Static Electricity
The scientific study of electricity and magnetism began with William Gilbert. Born in Colchester and educated at Cambridge, Gilbert was successful medical practitioner who became physician to Queen Elizabeth I in 1600.
In the same year he also published his books De Magnete, which recorded his conclusions from many year’s spare-time work on electrostatics and magnetism and for the first time, drew a clear distinction the two phenomena.
In a very dangerous experiment the American statesmen Benjamin Franklin showed that a kite flown in a thunderstorm became electrically charged.
His German contemporary Georg Wilhelm Richman was less fortunate: he was killed trying the same experiment at St Petersburg in 1753.
Franklin also studied the discharge of electricity from objects of different shapes, he suggested protection of buildings by lightning conductors and in the lights of his discharge experiments said that they should be pointed.
The discovery of the electric current, about 1800, did not end he story of static electricity. Two important machines of the nineteenth century were Armstrong’s hydroelectric machine and the Wimshurst machine.
William Armstrong was a solicitor and amateur scientist who founded an engineering business in Newcastle upon Tyne.
His attention was drawn to a strange effect noticed by an engine driver on a colliery railway. The driver experienced ‘a curious pricking sensation’ when he touch the steam valve on a leaking boiler.
Armstrong found that steam, issuing from small hole, became electrically charged.
He then built a machine with an iron boiler on glass legs and a hard wood nozzle through which steam could escape.
He found the steam was positively charged and he then made a larger machine which was demonstrated in London producing sparks more than half a meter long.
A War Office committee on mines suggested in 1857 that Armstrong’ machine, with its very high voltage output, could be used for detonating mines.
In practice magneto-electric machines were soon available, and Armstrong’s machine never saw a practical use.
During the nineteenth century numerous machines were made which multiplied static electric charges by induction and collected them in Leyden jars or other capacitors.
Static Electricity
Friday, July 3, 2009
Monday, June 22, 2009
History of Surgery - Trephination of the skull
History of Surgery - Trephination of the skull
Undoubtedly the most extraordinary story in the history of surgery is that, long before man could read or write, as long ago as 10,000 BC, surgeons were performing the operation of trephination or trepanning – boring or cutting out rings or squares of bones from skull – and just as remarkably, their patients usually recovered from the procedure.
Although the word ‘trepanation’ and trephination’ today are interchangeable in common practice, trepanation comes form the Greek trypanon, meaning a borer, while trephination is or more recent French origin and indicates an instrument revolving around a central spike.
Trepanation thus connotes scraping or cutting, while trephination describes drilling the skull, as in modern neurosurgical operations.
Different techniques of trepanation in ancient times, and in recent primitive communities, involved scraping away bone, making a circular groove so that a central core of the bone would loosen, boring and cutting away the bone, or making rectangular interesting incisions in the skull.
This story begins in 1865 when a general practitioner Dr Prunires, who was also an amateur archeologist, discovered in a prehistoric stone tomb in Central French a skull which bore a large artificial opening on its posterior aspect.
With it, he found a number of irregular pieces of bone which might have been cut from another skull.
He postulated that the skull had been perforated so that it might be used as a drinking cup.
Soon after this, a number of other holed skulls were found in other parts of France and Professor Paul Broca (1824-1880), a distinguished French physician, suggested that these opening were the result of an operation of trepanation and that the instrument employed was a flint scraper.
Broca suggested that survivors of operation were endowed with mythical powers and that, when they died, portions of their skull, especially those that included a part of the edge of the artificial opening, were in great demand as charms.
Following these discoveries, thousands of such specimens have been discovered from many parts of the world: the United Kingdom, Denmark, Spain, Portugal, Poland, the Danube Basin, North Africa, Palestine, the Caucasus, all down the Western coastline of the Americas and especially in Peru, where more than 10,000 specimens have been excavated.
History of Surgery - Trephination of the skull
Undoubtedly the most extraordinary story in the history of surgery is that, long before man could read or write, as long ago as 10,000 BC, surgeons were performing the operation of trephination or trepanning – boring or cutting out rings or squares of bones from skull – and just as remarkably, their patients usually recovered from the procedure.
Although the word ‘trepanation’ and trephination’ today are interchangeable in common practice, trepanation comes form the Greek trypanon, meaning a borer, while trephination is or more recent French origin and indicates an instrument revolving around a central spike.
Trepanation thus connotes scraping or cutting, while trephination describes drilling the skull, as in modern neurosurgical operations.
Different techniques of trepanation in ancient times, and in recent primitive communities, involved scraping away bone, making a circular groove so that a central core of the bone would loosen, boring and cutting away the bone, or making rectangular interesting incisions in the skull.
This story begins in 1865 when a general practitioner Dr Prunires, who was also an amateur archeologist, discovered in a prehistoric stone tomb in Central French a skull which bore a large artificial opening on its posterior aspect.
