Difference between solar and sideral day.?

Question

Simplfied

Answer 1

The above answer is pretty much correct. More specifically, the sidereal day is the length of time it takes for the Earth to rotate on it's axis one complete time (360 degrees), and it is 23 hours, 56 minutes and 4 seconds (and change) long. The mean solar day, which is what we talk about usually when referring to a "day" is the average amount of time between culminations of the sun (the amount of time it takes for the sun to return to the same azimuth in the sky). A solar day changes in length in a cyclical way slightly over the course of the year due to Earth's variable speed in it's orbit about the sun. The average or mean solar day however is exactly 24 hours (and 2 milliseconds technically).

Answer 2

The solar day is the time it takes for the sun to go from noon to noon in the sky. This time varies by as much as 15 minutes from the average 24-hour day because the earth moves at different speeds at different times of the year in its elliptical orbit around the sun.

The sidereal day is the time the earth takes to make one revolution with respect to the stars, which are so far away they appear to be in the same position no matter where the earth is in its orbit around the sun.

Viewed from far above the north pole, the earth rotates on its axis in a counter-clockwise direction, and also revolves around the sun in the same direction. This means that when the earth has spun around once so the stars are in the same direction it has also moved along its orbit by just under one degree (360/365), so the direction of the sun has changed such that it takes another 3 minutes 56 seconds before the sun is again at high noon from the day before.

In one year these extra 236 seconds per day add up to one complete day, and the sun has caught up to where it was in the sky the year before. And if you do the math you will also discover that there is one more sidereal than solar day in a year!

Answer 3

According to the website listed below, it looks to me like the sideral day is the length of time it takes for stars in the sky to be back in their original position - about 4 minutes less time than a 24-hour solar day. A solar day must be the length of time it takes for the sun to be back in its original position in the sky.