Why hours

The clepsydra, or water clock, was also used to record time during the night, and was perhaps the most accurate timekeeping device of the ancient world. The timepiece--a specimen of which, found at the Temple of Ammon in Karnak, dated back to B. Once both the light and dark hours were divided into 12 parts, the concept of a hour day was in place. The concept of fixed-length hours, however, did not originate until the Hellenistic period, when Greek astronomers began using such a system for their theoretical calculations.

Hipparchus, whose work primarily took place between and B. Despite this suggestion, laypeople continued to use seasonally varying hours for many centuries. Hours of fixed length became commonplace only after mechanical clocks first appeared in Europe during the 14th century. Hipparchus and other Greek astronomers employed astronomical techniques that were previously developed by the Babylonians, who resided in Mesopotamia. The Babylonians made astronomical calculations in the sexagesimal base 60 system they inherited from the Sumerians, who developed it around B.

Although it is unknown why 60 was chosen, it is notably convenient for expressing fractions, since 60 is the smallest number divisible by the first six counting numbers as well as by 10, 12, 15, 20 and Although it is no longer used for general computation, the sexagesimal system is still used to measure angles, geographic coordinates and time.

In fact, both the circular face of a clock and the sphere of a globe owe their divisions to a 4,year-old numeric system of the Babylonians. The Greek astronomer Eratosthenes who lived circa to B. A century later, Hipparchus normalized the lines of latitude, making them parallel and obedient to the earth's geometry. He also devised a system of longitude lines that encompassed degrees and that ran north to south, from pole to pole.

In his treatise Almagest circa A. Each degree was divided into 60 parts, each of which was again subdivided into 60 smaller parts. Keeping time While 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 time-keeping 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. Today, the standard definition for time is no longer based on the rotation of the Earth around the Sun, but on atomic time. A second is defined as: "9,,, periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium atom.

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Skip to navigation Skip to content. There's no good reason to have it; just a big inconvenience. Hog wash, just ask hog wash. Thanks for sharing your thoughts on this Wonder topic, Linda!

The time change is a debated topic for sure! We appreciate you sharing your thoughts about Daylight Savings Time, Mary! We're glad you stopped by Wonderopolis! Great question, Stanley! The Wonder tells us "the idea was first suggested in an essay by Benjamin Franklin in , and later proposed to British Parliament by Englishman William Willett Hi, Stanley!

Sometimes it may be annoying to change the clocks, but "Daylight Saving Time is most helpful to those who live farther from the equator, where daylight hours are much longer in the summer than in the winter. SueAnn, what you mean then is that you would like 'Daylight Savings Time' to extend all year long.. When we actually need to add an hour of light, they take it away in the winter, when the natural earth orbit already takes an hour away in the winter so we actually lose 2hrs of daylight in the evening.

That is a good point, SueAnn! Safety is always important. We're glad you being cautious! Thanks for sharing your thoughts about this Wonder! Hello, Macky! Thanks for sharing what you learned with us! Visit here to see a map of countries that do and do not participate in DST. Hello, Joanne Luce!

You make some interesting points. Thanks for sharing! That's true, jubiloodoodifu! Enjoy the warm weather! Hey, kc :p! Thanks for sharing your opinion about Daylight Saving Time. There are many people with differing opinions about Daylight Saving Time. One thing is for sure, it is never fun losing the hour of sleep the first night!

Great question, Owen Morgan! Countries farther away from the equator benefit more from Daylight Saving Time. Some countries close to the equator do not participate in it, as well as a few U. Welcome, pie! You do get more time with the sun out - you save daylight time! We are sorry you do not enjoy daylight savings time. Some people prefer the shorter days. That's what makes us all unique! We certainly do have Wonders about sports, Maren!

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Thank you for sharing additional information, Gary! We did some extra digging, and according to the Encyclopaedia Britannica, Englishman William Willett is credited with first proposing the implementation of Daylight Saving Time. We've updated the Wonder text to reflect that!

Thanks for sharing your opinion, Stanley! We have lots of Wonders for you to explore! Enjoy, Wonder Friend! Thanks for sharing those two great facts about your grandpa, WonderGirl! Please wish him a very happy birthday from your friends in Wonderopolis! WOW, Mrs. We're sure glad you visited today and let us know all the awesome new things you learned!

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Want to add a little wonder to your website? Help spread the wonder of families learning together. We sent you SMS, for complete subscription please reply. Follow Twitter Instagram Facebook. Why do we change the clocks twice a year? Why do we have Daylight Saving Time? Is Daylight Saving Time observed in the same way around the world? Tags: See All Tags American Samoa , Arizona , autumn , back , Benjamin Franklin , British Parliament , clock , conceived , Congress , Daylight Saving Time , December , energy , equator , equatorial , europe , fall , forward , geography , Government , Hawaii , hemisphere , history , hour , Iceland , Kyrgyzstan , longer , march , minute , month , November , observing , October , practice , Puerto Rico , save , season , spring , springing , standard , Standard Time , summer , time , U.

Wonder What's Next? Try It Out Ready to spring forward or fall back? Check out the following activities with a friend or family member: Does your country observe Daylight Saving Time? Wonder which other countries around the world do the same? Check out this map to see which countries observe DST around the world.

Plan ahead! If it's fall where you live and you observe Daylight Saving Time, then you have an extra hour coming your way soon! What will you do with it? We often lament the fact that we don't have enough hours in the day. Here's your chance to get an extra hour. How will you make the most of it? Brainstorm a list of clever and fun ideas you could do to take advantage of that extra hour afforded by Daylight Saving Time in the fall. We think we're going to use ours to think up more Wonders of the Day!

While the debate over the value of Daylight Saving Time continues, firefighters around the country are putting it to good use in order to promote a very important message. Changing the clocks is a great reminder to change your smoke detector batteries as well. It is also a perfect opportunity to review your family's fire escape plan with your child.

Ten is easy to count—you have 10 fingers and 10 toes—but 10 can only be divided by two and five. To tell time at night, the Egyptians looked to the stars.

Like the Sun, the stars move across the sky as time passes. By choosing a handful of stars to follow, the Egyptians could tell what time of night it was by looking up to check where they were in the sky. They chose 12 stars to track to help them measure the time when it was completely dark outside.