The History of Mechanical Clocks

During most of the Middle Ages, from roughly 500 to 1500 A.D., technological advancement was at a virtual standstill in Europe. Sundial styles evolved, but they didnt move far from ancient Egyptian principles.   Simple Sundials   Simple sundials placed above doorways were used to identify midday and four tides of the sunlit day in the Middle Ages. Several types of pocket sundials were being used by the 10th century -- one  English model identified tides and even compensated for seasonal changes of the suns altitude.   Mechanical Clocks In the early to mid-14th century, large mechanical clocks began to appear in the towers of several Italian cities. There is no record of any working models preceding these public clocks that were weight-driven and regulated by verge-and-foliot escapements. Verge-and-foliot mechanisms reigned for more than 300 years with variations in the shape of the foliot, but all had the same basic problem: The period of oscillation depended heavily on the amount of driving force and the amount of friction in the drive so the rate was difficult to regulate. Spring-Powered Clocks   Another advancement was an invention by Peter Henlein, a German locksmith from Nuremberg, sometime between 1500 and 1510. Henlein created  spring-powered clocks.  Replacing the heavy drive weights resulted in smaller and more portable clocks and watches. Henlein nicknamed his clocks Nuremberg Eggs. Although they slowed down as the mainspring unwound, they were popular among wealthy individuals because of their size and because they could be placed on a shelf or table instead of hung from a wall. They were the first portable timepieces, but they only had hour hands. Minute hands didn’t appear until 1670, and clocks had no glass protection during this time. Glass placed over the face of a watch didn’t come about until the 17th century. Still, Henleins advances in design were precursors to truly accurate timekeeping.   Accurate Mechanical Clocks   Christian Huygens, a Dutch scientist, made the first pendulum clock in 1656. It was regulated by a mechanism with a natural period of oscillation. Although Galileo Galilei  is  sometimes credited with inventing the pendulum and he studied its motion as early as 1582, his design for a clock was not built before his death. Huygens pendulum clock had an error of less than one minute a day, the first time such accuracy had been achieved. His later refinements reduced his clocks errors to less than 10 seconds a day.   Huygens developed the balance wheel and spring assembly sometime around 1675  and it’s still found in some of todays wristwatches. This improvement allowed 17th-century watches to keep time to 10 minutes a day. William Clement began building clocks with the new anchor or recoil escapement in London in 1671. This was a substantial improvement over the verge because it interfered less with the motion of the pendulum.   In 1721, George Graham improved the pendulum clocks accuracy to one  second a day by compensating for changes in the pendulums length due to temperature variations. John Harrison, a carpenter and self-taught clockmaker, refined Grahams temperature compensation techniques and added new methods of reducing friction. By 1761, he had built a marine chronometer with the spring and a balance wheel escapement that had won the British governments 1714 prize offered for a means of determining longitude to within one-half  a degree. It kept time aboard a rolling ship to about one-fifth of a second a day, nearly as well as a pendulum clock could do on land, and 10 times better than required.   Over the next century, refinements led to Siegmund Rieflers clock with a nearly free pendulum in 1889. It attained an accuracy of a hundredth of a second a day and became the standard in many astronomical observatories. A true free-pendulum principle was introduced by R. J. Rudd around 1898, stimulating the development of several free-pendulum clocks. One of the most famous, the W. H. Shortt clock, was demonstrated in 1921. The Shortt clock almost immediately replaced Rieflers clock as a supreme timekeeper in many observatories. This clock consisted of two pendulums, one a slave and the other a master. The slave pendulum gave the master pendulum the gentle pushes it needed to maintain its motion, and it also drove the clocks hands. This allowed the master pendulum to remain free from mechanical tasks that would disturb its regularity. Quartz Clocks   Quartz crystal clocks replaced the Shortt clock as the standard in the 1930s and 1940s, improving timekeeping performance far beyond that of pendulum and balance-wheel escapements.   Quartz clock operation is based on the piezoelectric property of quartz crystals. When an electric field is applied to the crystal, it changes its shape. It generates an electric field when squeezed or bent. When placed in a suitable electronic circuit, this interaction between mechanical stress and electric field causes the crystal to vibrate and generate a constant frequency electric signal that can be used to operate an electronic clock display.Quartz crystal clocks were better because they had no gears or escapements to disturb their regular frequency. Even so, they relied on a mechanical vibration whose frequency depended critically on the crystals size and shape. No two crystals can be precisely alike  with exactly the same frequency.  Quartz clocks continue to dominate the market in numbers because their performance is excellent and they are inexpensive. But the timekeeping performance of quartz clocks has been substantially surpassed by atomic clocks.   Information and illustrations provided by the National Institute of Standards and Technology and the U.S. Department of Commerce.

The Social And Economical Problems Of Nathaniel Bacon s...

Countless social and economical problems arise throughout 1676 in Virginia. Farmer Nathaniel Bacon promoted concerns about the numerous Indian assaults and the necessity for land; farmers needed economic independence as well as former indentured servants. This revolution was well-known as â€Å"Bacon’s Rebellion†. After numerous unsuccessful attempts to fight with the local government, directed by Royal Governor William Berkeley, to strike back against the Indians, Nathaniel Bacon led his revolution by accusing Berkeley and his associates for wrongdoing that went in opposition to the consent of its people. In return, Berkeley addressed Bacon’s objections, by doing an effort to justify his actions and turn down his demands. According to Bacon in his pronouncement against Governor William Berkeley, prepare in 1676, Nathaniel Bacon accused Governor William Berkeley for supporting the wealthy, who were also his acquaintances. â€Å"For raised greate unjust taxes up on the comonality for the advance- ment of private favorites and other sinister ends† placed on the needy farmers, while the wealthy were unjustly exempt. This tax increase were designated towards â€Å"the advancement of private favorites† as an alternative of colonial improvements such as â€Å"fortifications, towns, or trades† Bacon’s greatest criticism, was with the concern of local Indians who Bacon belief was that Indians were assaulting his people and Governor Berkeley refuse to resolve this issue. Bacon’s colony had dealShow MoreRelatedThe Effects That Slavery And Class Conflict Had On The American Republic1285 Words   |  6 Pagestogether and in turn have effected the creation of America as a republic. Bacons Rebellion, slavery as an institution, class division and conflict are the three events that will be discussed in this paper. Also, it will be shown how these three events impacted the creation of the American republic. The plot for Bacons Rebellion is the late 17th century in the backwoods of what is now Virginia, where poor

