If Earth makes one complete rotation on its axis every 23 hours and 56 minutes, how does day and night not being flipped on our clocks after six months? (6monthx30dayx4min/60=12hour)

Question

And why leap year happens once per 4 years only to address this?

In: 1081

Answer 1

so it does, sort of. The reason you don’t notice it is because of confusion between the length of a sidereal day which is 23hrs and 56 min and a solar day which is almost exactly 24 hours. A Sidreal day is the time it takes for the earth to do one 360 degree rotation, and if you started marking the time that the earth rotated 360 degrees at midnight on day one half a year later you would be marking time and midday and half a year after that you’d be marking time back at midnight.

However we mark our time on the solar day, which is the time it takes the same spot on the earth to face the center of the sun rotate and then face it again, the time between two noons. because the earth is orbiting the sun whilst rotating after 360deg of rotation the point on the earth that was facing the sun is now slightly offset, it turns out that to face the center of the sun again the earth needs to rotate just under 361 degrees.

so your confusion and many others is based around the belief that a solar day is one 360 degree earth rotation when in fact it is a little bit more.