Did you know.........
Why clockwise is CLOCKWISE?
You have to go back to the days of the sundial to understand why the hands of a clock or watch rotate in the direction they do.
Clocks were modeled on their predecessor, the sundial, so the hands follow the movement of the sun's shadow across a sundial. The shadow is cast by the gnomon, the raised projection that sits atop the dial plate showing the hour lines.
In the Northern Hemisphere, north of the Tropic of Cancer, the shadow on a sundial falls like this:
At dawn, the sun rises in the east and casts a shadow to the west; at noon, the sun is in the south, and casts a shadow to the north; at dusk, the sun sets in the west , and casts a shadow to the east. Since mechanical clocks were invented in the Northern Hemisphere, what we know today as clockwise is based on this West to North to East rotation.
Of course, had clocks been invented in the Southern Hemisphere, it would have been a different story. Below the Tropic of Capricorn, the shadow crossing the sundial moves in the opposite direction, and clockwise and anticlockwise would presumably mean the opposite direction of what they do today.
Interestingly, the above explanation only applies to horizontal sundials, the type often found in gardens. In the case of vertical sundials, most commonly seen on the sides of houses and churches, the shadow cast by the gnomon actually moves in an anti-clockwise direction, even though the movement of the sun through the sky is exactly the same.
Moreover, the direction the vertical sundial faces also affects its timekeeping capabilities. A vertical sundial facing due south will keep the time during daylight hours. On the other hand, if it faces due east, it can only show the morning hours from sunrise until local noon. Likewise, if it faces due west, it can only show afternoon hours from local noon until sunset.
Of course, when the sky is overcast, sundials can't tell the time at all. Not to worry, though, because we now have watches and clocks that run day and night, rain or shine, and they run in a clockwise direction, thanks to the sundial.
Why do we have leap second?
In the history of time, the leap second is very much a newcomer. There have been 21 leap seconds since the first was introduced on June 30, 1972, or slightly less than once a year.
Leap seconds have become necessary because tiny discrepancy that exists between the two scales we now use to measure time: astronomical time, which is based on the rotation of the earth, and Coordinated Universal Time (UTC), which is based on the performance of atomic clocks. In both scales, the second is the basic unit of timekeeping.
Seconds were long measured in terms of astronomical phenomena, but with the development of atomic clocks scientists abandoned the old definition and came up with a far more precise one, based on the natural periodicity of the radiation of a cesium-133 atom.
Everything was fine until it became apparent that there was a discrepancy between atomic time, which is extremely stable, and astronomical time, which is less so due to irregularities in the earth's rotation. These result in a net slowdown in the earth's rotational velocity so that astronomical time ends up lagging behind atomic time.
In 1972 this led to the introduction of a leap second, added to Universal Time to cancel out the difference between the two time scales. In effect, the atomic clock marks time for a second to allow the earth to catch up with it.
Twice a year, during the last minute of the day of June 30 or December 31, adjustments may be made to Universal Time to ensure that the accumulated difference between the two time scales does not exceed 0.9 seconds before the next adjustment is scheduled.
A leap second is not to be confused with a leap year, which sees an extra day added to the calendar every four years since it takes the earth longer than 365 days to rotate around the sun. (in fact approx. 365.242 days).
World Time Scales?
In the 1840s a Greenwich standard time for all of England, Scotland, and Wales was established, replacing several "local time" systems. The Royal Greenwich Observatory was the focal point for this development because it had played such a key role in marine navigation based upon accurate timekeeping. Greenwich Mean Time (GMT) subsequently evolved as the official time reference for the world and served that purpose until 1972.
The United States established the U.S. Naval Observatory (USNO) in 1830 to cooperate with the Royal Greenwich Observatory and other world observatories in determining time based on astronomical observations. The early timekeeping of these observatories was still driven by navigation. Timekeeping had to reflect changes in the earth's rotation rate; otherwise navigators would make errors. Thus, the USNO was charged with providing time linked to "earth" time, and other services, including almanacs, necessary for sea and air navigation.
With the advent of highly accurate atomic clocks, scientists and technologists recognized the inadequacy of timekeeping based on the motion of the earth which fluctuates in rate by a few thousandths of a second a day. The redefinition of the second in 1967 had provided an excellent reference for more accurate measurement of time intervals, but attempts to couple GMT (based on the earth's motion) and this new definition proved to be highly unsatisfactory. A compromise time scale was eventually devised, and on January 1, 1972, the new Coordinated Universal Time (UTC) became effective internationally.
UTC runs at the rate of the atomic clocks, but when the difference between this atomic time and one based on the earth approaches one second, a one-second adjustment (a "leap second") is made in UTC. NIST's clock systems and other atomic clocks located in more than 25 countries now contribute data to the international UTC scale coordinated in Paris by the International Bureau of Weights and Measures (BIPM). An evolution in timekeeping responsibility from the observatories of the world to the measurement standards laboratories has naturally accompanied this change from "earth" time to "atomic" time. But there is still a needed coupling, the leap second, between the two.
Why we have World's Time Zones?
Time zones did not become necessary in the United States until trains made it possible to travel hundreds of miles in a day. Until the 1860s most cities relied upon their own local "sun" time, but this time changed by approximately one minute for every 12 1/ 2 miles traveled east or west. The problem of keeping track of over 300 local times was overcome by establishing railroad time zones. Until 1883 most railway companies relied on some 100 different, but consistent, time zones.
That year, the United States was divided into four time zones roughly centered on the 75th, 90th, 105th, and 120th meridians. At noon, on November 18, 1883, telegraph lines transmitted GMT time to major cities where authorities adjusted their clocks to their zone's proper time.
