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Why are there 24 hours in a day?

There are many thing I'm interested in, but one in particular is the number of hours in a day. Well. I'm not obsessed with it or anything, but it's always made me wonder how on earth we got everyone on earth to agree to split the day into 24 segments. Splitting the year up into 365 days was easy - everybody knew what a day was, and everybody knew what a year was, so they just counted up how many days there were in a year. This happened all over the world, many times, independently in different cultures. When one group of invaders came along to politely ask another group if they would mind, say, changing their religion, the agressors would say "You've got a day to think about it before we smash you up". It's unlikely these two nations would speak the same language, so this would take a lot of hand waving and pointing at the sun and moon to get across, but across it would nevertheless be gotten. There was no need to go into deep astronomical calculations, because the concept of a day was universal - even newly introduced mortal enemies who didn't have a word or belief in common, would at least have a measurement in common.

But what about hours? Why 24? Why not 10? Why not 60? Time is not naturally split up into 24 anythings, so the division must be totally artificial. After a bit of googling, I found what I thought was the answer:

At which point Bryan crooked his right thumb to touch the base of his right index finger (please follow along and do it, too), and said, in much the same way as a Sumerian might have, 4,000 years ago... "One."

He then moved up a notch - see that? Each of your fingers has three distinct segments. I never really noticed that! - and, touching now the middle segment of his right index finger with his right thumb, he said... "Two."

I think you may sense where this is leading. By the time your right thumb has counted each of the three segments of his neighboring four fingers, you're up to 12.

Long before people were reading with their lips, one imagines, they were counting with their fingers.

So a day was divided into 12 segments, called hours; and, too, the night.

What a lovely story. It was all the ancient Sumerians' fault! The ancient Babylonians inherited this quaint practice, and presumably added their own 60-fetish to divide the hours into 60 minutes, and the minutes into 60 seconds. The Babylonian fascination with the number 60 is interesting in itself - so interesting, in fact, that this page suggests the Babylonians were the ones who split up the day, using geometric series:

... base 12 is more efficient than base 10, as base 10 ignores one of the hand configurations available - to wit:

  1. Open hand
  2. One finger folded
  3. Two fingers folded
  4. Three fingers folded
  5. Four fingers folded
  6. All fingers folded

Clams, naturally, have neither the means nor the necessity for such crude mnemonic devices. As well as being fond of twelve (3 x 4) the Babylonians actually used a base sixty notation (3 x 4 x 5) - hence your hours and minutes. The 360 (3 x 4 x 5 x 6) degrees in a complete revolution also stem back to their childlike fondness for these simple geometric series.

So there's another way of getting the number 12 out of our hands! Even though this explanation comes from the mightily respected "Doctor Clam", who as it happens, is an actual clam, it shows what we probably suspected: these explanations are total guesswork. How are we supposed to know what number a Babylonian saw when he looked at his hand? They don't seem to have written that one down.

Back to Google then. This page here has the world "science" in the URL, but the explanation it gives is still a little shaky:

Division of time into days and hours has gradually changed throughout history. In Babylonia the civil day and astronomical day were different. The civil day was divided up into watches [where] the length of a watch [was] not constant but varied with season. There were four watches during the day - 2 during the day, sunrise to midday and midday to sunset, 2 during the night from sunset to midnight and midnight to sunrise. The number of hours probably came from the use of base 6 as a counting system. It made sense to have each watch lasting 6 hours.

We know that the Babylonians used base 60, not base 6, but they did that because it is easily divisible by lots of other numbers, including 6. So the number 6 may have held a little significance. This explanation boils down to the Babylonians being 60-centric. Is that the real reason then? Did the Sumerians' hands play no part? Perhaps the 12-sectioned hands were a reason for liking base 60 in the first place. Or maybe it was something completely different, as this page suggests. I won't quote the whole thing, as it's quite long. Suffice to say that they've found an astronomical explanation involving stars, and it was the Egyptians, not the Babylonians. It all seems a little convoluted to me, but apparently "significant stages are documented in monuments and tombs" so maybe there's some evidence.

But wait! That's not all! Here we have a slightly different suggestion:

The Babylonians divided the sky into the 12 signs of the Zodiac, and a circle into 360 degrees. They divided the day and night each into 12 hours (although in many time systems the lengths of these varied between summer and winter! Babylon was rather nearer the equator than Liverpool, so they didn't get too confused with this). The hour was split into 60 minutes and a minute into 60 seconds.

Zodiac signs, eh? We're back to the unsubstantiated rumours about Babylon.

None of these solve the problem of getting the whole world to use 24 hours. Did Babylonian (or Egyptian) timekeeping spread naturally across the world in the same way Arabic and Hindu mathematical notation did? Did the Babylonians conquer some rival countries, which went on to conquer others, and so on? Are there, in fact, some countries which still don't use 24 hours? Some isolated island somewhere? Is it just a 'western' concept which has been forced onto the world recently by economic might? Come on! Somebody must know! Sorry for the inconclusive ending... how about I have a guess myself?

I reckon that the Babylonians (or somebody else, but if everyone else gets to blame the Babylonians, I will too) started out with the second as the basic unit of time. It's a nice convenient time interval - if asked to count upwards from one, you'd probably space the numbers about a second apart. Then, using their general love of all things base 60, they must've grouped seconds into groups of 60, and called them minutes. Then, they must've grouped the minutes into groups of 60, and called them hours. Then when they tried to group the hours into a group of 60, they saw that it spanned more than one day. So instead, they stopped naming time intervals, and simply stated that there were 24 hours in a day. Simple as that! It must be true!

If this really was true, they probably started out with something that wasn't quite what we know as a second. Perhaps shorter, perhaps longer. They probably went through the above calculation, and found that there were really 24.145 (or whatever) hours in a day, and to round the number down to exactly 24, they reduced the length of the second. Oh, and the human heart beats roughly once every second when resting, so perhaps that was what they started out with... sadly we'll never know.

Comments

  1. Ted D., on Monday 3rd May 2004, said:

    1.) I remember a documentary on the Discovery Channel talking about the 12hr day. Back when mechanical clocks were first were being built the numbers on a 24hr clock was too small and buched up to be read efficienlty. Someone suggested a "12hr" face and that gave us 12AM and 12PM.

    2.) Just a thought - Since the earths rotation is slowing down over time, will we adjust seconds accordingly? 500years from now will a second actually be 1sec plus .001?

  2. James, on Wednesday 5th May 2004, said:

    1) Interesting theory...

    2) Doubt it. The modern SI second is defined in terms of some property of Caesium atoms which is unlikely to ever change. They'll probably declare a leap-second to deal with the slowing down of the Earth.

  3. Dave, on Thursday 20th May 2004, said:

    When constructing a sundial, the angle between hours is 15 degrees. 15 degrees is a remarkable easy thing to construct just using a compass. You simply construct an equilateral triangle in the usual way, then split the 60 degree angle twice with the standard construction.

