# Thread: Hours in a day

1. I just read a statement offered as fact that I don't understand.

One full rotation of the earth takes 23 hours 56 minutes and 4 seconds

If this is true, thats a difference of 3 minutes and 56 seconds.
That would add up quickly and our clocks would start lagging.
Over the course of a year that accounts for almost an entire day.

How does that work?

2.

3. Do you not have to reset your clocks where you live? I imagine that time adds up to what is called a leap year?

4. That doesn't fly. We have a single day added every four years because it takes the earth 365.25 days to orbit the sun.
3 minutes and 56 seconds adds up to almost a full day every year. I don't see the two being related.

And no, I don't need to reset my clock where I live. That amount of time would be nearly
40 minutes every ten days. Do you reset your clock that amount every ten days?

5. Originally Posted by sleven
I just read a statement offered as fact that I don't understand.

One full rotation of the earth takes 23 hours 56 minutes and 4 seconds
Is that all it says?
Or was it part of a longer sentence?
i.e. "The Earth rotates once in about 24 hours from the point of view of the sun and once every 23 hours 56 minutes and 4 seconds from the point of view of the stars (see below)."

6. That's the length of a siderial day. A solar day is 24 hours. Siderial day is the time required for the earth to complete a rotation with respect to the fixed stars.

7. Thanks guys, it was a sidereal day in fact. Just finished reading the wiki on it, makes sense now, thanks.

8. Sure, One full rotation of the earth takes almost 23 hours 56 minutes. But by the cause of Earth and Sun have revolution, we are looking like that Sun is moving a little in the sky by rotation of Earth completely. Sun looks like taking almost completely same place 4 minites later by Sun moving in the sky. It's the reason of a day having 24 hours.

9. Originally Posted by overthelight
Sure, One full rotation of the earth takes almost 23 hours 56 minutes. But by the cause of Earth and Sun have revolution, we are looking like that Sun is moving a little in the sky by rotation of Earth completely. Sun looks like taking almost completely same place 4 minites later by Sun moving in the sky. It's the reason of a day having 24 hours.
Which is why the stars appear to rise approx 4 mins earlier each night.

10. I think that it is for sleeping better.

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