Wednesday, 4 December 2013

Stephen William Hawking

Stephen William Hawking was born on 8 January 1942 (300 years after the death of Galileo) in Oxford, England. His parents' house was in north London, but during the Second World War, Oxford was considered a safer place to have babies. When he was eight, his family moved to St. Albans, a town about 20 miles north of London. At the age of eleven, Stephen went to St. Albans School and then on to University College, Oxford; his father's old college. Stephen wanted to study Mathematics, although his father would have preferred medicine. Mathematics was not available at University College, so he pursued Physics instead. After three years and not very much work, he was awarded a first class honours degree in Natural Science.
Black hole is a region of space time from which gravity prevents anything, including light, from escaping. The theory of general relativity predicts that a sufficiently compact mass will deform space time to form a black hole. Around a black hole, there is a mathematically defined surface called an event horizon that marks the point of no return. The hole is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater.
Objects whose gravity fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, although its interpretation as a region of space from which nothing can escape was first published by David Finkelstein in 1958. Long considered a mathematical curiosity, it was during the 1960s that theoretical work showed black holes were a generic prediction of general relativity. The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality.
Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is general consensus that supermassive black holes exist in the centres of most galaxies.
Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as light. Matter falling onto a black hole can form an accretion disk heated by friction, forming some of the brightest objects in the universe. If there are other stars orbiting a black hole, their orbit can be used to determine its mass and location. These data can be used to exclude possible alternatives (such as neutron stars). In this way, astronomers have identified numerous stellar black hole candidates in binary systems, and established that the core of our Milky Way galaxy contains a supermassive black hole of about 4.3 million solar masses.

Tuesday, 3 December 2013

James Puckle

James Puckle (1667–1724) was an English inventor, lawyer and writer from London chiefly remembered for his invention of the Defence Gun, better known as the Puckle gun, a multi-shot gun mounted on a stand capable of (depending on which version) firing up to nine rounds per minute. The Puckle gun is sometimes considered the first machine gun and resembles a large revolver.
In 1718, Puckle demonstrated his new invention, the Defence Gun—a tripod-mounted, single-barreled flintlock weapon fitted with a multishot revolving cylinder, designed for shipboard use to prevent boarding. The barrel was 3 feet (0.91 m) long with a bore of 1.25 inches (32 mm) and a pre-loaded "cylinder" which held 11 charges and could fire 63 shots in seven minutes—this at a time when the standard soldier's musket could at best be loaded and fired three times per minute.
Puckle demonstrated two versions of the basic design: one, intended for use against Christian enemies, fired conventional round bullets, while the second variant, designed to be used against the Muslim Turks, fired square bullets, designed by Kyle Tunis, which were considered to be more damaging and would, according to its patent, convince the Turks of the "benefits of Christian civilization."
The Puckle Gun drew few investors and never achieved mass production or sales to the British armed forces, mostly because British gunsmiths at the time could not easily make the weapon's many complicated components. One newspaper of the period sarcastically observed, following the business venture's failure, that the gun has "only wounded those who hold shares therein."
According to the Patent Office of the United Kingdom, "In the reign of Queen Anne of Great Britain, the law officers of the Crown established as a condition of patent that the inventor must in writing describe the invention and the manner in which it works." James Puckle's 1718 patent for a gun was one of the first to provide such a description.
John Montagu, 2nd Duke of Montagu, Master-General of the Ordnance (1740-9), purchased several for an ill-fated expedition in 1722 to capture St Lucia and St Vincent. One remains on display at Boughton House and another at Beaulieu Palace (both former Montagu homes).
There is a replica of a Puckle Gun at Bucklers Hard Maritime Museum in Hampshire.
Blackmore's British Military Firearms 1650–1850 lists "Puckle’s brass gun in the Tower of London" as illustration 77.

Monday, 2 December 2013

George Stephenson

George Stephenson was born on June 9, 1781, in the coal mining village of Wylam, England. His father, Robert Stephenson, was a poor, hardworking man, that supported his family entirely from wages of twelve shillings a week.
Wagons loaded with coal passed through Wylam several times a day. These wagons were drawn by horses -- locomotives had not yet been invented. George Stephenson's first job was to watch over a few cows owned by a neighbor which were allowed to feed along the road; George was paid two cents a day to keep the cows out of the way of the coal-wagons; and also, to close the gates after the day's work of the wagons was over.
George Stephenson - Life in the Coal Mines
George Stephenson's next job was at the mines as a picker. His duty was to clean the coal of stone, slate, and other impurities. Eventually, George Stephenson worked at several coal mines as a fireman, plugman, brakeman, and engineer.
However, in his spare time George loved to tinker with any engine or piece of mining equipment that fell into his hands. He became skilled at adjusting and even repairing the engines found in the mining pumps, even though at that time he could not read or write. As a young adult, George paid for and attended night school where he learned to read, write, and do arithmetic. In 1804, George Stephenson walked on foot to Scotland to take a job working in a coal mine that used one of JAMES WATT’S steam engines, the best steam engines of the day.
In 1807, George Stephenson considered emigrating to America; but he was too poor to pay for the passage. He began work nights repairing shoes, clocks, and watches, making extra money that he would spend on his inventing projects.

A steam locomotive is a railway locomotive that produces its pulling power through a steam engine. These locomotives are fueled by burning combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine. Both fuel and water supplies are carried with the locomotive, either on the locomotive itself or in wagons (tenders) pulled behind.
Steam locomotives were first developed in Great Britain during the early 19th century and dominated railway transport until the middle of the 20th century. From the early 1900s they were gradually superseded by electric and diesel locomotives.