you have to wait until the Sun is back in the same spot… which takes four more minutes.

(Crossposted from Quora)