On November 1, 1884, the International Meridian Conference in Washington, DC, applied the same procedure to zones all around the world. The 24 standard meridians, every 15east and west of 0at Greenwich, England, were designated the centers of the zones. The international dateline was drawn to generally follow the 180meridian in the Pacific Ocean. Because some countries, islands and states do not want to be divided into several zones, the zones' boundaries tend to wander considerably from straight north-south lines.
Ancient Calendars?
Celestial bodies-the sun, moon, planets, and stars-have provided us a reference for measuring the passage of time throughout our existence. Ancient civilizations relied upon the apparent motion of these bodies through the sky to determine seasons, months, and years.
We know little about the details of timekeeping in prehistoric eras, but wherever we turn up records and artifacts, we usually discover that in every culture, some people were preoccupied with measuring and recording the passage of time. Ice-age hunters in Europe over 20,000 years ago scratched lines and gouged holes in sticks and bones, possibly counting the days between phases of the moon. Five thousand years ago, Sumerians in the Tigris-Euphrates valley in today's Iraq had a calendar that divided the year into 30-day months, divided the day into 12 periods (each corresponding to 2 of our hours), and divided these periods into 30 parts (each like 4 of our minutes). We have no written records of Stonehenge, built over 4000 years ago in England, but its alignments show its purposes apparently included the determination of seasonal or celestial events, such as lunar eclipses, solstices and so on.
The earliest Egyptian calendar was based on the moon's cycles, but later the Egyptians realized that the "Dog Star" in Canis Major, which we call Sirius, rose next to the sun every 365 days, about when the annual inundation of the Nile began. Based on this knowledge, they devised a 365-day calendar that seems to have begun in 4236 B.C., the earliest recorded year in history.
In Babylonia, again in Iraq, a year of 12 alternating 29-day and 30-day lunar months was observed before 2000 B.C., giving a 354-day year. In contrast, the Mayans of Central America relied not only on the sun and moon, but also the planet Venus, to establish 260-day and 365-day calendars. This culture flourished from around 2000 B.C. until about 1500 A.D. They left celestial-cycle records indicating their belief that the creation of the world occurred in 3113 B.C. Their calendars later became portions of the great Aztec calendar stones. Other civilizations, such as our own, have adopted a 365-day solar calendar with a leap year occurring every fourth year.
Revolution In Timekeeping?
In Europe during most of the Middle Ages (roughly 500 to 1500 A.D.), technological advancement was at a virtual standstill. Sundial styles evolved, but didn't move far from ancient Egyptian principles.
During these times, simple sundials placed above doorways were used to identify midday and four "tides" of the sunlit day. By the 10th Century, several types of pocket sundials were used. One English model identified tides and even compensated for seasonal changes of the sun's altitude.
Then, in the early-to-mid-14th century, large mechanical clocks began to appear in the towers of several large Italian cities. We have no evidence or record of the working models preceding these public clocks that were weight-driven and regulated by a verge-and-foliot escapement. Verge-and-foliot mechanisms reigned for more than 300 years with variations in the shape of the foliot. All had the same basic problem: the period of oscillation of this escapement depended heavily on the amount of driving force and the amount of friction in the drive. Like water flow, the rate was difficult to regulate.
Another advance was the invention of spring-powered clocks between 1500 and 1510 by Peter Henlein of Nuremberg. Replacing the heavy drive weights permitted smaller (and portable) clocks and watches. Although they slowed down as the mainspring unwound, they were popular among wealthy individuals due to their size and the fact that they could be put on a shelf or table instead of hanging from the wall. These advances in design were precursors to truly accurate timekeeping.
A bit of Citizen Watch history.
Established in 1930, Citizen is the world's largest manufacturer of watches and other timepieces. The company's mastery of precision mechanics and microelectronics has allowed Citizen to offer a wide range of products and services worldwide, developing a global presence operating in more than 13 countries with over 3,000 employees.
Citizen's leadership role is due to its unrelenting, uncompromising passion for technological innovation. This mission has resulted in a multitude of milestones, such as the following: The first shockproof watches made in Japan; the first waterproof and first electronic watches; the world's first water-resistant watch, the world's first analog quartz watch accurate to within three seconds per year; the first analog solar battery watch and the world's thinnest movement at 0.98mm.
Over the years, Citizen has successfully leveraged its expertise in microelectronics to become a major player in the field of office and information equipment. Products include printers, floppy disk drives, hard disk drives, and liquid crystal displays. Because microelectronics are at the core of these products, they afford users something else very valuable the ultimate in space efficiency.
From its work with quartz watches, Citizen parlayed its experience with liquid crystal and microelectronic technologies to begin developing liquid crystal televisions, liquid crystal color video projectors, and electronic health care equipment. Most notably, Citizen is the world-leader in the field of quartz oscillators, the heart of all electronic products.
The use of Citizen's ultra-precision machine tools are responsible for the development of many innovative high-tech products, and are found in a variety of industries worldwide. Fulfilling the present requirement for sub-micron precision in the field of factory automation are, for example, the CINCOM series of compact CNC automatic lathes, the BOARD-PACKER electronic parts inserters, the CYNECTRON automatic assembly machines, and assembly robots all leaders in their sectors.
In the production of jewelry and eyeglasses, Citizen is able to exploit not only its materials and manufacturing technologies developed in the production of timepieces, but also its sense of aesthetic appeal refined in the same area. In addition to its original design jewelry and eyeglasses, Citizen is continuously called on to manufacturer famous designer brand products under license contracts.
More than 60 years later the Citizen name has become synonymous with miniaturization. But the last six decades mark not only the history and evolution of Citizen the company, but the process and progress of the art of watchmaking and other products utilizing precision mechanics and microelectronics.
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