What is the definition of a Sidereal Day?
Passage of time is relevant to the person and how they measure it. Time is the measurement of one activity to the next same activity. So Sidereal day is the measurement from the location of a star in local sky to the next instance when that star is in the same position. (Sidereal and Stellar have the same root history) Solar day is the same type, the time from when the Sun is in one local sky position to the next time it is in that same position. Usually zenith (point directly overhead) is the point used in these measurements. Our day beginning at midnight or sunrise is a human definition of day. Sidereal time is the clock that allows us to find celestial objects. If the sidereal time is 1200 hours, then all objects with a Right Ascension of 1200 will be on our zenith or directly overhead. It is using this time plus or minus we set the circles on a telescope for the RA or right ascension for an object. The time difference of about 4 minutes is explained correctly above, as our orbit tr
