Ditani

Ernst Mach (1838-1916)

2009-02-05T20:48:00.000+08:00

Mach was an Austrian physicist who gave his name to the Mach number. This number is a method of relating an object's speed to the speed of sound in a particular medium, usually air.
He also worked on shock waves and inertia, coming to conclusions that conflicted with Einsteins' theory of relativity.

Speeds
Below Mach1 called subsonic.
Above Mach1 called Supersonic
Above Mach5 called hypersonic

Wikipedia

Milestones in Medicine

2009-01-13T21:05:00.001+08:00

Milestones in Medicine

2000BC Medicine practised in China and India.
1651 William Harvey describes the circulation of the blood
1700s John Hunter perfects surgical techniques
1846 William Morton uses ether as an anesthetic.
1895 Wilhelm Roentgen discovers X-rays
1920s Frederick Banting and Carles Best use insulin to treat diabetes.
1960 Albert Sabin develops oral polio vaccine.
1967 Christiaan Barnard carries out the first human heart transplant.
1985 Lasers are used during surgery to clean out clogged arteries.

Robert Koch (1843-1910)

2009-01-11T21:01:00.000+08:00

Koch was a German doctor who founded bacteriology, the study of bacteria.
He identified the bacteria that cause such diseases as anthrax, cholera and tuberculosis.
He also studied malaria and concluded that it is caused by mosquito bites, at the same time as the British doctor Ronald Ross.
Koch received the 1905 Nobel Prize in Medicine.

Wikipedia

Giovanni Schiaparelli (1835-1910)

2009-01-09T20:59:00.000+08:00

Schiaparelli was an Italian astronomer who believed he could see narrow lines on Mars.
He called them 'channels' meaning rivers or river beds. But his Italian word canali was mistranslated as 'canals', meaning artificial waterways.
American space probes have proved that there are no canals on Mars.

Wikipedia

Guglielmo Marconi (1874-1937)

2009-01-07T20:55:00.000+08:00

Marconi, Guglielmo was the Italian scientist who invented a system for sending messages (in Morse code)long distances without wires.
He began experimenting with transmitting Radio waves in 1894. He improved the Antennae and receivers available then and succeeded in sending bursts of radio energy over about 2.4km.
Two years later he worked with Sir William Preece, the post Office Chief Engineer in Britain.
He Increased the range of his transmissions to 14km (across the Bristol Channel) and set up a land station in Italy to communicate with warships (19km) at sea.
In 1899 British warships succeeded in communicating over 120km.
In 1901, Marconi sent radio messages from Poldhu in Cornwall, England, to St John's in Newfoundland: the beginning of worldwide radio Communications.

Wikipedia

William Gilbert (1540-1603)

2009-01-05T20:53:00.000+08:00

Gilbert was physician to Elizabeth 1 and James 1. He was the first to use the terms magnetic pole and electrical force,
and suggested that the Earth's magnetism could be explained if the Earth was likened to a huge bar magnet.
He thought (wrongly) that the planets held their orbits around the Sun by magnetic forces.

Wikipedia

Otto von Guericke (1602-1686)

2009-01-03T20:51:00.000+08:00

Von Guericke was a German physicist and engineer who in 1650 invented the first air pump (used in the Magdeburg spheres) and later, the first electric generator.
With the pump he was able to study objects in a vacuum. For instance, he showed that sound needs air to travel in and that air is essential for burning.

Wikipedia

Linnaeus, Carolus (1707-1778)

2008-12-29T20:43:00.000+08:00

Linnaeus was a Swedish botanist who introduced a standard method of naming and classifying living things.
Linnaeus spent much of his childhood collecting plants and animals before studying to become a doctor at the University of Uppsala.
In 1741 he was appointed Professor of medicine and Botany at Uppsala, and so spent more time studying the Ecology and distribution of plants.
He described nearly 8000 plant species and about 4400 animal species (almost everything known to Europeans at the time) and he gave each a scientific name in two parts.
For examples, he called the wolf canis lupus and the jackal canis aureus.
Canis is the genus to which the animals belong, and so the scientific name shows that the animal are related.

Wikipedia

Christiaan Huygens (1629-1695)

2008-12-27T20:41:00.000+08:00

Huygens was a Dutch physicist and mathematician who first suggested that light travels as waves.
He explained reflection and refraction in terms of wave motion. He invented new ways of making glass lenses for telescopes.
With his improved telescope, he was able to see the true shape of the rings around Saturn.

