The Natural Enquirer: The study of horology
I was asked about the origin of hours, minutes and seconds? I submit this for your edification.
Horology is the study of clocks and time. Not until somewhat recently (that is, in terms of human history) did people find a need for knowing the time of day. As best we know, 5,000 to 6,000 years ago great civilizations in the Middle East and North Africa began to make clocks to augment their calendars. With their attendant bureaucracies, formal religions and other burgeoning societal activities, these cultures apparently found a need to organize their time more efficiently.
This all dates back to the Ancient Babylonians, who liked to count in base 60. Ratios of 6, 12, 60, and 360 were seen by them as being “round” numbers in the same way that we use base 10 and see 5, 10, 100 etc. as useful numbers to divide things up into. 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. All these numbers have survived for 4,000 years, despite the fact that we have changed our numbering system to base 10. In England, when I was young, we still measured with feet, each divided into 12 inches. Americans still do!
The year is nearly 360 days long, and the Babylonians split it into 12 months. Other civilizations based their calendar on the moon and had 13 months. We still have problems with this today because Easter is based on the lunar calendar, and migrates around the Julian calendar in a complex way. Chinese new year is still based on the Lunar calendar.
Sun Clocks, the Sumerian culture was lost without passing on its knowledge, but the Egyptians were apparently the next to formally divide their day into parts something like our hours. Obelisks (slender, tapering, four-sided monuments) were built as early as 3500 BC. Their moving shadows formed a kind of sundial, enabling people to partition the day into morning and afternoon. Obelisks also showed the year’s longest and shortest days when the shadow at noon was the shortest or longest of the year. Later, additional markers around the base of the monument would indicate further subdivisions of time. Another Egyptian shadow clock, or sundial, possibly the first portable timepiece, came into use around 1500 BC. This device divided a sunlit day into 10 parts plus two “twilight hours” in the morning and evening. When the long stem with five variably spaced marks was oriented east and west in the morning, an elevated crossbar on the east end cast a moving shadow over the marks. At noon, the device was turned in the opposite direction to measure the afternoon “hours.”
A sundial described in 1300 BCE reveals that the Egyptians determined a daily cycle to be made up of ten hours of daylight from sunrise to sunset, two hours of twilight and 12 hours of night. Their calendar year was divided into 36 decans, each 10 days long, plus five extra days, totaling to a 365 day year. Each decan was equivalent to a third of the zodiacal sign and was represented by a decanal constellation. The night corresponded to about 12 decans, half a day to 18 decans. Similar to the system used in Oriental clocks, the night was thus divided into twelve hours, with seasonable variations of the hour’s length. Later, Hellenistic astronomers introduced equinoctial hours of equal length.
The Babylonians (in about 300-100 BCE) performed astronomical calculation in the sexagesimal (base-60) system. This was extremely convenient for simplifying time division, since 60 is divisible by 2, 3, 4, 5, 6, and 10. What we now call a minute derives from the first fractional sexagesimal place; the second fractional place is the origin of the second. So now you know where they came from. Maybe I will try to explain metric time later, it is much more difficult.
I hope this answers your question.
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So why do we have daylight saving time? Moving our clocks an hour ahead means more sunlight later in the day. Aside from its obvious brightening effect, this act of time trickery also conserves energy. By “springing ahead,” we shorten the peak period when electricity is needed to power lights, televisions, and other appliances before bedtime.
Benjamin Franklin was the first to suggest the idea in his essay, “An Economical Project.” But William Willett is considered the originator of daylight savings. He started the campaign that led to “summer time,” ratified in the U.K. in 1916. European countries adopted daylight saving time over the next two years, and the United States followed with an act in 1918, though the new system was practiced inconsistently.
In 1966, the U.S. Uniform Time Act established a set pattern for observing daylight saving time across the country. The act was revised in 1986, moving the start date a month earlier to the first Sunday of April. This saves an additional 300,000 barrels of oil each year.
Approximately 70 countries observe daylight saving time, but the start and end dates vary. And countries near the equator don’t participate since their daylight hours change minimally throughout the year.
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“Ever since the invention of the calendar, man’s days have been numbered.”
Peter Dring is a retired nature biologist and phenologist who lives in the Land ‘O Lakes area. To comment on this story, visit the “Outdoors” section of StarJournalNOW.com.