  4. William R. Cousert, on Saturday 28th August 2004, said:

    1,000 years from now, when 99.99999% of humanity is off the planet, will we still use the same calendar and clock we use now?

  5. Steve, on Monday 8th November 2004, said:

    This is an excellent discussion about the basis of our time system. This subject came up during a lunchtime talk today, and I was hoping to find an explanation like this.

  6. Bill, on Monday 15th November 2004, said:

    The solution may be a mystery but an elegant mystery and there may be something deeper. If one were to look at the face of a clock and go around the clock twice numbering from 1 to 24 a number of things emerge... -note the patern of prime numbers: 1 & 13; 5 & 17; 7 & 19; 11 & 23 -note the squares 1, 4, 9 & 16...4 and 16 overlay one another and is it possible that the relationship of 1, 4, & 9 represent the placement of the prymids? -if you continue the sequence there are 5 prime numbers lined up with the 5 position: 5, 17, 29, 41, 53 Coincidence? Right!

  7. Ali, on Tuesday 21st August 2007, said:

    i alway thought that the square root of 360 degrees is 24 and the 360 degrees is the earth circling

  8. James, on Tuesday 21st August 2007, said:

    The square root of 360 is 18.97.

  9. Mike, on Thursday 30th August 2007, said:

    Why 24 hours, ?

    I reckon they took the measure, as the time the moon takes, to move through its own diameter which is about half a degree. Anyone can observe this by watching the moon, against a field of stars.

    OK, interesting theory..

  10. inas.iman.zadi, on Friday 28th September 2007, said:

    I thougt I learnt the question I've ben asking myself and now I'm going to teach the restof my class it.Thanks and how did you find the anwer? Thanks again.

                                    Bye!!!!!!!!!!!!!!!
    
  11. Tyna, on Tuesday 23rd October 2007, said:

    I am just doing a math project so I need scientific information. More important, I need a site that will give me that information. Know of any?

  12. Nick, on Sunday 11th November 2007, said:

    According to Wikipedia:

    The day was subdivided sexagesimally, that is by 1/60, by 1/60 of that, by 1/60 of that, etc., to at least six places after the sexagesimal point by the Babylonians after 300 BC, but they did not sexagesimally subdivide smaller units of time. They did not use the hour, but did use a double-hour, a time-degree lasting four of our minutes, and a barleycorn lasting 3⅓ of our seconds (the helek of the modern Hebrew calendar). The Egyptians had subdivided daytime and nighttime into twelve hours each since at least 2000 BC, hence their hours varied seasonally. The Hellenistic astronomers Hipparchus (c. 150 BC) and Ptolemy (c. AD 150) subdivided the day sexagesimally and also used a mean hour (1/24 day), but did not use distinctly named smaller units of time. Instead they used simple fractions of an hour. Medieval astronomers first subdivided the hour sexagesimally in 1200[2] into pars minuta prima (first small part, our modern minute), pars minuta secunda (second small part, our modern second), pars minuta tertia (third small part) and so on.

    So it seems we owe the division of the day into 24 hours of sixty minutes of sixty seconds to a combination of ancient Babylonian and Egyptian thought, as well as the intervention of medieval astronomers....

  13. David Kidd, on Tuesday 25th December 2007, said:

    I believe Sumerians took the day to be dawn to dusk, and considered the night to be a different thing altogether, so we are talking about daylight hours. So the question is really "why are there twelve hours in daylight?"(at the equinoxes) The answer is that they picked 12 because they saw twelve months in a year (approx 12 moons). And they liked to have "as above so below" i.e. they liked to see small patterns reflect grand patterns. Hence they wanted the daylight period to be divided like a year so they divided daylight by 12.

  14. taylor, on Friday 8th February 2008, said:

    i have wondered about this too. ive wondered, since there are not really 24 hours in a day, how much time have we 'lost' or 'gained' over all these years?? wat year is it really?!

  15. ASIF ASSAR ALI, on Saturday 9th February 2008, said:

    it was such nice explanation but there are certain assumpttion

  16. Dave, on Monday 24th March 2008, said:

    According to Wikipedia: the number of African elephants has tripled in the past fee years. Never listen to Wikipedia. At best, it's just Google scraping. At worst, it's propaganda by governments and corporations. Most often, it's poorly written crap in a nice package.

  17. dave, on Wednesday 26th March 2008, said:

    That wasn't me.

    Obviously. lol

  18. Alice, on Monday 31st March 2008, said:

    This Is Ridiculous

  19. marendo, on Tuesday 29th April 2008, said:

    Dimensional/Geometric Reason Why Ancient Egypt Chose 24H/Day:

    http://youtube.com/watch?v=RhNmlQqQOTw

  20. Chris, on Tuesday 10th June 2008, said:

    It probably all goes back to a mix of superstition and geometry. 12 can be divided by the whole numbers 12,1,6,2,4 and 3. 10 can only be divided by 10,1,5 and 2. This makes 12 the more convenient number for thinking in segments. Add to this your zodiacs, gods, apostles and whatnot and Bob's your uncle. In Japan they used to give the hours names, for example "I'll meet you by the well at the hour of the Ox," which possibly came from Chinese zodiac or equivalent. Interesting question though.

  21. Todd, on Tuesday 24th June 2008, said:

    Chris is getting closer to the answer. Our earliest ancestors only had three things to determine time. Sun, moon and stars. Many civilizations attribute gods to these entities. The Sunrise and Sunset would be half of this period of time. At night, they would watch the stars. They noticed that after about 360 times that the sun went up and went back down that the stars were in the same place in the sky. They would have also noticed that the moon would appear full 12 times, every 28 1/2 days. Thus, a system is created that is shown in our modern calendar 365 days (Sun/star ratio) 12 months(moon). Don't you also suppose that they would honor the Sun, Moon and stars in the way they calculate time within the day? 60 seconds X 60 minutes = 3600 Sun/Star ratio. Two subsets for day and night (Sun and Moon), and then a way to honor the moon cycles (12) hours. E-mail me if you have any further questions about this.

  22. Danny, on Monday 18th August 2008, said:

    Hello!

    This is the first time I have EVER posted a comment on the internet, and boy am I excited!!!

    When you asked, "Are there, in fact, some countries which still don't use 24 hours? Some isolated island somewhere?" I have the answer! Immediately a very interesting story about the Moken people on 60 minutes came to mind. Here it is:

    The Moken don't know how old they are. Ivanoff says this is because, "Time is not the same concept as we have. You can't say for instance, 'When.' It doesn't exist in Moken language."

    Is there any other word missing from the Moken language? "No goodbye, no hello," says Ivanoff. "That's quite difficult. Imagine after one year, you live with them, and then you go. You go. That's it. Finish."

