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President Trump delivered his first address to a Joint Session of Congress on February 28th, 2017. You can watch the full address here.

Watch - Wikipedia. A watch is a small timepiece intended to be carried or worn by a person.

It is designed to keep working despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached by a watch strap or other type of bracelet. Bedeviled (2017) Watch Online.

A pocket watch is designed for a person to carry in a pocket. Watches evolved in the 1. During most of its history the watch was a mechanical device, driven by clockwork, powered by winding a mainspring, and keeping time with an oscillating balance wheel.

In the 1. 96. 0s the electronic quartz watch was invented, which was powered by a battery and kept time with a vibrating quartz crystal. By the 1. 98. 0s the quartz watch had taken over most of the market from the mechanical watch.

Today most inexpensive and medium- priced watches, used mainly for timekeeping, have quartz movements. Expensive collectible watches, valued more for their elaborate craftsmanship, aesthetic appeal and glamorous design than for simple timekeeping, often have traditional mechanical movements, even though they are less accurate and more expensive than electronic ones. Various extra features, called . Time- related features such as timers, chronographs and alarm functions are common. Some modern designs incorporate calculators, GPS. Some watches use radio clock technology to regularly correct the time. Developments in the 2.

They generally incorporate timekeeping functions, but these are only a small subset of the smartwatch's facilities. The study of timekeeping is known as horology. History. Watches weren't widely worn in pockets until the 1. One account says that the word . This innovation increased watches' accuracy enormously, reducing error from perhaps several hours per day.

The first thing to be improved was the escapement. The verge escapement was replaced in quality watches by the cylinder escapement, invented by Thomas Tompion in 1. George Graham in the 1. Improvements in manufacturing such as the tooth- cutting machine devised by Robert Hooke allowed some increase in the volume of watch production, although finishing and assembling was still done by hand until well into the 1. A major cause of error in balance wheel timepieces, caused by changes in elasticity of the balance spring from temperature changes, was solved by the bimetallic temperature compensated balance wheel invented in 1. Pierre Le Roy and improved by Thomas Earnshaw. The lever escapement was the single most important technological breakthrough, and was invented by Thomas Mudge in 1.

Josiah Emery in 1. Britain. The British had predominated in watch manufacture for much of the 1. Aaron Lufkin Dennison started a factory in 1. Massachusetts that used interchangeable parts, and by 1.

Waltham Watch Company. Elizabeth I of England received a wristwatch from Robert Dudley in 1. The oldest surviving wristwatch (then described as a bracelet watch) is one made in 1. Jos. The Garstin Company of London patented a . Officers in the British Army began using wristwatches during colonial military campaigns in the 1.

Anglo- Burma War of 1. The company Mappin & Webb began production of their successful . The Swiss company Dimier Fr. Hans Wilsdorf moved to London in 1.

Wilsdorf & Davis, with his brother- in- law Alfred Davis, providing quality timepieces at affordable prices; the company later became Rolex. The creeping barrage artillery tactic, developed during the war, required precise synchronization between the artillery gunners and the infantry advancing behind the barrage. Service watches produced during the War were specially designed for the rigours of trench warfare, with luminous dials and unbreakable glass. The British War Department began issuing wristwatches to combatants from 1.

The first successful self- winding system was invented by John Harwood in 1. The introduction of the quartz watch was a revolutionary improvement in watch technology.

In place of a balance wheel which oscillated at perhaps 5 or 6 beats per second, it used a quartz crystalresonator which vibrated at 8,1. Hz, driven by a battery- powered oscillator circuit.

Since the 1. 98. 0s, more quartz watches than mechanical ones have been marketed. Movement. The left watch has a 2. The movement is fitted with a cylinder escapement. A movement of a watch is the mechanism that measures the passage of time and displays the current time (and possibly other information including date, month and day). Movements may be entirely mechanical, entirely electronic (potentially with no moving parts), or they might be a blend of both. Most watches intended mainly for timekeeping today have electronic movements, with mechanical hands on the watch face indicating the time.

Mechanical. Nevertheless, the craftsmanship of mechanical watches still attracts interest from part of the watch- buying public, especially among the watch collectors. Skeleton watches are designed to leave the mechanism visible for aesthetic purposes. A mechanical movement uses an escapement mechanism to control and limit the unwinding and winding parts of a spring, converting what would otherwise be a simple unwinding into a controlled and periodic energy release. A mechanical movement also uses a balance wheel together with the balance spring (also known as a hairspring) to control motion of the gear system of the watch in a manner analogous to the pendulum of a pendulum clock. The tourbillon, an optional part for mechanical movements, is a rotating frame for the escapement, which is used to cancel out or reduce the effects of gravitational bias to the timekeeping. Due to the complexity of designing a tourbillon, they are very expensive, and only found in prestigious watches.

