How does an obelisk tell time

But a lot of things we are used to would have to change. Life would be different, that's for sure! Thanks, Matthew! We Wonder if people were less obsessed with time without so many clocks around? We think that's ok. It is a very technical term, as opposed to other words out there.

But thanks for joining the conversation! Maybe so, Myles but it can certainly be very useful. We are glad you took the time to check out this Wonder! Thanks for sharing, Xavier! That's a cool connection to this Wonder. Have you ever seen the Washington monument in person before? That's a great question, Blayzifer! You should submit it to our Wonder Bank.

That is a great question, Ava some would say the most important question of all! There are a lot of answers out there, so we will have to leave it up to you to decide which one you think is the right one.

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Help spread the wonder of families learning together. We sent you SMS, for complete subscription please reply. Follow Twitter Instagram Facebook. How did people keep time before clocks? What were some of the earliest timekeeping devices? Why are sundials not always reliable? Wonder What's Next? No need to hurry. Try It Out Got some extra time to spare? Use it to explore the following activities with a friend or family member: How do you keep track of the time today?

Spend a few minutes scouring your house, writing down every example of a timekeeping device you can find. How many clocks do you have? What about wristwatches? Appliances with clocks?

Share your list with a family member. Can they think of any you missed? Want to try your hand at crafting your own ancient timekeeping device?

With just a few simple materials you probably already have around the house, you can Make a Sundial from a Plate! After you finish your homemade sundial, give it a try in a sunny spot outside. Adjust it so that it displays the current time, and then keep track to see how accurate it is. The hourglass was a popular timekeeping device long, long ago.

Today, you might use a small hourglass as an egg timer or to time game play during a board game. You can also make your own homemade hourglass. Did you get it? Test your knowledge. What are you wondering? Wonder Words recess clock oven cycle cast means typical shortage device section obelisks natural fortunately appliance appointment constellation hourglass particular Take the Wonder Word Challenge.

Join the Discussion. Maya Apr 4, One version was the hemispherical dial, a bowl-shaped depression cut into a block of stone that carried a central vertical gnomon or pointer and was scribed with sets of hour lines. The hemicycle, said to have been invented around BCE, removed the useless half of the hemisphere to give an appearance of a half-bowl cut into the edge of a square block.

Water clocks were among the earliest timekeepers that did not depend on the observation of celestial bodies. Other clepsydras were cylindrical or bowl-shaped containers designed to slowly fill with water coming in at a constant rate. Markings on the inside surfaces measured the passage of "hours" as the water level reached them. These clocks were used to determine hours at night, but they may have been used in daylight as well.

Another version consisted of a metal bowl with a hole in the bottom. The bowl would fill and sink in a certain time when placed in a container of water.

These are still in use in North Africa in the 21st century. More elaborate and impressive mechanized water clocks were developed between BCE and CE by Greek and Roman horologists and astronomers.

The added complexity was aimed at making the flow more constant by regulating the pressure of the water and at providing fancier displays of the passage of time. Some water clocks rang bells and gongs. Others opened doors and windows to show little figures of people or moved pointers, dials, and astrological models of the universe.

The rate of flow of water is very difficult to control accurately, so a clock based on that flow could never achieve excellent accuracy. People were naturally led to other approaches. This octagonal structure showed both sundials and mechanical hour indicators. It featured a hour mechanized clepsydra and indicators for the eight winds from which the tower got its name. It displayed the seasons of the year and astrological dates and periods.

The Romans also developed mechanized clepsydras, but their complexity accomplished little improvement over simpler methods for determining the passage of time.

Third-century Chinese clepsydras drove various mechanisms that illustrated astronomical phenomena. One of the most elaborate clock towers was built by Su Sung and his associates in CE. Su Sung's mechanism incorporated a water-driven escapement invented around CE. The Su Sung clock tower, over 30 feet tall, possessed a bronze power-driven armillary sphere for observations, an automatically rotating celestial globe, and five front panels with doors that permitted the viewing of changing manikins which rang bells or gongs.

It held tablets indicating the hour or other special times of the day. When the long stem with 5 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. The merkhet , the oldest known astronomical tool, was an Egyptian development of around BCE. A pair of merkhets was used to establish a north-south line or meridian by aligning them with the Pole Star. They could then be used to mark off nighttime hours by determining when certain other stars crossed the meridian. In the quest for better year-round accuracy, sundials evolved from flat horizontal or vertical plates to more elaborate forms.

One version was the hemispherical dial, a bowl-shaped depression cut into a block of stone, carrying a central vertical gnomon pointer and scribed with sets of hour lines for different seasons. The hemicycle, said to have been invented about BCE, removed the useless half of the hemisphere to give an appearance of a half-bowl cut into the edge of a squared block. Before we continue describing the evolution of ways to mark the passage of time, perhaps we should broadly define what constitutes a clock.

All clocks must have two basic components:. The history of timekeeping is the story of the search for ever more consistent actions or processes to regulate the rate of a clock.

Water clocks were among the earliest timekeepers that didn't depend on the observation of celestial bodies. Later named clepsydras "water thieves" by the Greeks, who began using them about BCE, these were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. Other clepsydras were cylindrical or bowl-shaped containers designed to slowly fill with water coming in at a constant rate.

Markings on the inside surfaces measured the passage of "hours" as the water level reached them. These clocks were used to determine hours at night, but may have been used in daylight as well.