Wikipedia

Leonardo da vinci (1452-1519)

2008-12-25T20:38:00.000+08:00

Leonardo da vinci was a great Italian painter,sculptor,architect and engineer who contributed more to science, TECHNOLOGY and art than anyone else of this time.
Many of his ideas were hundreds of years ahead of their time. For example, his drawings included plans of helicopter long before the MATERIALS and technology were available to build one.
He was trained as an artist by the painter and sculptor Andrea del Verocchio. While learning to draw things, he became interested in how they worked.
His great paintings include The Last Supper and Mona Lisa. In 1513 Leonardo was invited to France by the French king, Francis 1.
He spent his last years living in a castle given to him by the king in Cloux, near Amboise.
Many of Leonardo's sketch books are preserved in museums.

Wikipedia

Augustine Fresnel (1788-1827)

2008-12-23T20:33:00.000+08:00

Fresnel was a French physicist who developed the transverse-wave theory of light, as a result of his work on lenses and optical interference.
Fresnel showed that normal sunlight consisted of vibrations that were at right angles (transverse) to the direction travelled by the light.
He also invented a type of lens in wich the surface is cut into a series of concentric steps resizing forwards the centre. These lenses are still widely used in light house

Wikipedia

Ivan Pavlov (1849-1936)

2008-12-21T20:31:00.000+08:00

Pavlov was a Russian biologist who was the first to make a scientific study of learning by association.
He worked with dogs and noticed how their saliva. began to run every time they were fed .
This was a normal reflex action-the dogs did not have to think about it.
Then Pavlov rang a bell every time the dogs were fed. After a while, he saw that the dogs' saliva began to run as soon as they heard the bell - even before the food arrived.
The dogs had learned to associate the sound of the bell with food.
Pavlov Called this type of reaction a conditioned reflex.

Wikipedia

Theodore Maiman (1927- )

2008-12-19T20:28:00.001+08:00

The United states physicist Theodore Maiman constructed the first working laser in 1960.
After developing the master (a device that generates or amplifies microwaves) in 1955 he began to work on an optical maser, or laser.
His device consisted of a cylindrical artificial ruby crystal with parallel mirror coated ends, one of which was semi-transparent.
Bursts of intense white light were provided by a flash lamp.

Wikipedia

Lamarck, Jean Baptiste (1744-1829)

2008-12-17T20:26:00.000+08:00

Jean Baptiste Lamarck was a French biologist, best known for his attempts to explain Evolution.
He suggested that useful features acquired during the life of an individual could pass to the next generation,
thus making each generation more efficient.
Lamarck believed that giraffes stretched their necks as they reached for leaves, and then passed their longer necks on to their offspring.
According to his theory, a person who trained to become an athlete would have athletic children.
Neither Lamarck nor anyone else could provide any evidence for this kind of evolution and few people believed his theory.
Body cells and reproductive cells are quite separate, and only the genes in the reproductive cells are passed on to the offspring.

Wikipedia

Kepler, Johannes (1571-1630)

2008-12-15T20:20:00.001+08:00

Kepler proved that the Earth and the other planets in the solar system orbit the sun in elliptical paths.
Kepler was born in what is now southwestern Germany. He was very frail, and often ill but a brilliant mathematician.
He worked with Tycho Brahe in Prague and built on his theories and those of Copernicus.
Copernicus was the first to show that the Earth revolved around the sun.
After years of painstaking observations and calculation Kepler discovered planets do not move in circles as Copernicus believed,
but ellipses, which are like flattened circles.
Finally he published his laws of planetary motion to explain the motion of the planets.
Kepler also believed in astrology and earned money casting horoscopes.

Wikipedia

Kelvin, William Thomson (1824-1907)

2008-12-13T21:33:00.000+08:00

William Thomson , later Lord Kelvin of Largs, was a British physicist and engineer who was born in Belfast and died near Largs, Scotlands.
He entered the University of Glasgow when he was 10, published his first scientific article at 16 and went on to study at Cambridge.
In 1846 he became a professor in Glasgow.
He was one of the first people to state the Second Law of Thermodynamics that Heat cannot be completely converted into work.
He also estimated the age of the Earth from its temperature, although he was wrong because he did not know about the production of heat through Radioactivity in the Earth.
He became rich because of his design for a Galvanometer to receive the signals sent through underwater Telegraph cables.

