Why are there 24 hours in a day?

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!


14 Responses to “Why are there 24 hours in a day?”

  1. Lyndon Cooney Says:

    Thanks for that Mike. I’m going to talk about that with my top maths group as we are doing fractions at the moment.
    I’m sure my dad will enjoy reading it too.

  2. Thanks Mike – although your conclusion is just one of the versions floating around on this subject. You are right how we easily take things for granted, and the universal standard time we adhere to today has only been with us for around 100 years.

    Another recalls the Egyptians counting the ‘hours’ which were a series of twelve stars that rose at roughly equal intervals during the night. To create balance they then divided the daytime into 12 hours – so for most of human history there were 12 hours of night and 12 of day.

    It wasn’t until the 1400s with the invention of mechanical clocks that we started having standard length hours giving us longer nights and shorter days in winter. etc.

    I’ve been collating a lot of material and notes on this subject and am in the process of putting together a paper on the subject over the next few months.

    • Excellent, Peter! You have given me some more information that I hadn’t been aware of. I’d be interested in reading that paper when it’s done. Unfortunately I cannot lay claim to the above being my own conclusion – I was simply passing on what I remembered of a presentation from a guest astronomer, because it was not something that had even occurred to me before. But thank you for your comments 🙂

  3. Hi mike this helped me a lot with a project im doing right now. Thanks

  4. Nice blog, interesting…now following you, maybe check mine out too?

    • Thanks Nick! It’s been far too long since I’ve done anything with this blog, but I appreciate the follow 🙂
      I have followed you back on your blog too, which I found very cool – loved the colours, layout and variety of content!

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  6. tats just wow!! never thought about “why it is like that!!?” thanx fr d info.

  7. Your blog is absolutely amazing! I love astronomy, and this is among the best I have seen in terms of astronomy blogs. There is so much information! I have some stuff on astronomy on my blog, but I don’t dedicate nearly as much time to that section as I should. I have recently started an astronomy club however, which you can feel free to join. 🙂

  8. eddie nepi Says:

    also a month came from the word moon because of the 30 day moon cycle… get it …. a moonth

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