Solar and Sidereal Day
Listen now
Description
Transcript: A sidereal day is a period of the Earth’s rotation with respect to the celestial sphere, the time it takes for a star to appear at the same angle in the sky from one day to the next. A solar day is a period of the Earth’s rotation with respect the Sun, the time it takes for the Sun to appear at the same angle in the sky from one day to the next. The solar day is 4 minutes longer than the sidereal day. You can see this if you realize that the Earth is spinning as it orbits the Sun, so it takes an extra little bit of time for the Earth to rotate to the point where the Sun is overhead in the sky compared to the celestial sphere. This extra motion corresponds to the distance the Earth travels in its orbit of the Sun in one day, about one degree. One degree on the rotating Earth is 1/360 of the motion. 24 hours divided by 360 is 4 minutes, so the solar day is 4 minutes longer than the sidereal day.
More Episodes
Transcript: In the year 584 B.C., on the coast of Asia Minor, two warlike tribes were engaged in a fierce battle: the Medes and the Lydains. As written by the Greek poets, these two cultures were hacking away at each other on the battlefield with burnished swords and shields, when suddenly the...
Published 07/12/11
Transcript: Thales was a philosopher who lived in the 6th century B.C. in Miletus, in what is now Turkey. No written work by Thales survives, but we know that he kept accurate eclipse records and he speculated about astronomy. He decided that the source of all things was one thing, and that...
Published 07/12/11
Transcript: The apparent motions of the stars in the night sky depend on your position on the Earth’s surface. At a northern temperate latitude, the stars rise in the east and set in the west, and they travel on slanting paths across the sky. The north celestial pole sits in the northern sky...
Published 07/12/11