Wikipedia

James Joule (1818-1889)

2008-12-11T21:30:00.000+08:00

James Prescott Joule was a British physicist who studied with Lord Kelvin and the chemist John Dalton.
His experiments showed that the production of heat is always accompanied by a loss of another form of energy and so he deduced that heat itself is a form of energy.
The unit of energy is named after him.

Wikipedia

Frank Whittle (1907-1987)

2008-12-09T21:28:00.000+08:00

Whittle, an officer in the British Royal Air Force, built the first successful jet engine in the 1940s.
Whittle's turbojet design powered the world's first practical jet aircraft, the Gloster Meteor, the prototype of which first flew in 1941.
The first jet-engined aircraft actually to fly was the German Heinkel He-178 in 1939.
But this later proved impractical.

Wikipedia

Frederick Soddy (1877-1956)

2008-12-07T21:27:00.000+08:00

Soddy was a British chemist who worked alongside Ernest Rutherford and carried out pioneering research into radioactive decay.
As a result, Soddy was able to formulate the theory of isotopes, and in 1921 he was awarded the Nobel prize for chemistry.
Aware of the great potential of the energy contained in uranium, he became increasingly concerned about the use of atomic energy and the social responsibility of scientists.

Wikipedia

Henry Bessemer (1813-1898)

2008-12-05T21:25:00.000+08:00

Bessemer was a British steel manufacturer who invented a cheap method for making large quantities of steel.
At the heart of the process was the Bessemer converter, a large pear-shaped blast furnace.
In the united states, Henry Kelly independently devised a similar process.

Wikipedia

Edward Appleton (1892-1965)

2008-12-03T21:24:00.000+08:00

Appleton was the British physicist who discovered one of the layers of ionized particles that reflect radio waves in ionosphere.
This layer was often known as the Appleton layer, but is now understood to be two separate layers that are known as F1 and F2.
Appleton's work in atmospheric physics was important to the development of radar, and in 1974 he was awarded the Nobel prize for Physics.

Wikipedia

Nikolaus Otto (1832-1891)

2008-12-01T21:22:00.000+08:00

Otto was a German engineer who developed a four-stroke, gas -fuelled internal combustion engine which he potented in 1877.
Otto did not invent the four-stroke cycle but was the first to incorporate it into a successful design.
Otto's smooth running gas engines were widely used before World War I, after which they were superseded by petrol engines.

Wikipedia

Joseph Henry (1797-1878)

2008-11-29T21:19:00.000+08:00

The United States physicist Joseph Henry was one of the earliest pioneers of electricity.
He discovered electromagnetic induction (the unit of inductance, the Henry, is named after him) and invented an electric telegraph.
Henry Was appointed as the first director of the Smithsonian Institution in Washington.

Wikipedia

Julius Robert Oppenheimer (1904-1967)

2008-11-27T21:17:00.000+08:00

Oppenheimer was an American physicist, and is often described as the father of the atomic bomb.
He was the senior scientist on the Manhattan Project which developed the atom bombs dropped on japan at the end of the World War II.
After the War, Oppenheimer argued for the peaceful use of nuclear power.
He continued working as a physicist and did important work on black holes.

Wikipedia

Andrei Sakharov (1921-1989)

2008-11-25T21:16:00.000+08:00

Sakharov was a Soviet physicist who played a major role in the development of the Soviet hydrogen bomb.
He later became a vocal campaigner for nuclear disarmament, and was labelled a dissident by the Soviet Authorities and sent into internal exile.
In 1975, Sakharov was awarded the Nobel Peace prize.
The more tolerant policies of the Soviet authorities allowed him to same out of exile in 1989.
He died in Moscow shortly afterwards.

Wikipedia

Henry Cavendish (1731-1810)

2008-11-23T21:12:00.000+08:00

Cavendish who was both a chemist and a physicist.
He is most famous for his work on the composition of air.
Cavendish discovered the properties of hydrogen, and showed that air was a mixture of more than one gas.
He was also the first to show that water is in fact a compound, and not an element.

Wikipedia

Charles Lyell (1797-1875)

2008-11-21T08:21:00.000+08:00

Lyell was a British scientist. He is often called the father of modern geology. In his book Principles of Geology,
published between 1830 and 1833, he showed that the Earth has changed slowly and gradually through the ages by means of processes that are still going on.
He was one of the first scientists to accept modern theories about the Ice Age and Evolution.