The pin- lever escapement (called the Roskopf movement after its inventor, Georges Frederic Roskopf), which is a cheaper version of the fully levered movement, was manufactured in huge quantities by many Swiss manufacturers as well as by Timex, until it was replaced by quartz movements. Introduced by Bulova in 1. The task of converting electronically pulsed fork vibration into rotary movements is done via two tiny jeweled fingers, called pawls.

Tuning- fork watches were rendered obsolete when electronic quartz watches were developed. Quartz watches were cheaper to produce besides being more accurate.

Traditional mechanical watch movements use a spiral spring called a mainspring as a power source. In manual watches the spring must be rewound periodically by the user by turning the watch crown. Antique pocketwatches were wound by inserting a separate key into a hole in the back of the watch and turning it.

Most modern watches are designed to run 4. Automatic watches.

The first self- winding mechanism was invented for pocket watches in 1. Abraham- Louis Perrelet. This type of watch winds itself without requiring any special action by the wearer. It uses an eccentric weight, called a winding rotor, which rotates with the movement of the wearer's wrist. The back- and- forth motion of the winding rotor couples to a ratchet to wind the mainspring automatically. Self- winding watches usually can also be wound manually to keep them running when not worn or if the wearer's wrist motions are inadequate to keep the watch wound.

In April 2. 01. 4 the Swatch Group launched the sistem. It has a purely mechanical movement consisting of only 5. So far, it is the only mechanical movement manufactured entirely on a fully automated assembly line. A varying electric voltage is applied to the crystal, which responds by changing its shape so, in combination with some electronic components, it functions as an oscillator.

It resonates at a specific highly stable frequency, which is used to accurately pace a timekeeping mechanism. Most quartz movements are primarily electronic but are geared to drive mechanical hands on the face of the watch to provide a traditional analog display of the time, a feature most consumers still prefer.

The Seven Wonders Of The World - BBC Documentary. The most prominent of these, the versions by Antipater of Sidon and an observer identified as Philo of Byzantium, comprise seven works located around the eastern Mediterranean rim.

The original list inspired innumerable versions through the ages, often listing seven entries. Of the original Seven Wonders, only one—the Great Pyramid of Giza, the oldest of the ancient wonders—remains relatively intact. Background. In this painting by Maerten van Heemskerck, the seven wonders of the ancient world are depicted as a background for the abduction of Helen by Paris. The Walters Art Museum.

The Greek conquest of much of the known world in the 4th century BC gave Hellenistic travellers access to the civilizations of the Egyptians, Persians, and Babylonians. Impressed and captivated by the landmarks and marvels of the various lands, these travellers began to list what they saw to remember them. Instead of . Hence, the list was meant to be the Ancient World's counterpart of a travel guidebook. Each person had his own version of the list, but the best known and earliest surviving was from a poem by Greek- speaking epigrammist Antipater of Sidon from around 1. BC. He named six of the seven sites on his list—leaving out the lighthouse—, but was primarily in praise of the Temple of Artemis at Ephesus.

Another 2nd century BC observer, who claimed to be the mathematician Philo of Byzantium, wrote a short account entitled The Seven Sights of the World. However, the incomplete surviving manuscript only covered six of the supposedly seven places, which agreed with Antipater's list. Earlier and later lists by the historian Herodotus (4. BC- -ca. 4. 25 BC) and the architect Callimachus of Cyrene (ca. BC), housed at the Museum of Alexandria, survived only as references.

The Colossus of Rhodes was the last of the seven to be completed, after 2. BC, and the first to be destroyed, by an earthquake in 2. BC. Hence, all seven existed at the same time for a period of less than 6. Antipater had an earlier version which replaced Lighthouse of Alexandria with the Walls of Babylon. Lists which preceded the construction of Colossus of Rhodes completed their seven entries with the inclusion of the Ishtar Gate.

Scope. It is thought that the limitation of the lists to seven entries was attributed to the special magical meaning of the number. Geographically, the list covered only the sculptural and architectural monuments of the Mediterranean and Middle Eastern regions, which then comprised the known world for the Greeks. Hence, extant sites beyond this realm were not considered as part of contemporary accounts. The primary accounts, coming from Hellenistic writers, also heavily influenced the places included in the wonders list.

Five of the seven entries are a celebration of Greek accomplishments in the arts and architecture (the exceptions being the Pyramids of Giza and the Hanging Gardens of Babylon).