Archive for the Tips & Hints Category

Why are there 24 hours in a day?

Posted in News & Events, Tips & Hints with tags , , , on June 6, 2011 by astronomymike

To be honest, there are some things in this life that I have never given a second thought to…and this question was one of those things. At least, that was until our small astronomy group had the pleasure of hosting Wellington-based astronomer Frank Andrews at one of our monthly meetings!

Human beings are a remarkable species, but we also have an incredible ability to just accept everyday things, without question, just because “they are”. For me, having 24 hours in a day definitely fell into that category. It wasn’t until our esteemed presenter asked the question, “why?”, that I had to admit I hadn’t the slightest clue! Do you? Doesn’t 24 seem rather arbitrary when you think about it?

Well, you’ll have to forgive me if I get some of the finer detail wrong, but in truth I was more interested in the “why” than the “who”. Let’s just say it was in “ancient times”, perhaps the Sumerians or the Babylonians, and in those ages everything was related to “the gods”. The gods were perfect, they lived in the sky (represented by the stars) and passed overhead in an arc every night. So how does one represent the perfection of the gods watching over us during the cycle of day and night? Well, with a perfect circle of course! So, how do we divide up a 360° circle into even pieces? The most obvious is to divide it into half, making 2 x 180° pieces. Dividing each of those in half again gives 4 x 90° pieces, and again 8 x 45° chunks. But if we again try to divide the pieces, we end up with a non-whole (and therefore “imperfect”!) number – 22.5°. It also leaves us with a “clock” that represents an entire day/night cycle of only 8 evenly-divisible pieces – not particularly accurate at describing a time of day or night.

So, how else can we divide a perfect circle into “even” pieces of smaller size and whole (perfect) numbers? How about thirds? The first division give us 3 x 120° pieces, the second 6 x 60°, the third 12 x 30° and finally, the fourth division will give us 24 x 15° pieces. Nice! A further division will, of course, give us a non-whole and therefore imperfect number, but 24 pieces is a much more accurate way to be able describe a particular time than 8 pieces, don’t you think?

Oh, and one more thing – why do we call a “minute” a minute and a “second” a second? The first comes from the Latin word “minuta”, meaning “small”, and refers to the (first) minute (part) – in other words, it is the first minute part (or division) of the hour. Naturally the “second” refers to the second minute part, achieved by dividing the first minute part into smaller pieces.

I hope you learned something from that…I know I certainly did.

Thanks for reading, and wishing you clear skies!