Wikipedia

Jacques Charles (1746-1823)

2008-11-19T08:14:00.000+08:00

Charles was a French chemist who was also a teacher and a minor government official.
Charles is best known for stating the law that every gas expands by the same amount for a rise in temperature of one degree.
This means that the volume of a fixed amount of gas is directly proportional to the temperature if the pressure remains constant.
Charles did not publish his research and it was later duplicated by Gay-Lussac.
He was also interested in ballooning and suggested balloons could be filled with the very light hydrogen gas.

Wikipedia

Dennis Gabor (1906-1979)

2008-11-17T08:40:00.001+08:00

Gabor was a Hungarian-born physicist who worked in Britain.
He developed the theory behind holography during the 1940s, but actual holography became possible only after the laser was developed at the beginning of the 1960s.
The powerful light of the laser allowed high-quality holograms to be made.
Gabor eventually received the Nobel Prize for Physics in 1971.

Wikipedia

Hyppocrates (ca. 460 BC – ca. 370 BC)

2008-11-15T08:37:00.000+08:00

Hyppocrates was an ancient Greek philosopher and physician who was born about 460 BC on the island of Kos.
Little is known of his early life, but he travelled widely in Greece and the Middle East, teaching his theories of Medicine.
He is often referred to as 'the father of medicine'. However, little is known about 'Hippocrates' own work,
and most of the Hippocratic medicine we know about today was developed later by his followers.
The most lasting influence of Hippocrates is the Hippocratic oath, which lays down a code of principles for the doctor,
ensuring that the good of the patient is always the most important part of treatment.

Wikipedia

Gregor Mendel (1822-1884)

2008-11-13T08:31:00.002+08:00

Gregor Mendel
Mendel was an Austrian monk and amateur botanist who pioneered the study of heredity.
Through his experiments on pea plants he noticed patterns from one generation to the next, now known as Mendel's laws of heredity.
The importance of his work was not recognized until after his death.

Wikipedia

Edmund Halley (1956-1742)

2008-11-11T08:27:00.000+08:00

Halley was an English astronomer and physicist. He is best known for his discoveries about the orbits of comets.
He calculated that the orbits of comets seen in 1531,1607 and 1682 were very similar and from this predicted that the comet he had observed in 1682 would return in 1758.
The comet appeared on Christmas Day 1758 and was named Halley's Comet in his honour.

Wikipedia

Wilhelm Weber (1804-1891)

2008-11-09T08:24:00.001+08:00

Weber was a German physicist known for his work on geomagnetism. He researched wave motion in 1824 and the mechanics of walking in 1833.
The Weber unit of magnetic flux (Wb) is named after him. have a strength of two or more Weber's per square metre.

Wikipedia

Barbara McClintock (1902-1992)

2008-11-07T08:19:00.000+08:00

In 1983 McLintock won the Nobel Prize for Physiology and Medicine for her discovery that some genes can change position on the chromosomes.
Earlier, she had shown that when eggs or sperm are produced the chromosomes can break apart and join up again in different combinations of genes in the offspring.

Wikipedia

Joseph Louis gay-Lussac (1778-1850)

2008-11-01T08:12:00.000+08:00

Gay-Lussac was a French chemist. In 1802, working independently, he repeated the discovery that another chemist, Jacques Charles,
had already made about the constant expansion of gases with each degree rise in temperature.
Gay-Lussac later showed that, when gaseous elements combine to form compounds, they do so in proportions by volume that can be expressed as simple whole numbers.
For example, forming water, two parts by volume of hydrogen combine with one part by volume oxygen.

Wikipedia

Luigi Galvani (1737-1798)

2008-10-29T08:08:00.000+08:00

Galvani was an Italian scientist. He is known for his experiments showing the effects of electricity on living tissue,particularly on muscles.
He discovered that touching the nerves in a dead frog's leg with a pair of scissors during a thunder storm caused the muscles to twitch.
Galvani believed that he had discovered a new type of electricity, animal electricity,but Alessandro Volta showed that this was not the case.
Galvani's name lives on in word 'gavanized' which means stimulated as if by electricity.