With it, he found a number of irregular pieces of bone which might have been cut from another skull.
He postulated that the skull had been perforated so that it might be used as a drinking cup.
Soon after this, a number of other holed skulls were found in other parts of France and Professor Paul Broca (1824-1880), a distinguished French physician, suggested that these opening were the result of an operation of trepanation and that the instrument employed was a flint scraper.
Broca suggested that survivors of operation were endowed with mythical powers and that, when they died, portions of their skull, especially those that included a part of the edge of the artificial opening, were in great demand as charms.
Following these discoveries, thousands of such specimens have been discovered from many parts of the world: the United Kingdom, Denmark, Spain, Portugal, Poland, the Danube Basin, North Africa, Palestine, the Caucasus, all down the Western coastline of the Americas and especially in Peru, where more than 10,000 specimens have been excavated.
History of Surgery - Trephination of the skull
Monday, June 15, 2009
History of Information Retrieval
History of Information Retrieval
Information retrieval is the process of searching within a document collection for a particular information need (called a query).
Although dominated by recent events following the invention of the computer, information retrieval actually has a long and glorious tradition.
The earliest document collections were recorded on the painted walls of caves. A cave dweller interested in searching a collection of cave paintings to answer a particular information query had to travel by foot, and stand, staring in front of each painting.
Unfortunately, it’s hard to collect and artifact without being gruesome.
Before the invention of paper, ancient Romans and Greeks recorded information on papyrus rolls.
Some papyrus artifacts from ancient Rome had tags attached to the rolls. These tags were an ancient form of today’s Post-it Note, and make an excellent addition to our museum.
A tag contained a short summary of the rolled document and was attached in order to save readers from unnecessarily unraveling a long irrelevant document.
These abstract also appeared in oral form. At the start of Greek plays in the fifth century B.C., the chorus recited an abstract of the ensuing action.
While no actual classifications scheme has survived from the artifacts of Greek and Roman libraries, we do know that another elementary information retrieval tool, the table of content, first appeared in Greek scrolls from the second century B.C.
As the stories goes, the Libraries of Pergamum threatened to overtake the celebrated Library of Alexandria as the best Library in the world, claiming the largest collection of papyrus rolls.
As the result, the Egyptians ceased the supply of papyrus to Pergamum, so the Pergamenians invented an alternative writing material parchment, which is made from thin layers of animal skin.
Unlike papyrus, parchment did not roll easily, so scribes folded several sheets of parchment and sewed them into books.
Other documents collections sprung up in a variety of fields. This dramatically accelerated with the re-invention of the printing press by Johann Gutenberg in 1450.
The wealthy proudly boasted of their private libraries and public libraries were instituted in America in the 1700s at the prompting of Benjamin Franklin.
More orderly ways of maintaining records of a collection’s holdings were devised.
These inventions were progress, yet still search was not completely in the hands of the information seeker. It took the inventions of the digital computer (1940s and 1950s) and the subsequent inventions of computerized search systems to move forward that goal.
The first computerized search systems used special syntax to automatically retrieve book and article information related to a user’s query.
Unfortunately, the cumbersome syntax kept search largely in the domain of libraries trained on the systems.
In1989 the storage, access and searching of document collections was revolutions by and invention named the World Wide Web by its founder Tim Berners-Lee.
Of course, our museum must include artifacts from this revolution such as a webpage, some HTML, and a hyperlink or two.
The World Wide Web became the ultimate signal of the dominance of the Information Age and the death of the Industrial Age.
Yet despite the revolution in information storage and access ushered in by the Web users initialing web searches found themselves floundering.
They were looking for the proverbial needle in an enormous, ever growing information haystack.
Al this change in 1998 when link analysis hit the information retrieval scene. The most successful search engines began using link analysis, technique that exploited the additional information inherent in the hyperlink structure of the Web, to improve the quality of search results.
Web search improved dramatically, and web searchers religiously used and promoted their favorite engines like Google and AltaVista.
History of Information Retrieval
Information retrieval is the process of searching within a document collection for a particular information need (called a query).
Although dominated by recent events following the invention of the computer, information retrieval actually has a long and glorious tradition.
The earliest document collections were recorded on the painted walls of caves. A cave dweller interested in searching a collection of cave paintings to answer a particular information query had to travel by foot, and stand, staring in front of each painting.
Unfortunately, it’s hard to collect and artifact without being gruesome.
Before the invention of paper, ancient Romans and Greeks recorded information on papyrus rolls.
Some papyrus artifacts from ancient Rome had tags attached to the rolls. These tags were an ancient form of today’s Post-it Note, and make an excellent addition to our museum.
A tag contained a short summary of the rolled document and was attached in order to save readers from unnecessarily unraveling a long irrelevant document.
