Clock

History About Clock

A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece.[1] In general usage today a "clock" refers to any device for measuring and displaying the time. Watches and other timepieces that can be carried on one's person are often distinguished from clocks.[2]
The Shepherd gate clock at the Royal Observatory, Greenwich
Replica of an ancient Chinese incense clock

The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.

Questions of time

5)A road widening project started on 23 July 2007. It is scheduled to be completed in 5 months 15 days. When will it be completed?

6)Find the duration from August 2004 to October 2008.

7)Find the duration from 19 June 2005 to 3 March 2008.

Questions of time

1)Find the duration from March 2008 to October 2008.

2)Find the duration from 1957 to2008.

3)Find the duration from 18 September 2007 to 5 December 2007.

4)A few groups of junior football teams were at a training camp from 14 October 2007 to 6 February 2008.How long were they at camp?

game about clock

A sundial is a device that measures time by the position of the Sun. In common designs such as the horizontal sundial, the sun casts a shadow from its style onto a surface marked with lines indicating the hours of the day. The style is the time-telling edge of the gnomon, often a thin rod or a sharp, straight edge. As the sun moves across the sky, the shadow-edge aligns with different hour-lines. All sundials must be aligned with the axis of the Earth's rotation to tell the correct time. In most designs, the style must point towards true celestial north (not the north magnetic pole or south magnetic pole). That is, the style's horizontal angle must equal the sundial's geographical latitude.
Unfortunately, it is common for inexpensive decorative sundials to have incorrect hour angles, and these cannot be adjusted to tell correct time.

did time is use for us????

time help us to wake up at morning...
time help us to now when we have do something....

THE BEGINNING OF TIME

The Egyptians were the first people who created a twenty-four hour day.  Time was a little bit different in those days.  The night was divided up into twelve hours, which were designated by the position of stars in the sky.  The day was divided into ten hours and a shadow clock was used to keep track of these hours.  The twilight hours were the hours before dawn and after sunset.

   The Egyptians thought they were the first to invent the shadow clock, but they were mistaken.  At the same time, the Chinese, Babylonians, Greeks and the Romans were using instruments to tell time.  Sundials were used in some of these groups, not because they work better, just because that's how they decided to tell time.

      After a while, the Egyptians and other ancient societies realized that the sun rose and set in different places in the summer and winter.  In fact, the sun never took the same course on any one day throughout the year!  They tried everything, until they realized that if they would just put the post of the sundial in at a special angle, it would work all year.  

TIME PAST.....

The measurement of time began with the invention of sundials in ancient Egypt some time prior to 1500 B.C. However, the time the Egyptians measured was not the same as the time today's clocks measure. For the Egyptians, and indeed for a further three millennia, the basic unit of time was the period of daylight. The Egyptians broke the period from sunrise to sunset into twelve equal parts, giving us the forerunner of today's hours. As a result, the Egyptian hour was not a constant length of time, as is the case today; rather, as one-twelfth of the daylight period, it varied with length of the day, and hence with the seasons. It also varied from place to place on the surface of the Earth. And of course, time as a measurable concept effectively ceased during the hours of darkness.

The need for a way to measure time independently of the sun eventually gave rise to various devices, most notably sandglasses, waterclocks, and candles. The first two of these utilized the flow of some substance to measure time, the latter the steady fall in the height of the candle. All three provided a metaphor for time as something that flows continuously, and thus began to shape the way we think of time.

Candle clocks

A candle clock

It is not known specifically where and when candle clocks were first used; however, their earliest mention comes from a Chinese poem, written in 520 by You Jianfu. According to the poem, the graduated candle was a means of determining time at night. Similar candles were used in Japan until the early 10th century.^[38]
The candle clock most commonly mentioned and written of is attributed to King Alfred the Great. It consisted of six candles made from 72 pennyweights of wax, each 12 inches (30 cm) high, and of uniform thickness, marked every inch (2.5 cm). As these candles burned for about four hours, each mark represented 20 minutes. Once lit, the candles were placed in wooden framed glass boxes, to prevent the flame from extinguishing.^[39]
The most sophisticated candle clocks of their time were those of Al-Jazari in 1206. One of his candle clocks included a dial to display the time and, for the first time, employed a bayonet fitting, a fastening mechanism still used in modern times.^[40] Donald Routledge Hill described Al-Jazari's candle clocks as follows:

