A Conversation for A Chronology of Time

24 hours in a day

Post 1

hikermike - guardian of the wa

I`ve been wondering just why we decided that there are 24 hours in a day (and 60 minutes in an hour), I mean a day is earth rotation, right, but what you divide that into could be anything right? SO why did we, and all civilisations, apparently choose 24 hours?

Just wondering, too much time on my hands I guess.

Can anyone enlighten me because Its beginning to bug me now...

Hikermike


24 hours in a day

Post 2

msmonsy

A day really isn't 24 hours long...sort of. In actuality, it is a Sidereal Day and is 23 hours 56 minutes and 4 seconds long. They define a day by how long it takes the earth to spin once around on its axis relative to an inertial reference system. We measure the solar day of 24 hours by the time between the moment of sunrise and the same moment the next day. The sun will move across the sky a little bit so that in 365.24 days it will complete a full traverse along the ecliptic. This is the mean solar day. Here is how we get 24 hours instead of 23 hours 56 minutes and 4 seconds; the motion of the sun is not at a constant speed as the earth moves in its path. It kind of slows down and speeds up so that it gets behind or ahead of the solar mean day by up to 10 minutes or so. They call it the equation of time. So we aren't adding any extra minutes or loosing any, they work themselves out in the end. Kind of strange but it works smiley - magic.
monsy


24 hours in a day

Post 3

hikermike - guardian of the wa

but why did we choose 24? Why not 10, or 68 or 32,?


24 hours in a day

Post 4

msmonsy

Ok, I think I might understand what you are asking now. Why did we choose 60 for seconds and minutes instead of another number. This dates back to the ancient babylonians who seemed to have a preference for counting in a base 60. they saw ratios of 6, 12, 60 and 360 as round numbers...kind of like how we use a base 10 and see 5, 10 and so on as easy to divide things up into. They also divided the sky into the zodiac signs (12 of them) and made a circle 360 degrees. Between their zodiac and ratios it had them dividing the day and night into two twelve hour periods. And again, their liking of the base 60 instead of our base 10 was the reason for them choosing to break hours and minutes into 60. and that is why we have it divided like we do, just because that is the way it started with the babylonians and we just haven't changed it yet. I guess it is a case of 'if it isn't broke then why fix it'. smiley - smiley
monsy


24 hours in a day

Post 5

hikermike - guardian of the wa

Ta mate. Just one of many random questions that arive in my brain when Im trying to do other things.


24 hours in a day

Post 6

hikermike - guardian of the wa

Ta mate. Just one of many random questions that arrive in my brain when Im trying to do other things.


24 hours in a day

Post 7

hmd6364

But when did ALL countries agree on this?

Surely there have been alaternatives? Did the ancient Chinese, SouthAmericans and Babylonians all have the same answer of 24hours in a day?


24 hours in a day

Post 8

Phreak. a.k.a OLLLLLLL

It started with the aincent Egyptians, didn't it? And presumably to want to calculate time to the nearest hour you need quite an advanced civilisation where it is important that everything is done together, so they probably had links between them before anywhere else was advanced enough to need to be so exact. I have no proof of this, it's just a thought.


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24 hours in a day

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