Where do the missing four minutes go???

Question

So the Earth revolves on its axis and rotates around the sun right? well, i have been told that one complete rotation of the Earth on its axis takes almost exactly 23 hours and 56 minutes... so what does it do with the remaining four mintues? just stays still?

so u r saying that there is 24hours remaining every year that is unaccounted for right? and that this goes into the leap year? but then the leap year only happens every four years, so isnt there an accumulation of 96hours to get rid off, n the leap year is just an extra 24hrs? sorry, not arguing am just trying 2 see why :)

Answer 1

Ok, this is really tricky to explain without a demonstration, but here goes...

Right, as you correctly state, the Earth takes about 23 hours and 56 minutes to make one turn about its axis. So why do we say that 1 day is 24 hours and not 23hrs 56mins?

It's because we only notice the turning of the Earth based on our observation of other objects moving across the sky as we turn - most specifically, the Sun.

It does take 24hrs for the Sun to get from directly overhead one day, to directly overhead again the next day.

So, why the difference? Why does it take only 23hrs and 56 minutes for the Earth to turn, but 24hrs for the Sun to get back to directly overhead?

That's because, as you also stated, the Earth is orbiting the Sun, so by the time the Earth has turned, the Sun has moved a bit in the sky, so the Earth needs to turn a bit more to get the Sun back to directly overhead. This extra turn takes 4 minutes.

Not following that? Well here's where the demo comes in. I hope I can explain this clearly enough...

OK, *you* are the "Earth". Find yourself a bit of wall with an object on it - a picture, or a light switch even - this object is the "Sun"

Stand facing the object (your "Sun") about a metre or two from the wall.

Now, turn yourself, to the left, a full 360°. This takes you 23hrs and 56 minutes (though you might want to do it a bit quicker for this demo!), and you're facing the "Sun" again, yes? But, you've also moved through space, so now take a step sideways, to your right, along the wall (don't turn at all, just step sideways). Now you're not facing the "Sun" anymore, are you? Now, you need to turn a bit more to get the "Sun" directly in front of you again. It's this *extra* turn, to get the Sun back overhead, that takes the extra 4 minutes.

Clear as mud? :)

BTW, all this has nothing to do with "leap years" and the extra day we get in February. That's down to the fact that the Earth takes 365 *and a quarter* days to orbit the Sun. So every four years we add an extra day to the year to keep everything constant.

:::edit:::

Just responding to your Additional Details....

Yes, you are absolutely correct. This does mean that there is a difference between the number of "Days" in a year - 365.25, and the number of times the Earth turns in a year - 366.25 - i.e. the Earth actually turns one *more* time than we actually have "Days" in the year.

Why can this be? Because of how we define one "day". A "day" is *not* the time it takes the Earth to turn, but rather, the time it takes for the Sun to return to directly overhead.

That way, 12 o'clock (mid-day) is always when the Sun is directly overhead (or thereabouts).

If we based a "day" on the turning of the Earth, each "day" would be 4 minutes shorter than we are used to. And that would mean that each "day" the Sun would 'lag-behind'. So, the next day at 12 o'clock, it would be four minutes before the Sun was directly overhead. After 10 days, the Sun would be 40 minutes behind schedule. After 100 days, the Sun would be 400 minutes behind - that's 6 hours 40 minutes! - so at 12 o'clock the Sun would just be rising. After six months, 12 o'clock would be the middle of the night!

This is why we base our "day" on the Sun, and not the turning of the Earth.

Answer 2

The leap year answers are complete nonsense.

After 23 hours 56 minutes, the Earth has turned exactly once relative to the distant stars. It is called a "sidereal day" (Greek sideros = star).

But the Earth's curved path around the sun means that it has to make a little bit more than one full turn to bring the Sun directly overhead again. That's what takes the extra four minutes.

Answer 3

Sidereal time is not the same as the solar day. Using the stars as a reference the spin rate is 23h 56m.

Now why is the solar day different? Because we are in orbit around the sun so we see the sun from a different angle every day.

So if you lose 4 minutes a day over 365 days over a year you find that is about 24hrs. One complete day. Each revolution around the sun brings you back to the same point.

Answer 4

More specifically, our rotation period (the time elapsed for one rotation) with respect to the stars is called a sidereal day. A sidereal day is 24 sidereal hours, or 23 hours and 56 minutes on a normal clock. Our clock time is based on the earth's rotation with respect to the sun from solar noon to solar noon. This is a solar day, and it is divided into 24 hours. Because Earth travels about 1 / 365 of the way around the sun during one day, there is a small difference between solar time and sidereal time.

The earth takes about 1/365 of a day or about 4 minutes more to get into the same
position with respect to the sun after it reaches the same position with respect to the stars. We use sun-based time because it is more important to most of us whether the Sun is up than whether a given star is up. Those who care which star is up (like astronomers) may also use sidereal time.

VR

Answer 5

It's all about the Relative Path around the Sun. At certain time's the path depending on time and Relative motion around the Sun you could say like a Magnetic clock in solar rotation.

Answer 6

The four minutes per day add up to make the 366th day of the siderial year. The siderial year has an extra day per year, because the stars rotate around the Earth 366.25 times per year.

Answer 7

That's when the Earth is checking his email account for messages ... lol

4 mins x 365 days = 1460 mins per yer
1460 / 60 mins = 24.3 hours
there goes the extra day that is there during a leap year

Answer 8

In the UK, the Government takes it; does a cover-up, then commissions a quango - which reports back in 3 years when everyone has forgotten about it. Just in time for the next one!
Or is it a decree from the European Union?

Answer 9

Every year sees 365 and a 1/4 day and then every 4 years we have a leap year to make up the four 1/4 days so maybe this is it?? I never did understand when my tutors were trying to drum it into us!

Answer 10

Every four years, we add an extra day to February's calendar. Leap Year.