The candle, whose rate of burning was known, bore against the underside of the cap, and its wick passed through the hole. Wax collected in the indentation and could be removed periodically so that it did not interfere with steady burning. The bottom of the candle rested in a shallow dish that had a ring on its side connected through pulleys to a counterweight. As the candle burned away, the weight pushed it upward at a constant speed. The automata were operated from the dish at the bottom of the candle. No other candle clocks of this sophistication are known.^[41]

history

With respect to human history, timekeeping is a relatively recent human desire—probably 5000 to 6000 years old. It was most likely initiated in the Middle East and North Africa

Introduction

You can't add any more hours to your day so learning to manage your time more effectively will help you plan your work more efficiently and ensure deadlines are met. Managing time effectively is a particularly crucial ingredient in successful projects. It is important to manage both your personal and professional lives because as much as you try to keep them separate they cannot help but infringe upon one another. Managing your own time will not only benefit you but those around you as well.
Within your team you will need to recognise that people work differently, some may have a structured view of working (where promptness is highly valued and most tasks are done one at a time) whereas others have a non-structured view of working (where promptness is more context related and greater emphasis is placed on multitasking). All project work requires a degree of flexibility but as a project manager you need to know when to be strict with schedules and plans and when to take a less structured approach. If your work requires you to deal with different countries then you will need to appreciate that different cultures have different perceptions of time i.e. in terms of how they view punctuality and average number of work hours.
One of the most important messages about time management is that it takes place in the present moment; the choices of how you manage your time are only available to you now.
This resource aims to help you manage your time more effectively by suggesting a number of tools and approaches that you may find applicable to your own circumstances.

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© 2009 Northumbria University, on behalf

Water Clocks

Joseph Needham speculated that the introduction of the outflow clepsydra to China, perhaps from Mesopotamia, occurred as far back as the 2nd millennium BC, during the Shang Dynasty, and at the latest by the 1st millennium BC. By the beginning of the Han Dynasty, in 202 BC, the outflow clepsydra was gradually replaced by the inflow clepsydra, which featured an indicator rod on a float. To compensate for the falling pressure head in the reservoir, which slowed timekeeping as the vessel filled, Zhang Heng added an extra tank between the reservoir and the inflow vessel. Around 550 AD, Yin Gui was the first in China to write of the overflow or constant-level tank added to the series, which was later described in detail by the inventor Shen Kuo. Around 610, this design was trumped by two Sui Dynasty inventors, Geng Xun and Yuwen Kai, who were the first to create the balance clepsydra, with standard positions for the steelyard balance.^[36] Joseph Needham states that:

... [the balance clepsydra] permitted the seasonal adjustment of the pressure head in the compensating tank by having standard positions for the counterweight graduated on the beam, and hence it could control the rate of flow for different lengths of day and night. With this arrangement no overflow tank was required, and the two attendants were warned when the clepsydra needed refilling.^[36]

Between 270 BC and 500 AD, Hellenistic (Ctesibius, Hero of Alexandria, Archimedes) and Roman horologists and astronomers were developing more elaborate mechanized water clocks. The added complexity was aimed at regulating the flow and at providing fancier displays of the passage of time. For example, some water clocks rang bells and gongs, while others opened doors and windows to show figurines of people, or moved pointers, and dials. Some even displayed astrological models of the universe.
Some of the most elaborate water clocks were designed by Muslim engineers. In particular, the water clocks by Al-Jazari in 1206 are credited for going "well beyond anything" that had preceded them. In his treatise, he describes one of his water clocks, the elephant clock. The clock recorded the passage of temporal hours, which meant that the rate of flow had to be changed daily to match the uneven length of days throughout the year. To accomplish this, the clock had two tanks: the top tank was connected to the time indicating mechanisms and the bottom was connected to the flow control regulator. At daybreak the tap was opened and water flowed from the top tank to the bottom tank via a float regulator that maintained a constant pressure in the receiving tank.

Timekeepng Devices

Sundials have their origin in shadow clocks, which were the first devices used for measuring the parts of a day.^[12] The oldest known shadow clock is from Egypt, and was made from green schist. Ancient Egyptian obelisks, constructed about 3500 BC, are also among the earliest shadow clocks.^[6][13][14]

