Math Is Fun Forum

Nehushtan

Member

Registered: 2013-03-09

Posts: 957

Why we have 12 and 60 in our time system

There are 60 seconds in a minute. There are 60 minutes in an hour. And a day has twenty-four hours – 12 hours of daylight and 12 hours night averaged through the year.

What makes the numbers 12 and 60 so special?

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ShivamS

Member

Registered: 2011-02-07

Posts: 3,648

Re: Why we have 12 and 60 in our time system

Hmm...

Bob

Administrator

Registered: 2010-06-20

Posts: 10,619

Re: Why we have 12 and 60 in our time system

hi Nehushtan

I think it starts with the Babylonians and 360.

If you observe the night sky carefully, day after day (or should that be night after night )  you'll notice that the stars move on a bit each night.  Without access to a digital watch, it's reasonable to define this amount as one degree, and a whole year's worth as 360 degrees.  It's a little out but not bad for the time.

360 has lots of factors, including 60, 30, 24, and 12; so a time system based on those numbers makes a lot of sense.  30 days in a month, and 12 months in a year; yes, it all makes lots of sense.  In fact, their astronomers were accurate enough in their observations to know that none of these numbers quite works, but many civilisations have based their philosophy and religion around the mystical power of certain numbers, so why spoil a good thing? If the 'ordinary' folk cannot get it right and the leaders can, that just enhances their power.

Exercise: If a year is 365 days, and assuming the Earth's orbit is a circle, how long does it take for the Earth to rotate exactly once on its axis?  (The answer is not 24 hours)

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob