Human beings account each passing day with an equal number- 24 hours.
This is not completely correct as 24 hours is only the average time our planet takes in completing one rotation.
- In reality, many days are either longer or shorter than exactly 24 hours. Today is one such day.
- Today, the earth will complete a full 360 degrees in 23 hours and 56 minutes.
- This phenomenon is referred to as a sidereal day. This is different from the Solar day.
- The earth needs to rotate a little more than 360° in order for the sun to be in the exact same relative place in our skies. This is the reason behind a sidereal day.
- Two main factors lead to this: the axial tilt of our planet and the ellipticity of earth’s orbit.
- Over the course of 365 days, the sun moves not only up and down but also ahead and behind, as determined by the orbit of the earth.
- When both these effects are combined, the result can be seen in the form of a pinched eight figure.
The fact that earth’s speed changes depending on the time of the year also causes a change in the time it takes for a day to pass.
- The orbital speed is faster during January and slower during early July.
- Factoring the data in, the earth takes plus/minus 4 seconds to complete one full rotation throughout the year.