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| Thread ID: 82484 | 2007-08-28 23:31:00 | Why is an hour 1/24 or a day? | mejobloggs (264) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 585796 | 2007-08-29 06:18:00 | I believe this might answer the original question. The rotation of the earth has an effect on how many time zones we have. The earth rotates every 24 hours which is why we have 24 hours in a day. We also have 24 time zones, each time zone stands for one hour. There are 360 degrees in a circle so it is 360 degrees around the earth. If we chopped the earth into hunks of 24, since there are 24 hours in a day, we would end up with each chunk being 15 degrees. Each time zone is 15 degrees wide at the equator. Here it is mathematically: 15 degrees x 24 hours = 360 degrees or 360 degrees/24 hours = 15 degrees. library.thinkquest.org Also there are 60 minutes in 1 hour and 60 seconds in 1 minute. |
winmacguy (3367) | ||
| 585797 | 2007-08-29 06:37:00 | I like that..it's better than the idea I had about humans originally having six fingers on each hand and six toes on each foot. :lol: From Joe who doesn't believe in evolution! :lol: |
andrew93 (249) | ||
| 585798 | 2007-08-29 11:26:00 | The Solar Day is the period between 2 successive transits of the sun on the observers meridian - actually each solar day is slightly different in period due to the Earths orbit round the sun being elliptical, and hence the use of Mean time or the average length of a day. This is a simplified explanation, as while the concept is relatively straight forward, the exact mechanics of the process are slightly more complicated. So we end up with a relationship between arc and time - the earth rotates 360 degrees in a mean solar day, therefore it will rotate 15 degrees in 1 hour of mean time, 1 degree in 4 minutes of mean time, 15 minutes of arc in in 1 minute of mean time etc etc, Greenwich Mean Time is the Local Mean Time on the Greenwich meridian (zero degrees), but every location has it's own Local Mean Time (LMT) dependent on its Longitude. For example Auckland International Airport is at Longitude 174 deg 47.5 min East so Local Mean Time is 11 hours 39 minutes and 10 seconds ahead of Greenwich Mean Time. Christchurch Intl Airport is at Longitude 172 Deg 32 min East so their Local Mean time is 11 hours 30 minutes and 8 seconds ahead of Greenwich - so Auckland Airport is 9 minutes and 2 seconds ahead of Christchurch Airport. This illustrates the relationship between Arc and Time, and explains the need for precise timing when taking Astronomical observations for Navigation. Obviously we cannot have every geographical location operating on its own Local Mean Time, so Countries adopt a Standard Time, for local time keeping. If it explains time to those who have doubts, I am happy to oblige, if it has confused any of you more, Sorry about that. |
KenESmith (6287) | ||
| 585799 | 2007-08-29 12:30:00 | I believe this might answer the original question. The earth rotates every 24 hours which is why we have 24 hours in a day Also there are 60 minutes in 1 hour and 60 seconds in 1 minute. i'm sorry, just like KenESmiths explanation (which was more nautical than anything else) that is circular logic. please consider that a mere few hundred years ago we thought the earth was flat, so timezones and the like would not have been a consideration - especially as it would have taken over a week to cross one had we 'invented' them back then. the answer is the fact that 12*, 24, 60 and 360 are all easily divisible, which way back in greek(?) times was a very handy thing. - and years are 355 day because 365 days is (almost) the time taken by the earth to orbit the sun. they then threw in leap years because a year is really 365.25 days, and if you don't account for that the seasons shift and calendars, used to predict moons and harvests, become useless and/or unreliable over the course of a century Notice also 24 = 2 x 3 x 4 and 60 = 3 x 4 x 5 (why they didn't use 120 is beyond me) and 360 = 3 x 4 x 5 x 6 which I think lends credence to the (very smart) laziness factor. uhh, that's just what was said in the first place about divisibility. multiples of 12 sharing the same factors is no surprise:lol: *note your 12 hour display on analouge clocks - i speculate 24 was too hard to fit/read when the only clock was a clock tower in the town square, and again when pocket watches came out. |
motorbyclist (188) | ||
| 585800 | 2007-08-29 22:10:00 | uhh, that's just what was said in the first place about divisibility. multiples of 12 sharing the same factors is no surprise:lol: Whats so funny? I'm the one that came up with the divisibility answer. :illogical Multiples of 12 is a consequence. 12 has very little to do with the fact the these numbers are divisible by 12. Any number that has 3 and 4 as a factor will be divisible by 12. What do all of those numbers have? 3 and 4 as their factors - hence they are divisible by 12. So aren't we saying the same thing? The point I illustrated with the choice of numbers, was quite possibly the (lazy) method used to select those numbers (i.e. consecutive low numbers). On the subject of degrees in a a circle, I don't know why they didn't pick 2520 degrees for a circle because there must have been a debate at the time. A number like 2520 is divisible by every single digit integer and a whole bunch of double digit integers too. Maybe the inventor perceived mental arithmetic was 10 times more difficult with a 4 digit number compared to a 3 digit number.....? I agree with your comments about the circular argument because it doesn't explain where the 24 came from. As for the nautical argument, we could just as easily use 15 hours and 24 degrees if we wanted to stick to 360 degrees in a circle. The numbers selected of 24 hours, 60 minutes, 360 degrees are entirely invented by humans. To someone who doesn't know what an hour is, to say the earth revolves around the sun in 24 hours you might as well say it revolves around the sun in 1 revolution......anyway, time to go and do so work for about 1/3rd of a revolution or 3.3 deci-hours. Andrew :cool: |
andrew93 (249) | ||
| 585801 | 2007-08-30 01:20:00 | :lol: From Joe who doesn't believe in evolution! :lol: No...No...No....that's DEVOLUTION! Not Evolution! :lol: :waughh: :eek: |
SurferJoe46 (51) | ||
| 585802 | 2007-08-30 01:25:00 | Why not? The French tried decimal time for a short time after the Revolution; the unit is arbitrary, but a 10-hour day meant that hours were inconveniently long. The widely purchased (if not widely read) book A Short History of Time will not help. Here's an astronomer's answer (curious.astro.cornell.edu/question.php?number=594). |
Graham L (2) | ||
| 585803 | 2007-08-30 01:54:00 | No...No...No....that's DEVOLUTION! Not Evolution! Devolution? There was no advantage to having 6 fingers so humans lost one from each hand? A bit like the tail I suppose......... |
andrew93 (249) | ||
| 585804 | 2007-08-30 01:56:00 | The French tried decimal time for a short time after the Revolution; the unit is arbitrary, but a 10-hour day meant that hours were inconveniently long. If each hour was made up of 100 minutes and 100 or 1000 seconds then it would only require a change in our mind-set. |
andrew93 (249) | ||
| 585805 | 2007-08-30 01:59:00 | The French weren't prepared to make that change. They didn't like the 10 day week, either, even though they did have 10 fingers each. (Some didn't have even one head, after their Tribunal appearances.) | Graham L (2) | ||
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