Question

WHAT IS A SIDEREAL DAY?DON'T COPY FROM OTHER WEBSITES....NO SPAM

Answer 1

The sidereal day is the time required for the Earth to rotate once relative to the background of the stars—i.e., the time between two observed passages of a star over the same meridian of longitude.

this is the proper definition

hope it is helpful

Answer 2

≛ Question ≛

WHAT IS A SIDEREAL DAY?

☆ Answer ☆

1. Sidereal Day is time measured with respect to the apparent motion of the 'fixed' stars in the sky due to the Earth's rotation.

2. The time between two successive passages of the vernal equinox across the meridian: it measures one rotation of the earth and equals 23 hours, 56 minutes, 4.1 seconds of mean solar time.

3.  While the Earth is rotating on its axis it is also moving along its orbit around the Sun. Over the course of a day the Earth moves about one degree along its orbit (360 degrees in a full orbit divided by 365.25 days in a year is about one degree).

4. Therefore, from our perspective, the Sun moves about one degree from west to east with respect to the 'fixed' stars.

5. A sidereal day measures the rotation of Earth relative to the stars rather than the sun.  It helps astronomers keep time and know where to point their telescopes without worrying about where Earth is in its orbit.

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