    And, there are no greetings. While 60 Minutes was on a Thai Moken island, a flotilla from Burma dropped by. They didn't seem terribly excited by this. But visits from relatives, and they're all relatives, happen all the time. And since there is no notion of time, it doesn't matter if the last visit was a week ago or five years ago. There's just a constant commingling. And, in the wake of the tsunami, they're all busy now, rebuilding their boats and their lives.

    Interesting, eh?

  23. Kyle, on Thursday 4th September 2008, said:

    According to some research on other things, I ran across the fact that Jupiter's orbit can be tracked across the sky for most of the year (except when its behind the sun). Jupiters orbit is 11.86 years and for convenience most round to twelve, now in ancient times a moving star in the sky seen most of the time is of great importance, so important that Greeks and Romans bases there God Kings after the planet. They can track the movement of Jupiter and know when it returns to the same position after about twelve years. Hence the twelve year cycles that happen all over the planet. Dividing day and night into such makes sence too because dawn and dusk are very easily measurable points of the day. Twelve of light and twelve of dark.

    Kyle

  24. Kent, on Sunday 14th September 2008, said:

    Thanks for all the info on how we ended up with a 24 hr day. But I'm wondering if cultures other than those in Babylonia or Egypt had a completely different system for keeping time during a day. Did the Aztecs, ancient Chinese, or Native Americans divide a day into units? The Aztecs and Chinese had sophisticated calendars, but I can't find any information on whether they had a system for hours.

  25. Bill, on Monday 20th October 2008, said:

    All very interesting, however, about the whole 12 month thing... most of you DO realize that we only had 10 months on the christian calendar until Julius and Augustus Caeser came around right?

  26. LiQmlight, on Saturday 15th November 2008, said:

    Yeah, and what if it was totally random, had nothing at all to do with math, and it just worked?

    Bill, we're talking thousands of years before the Christian calendar. Like Babalon and Egypt and Ancient China and cavemen old. (jk)

  27. eMon, on Tuesday 18th November 2008, said:

    Every generation has to learn Everything all over again. To survive, this knowledge has to be easily transferred. Looking at the stars is great for those of leisure. Navigation on the earth is a matter of survival for caravans, armies, sailors, and explorers. Geometry, not astronomy, is the science required to move from place to place on the earth. How do you teach geometry to a simple people with simple tools ? A Stick and a String ! You draw a circle. You divide the circle. You can use it in a boat to find safe harbor, you can use it in the desert to find an oasis. Divide a circle (day/year) by twelve shows an understanding of geometry. Divide a circle by 24 shows a higher understanding. The more different ways you can divide the circle, the better you chances of success. Note for you architects (arc) and engineers, you can also divide the Stick with the String as well as dividing the String with the String. And yes, of course the Stick and String can be used to measure shadows on the ground (time of day/season of year), but it is highly unlikely that early people were that concerned with the time of day, the day of the month, the month of the year, or even the number of the year. Imagine two guys standing in the desert 5000 years ago. One guy turns to the other and says "Do you know what time it is ?" Imagine two guys standing in the desert 5000 years ago. One guy turns to the other and says "Do you know what direction it is ?" What do you think makes more sense ? Astronomy is great fun but it was geometry (GEOmetry) that built the cities, expanded the empires, and mapped the heavens.

  28. zazuge, on Monday 1st December 2008, said:

    hello! interesting question ,i was too thinking about it those days i noticed that the moon travel it's size in the sky in a hour (i believe this is the real reason they chose the hour as such to mesure time) the moon take 29.5 aprox days to turn around the sky (witch is different then turning around earth) in one day the moon travel 12° or one handbreadth and in one hour it makes 0.5° or one little fingerbreadth witch is it's apparent size so to resume it the moon travel in one day 24 times it's apparent size that came to no surprise because the moon is the center of time measurement in ancient times the lunar month was the real month (and it's still used in some lunar calendars) if you want to continue this discussion by emailing me at dummy@mail.com abderdar at yahoo.fr ;)

  29. BasantJ, on Friday 5th December 2008, said:

    I was interested in this when I was in school - 35 years back. I found out that all the calculations for time were based on astronomical observations. Indian astrology also evolved from these observations. The heavens were divided into 12 houses (cusps, signs). No "planet" moves 12 houses in 12/24 hours, but the horizon moves through these 12 signs in 12 hours night and 12 hours day making up for 24 hours in a "day".

  30. Thewaddlehead, on Tuesday 10th February 2009, said:

    Actualy, idk how credible your article was, however from my understanding the earth completes a full rotation every 25.something hours. It was rounded off for neatness. To make up for this, an extra day is placed every 4 years or something, the leap year day 29 of February. I don't know the exact thing off the top of my head though, lol

  31. Sol, on Sunday 15th February 2009, said:

    There are 24 hours in a day because we need 8 hours sleep, we need to work 8 hours and then have 8 hours to eat/play/workout/socialize/procreate etc. Simple!

  32. BAT, on Saturday 28th February 2009, said:

    While doing "dimensional analysis" with 8th graders, they became very inquisitive on this topic while converting minutes/seconds/hours/days/etc... Normally, they would have trouble remembering and analyzing what they ate for breakfast! I had never thought about these questions until they kept pounding me for an answer. I knew some of the issues were based on astronomical types of concepts, but never studied the topic in any depth. THANKS for all these postings. It has been fun and informative to read. I will pass on all these theories, assumptions, and facts to inquiring minds. If nothing else, I have been inspired by the fact that my students were thinking "outside the box".

  33. HEINRICH COETZEE, on Saturday 28th March 2009, said:

    The day should be changed to 48 hours and the week to 14 days.

  34. Amit Karia, on Sunday 26th April 2009, said:

    the Earth completes one rotation about its axis every 24 hours, but it completes one revolution around the Sun every 365 days..hence 24 hrs a day and 365 days a year..

  35. Beth, on Monday 4th May 2009, said:

    Everyone has different theories, but instead of all these theories floating around they should look for one basic answer. Until the real answer is found everyone is going to keep arguing about who's got a better solution. I'm doing a paper on days and months for school. As a part of my paper I'm digging into different things to make my paper interesting and meet the requirements for a good score. So if someone knows the real answer or is 99.999% close to what the possible real answer is, please let me know.

  36. Tuck Poh, on Saturday 9th May 2009, said:

    Guys, have anyone of you ever ask a question of why we change from inches to cm/meters, why we change from pounds to grams/kgs etc?I am suggesting, for the sake of convenient (we change the above make our life easier, aren't we?), we have 10 hours a day, 100 minutes an hour, 100 seconds a minute, 10 months a year, and 35-36 days a month. Challenge are welcome.