Wikipedia

Galileo Galilei (1564-1642)

2008-10-27T08:05:00.000+08:00

Galileo Galilei, who lived in Italy, is remembered ass the first person to turn a Telescope to the sky and make important astronomical discoveries.
He observed craters on the moon, the bright satellites of Jupiter, Sunspots and other things.
He made himself unpopular, because he lived at a time when belief about the world and the Universe was based on the Bible and on Aristotle's teachings of 2000 years earlier.
For example, Aristotle had said that a heavy weight fell more quickly than a light one,
but Galileo showed that they both fell at the same speed. The Bible said that everything moves around the Earth,
but Galileo's observations showed that the Earth moves round the Sun.
He was imprisoned, and ended his life near Florence under 'house arrest'.

Wikipedia

Freud, Sigmund (1856 – 1939)

2008-10-25T07:59:00.001+08:00

Sigmund Freud was born in Freiberg, then a part of the Austrian empire, in 1856.
He was a neurologist who pioneered psychoanalysis, a technique for examining the motivations and hidden activities of the mind.
Studying in Paris. Freud noted that, in patients suffering from hysteria, physical illness could also appear.
This association of mind with body led him to study patients with metal disorders, and to develop psychoanalysis,
in which patients were encouraged to tell him their dreams and deepest thoughts.
Freud would prompt them to reconsider their dreams and earliest memories, in the belief that these had an effect on their current behaviour.
In the early 20Th century, his theories became extremely popular, having a lasting effect on art, literature,
education and social attitudes. He died in London in 1939.

Wikipedia

Heinrich Hertz (1857-1894)

2008-10-23T07:56:00.000+08:00

Heinrich Hertz
hertz was a German scientist. He was the first person to broadcast and receive radio waves.
In 1883 he began working on electromagnetic radiation.
He produced radio waves by using a rapidly oscillating electronic spark and was able to measure their velocity and their wavelength.
This confirmed the theory developed by James clerk Maxwell. The unit of Frequency, the hertz, was named after him.
One Hertz (1Hz), is equivalent to one cycle or oscillation per second.

Wikipedia

Franklin, Benjamin (1706-1790)

2008-10-21T07:53:00.000+08:00

Benjamin Franklin an American printer,scientist,publisher and statesman who played an important part in the
formation of the United States of America as a nation.
Franklin was born in Boston, Massachusetts, the tenth son of 17 children.
At 12 years he went to work for his brother, a printer in Philadelphia, but gave it up in 1748 to study science.
He proved that Lightning is electrical and later invented the lightning Conductor to protect buildings.
He came to England to try to settle some tax disputes but returned to the United States in 1775, before the American War of Independence.
Franklin helped draft their Declaration of Independence and was one of those who signed the Constitution.

Wikipedia

George Cayley (1773-1857)

2008-10-19T07:45:00.001+08:00

George Cayley
A British engineer, Caley is known for the many ideas he contributed to the early history of aviation,
and is often called the father of modern aeronautics.
He invented the biplane and built a glider that travelled 270m.
He wrote about helicopters, parachutes and streamlining the design of aircraft.

Milestones in the History of Flight

1492 Leonardo da vinci draws concept of a flying machine.
1890 Adler's Eole bacomes first full-sized aircraft to leave the ground under its own power.
1903 Orville Wright makes first sustained powered flight.
1908 Orville Wright makes first aircraft flight lasting 1 hour.
1909 Farman completes first aircraft flight of 100 miles (161km).
1913 Sikorsky builds and flies a 4-engine aircraft.
1939 Sikorsky builds first modern helicopter.
1947 first aircraft flies at supersonic speed in USA.
1970 First Jumbo-Jet Boeing 747 brought into service.
1986 Rutan and Yeager pilot aircraft Voyager round the World whithout refuelling in a 9-day flight.

Wikipedia

Faraday, Michael (1791-1867)

2008-10-17T07:40:00.002+08:00

Michael Faraday (1791-1867)
Was a British physicist and chemist.
His experiments are the basis for our understanding of the forces of Electricity and Magnetism.
His father was a blacksmith and Faraday had very little formal education, but he read science books in the shop where he worked.
He went to Humphry Davy's lectures at the Royal Institution in London and persuaded Davy to let him work as his assistant.
In 1821, he began to study the magnetic effects of an electric current which Oersted had discovered.
He become the director of the Royal Institution in 1825 and in 1831 he found that when he moved a magnet through a coil of wire,
an electric current was produced in the wire.
This enabled him to make the first electrical generator or dynamo. He also investigated Electrolysis.

