Answer to Question #25616 in Astronomy | Astrophysics for Carmen Cowick

Question

Why is a sidereal year longer than a solar year if a sidereal day is SHORTER than a solar day?

Answer 1

If the Earth stayed stationary in its orbit around the sun thena sidereal day and a solar day would be exactly the same. But that isn't the case - the Earth moves through space in its orbit around the sun.


It takes one sidereal day for the Earth to make a single rotation about itsaxis. This is a true day. But once that sidereal day has been completed, the Earth has moved and no longer lines up with the sun the way it did. It must rotate a little more still for a solar day (a day relative to the sun) to complete.