We divide the day into 24 hours, one hour into 60 minutes and one minute into 60 seconds. What other comparably accurate methods have been used throughout history? Show By Kylie Andrews Tick, tock: our time system came from the ancient Egyptians and Babylonians. (Source: iStockphoto) Related Stories
While each country has (in broad terms) historically had distinct measurements for distance, weights etc the method of splitting the day into 24 hours, one hour into 60 mins and one minute into 60 seconds seems to be the only one in use, and indeed to me the only one I know of. This nonmetric measurement of time is far from ideal, but what other comparably accurate methods have been used historically? "The origin of our time system of 24 hours in a day with each hour subdivided into 60 minutes and then 60 seconds is complex and interesting," says Dr Nick Lomb, consultant curator of astronomy, from the Sydney Observatory. Our 24hour day comes from the ancient Egyptians who divided daytime into 10 hours they measured with devices such as shadow clocks, and added a twilight hour at the beginning and another one at the end of the daytime, says Lomb. "Nighttime was divided in 12 hours, based on the observations of stars. The Egyptians had a system of 36 star groups called 'decans' — chosen so that on any night one decan rose 40 minutes after the previous one. "Tables were produced to help people to determine time at night by observing the decans. Amazingly, such tables have been found inside the lids of coffins, presumably so that the dead could also tell the time." In the Egyptian system, the length of the daytime and nighttime hours were unequal and varied with the seasons. "In summer, daytime hours were longer than nighttime hours while in winter the hour lengths were the other around," says Lomb. ^ to top Ancient Babylonians: hours and minutesThe subdivision of hours and minutes into 60 comes from the ancient Babylonians who had a predilection for using numbers to the base 60. For example, III II (using slightly different strokes) meant three times 60 plus two or 182. "We have retained from the Babylonians not only hours and minutes divided into 60, but also their division of a circle into 360 parts or degrees," says Lomb. "What we have not retained is their division of a day into 360 parts called 'ush' that each equalled four of minutes in our time system." Lomb says it's likely that the Babylonians were interested in 360 because that was their estimate for the number of days in a year. Their adoption of a base 60 system was probably allowed them to make complex calculations using fractions. ^ to top Ancient ChineseThe ancient Chinese used a dual time system where they divided the day into 12 socalled, 'double hours', originally with the middle of the first double hour being at midnight. They also had a separate system in which a day was divided into 100 equal parts called 'ke', that are sometimes translated as 'mark' into English. "What complicated this arrangement was that the two systems did not mesh well since there were a nonintegral number of ke in each double hour, specifically 8 1/3. Because of this inconvenience, much later on, in the year 1628 of our era, the number of ke in a day was reduced to 96," says Lomb. ^ to top Other culturesWhile many cultures had their own calendars, there doesn't appear to be evidence for equivalent methods for keeping time. "There is a lot of information available on the Mayan calendar, but I have not seen anything to indicate if, and how, they subdivided the day," says Lomb. "Similarly, though it is well known that the Australian Aboriginal people had seasonal calendars and used the sky to indicate the seasons, I have not seen anything on how they kept time." ^ to top Metric time?In 1998, the Swiss watch company Swatch introduced the concept of a decimal Internet Time in which the day is divided into 1000 'beats' so that each beat is equal to 1 minute 26.4 seconds. The beats were denoted by the @ symbol, so that, for example, @250 denotes a time period equal to six hours. "So far this system has not caught on," says Lomb. "For each country the immense cost and difficulty in switching over to this or another metric time system would be enormous, possibly as great, if not greater, than it was for Australia to switch to decimal currency back in 1966," he says. "The insurmountable difficulty though would be the prior hurdle of getting each country in the world both to agree to change and to agree on a common system of decimal time. I think that I am safe in stating that there will be no change from the present system of time measurement in the foreseeable future." Keeping timeWhile our units for measuring time seem to be here to stay, the way we measure time has changed significantly over the centuries. The Ancient Egypitians used sundials and waterclocks, as did several civilisations after them. Hourglasses were also an important timekeeping device before the invention of mechanical and pendulum clocks. The development of modern quartz watches and atomic clocks has enabled us to measure time with increasing accuracy. Dr Nick Lomb was interviewed by Kylie Andrews. Tags: archaeology, inventions, mathematics, physics ^ to top Published 15 November 2011 Email ABC Science
[an error occurred while processing this directive] Use these socialbookmarking links to share Why are there 24 hours in a day?. Use this form to email 'Why are there 24 hours in a day?' to someone you know: By clicking 'Send to a friend' you agree ABC Online is not responsible for the content contained in your email message. Is 24 hours one day or two days?However, 24 hours is only the length of one Earth day on average; in reality, most days are either longer or shorter. Although it takes Earth 23 hours and 56 minutes and 4.09 seconds to spin 360 degrees on its axis,...
Is a day 24 hours exactly?Day Length
On Earth, a solar day is around 24 hours. However, Earth's orbit is elliptical, meaning it's not a perfect circle. That means some solar days on Earth are a few minutes longer than 24 hours and some are a few minutes shorter.
Is 24 hours all day and night?There are 24 hours in a day. The day is divided into day(time) and night(time). Daytime is from sunrise (this varies, but we can say approximately 6am) to sunset (we can say approximately 6pm). Nighttime is from sunset to sunrise.