These abstract also appeared in oral form. At the start of Greek plays in the fifth century B.C., the chorus recited an abstract of the ensuing action.
While no actual classifications scheme has survived from the artifacts of Greek and Roman libraries, we do know that another elementary information retrieval tool, the table of content, first appeared in Greek scrolls from the second century B.C.
As the stories goes, the Libraries of Pergamum threatened to overtake the celebrated Library of Alexandria as the best Library in the world, claiming the largest collection of papyrus rolls.
As the result, the Egyptians ceased the supply of papyrus to Pergamum, so the Pergamenians invented an alternative writing material parchment, which is made from thin layers of animal skin.
Unlike papyrus, parchment did not roll easily, so scribes folded several sheets of parchment and sewed them into books.
Other documents collections sprung up in a variety of fields. This dramatically accelerated with the re-invention of the printing press by Johann Gutenberg in 1450.
The wealthy proudly boasted of their private libraries and public libraries were instituted in America in the 1700s at the prompting of Benjamin Franklin.
More orderly ways of maintaining records of a collection’s holdings were devised.
These inventions were progress, yet still search was not completely in the hands of the information seeker. It took the inventions of the digital computer (1940s and 1950s) and the subsequent inventions of computerized search systems to move forward that goal.
The first computerized search systems used special syntax to automatically retrieve book and article information related to a user’s query.
Unfortunately, the cumbersome syntax kept search largely in the domain of libraries trained on the systems.
In1989 the storage, access and searching of document collections was revolutions by and invention named the World Wide Web by its founder Tim Berners-Lee.
Of course, our museum must include artifacts from this revolution such as a webpage, some HTML, and a hyperlink or two.
The World Wide Web became the ultimate signal of the dominance of the Information Age and the death of the Industrial Age.
Yet despite the revolution in information storage and access ushered in by the Web users initialing web searches found themselves floundering.
They were looking for the proverbial needle in an enormous, ever growing information haystack.
Al this change in 1998 when link analysis hit the information retrieval scene. The most successful search engines began using link analysis, technique that exploited the additional information inherent in the hyperlink structure of the Web, to improve the quality of search results.
Web search improved dramatically, and web searchers religiously used and promoted their favorite engines like Google and AltaVista.
History of Information Retrieval
Monday, June 1, 2009
Archimedes of Syracuse
Archimedes of Syracuse
He was Greek engineer who made the first measurement of specific gravity.
He studied in Alexandria, after which he returned o Syracuse where he spent most of the rest of the life.
He made many mathematical discoveries, including the most accurate calculation of pi made up to that time.
In engineering he was the founder of the science of hydrostatics. He is well known for the discovery of ‘Archimedes Law’ that a body wholly or partly immersed in a fluid loses weight equal to the weight of the fluid displaced.
He thus made the first measurement of specific gravity.
Archimedes also proved the law of the lever and developed the theory of mechanical advantage boasting to his cousin Hieron, ‘Give me a place to stand on and with a lever I will move the whole world.’
To prove his point, he launched one of the biggest ships built up to that date.
During his time in Egypt he devised the ‘Archimedean Screw’, still used today in Middle Eastern countries for pumping water.
He also built an astronomical instrument to demonstrate the movements of the heavenly bodies, a form of orrery.
He was General of Ordnance to Heiron and when the Romans besieged Syracuse, a legionary came across Archimedes geometrical diagrams in he sand.
Archimedes immediately told him to ‘Keep off’ and the soldier killed him.
He also experimented with burning glasses and mirrors or setting for to wooden ships.
Archimedes of Syracuse
He was Greek engineer who made the first measurement of specific gravity.
He studied in Alexandria, after which he returned o Syracuse where he spent most of the rest of the life.
He made many mathematical discoveries, including the most accurate calculation of pi made up to that time.
In engineering he was the founder of the science of hydrostatics. He is well known for the discovery of ‘Archimedes Law’ that a body wholly or partly immersed in a fluid loses weight equal to the weight of the fluid displaced.
He thus made the first measurement of specific gravity.
Archimedes also proved the law of the lever and developed the theory of mechanical advantage boasting to his cousin Hieron, ‘Give me a place to stand on and with a lever I will move the whole world.’
To prove his point, he launched one of the biggest ships built up to that date.
During his time in Egypt he devised the ‘Archimedean Screw’, still used today in Middle Eastern countries for pumping water.
He also built an astronomical instrument to demonstrate the movements of the heavenly bodies, a form of orrery.
He was General of Ordnance to Heiron and when the Romans besieged Syracuse, a legionary came across Archimedes geometrical diagrams in he sand.
Archimedes immediately told him to ‘Keep off’ and the soldier killed him.
He also experimented with burning glasses and mirrors or setting for to wooden ships.
Archimedes of Syracuse
Subscribe to:
Posts (Atom)