  37. Drake, on Friday 22nd May 2009, said:

    While playing around with POV-Ray (a 3D raytracing program), I modeled a simple earth-only solar system using the distance to the sun and the diameter of the earth. Once I got it working, I made a small scene at 30 degrees latitude and oriented the system at the first of the year. As I spun the 'earth' around, I noticed that the sun broke over the horizon at 7:00 am, and set at 5:00 pm. Halfway through the year, it rose at 5:00 am and set at 7:00 pm. At a quarter of the way, and three quarters of the way, it rose at 6:00 am and set at 6:00 pm.

    I found it odd that it was rising and setting at these precise times, exactly at hour intervals. Is it possible that the hour was based upon the time difference between sunrises at these significant intervals in the year?

  38. asim khadim, on Saturday 20th June 2009, said:

    I was interested in this when I was in school - 35 years back. I found out that all the calculations for time were based on astronomical observations. Indian astrology also evolved from these observations. The heavens were divided into 12 houses (cusps, signs). No "planet" moves 12 houses in 12/24 hours, but the horizon moves through these 12 signs in 12 hours night and 12 hours day making up for 24 hours in a "day".

  39. Michael Farr, on Monday 6th July 2009, said:

    Actually the horizon only moves through the full zodiac or 360 degrees of the compass in 24 hours. This makes sense if you think of the sky as fixed and it would take a full rotation of the earth.

    There are roughly 12 cycles of the moon (full to new moon) in a year. (The word "month" is even derived from the word "moon". If you picture the stars as being painted on a huge bowl covering the solar system, every time the moon goes around the earth and is once again directly away from the sun (full moon) the earth is approximately 1/12 the way around the sun. There will be a different constellation of stars behind the moon. There are 12 of these around the horizon: the constellations of the Zodiac. That's how the ancients figured time.

    I believe that Babylon actually divided the day into 12 periods. The egyptians gave us the 12 hour day but I've not be convinced as to why other than it was a practical number for dividing up labor.

  40. Michael Farr, on Monday 6th July 2009, said:

    Clarification: the Babylonians divided the full day into 12, 2 hour segments. The Egyptians divided daylight into 12 periods and night into 12 periods. The length of the periods varied depending on the time of the year thanks to the Earth's tilt.

  41. joe, on Monday 6th July 2009, said:

    there aren,t 24 hours in a day there are 23 hours .56 minutes .3seconds

  42. kathi', on Friday 14th August 2009, said:

    how do you take medication 3 times a day? what are the times?

  43. Mihai, on Saturday 29th August 2009, said:

    What if breath time has a thing to do with all of it? 21600 breaths a day, because a breath average time is 4seconds. 21600 = 360 x 60. 1year = 360 days (approx) So 1 degree of time would be 60 breaths. meaning: 60 breaths in 4 minutes. 4 minutes=1 degree of Earth's rotation.

    1 hour = 15 * 4 minutes = 900 breaths = 15 * 60 breaths

    Now I'm stuck:)

    What's with 900 that's so special? ..If it's special, then it would be obvious that they would prefer 24 hours (1 hour = 900 breaths)

    But interesting theories anyway.

  44. Nikolai, on Saturday 15th May 2010, said:

    Great question.

    First I will lay out the information I know:

    How did it all happen?

    1) Defining a day. First, human civilization observed day and night. They defined it as a "sun". One "sun", five "suns" etc. Basically, defining roughly a day.

    2) Defining a month Now, they've abserved an astrological phenomenon. A moon phase. So they defined a month. One moon, three months, meaning 3 months. They also observed, that the moon cycle takes 30 suns. So, they derived that a month consists of 30 days.

    3) Defining a year. Or why circle has 360 degrees. Ancient scientists were trying to discover arithmetics and astronomy. They started to observe, that it takes roughly 12 moons (+- 1moon) to a) Go back to the same weather b) Get the the same view of the night sky from the same observation point.

    So thats the way we have our 360 degree circle :)

    Lets summarize: We have defined a day, month(30 days), year(12 months and 360 days), circle(360 degrees)

    Now, here come my speculations about hours.

    4) Sun clock As far as I know, they used a sun clock. A sun clock is basically a circle.

    So we end up with a circle to measurement unit.

    The rest is unknown to me.

  45. Jun A., on Sunday 16th May 2010, said:

    Actually it is not 24 hours we have in a day...it is 23 hours and 20 minutes. Referring to Joshua 10: 12-13;" O sun, stand still over Gibeon....The sun stopped in the middle of the sky and delayed going down about a full day?....and 2 Kings 20:9-11;"Isaiah answered, This is what the LORD's sign to you that the LORD will do want he has promised: Shall the shadow go forward ten steps, or shall it go back ten steps....."then the LORD made the shadow go back the ten steps it had gone down...". Since 360 degrees [complete rotation of earth on its axis] represent 24 hours; then 15 degress is equal to 1 hour or 60 minutes; or 1 degree = 4 minutes; for ten steps [degrees]back made by the LORD in that day is equal to 40 minutes....therefore for 1 day we have 24hours-40 minutes= 23 hours and 20 minutes as what the Bible says.

  46. subodh dixit , on Saturday 22nd May 2010, said:

    24 hours in aday depend on planet VENUS . VENUS one rotation on its axis =243 earth days and arround the SUN it takes 225 earth days so now start the calculation .

    calculation of 24 hours in a day

    Venus=shukra=planet name

    Venus (one rotation on its own axis) = 243 Earth day

    Venus ( one round arround the sun ( orbit )= 225 earth day

    243 – 225 = 18

    225 x 243 = 54 675

    54 675 / 18 = 3 037.5

    3 037.5 / 243 = 12.5

    3 037.5 / 225 = 13.5

    12.5 + 13.5 = 26

    26 / 2 = 13

    18 x 13 = 234

    every next morning on venus will be

    234 / 2 = 117 days time of earth

    it means one Venus day = 117 earth day aprox.

    actual Venus day 54675 / 234 =233.6538

    233.6538 / 2 = 116.826 earth days .

    18 + 13 = 31

    31 / 2 = 15.5

    earth one year

    365 / 15.5 = 23.5

    actual earth year = 365.256 days

    365.256 / 15.5 = 23.564

    one earth rotation as par nasa 23 hour 56 minut 4 sekend.

    but now there are 24 hour in a day

    this is not only round off in full hour without aney reason

    there are 366 full rotation in 365 days (mornings) apear on earth

    so

    23 hour 56 minut 4 sekend. x 366 / 365 = 24 hours

    so this is the complete calculation of 24 hours in a day .

    now if you want to know the Synodic period

    234 + 365.254 - 15.5 = 583.754 earth days

    thanks a lot for reading my calculation .

    you can not find this calculation aney where in the world .if you find let me know about .

    Autor: Subodh Kumar Dixit

  47. Frank DiNunzio, on Sunday 13th June 2010, said:

    None of the answers above have a provable, logical, mathematical answer.

