source: How long is a day?⌚ | How long is a day?⌚ | By StarTalk | Facebook
What
- It is changing continually throughout the year.
- The Sun gets to its highest point in the sky not always at clock noon (up to +-14 minutes).
Why
- The orbit of the Earth around the Sun is elliptic. So it move faster when it’s closer to the sun than when it’s further from the sun.
Hence
- We just average it out and define a day = 24 hours (on average).