Where are the rest of the 3 days are going if the earth is revolving around its own axis in 23 hours 56 minutes 4 seconds?

Question

Earth revolves around its own axis in approximately 23 hours 56 minutes 4 seconds. If we measure the length of a day by 24 hours we hour saving 180+56=234 seconds a day. In a year that is 234 * 365 = 85, 410 seconds. In 4 years that is 341,640 seconds. Now a say has 86400 seconds, so we are the end of 4 year we have 341,640/86400 = 3.95 days. But we add 1 day to February after 4 years. Why is this?

In: 2

Answer 1

Well our day is measured in Solar days and not Sidereal days (23hrs 56 minutes 4 seconds). To understand this, the earth has to rotate a bit more than 360 degrees before the same point returns to the same relationship to the sun because the earth is also orbiting the sun while it rotates (it moves about 1 degree of orbit per “day”). This is the solar day of 24 hours – because we define a day from “noon to noon” which is the relationship to the sun.

EDIT: If we used sidereal days (earth’s absolute rotation) to measure days, then midnight becomes noon after 6 months before becoming midnight 6 months later.