    Is it then just a fluke that the earth is 24,000 miles in circumference and a day is 24 hours and the speed of rotation is 1,000 mph and 1 day brings the sun's shadow back into approximately the same spot on a sun dial each day?

    How did the ancient civilizations know any of these facts?

    Frank DiNunzio

  48. ilupper, on Tuesday 6th July 2010, said:

    How did the ancient ppl use minutes. I haven't seen an ancient sundial with minutes on it before? And if they did use minutes, it would be required to fit in between two hourly pts since the sundial does Not have rotations around the clock until maybe Ben Franklin or someone before him made a modern clock?

  49. Steve Sidley, on Saturday 17th July 2010, said:

    Simple. The circumference of the planet is 24,000 miles. It rotates at 1,000 m.p.h. Hence 24hours in a day adjusted every leap-year because the planet is not exactly 24,000 miles round and not spinning exactly at 1,000 m.p.h. Sorted! Hmmmmm....

  50. jeff, on Monday 9th August 2010, said:

    cause it takes 24 hours for the earth to spin round

  51. luis, on Wednesday 11th August 2010, said:

    I think a day should be 23 hours and 59 minutes 59 seconds. but im sure its wrong

  52. travis listen up, on Thursday 2nd September 2010, said:

    Listen up! There is only one measurement of time that makes sense, and that is the day. Noone ever has problems counting the days, and there is no disagreement about it.

    The idiots that say duuuuuuuu we have 24 hrs in a day because that is how long it takes for the earth to spin round, you are MISSING THE POINT. IT IS ABOUT WHAT WE CHOOSE TO CALL IT. There is no such thing as an hour, second, minute... These are human inventions and are ways of dealing with a problem, that works semi-well.

    The sensible thing to do is to make a metric clock, with, say, 100 blargnorfs in a smerglin, 100 smerglins in a turdnark, 100 turdnarks in a day (that's right, we should keep this one), 100 days in a remlins, and 100 remlins in a zomglol.

    I decided not to use words like seconds and minutes because so many out there don't bloody understand that a minute does not HAVE to be sixty seconds, it can be 5, or 100, or 127.0.0.1 depending on what WE CHOOSE IT TO BE.

    So wise up and use the metric clock! No more wasting time on trying to wrap your head around am/pm and bullcrap, just easy metric conversions in your own head!

    And change to the metric system god darn it!

  53. James, on Friday 3rd September 2010, said:

    Metric units are no less a human invention. They are slightly easier to calculate with, but are still arbitrary. The kilogram is defined to be the mass of a lump of platinum-iridium in a vault in Paris. The second is an arbitrary integral number of cycles of a caesium-133 atom. And the speed of light is a universal constant, so by counting how far light gets in a certain arbitrary number of seconds, you define the meter, which turns out to be a derived unit!

    I suspect most angry cheerleading for the metric system is a thin disguise for anti-American braggadocio. If you want to promote a truly fundamental system of weights and measures, try Planck units. Universal constants like G are set to one, so the downside is that since we don't have an accurate measurement of G, quantities like distance become somewhat uncertain! And while we're at it, why not drop the highly anthropocentric base 10 notation and use base 2? Even base 12 is more mathematically justifiable than base 10, due to its abundance. Finally, let's all dump the old, outdated, Anglocentric English language, and switch to something like lambda calculus :)

  54. al dog, on Tuesday 7th September 2010, said:

    this is so confusing but inspirational

  55. Dagnabit, on Sunday 12th September 2010, said:

    Some of you are very close but all of you are wrong. This is the true calculation of why there is 24 hours in a day. Time was discovered long before the invention of the first clock. And days were marked by the sun and months were marked by the moon. Time was based on a simple theory to break the days into smaller segments. The smallest being the second. What is a second and how was it first measured? A second is the average of all the numbers a human can count in a full day i.e. 1,2,3,4,5,6 etc. From the mark of the first sun to the mark of the second sun a person could count to 1440 using the same speed per number of course. If you were to start counting at the same speed, single digit numbers would of course come out faster than 4 digit numbers however if 100 people started counting at the same time, the average number would be 1440. Back in the beginning days of counting, a parent might say; "You had better have it done by the time I count to 20." Counting was invented well before time was discovered. Hence, 1440 seconds in a day will not divide evenly into 100 because it would give us a 14.4 hour day. 1440 does divide evenly by 12 and 60. This is the only reason we have 24 hours in a day. If we wanted to change it to a 10 hour day then we simply have to count slower to make our seconds slower. Our hours would be longer and the change would drive everyone crazy. Question answered.

  56. bob, on Monday 1st November 2010, said:

    isnt it 24 hours not 12

  57. chris, on Monday 8th November 2010, said:

    be careful crash the this 24 hour 60 min 60 sec and u might end up changing the speed of light

  58. chris, on Tuesday 9th November 2010, said:

    on the nasa web page it says it takes 23hours 56 min 4.09 sec for the earth to rotate lets take that number and bring it down to see how long a second really is

    31558149.45 sec year /365 86460.68342 /24 3602.5284 /60 60.0421 /60 =1.000702354452 thats closer to a real second the whole 24 hour thing will work out evenly with no leap years if u just fix the second

  59. Ian, on Wednesday 10th November 2010, said:

    The 12 surely didn't come from months. Christians had 10 for a long time, but that was recent (relatively). Go back to real early times and months were lunar and there were 13 of them in a year. The Chinese races still use the 13 month calendar for just about everything but dealing with the west. Dividing up days and nights into equal bits only works properly on the equator, so the 24 hour day probably didn't come from that either. All measuring devices are ruled out because they were made to suit a pre existing system, be they time candles, sand timers or water clocks. Babylonian is the best answer I've seen so far, but far from a proven fact. Great thread and very interesting concept to play with, as many posters have shown :-)

  60. G Main, on Friday 3rd December 2010, said:

    Anyone who has tried to explain fractions to kids realizes the convenience of being able to say, 1/3 of a day to mean 8 hours instead of 3.3333 hours.

    The common factors of 24 being 2, 3, 4, 6, 8, and 12 is nicer than a number with 2, 5, and 10 as common factors.

    This reason also works for explaining 60 minutes, 360 degrees, and 360 seconds.

  61. Sid, on Monday 13th December 2010, said:

    In the division of a day if the 24hrs wasn’t a correct fact, overtime would we not be left with either a) accumulating minutes and hours or b) fewer minutes and hours from the existing time? How would you account for these more or less “time”? Where are they going or coming from?

  62. Nate, on Tuesday 14th December 2010, said:

    Very interesting discussion! I don't think we are any closer to finding a solid answer, but congrats to the original post for keeping a discussion going for 7 years!