Persuasive Paper Evolution Essay Example For Students

Persuasive Paper Evolution Essay Like the biblical hero Adam, a single cell let partof its body become another being, now one of apair. Like the heroin Eve this duplicate createdmore of its species. These multiplying cells joinedtogether into a legacy long in running. The historyof our evolution is dark, we fumble for answersyet still need more light to unlock the mysteriesbeneath. One must remember that when speakingof the theory of evolution one is not only referringto humans but to other species of the kingdomAnimalia as well. Some of the most prominantevolutionary theories of all time can be found inCharles Darwins Origin of Species. Hisconclusions linked homo sapiens skeletal systemsto an ungodly creature, Primates such as apes,gorillas, and monkeys were found to be closelylinked to the evolved human of the time. Within500,000 years time, he claimed, that we hadevolved from Australopithicus Ramidus to thepresent Homo Sapiens that we are catoragized as. He sums the entire evolutionary theory up bystating in his book, We must.acknowledge, as itseems to me, that man with all his noble qualities,sympathy, benevolence, and god-like intellectwhich has penetrated into the movements andconstitution of the solar system itself-with all theseexalted powers-Man still bears in his bodily framethe incredible stamp of his lowly origin. Thisstatement may be backed by any number ofappeals, yet one must ring forth as the answer. Survival of the Fittest, the natural idea that anysingle being in a species will survive if it is the bestat hunting, existing, and passing down its genepool. These super animals, inside a singlespecies, may have developed some sort of geneticmutation allowing for easier grip on prey, fastermovement, quicker reflexes, or just plainly madethem more attractive to the opposite sex in theirspecies. In any case, this mutation, this freak ofnature, has caused the animals to live, and breed,and pass down its mutation to its offspring. Whena primitive Homo Habillis gave birth to young thatcould eventually stand taller and straighter than itsancestors was anything marvelous thought of it?When this taller primate gave birth to increasinglyupright offspring, again, was anything marvelousthought of that? Yet finally when an adult HomoHabillis stood vertically enough to reach fruit onthe trees, to use more force than its counterparts,and stand erect there was a breakthrough. Thisnew hominid speci es, Homo Erectus, took nearly50,000 years to develop, yet with time and thesurvival of the fittest, the one who could run faster,hunt longer, and go farther, the one who couldsurvive above all others conquered and created anew species all his own. This species evolved, itprogressed to a better state by a abnormality in itsgene sequence. Man does not produce variabilityin which he creates new bodily devices to survive. It is accidental, it is a mutation of scientific mishapthat lets the giraffe evolve from the horse, thewhale evolve from a wolf, and the human evolvefrom the primal ape. Natural selection has formednot only our anatomy, but our facial characteristicsas man and woman. Natural selection is like aforce, letting stronger and more intelligent animalssurvive. 400 million years ago a prehistoric reptilein Africa developed turbinates, these are fleshymembranes which allow for an animal to retainmoisture in their breath while exhaling, any animalwishing to keep a constant temperture to therebody must have turbinates to reserve heat. Theseorgans are found in the nose of everywarm-blooded animal ever in the history of thefossil record, this lizard began a long journey, andthrough the next 10 million years this lizardevolved into the first mammal. By 300 millionyears ago this lizard had changed and morphed inmany different ways, this lowly reptile had grownhair, he had a forhead, and larger brai n than anyother animal ever known to the planet, this lizardhad 4 appendages, 2 of which were used forgrappling and climbing, this lizard had progressedinto the primate, spreading all over the african andasain continents. This lizard is our beginning, he isour ancestor, we owe life to this reptile in everyimaginable way. .ud489964093271c3ec830713d008f3826 , .ud489964093271c3ec830713d008f3826 .postImageUrl , .ud489964093271c3ec830713d008f3826 .centered-text-area { min-height: 80px; position: relative; } .ud489964093271c3ec830713d008f3826 , .ud489964093271c3ec830713d008f3826:hover , .ud489964093271c3ec830713d008f3826:visited , .ud489964093271c3ec830713d008f3826:active { border:0!important; } .ud489964093271c3ec830713d008f3826 .clearfix:after { content: ""; display: table; clear: both; } .ud489964093271c3ec830713d008f3826 { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .ud489964093271c3ec830713d008f3826:active , .ud489964093271c3ec830713d008f3826:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .ud489964093271c3ec830713d008f3826 .centered-text-area { width: 100%; position: relative ; } .ud489964093271c3ec830713d008f3826 .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .ud489964093271c3ec830713d008f3826 .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .ud489964093271c3ec830713d008f3826 .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .ud489964093271c3ec830713d008f3826:hover .ctaButton { background-color: #34495E!important; } .ud489964093271c3ec830713d008f3826 .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .ud489964093271c3ec830713d008f3826 .ud489964093271c3ec830713d008f3826-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .ud489964093271c3ec830713d008f3826:after { content: ""; display: block; clear: both; } READ: Founding Fathers of the USA EssayCategory: English