Earth actually completed one orbit in roughly 365.256363 days…and it rotates on it's axis through 360 degrees in 23 hours 56 minutes and 4 seconds.
This seems a bit confusing….right?
The reason our day is 24 hours long and not 23:56 is because the Earth has moved a bit around the orbit during that time…and 'a day' is the time it takes for the sun to return to the same place in the sky…which is a little bit more than a 360 degree revolution because we've edged a bit further along the orbit.
The other problem is that the time it takes us to go around the sun once isn't an exact number of days…it’s more like 365 and a quarter days. But since it would be incredibly messy to have “a year” not be an exact number of days, we've adopted a system where we pretend that a year is exactly 365 days, and every four years, add an extra day to allow for the four quarter days that we didn't count!
It's actually even worse than that…it’s not EXACTLY 365.25 days even. So every 100 years we skip a leap day…and every 400 years add it back in again. That keeps the average length of our human years roughly in time with the duration of an orbit…but even so, it's not exactly right. So every now and then we add an extra “leap second” to our clocks to make that day be 24 hours, 0 minutes and 1 second long!
Sadly, the universe doesn't feel the need to keep planets moving and rotating in ways that suit human desires for nice round numbers, simple clocks and calendars…so we have this messy pile of botches and fixups to take account of that try to keep our time keeping and our calendars working nicely.
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Answer:
Earth actually completed one orbit in roughly 365.256363 days…and it rotates on it's axis through 360 degrees in 23 hours 56 minutes and 4 seconds.
This seems a bit confusing….right?
The reason our day is 24 hours long and not 23:56 is because the Earth has moved a bit around the orbit during that time…and 'a day' is the time it takes for the sun to return to the same place in the sky…which is a little bit more than a 360 degree revolution because we've edged a bit further along the orbit.
The other problem is that the time it takes us to go around the sun once isn't an exact number of days…it’s more like 365 and a quarter days. But since it would be incredibly messy to have “a year” not be an exact number of days, we've adopted a system where we pretend that a year is exactly 365 days, and every four years, add an extra day to allow for the four quarter days that we didn't count!
It's actually even worse than that…it’s not EXACTLY 365.25 days even. So every 100 years we skip a leap day…and every 400 years add it back in again. That keeps the average length of our human years roughly in time with the duration of an orbit…but even so, it's not exactly right. So every now and then we add an extra “leap second” to our clocks to make that day be 24 hours, 0 minutes and 1 second long!
Sadly, the universe doesn't feel the need to keep planets moving and rotating in ways that suit human desires for nice round numbers, simple clocks and calendars…so we have this messy pile of botches and fixups to take account of that try to keep our time keeping and our calendars working nicely.