  63. lava, on Saturday 1st January 2011, said:

    the circumference of the earth is 24,901 miles. Roman miles were smaller, 1,000 paces or 5,000 Roman feet - 1,617 yards vs 1,760 yards in our standard mile.

    Suffice is to say that our ancient cousins knew geometry and could do the math, having the same brains as us but having no cable access, their measurements had to be based on observable standard units. My cubit is bigger than your cubit and my heart beats faster etc.

    12 and 60 base counting systems make sense. Especially to a mathematician living in an agrarian economy. The moon traveling at 12° per day makes a 30 day lunar month. An hour is a comfortable 1/2 a degree. 12/24/30/360/3600 are good to work with and do fit (approximately into things we can observe).

    Apart from clean math, the observable are convenient approximations. 60 minutes in an hour divided into 60 seconds makes sense for rough calculation and formulation but has no possibility of standard duplication in measurement without significant technical advancement. We are only able now to give standard measurements for the concept of time we have agreed on.

  64. Muhummad Rohan, on Wednesday 12th January 2011, said:

    The year, the month and the day are "natural" in that they relate to the Sun (earth's rotation), the moon , and the earth (spin). Each of which would be the principal terms of reference for any community hence the universality of these units of time. Hours at first glance seem arbitrary, one suggestion given on this forum was that our search for meaning makes us mirror what we see in the bigger picture in our own smaller unit hence the 12 hour division of a day as mirroring the 12month division of the year. This to me seems persuasive,but why should this apparently arbitrary division be so universal?

    Let us now turn to theology, the big question which arises naturally after considering the Sun,Moon and Earth is one's own existence and the reason for it. Observing that these bodies rise and set implies that they cannot be the absolute cause "or God" since they are subjected to the natural order and not the cause of it consequently one is left with:

    1. There are No Gods (This is the position of the disbeliever but can also be a starting position of faith)

    2. Except the one true God (This is the position of a believer)

    3. The following of a specific religion that connects faith(the latent "night state") to doing good deeds(the "day state")

    The first two steps therefore include everyone believer and non believer as latent states and the latter is a for the awakened soul. These questions are universal to all people and particularly interesting to desert peoples who see unobstructed skies and have time to reflect on the meaning of life.

    In Arabic the first two steps "the latent night steps" contain 12 letters and 4 words; 'la ilah ill-Allah'. It is made up of four words, la (no), ilah (that which is worshipped), illa (except) and Allah (the proper name of the Divine Being).

    The awakened state accepting that God guides a latent state to an awakened state through prophets who prescribe Prayer and Charity represents religious truth. The declaration of the prophet hood of Muhummad (saw)also contains 12 letters.

    It is natural that Islam fits these facts as it is "God who determines night and Day" and Islam is the natural universal religion that your heart directs you to.

    To become muslim you say with your tongue and heart 'la ilaha illal lahu Muhammadur rasulullah.'

  65. Muhummad Rohan, on Wednesday 12th January 2011, said:

    Incidentally for the mathematically minded among you, Islam seems to be connected with mathematics. There is a common theme of dualism in Islam's holy book the Quran for example "Night and Day", "This Word, the Hereafter", "Odd and Even" etc. Below is a powerful numeric miracle that is easy to verify:

    The Quran says "consider the even and the odd". (Chapter 89 : Verse 3)

    Now turn to the index of the Quran and write down the Chapters (1,2,3...114) in one column and the number of verses in the chapter (7, 286, 200...6) in another

    Then add the two columns, that is add Chapter numbers to the number of Verses in that Chapter so we get 8(1+7), 288(2+286),203(3+200)....120(114+6)

    Then separate these numbers into odd and even and add up all the odd numbers and you will get 6555 and add up all the even numbers and you will get 6236.

    But also 1+2+3+...114 = 6555 and that 7+286+200+....+6= 6236.

    Conclusion: What is remarkable is that one total is exactly equal to the sum of the index numbers and the other is exactly equal to the sum of the verse numbers. It is like having 6555 coins in one bag ,6236 in another bag and then mixing them up and throwing them all in the air only to find that 6555 landed heads and 6236 landed tails!

    (For more detail http://www.simetrikkitap.com/binary/binary.html )

  66. Travis G., on Friday 14th January 2011, said:

    Interesting, but I'm also curious to know why we start our days at 12:00 rather than 1:00. I mean, numerically it makes more sense for the clock face to start at 1:00 and end at 12:59 before resetting.

  67. James, on Friday 14th January 2011, said:

    Travis G., see modular arithmetic and zero-based numbering for a likely explanation.

  68. Aryan, on Wednesday 19th January 2011, said:

    Because the Earth completes a whole rotation in 24 hours and an orbit in 365.25 days.

  69. Wayne Holiday, on Thursday 20th January 2011, said:

    The day does not start at 12.00, it starts at 00.00, a clock shows 23.59, then 00.00, just like age you don't start at 1, you also start from 0

  70. Edmundo, on Thursday 10th February 2011, said:

    Here is the response for Kent about how the Aztecs divided the day, they divided the day in a total of 8 intervals with 4 "main divisions" as follows:

    1) From midnight to sun rise (ruled by Iquiza Tonatiuh) 2) From sun rise to noon (ruled by Nepantla Tonatiuh) 3) From noon to sunset (ruled by Onaqui Tonatiuh) 4) From sunset to midnight (ruled by Youalnepantla)

    Each of these intervals was divided in two, giving a total of 8 divisions, these smaller subdivisions were called Izteotl (here is the god), and they corresponded to three hours of our time.

  71. Ben, on Friday 11th February 2011, said:

    Hey, You have a great writing style, "but across it would nevertheless be gotten" that's great. It's a good read.

  72. Steve, on Wednesday 30th March 2011, said:

    After reading this there are some interesting arguments.

    To me however, I see the answer as:

    The sun and the moon are both circles in the sky, and to depict a cycle as a year is (the same beginning and end as the seasons) would be done with a circle. The year is split (ish) into 12 lunar months (when observing the moons position using a reference in the sky) so this would have been the representation of the year in a picture. A circle split into 12 segments which when drawn in sand or on a wall wud easily overcome language barriers.

    Doing the same with a day would just follow suit, and would help to also explain why a clock is round :-)

    Anyways, grats on the (almost) 7 year thread

  73. شات الخليج, on Monday 18th April 2011, said:

    good ,,, ^_^ i liked

  74. Ben Prendergast, on Monday 13th June 2011, said:

    Err, we have two hands right? Thus accounting for the Sumerian 24 segments of aforementioned finger. It's a little known fact that they bleached one hand for night time accuracy.

    The end (of time).

  75. Jason, on Monday 12th September 2011, said:

    I'm finding it interesting that there are also 12 pairs of cranial nerves in the brain. Twelve for each side of the brain. Light and dark sides. Could the outward display of 12 hour ascent of the sun and 12 hour ascent of the moon just mirror the workings of our brain? It's so interestion to try and contemplate the unexplainable. A lot of good explanations that we can wrap ourselves around, though.