The Luxor Obelisk in Place de la Concorde, Paris, France

                                                                                                                                                        Egyptian shadow clocks divided daytime into 10 parts, with an additional four "twilight hours"—two in the morning, and two in the evening. One type of shadow clock consisted of a long stem with five variable marks and an elevated crossbar which cast a shadow over those marks. It was positioned eastward in the morning, and was turned west at noon. Obelisks functioned in much the same manner: the shadow cast on the markers around it allowed the Egyptians to calculate the time. The obelisk also indicated whether it was morning or afternoon, as well as the summer and winter solstices.^[6][15] A third shadow clock, developed c. 1500 BC, was similar in shape to a bent T-square. It measured the passage of time by the shadow cast by its crossbar on a non-linear rule. The T was oriented eastward in the mornings, and turned around at noon, so that it could cast its shadow in the opposite direction.^[16]
Although accurate, shadow clocks relied on the sun, and so were useless at night and in cloudy weather.^[15][17] The Egyptians therefore developed a number of alternative timekeeping instruments, including water clocks, hourglasses, and a system for tracking star movements. The oldest description of a water clock is from the tomb inscription of the 16th-century BC Egyptian court official Amenemhet, identifying him as its inventor.^[18] There were several types of water clocks, some more elaborate than others. One type consisted of a bowl with small holes in its bottom, which was floated on water and allowed to fill at a near-constant rate; markings on the side of the bowl indicated elapsed time, as the surface of the water reached them. The oldest-known waterclock was found in the tomb of pharaoh Amenhotep I (1525–1504 BC), suggesting that they were first used in ancient Egypt.^[15][19][20] The ancient Egyptians are also believed to be the inventors of the hourglass, which consisted of two vertically aligned glass chambers connected by a small opening. When the hourglass was turned over, grains of sand fell at a constant rate from one chamber to the other.^[17] Another Egyptian method of determining the time during the night was using plumb-lines called merkhets. In use since at least 600 BC, two of these instruments were aligned with Polaris, the north pole star, to create a north–south meridian. The time was accurately measured by observing certain stars as they crossed the line created with the merkhets.

Time for Change

Since 1761, timekeeping has significantly changed.  In 1900, pendulum clocks had been finely tuned so as to only be off by 1/100 of a second each day.  In the '20s, scientists discovered quartz crystals could keep even more accurate time than a pendulum and were only off about 1/500 of a second each year.  Half way through the 20th century, atomic clocks were built that would only be off by one second every 300 million years.   Who really needs a clock that accurate? 

    It is evident that times have certainly changed.  Clocks have made major leaps and bounds since the days of the shadow clock.  Now we have accurate, reliable clocks that we can use day and night.   Some of our clocks will run for years without so much as a change of batteries or a twist of a little knob.  We have certainly developed the concept of time and incorporated it into every moment of our lives.

The Contest

When sailors sailed across the ocean, they could only tell their position using two methods.  When they were traveling from North to South, they could tell their position using Polaris, the North Star.  But, when they were traveling from East to West, they ran into a problem.  Pendulum clocks couldn't be used because the pendulums were highly sensitive and could be easily shaken, making the clocks inaccurate.   In 1707, a British fleet crashed into the Scilly Islands, killing two thousand soldiers and destroying four ships.  Seven years late, the British government offered twenty thousand pounds to whoever built a clock that would keep accurate time at sea.   This clock would have to be accurate to the second, so as to avoid another unfortunate accident.

    John Harrison, a carpenter, was the winner of the contest.  In 1728, John heard about the contest and began work on a solution.  Thirty-three years and three enormous clocks, John's small fourth clock was tested.  When the testing crew arrived in Jamaica 161 days later, the clock was only five seconds off.  John Harrison collected his prize money at the age of seventy-nine.

Galileo's Discovery

Galileo made an amazing contribution to the world of time, simply by not paying attention in church.  The year was 1581 and Galileo was 17.  He was standing in the Cathedral of Pisa watching the huge chandelier swinging back and forth from the ceiling of the cathedral.  Galileo noticed that no matter how short or long the arc of the chandelier was, it took exactly the same amount of time to complete a full swing.  

   The chandelier gave Galileo the idea to create a pendulum clock.  While the clock would eventually run of energy, it would keep accurate time until the pendulum stopped.  If the pendulum was set swinging again before it stopped, there would never be a loss in accuracy.  Because of this, pendulums caught on and are still widely used today.   Can you imagine making such a big discovery?