  76. Art, on Tuesday 6th December 2011, said:

    Hello All! Chicken and Egg argument, brushing aside the notion of "unexplainable".

    Why we use 24 hour days currently: Time, mass, distance, speed, dimensions and all other concepts we have created to deal with the framework of the environment that life on Earth operates within are all arbitrary and probably mostly meaningless nonsense in the scheme of what we assume may be a multiverse. Society and religion, be they ancient societies or belief systems like Christianity and Islam (only 1800 and 1300 years old respectively...recent even in the length of recorded history) are no basis for creating measurement systems that are reproduceable. What we really want to know here is "why are there 24 hours" in a common day. I think the answer is very much the same arbitrary answer as why VHS won over Betamax video tape in the 80's: The most conveniently available technology at that time happened to use that standard! If the Tower of the Winds in Athens or even Big Ben ever promoted a different standard, we would probably use it instead. That is not the reason why for the first clock builders, but precedence is the reason we still use it.

    Hours seem to me to be cleanly based on geometry. Astronomical measure enforce this if you look for rationalization, but the understanding of geometry had to come FIRST, before you could do much with the stars. It is quite easy to divide a circle into twelve segments with a compass (or stick and string) by segmenting it by it's radius, then splitting each for half-measures. Sun dials were circles, and base 12 also gives you cardinal points as well as a chance to use your geometry skills to your boss, the King of the Upper and Lower Nile.

    Base 60 counting of the human heartbeat (despite historical and individual variability of anatomy, very likely an easily reproducable average standard) easily converts into a usable minimum of time, which if again multiplied by 60 gives you that hour, very neatly in fact. Why 12/24? Egyptians used 10 hour days and nights, with two hours of variable twilight in-between. They were influenced by other cultures, all of whom figured Pi to be about 3.15 (pretty accurate).
    The Greeks were heavily influenced by the Egyptians, the Romans (6 watches of 4 hours, miles being fast march 1/4 hour distances etc..) were heavily influenced by Greeks and Egyptians...leading to the Byzantines and eventually the Holy Roman Empire and Europe's 13th century clock towers...and accessibility to the common scum. Simple really. Astronomical stuff never completely provides a satisfactory answer. Simple dirt, stick and string geometry gives us the answer every time. What is the reality behind what we call time...well, I bow out of that discussion.

  77. Tailspin, on Thursday 29th December 2011, said:

    "It is quite easy to divide a circle into twelve segments with a compass (or stick and string) by segmenting it by it's radius, then splitting each for half-measures"

    If I understand you correctly, if you segment a circle by it's radius and then split each segment in half, do you not end up with 16 segments and not 12? This would be base-2 since you keep halving segments.

  78. Symone, on Saturday 21st January 2012, said:

    So why did you split the year into 365 days.

  79. Phil Andy, on Thursday 26th January 2012, said:

    I dissent against this hour idea, even if it divides evenly; or, I dissent against the 60 divisions. What is interesting is that 24 (15), 60 (6), 12 (30), and even 10 (36) all go into 360 (the "convenient" year) evenly.

    Science is nothing if people aren't educated enough for it. Why teach children overly complex, silly, anti-fun, and dry systems for accuracy? Doing this is like converting the entire postal system to latitudes and longitudes to an accuracy of 3 places. Society works differently than all of this. We embrace all these complexities to make us unique, and it would be a much easier undertaking to jump on the whole metric bandwagon first. Seriously, 12 inches yet 16 ounces? Bah.

    Personally, I'd like to go for base 60 for everything. We just agree to create some other decans for hours that lets us divide by 60. We can also throw away the 5 extra days at the end of a year to scientific use only and celebrate a "scientific" year to make up for everything about every 60 years. So let's assume we want to make this as simple as possible and turn everything into base 60.

    • The convenient units of time in base 60. Screw metric.
    • 60 frames (divide by another 60 for photo finish accuracy)
    • 60 seconds (more than twice as fast as the old second)
    • 60 minutes
    • 60 hours (divide by 5 and you get back to the 12 you know and love)
    • 60 days (easy to divide in half for the 30)
    • 60 months (divide by 6 for a convenient year of 360 days)
    • 60 decades
    • +1 scientific decade.

    Computer application power plus a simple Sharpie on your perpetual calendar will let you know when the scientific milestones should happen, completely in parallel to your new simplified life. This system can easily be translated into any base of your choice including base 2, hex, 12, decimal, or even octal. With even less work you could try for a base degree (360) so you can truly think like a compass; a degree of a day is...?!

  80. Toolong, on Tuesday 31st January 2012, said:

    Why is it so long

  81. TOOTONGTOREADALLCOMMENTS, on Wednesday 1st February 2012, said:

    WHY IS THIS ARTICLE HAVE THE LONGEST COMMENTS SECTION I HAVE EVER SEEN BUT IS A GOOD ARTICLE AND IM USING IT FOR AN ASSIGNMENT IM GUNNA ACE

  82. Lauren, on Thursday 15th March 2012, said:

    My 9-year-old brother is insisting that because "day" is when the sun is out, there can't possibly be 24 hours in a day because if there were, there would be no night. When I told him that approximately 6,000,000,000 other people in the world all agreed that the day started at midnight and ended about 24 hours later at 11:59 PM, he said firmly, "Well, they're wrong." I told him that 6,000,000,000 people couldn't possibly all be wrong, especially when arguing with the opinion of one 9-year-old boy who just likes to argue with EVERYTHING, but he refuses to believe it, because, "If theh weh twenty foh hou-wahs in the day, theh would be no night." (Yes, he is adorable, even when he is being the single most stubborn and argumentative person on the planet.) I'm not much of a teacher -- I'm better at telling stories -- so how do I explain to him that (OMG HE'LL NEVER BELIEVE IT, HOW IN THE WORLD COULD IT BE TRUE) he's actually WRONG?

  83. Ncat, on Thursday 22nd March 2012, said:

    In my opinion: An idea of counting time of the day should be a simple division of the whole. The ancient civilizations counting method theory (12 or 60) doesn't make sense to me. If one divides anything (including the time of Earth's rotation) it is simplest and possibly the most accurate way to start with 1/2. Solar, Lunar and day cycles should have their own counts. If one continues with the division by 2 we end with 16, 32 or 64 "H" units a day. A further simple division of one "H" will give us 16, 32 or 64 "M" units for each "H". And further simple division of "M" give us 16, 32 or 64 "S". Now, one can go beyond this and explore how this fits into the solar and lunar cycles. I believe that the instituting the count of 24 hours has other reasons.

  84. Cammie, on Wednesday 4th April 2012, said:

    There isn't 24 hours in a full day because there's 365 1/4 days in a year so every 4 years it adds up to 4/4 and that equals 1 so that's a whole extra day so they put it there. So that has to effect the hours of a day.

  85. Cammie, on Wednesday 4th April 2012, said:

    They put it in Feb.

  86. Rudster, on Thursday 5th April 2012, said:

    it takes 23 hours 57 mins for the earth to rotate around the sun. But it was rounded up to 24 because it is an easier number. The 3 mins we miss is added up after 4 years it becomes a leap year. the shorter each day becomes will eventually lead to us adding more leap years.

  87. ReverendTed, on Sunday 20th May 2012, said:

    Someone asked this question on a messageboard and the "answer" I fabricated on the spot was that we started with the resting human heartbeat (about 60bps) as a smallest unit, then used this article's justification of 60 heartbeats to a "minute", 60 minutes in an "hour", and finding approximately 24 "hours" in a day, then working back from there to define seconds more precisely. (I did own up to the fact that this was a fabricated answer in the post.) But I think that misses the point that the Egyptians have been shown to have used the 12-hour clock before the Babylonians got their preference for 60 mixed into it. Perhaps it's all because a shadow traces a circle, and a circle divided in half, half, and halves again ends up with 12 segments.

  88. Shawn, on Friday 25th May 2012, said:

    1 What figure only has one side. Circle 2 Let's let the shape of a Cirlcle correspond to the value of 1 then 3 Draw a Circle and pretend it's Diameter is 1 unit of whatever measurement 4 Now determine the radius of the circle and move that radius so it is centered on the circle. 5 Follow the numbers 1 circle 1 diameter the radius would be .5 6 Now reduce all numbers by 10 times .1 .1 .05 7 If you were to place these circles into your original circle with the centers being mapped out on the end of the centered radius you will be able to fit exactly 24 circles with no overlaps.

  89. John Becker, on Thursday 28th June 2012, said:

    How about this for a simple answer?: This works for most people so be sure to try it yourself. Hold your closed fist (thumb up) at arm's length pointing at the horizon with the bottom of fist just at the horizon. As you raise your arm each distance covered by the closed fist very nearly equates to an hour of time. Most people will be pointing straight up after six fists. Do the math and it adds up to 24 for a full sweep of the day. Earliest man could then roughly tell how much time was remaining until midday or nightfall by measuring how many fists the sun would travel until then. All you need to know is what direction you are facing and it is a remarkably accurate way to measure time.

  90. william, on Thursday 9th August 2012, said:

    i think 24 hours is over complicated. like the oz, lb, mile, yard ect. we do every thing in 10's 100's or 1000's these days. 10mm to 1cm, 100cm to 1m, 1000m to 1km, 1000ml to 1l, 1000g to 1kg, 1000kg to 1 metric ton. and all of these are based on the planets most valuable resource, water. (1m^3 of water weighs 1 metric ton and that is exactly 1000 liters.) why can't we do the same with the hour, minuet, second, degree. 100 seconds to the Minuit, 100 minuets to the hour or degree, 10 hours to the day, 100 degree to the circle. it would make teaching kids low level geometry and how to tell the time easier. (i'm good at maths so i don't need it but my sister could have done with this. she's 8 and didn't know what an odd or even number was until 10 weeks ago.) the only cost to humanity would be changing all speed limits because the length of the hour would have changed, changing the length of a parsec because of the change to seconds, and probably some changes to how trig works.

    the rest of the world is going slowly metric while us in the UK and our cousins over the Atlantic (USA) stick to the imperial. i think it's time for metric to become the only way. leave imperial behind!

  91. dayne laird, on Friday 17th August 2012, said:

    I'm with John Becker (28thJune2012) because I like the simple answer that stands a chance of occuring naturally. It's a pretty natural thing to use your hand to measure the passage of an object like the sun across the sky. I've been using the technique John describes to figure out where Venus should be during the middle of the day to see if it's possible to see with binoculars, eg if I know it rises 2 hours before the sun, then when the sun is overhead Venus should be about two hands to the left (I'm in NZL). While doing this I found out that there were about 6 handwidths from the eastern or western horizon to overhead, and that makes 12 handwidths in a day. It got me thinking about maybe that was where 12 hours in a day came from (and then I ended up on this forum). I can easily imagine a couple of blokes from way in the past wanting to meet for a beer in a few days at a particular time of day and using that approach. They might say, "we meet in 4 days when the sun is 3 of (h)our hands above where the sun sets" - which would be about 3pm. While the number of hands across the sky may not be the actual origin of 12 hours in a day, it's proving a simple way to explain to my 6yo daughter that a clock doesn't have a "small hand and a big hand" it has an "Hour and Minute" hand, and the Hour hand measures time like "Our" hands can measure the sun's passage across the sky. Not sure how I'm going to explain the Minute hand yet....

  92. kendawg, on Thursday 6th September 2012, said:

    who cares?

  93. Philip, on Friday 7th September 2012, said:

    There are twelve inches in a foot. An inch is the width of your thumb. Coincidence? I think this has more to do with the number 12 than the number 24, since only half the sky is visible. (you have two feet, moon and sun) HOWEVER, you could fit WAY more than 12 moons or 12 suns (approx. same size) along a single path in the sky, so that is out! BUT, if you had the right size hands, there would be 12 in the sky, and this is elegant. Even if it didn't fit exactly you could choose twelve as a good estimate, to fit with the moon and the zodiak system. 12 hours in a day came from the hands.

    Each day has a clear beginning and ending, making it exactly 24,

    The division of time known as a second may have come from the heart rate, of a chill aboriginal; while the hour came from the number hands in the sky, to mark the sun at each hour. Then everything is stitched together, with approx. 3600 seconds in an hour.

  94. Tom, on Monday 3rd December 2012, said:

    Think about it! The decision had to involve the French! How else could you account for 24 segments in 360 degrees of rotation.

  95. Jim, on Thursday 6th December 2012, said:

    There are lots of interesting answers here, but my feeling is that we use 12 because of the 12 lunar cycles in a year. Measurements of time have always been based on astronomical observations. A day is one rotation of the earth, a month is an orbit of the moon, and a year is an orbit around the sun...

    Early cultures observed the phases of the moon and developed lunar calendars long before having the same level of understanding about a solar year. Saying "many moons ago" is an homage to this lunar calendar system. After the solar year was adopted (probably when we learned agriculture), we counted that it was 12 moons long... After that, dividing time by 12's was the natural thing to do.

  96. Forrest , on Tuesday 19th November 2013, said:

    Our time is unique to our existence on planet earth, find another planet in the cosmos that has the same 365.25 days, 24 hours in a day, 60 minutes in an hour, and 60 seconds in a minute, you will then find some alien on another world puzzling over the same thing we are puzzling over now.

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