TIME

For thousands of years, devices have been used to measure and keep track of time. The current sexagesimal system of time measurement dates to approximately 2000 BC, in Sumer. The Ancient Egyptians divided the day into two 12-hour periods, and used large obelisks to track the movement of the Sun. They also developed water clocks, which were probably first used in the Precinct of Amun-Re, and later outside Egypt as well; they were employed frequently by the Ancient Greeks, who called them clepsydrae. The Shang Dynasty is believed to have used the outflow water clock around the same time, devices which were introduced from Mesopotamia as early as 2000 BC. Other ancient timekeeping devices include the candle clock, used in China, Japan, England and Iraq; the timestick, widely used in India and Tibet, as well as some parts of Europe; and the hourglass, which functioned similarly to a water clock.
The earliest clocks relied on shadows cast by the sun, and hence were not useful in cloudy weather or at night and required recalibration as the seasons changed (if the gnomon was not aligned with the Earth's axis). The earliest known clock with a water-powered escapement mechanism, which transferred rotational energy into intermittent motions,^[1] dates back to 3rd century BC ancient Greece;^[2] Chinese engineers later invented clocks incorporating mercury-powered escapement mechanisms in the 10th century,^[3] followed by Arabic engineers inventing water clocks driven by gears and weights in the 11th century.^[4]
Mechanical clocks employing the verge escapement mechanism were invented in Europe at the turn of the 14th century, and became the standard timekeeping device until the spring-powered clock and pocket watch in the 16th century, followed by the pendulum clock in the 18th century. During the 20th century, quartz oscillators were invented, followed by atomic clocks. Although first used in laboratories, quartz oscillators were both easy to produce and accurate, leading to their use in wristwatches. Atomic clocks are far more accurate than any previous timekeeping device, and are used to calibrate other clocks and to calculate the proper time on Earth; a standardized civil system, Coordinated Universal Time, is based on atomic time.

How Can I Tell My Story?

I am a veteran and want to share my experience. What type of story is suitable for the project?

The Veterans History Project is interested in stories from veterans of all wars and those who served stateside as well as abroad. The project is interested in any aspect of your military experience that you feel is important to share. That experience can be about how you got into the service initially. Did you enlist or were you drafted? You can discuss direct war experiences such as combat actions, places you were stationed, any medals you received as a result of your actions. You can discuss life in the service in general. What did you do on leave? Was there something you did for "good luck"? Did you meet your sweetheart while in the service? And of course any stories that relate to your life after the service and what impact being in the service had on you both good and bad.

If you are willing to share any one of these experiences contact Barb Zaborowski at 814-262-6425 and arrangements will be made to have a trained interviewer capture your story.

I was not in the military but supported the war effort on the home front. Are you interested in my story?

Yes. Civilian activities varied depending on the war. Some examples include people employed in the defense industry building planes or weapons; civilians who worked on militray bases in the United States and overseas; Red Cross workers and other civilian medical personnel; and home front volunteers active in civilian defense work and health services.

If you were involved in activities that supported the war effort please contact Barb Zaborowski at 814-262-6425 and arrangements will be made to have a trained interviewer capture your story.

the first stick

The first mechanical clocks had a weight that would slowly lower, moving gears which moved a hand which showed the hour.  They could only be build in tall towers because the weights needed to fall a great distance or else the clocks would only work for a short amount of time.   People were amazed that these clocks were only off about 2 hours a day.  Think if our clocks today were off by that much?  If we were 2 hours late for school, we could blame it on the clock.      While these clocks were inaccurate long ago, some of them were created with such care that they still work today.  In Normandy, France, a big clock exists that was built in 1389.  In Salisbury, England you can see the oldest clock in the world, built in 1386.  Today, cuckoo clocks are still built using a weight-dropping mechanism.

January 6, 2004 The Veteran Community Initiative, Inc. has made a generous contribution of $350.00 to the Penn Highlands Veterans History Project. This contribution will enable the College to purchase a camcorder to record video interviews with veterans.

If any veterans group would like to post information on this website about any upcoming events please contact Barb Zaborowski at 814-262-6425.

the sand of time

The major fault with sundials and shadow clocks is obvious...They don't work at night!  Amenophis I, the king of Egypt, wanted to know what time it was all through the night without having to check the position of the stars.  As you can imagine, it would be inconvenient to get up and out of bed every time you want to know the time.  So, Prince Amenemhet made the king a clepsydra or a water clock.  He took a big bucket of water, filled it with water up to a specific line.  He then cut a small hole in the bottom of the bucket and marked off lines on the bucket after each hour had passed. 
    There were, of course, some problems with this water clock as well.  Water would flow more slowly or quickly when the temperature changed.  This is where sand came into effect.  The inventor of the sand clock is unknown but the sand clock or hourglass was commonly used in ancient times and is still used today.  They are often found in board games or are used as kitchen timers.  Is there an hourglass in your home?