Wikipedia

Vladimir Kozmich Zworykin (1889-1982)

2008-10-05T22:02:00.000+08:00

Zworykin was a Russian-born American physicist and electronics engineer.
He is most famous for his work in developing and perfecting the electron microscope.
he is known for his contribution to advances in radio and television.
He helped develop the television camera and picture tube.
By 1929, his television camera had replaced the mechanical system developed in Britain by Baird.

From : Wiki

Robert Millikan (1868-1953)

2008-10-03T22:01:00.000+08:00

Millikan was a United States physicist. He won the Nobel Prize for physics in 1923 for being the first scientist to measure the charge of an electron.
He did an experiment, known as the oil drop experiment, in which he was able to measure the amount of an electric force,
and the size of an electric field acting on a charged droplet of oil.
From this he calculated the size of the charge carried by an electron.
During the 1920s Millikan researched into cosmic rays and showed that they come from space.

From : Wiki

Joseph John Thomson (1856-1940)

2008-10-01T22:00:00.000+08:00

Thomson was a British physicist.
He won the Nobel Prize for Physics in 1906 for his work on gases. He also discovered the electron.
In 1895, he investigated the rays produced when an electric current passed through a vacuum in a glass tube.
The rays came from the negative end of the tube (the cathode)and were called cathode rays.
He showed that the rays consisted of particles (electrons) which were negatively charged and are found in every atom.

From : Wiki

Oliver Joseph Lodge (1851-1940)

2008-09-29T21:58:00.000+08:00

Lodge was a British physicist.
He carried out experiments to produce and detect the electromagnetic radiation predicted by Maxwell in 1864.
In 1881, he became professor of physics at Liverpool University, where he carried out his experiments on electromagnetic waves and later worked to improve the reception of radio signals.
In 1900, he became the first principal of Birmingham University, and retired in 1919 because he wanted to study 'psychic phenomena'.
He strongly opposed Einstein's theory of general relativity in its early years.

From : Wiki

Hans Christian Oersted (1777-1851)

2008-09-27T21:56:00.000+08:00

Oersted was a Danish physicist. He discovered that an electric current produces magnetism.
His public lectures and scientific demonstrations were very popular in Copenhagen.
It was during one of his lectures in 1820 that he accidentally discovered that an electric current changes the direction of a nearby compass needle.

From : Wiki

James Clerk Maxwell (1831-1879)

2008-09-25T21:54:00.000+08:00

Maxwell was a British theoretical physicist.
He was the first to write down the laws of electricity and magnetism in mathematical form.
In 1864, he put Faraday's ideas into mathematical form and predicted the existence of electromagnetic radiation.
He is also famous for his work on the speeds of molecules in gases.

From : Wiki

Daniel Bernoulli (1700-1782)

2008-09-23T21:52:00.001+08:00

Bernoulli was a Swiss doctor and mathematician. He showed that when the speed of a liquid increases, the pressure of the liquid drops.
In the same way air , flows faster over the curved upper surface of an aircraft wing than the air passing under the flatter lower surface.
This means that the air pressure below the wing is greater than the pressure above,which creates an upward lift.

From : Wiki

Alessandro Volta (1745-1827)

2008-09-21T21:51:00.000+08:00

Alessandro Volta was an Italian scientist. In 1794, he explained why a frog's leg twitched when its muscles were touched with two different metals.
Volta showed that this was because an electric potential difference was produced between the two metals.
Potential difference is set up when there is a difference in charge between two point.
He then went on to make the first battery in 1800.

From : Wiki

Einstein, Albert

2008-09-19T21:50:00.000+08:00

Albert Einstein was a physicist who was born in Ulm, Germany in 1879; he become a Swiss citizen in 1901 and left Germany for the United States in 1933, where he died in 1955.
He is most famous for developing the theory of Relativity, out of which came the famous equation E=mc².
In 1905 he suggested that light is absorted in the form of packets of Energy, now called photons; for this he received the Nobel Prize for Physics in 1921.
Also in 1905 he developed the special theory of relativity and later, in 1915, he arrived at the general theory of relativity.
These theories are the basis for all our ideas about the history and structure of the Universe.
Einstein's work on photons helped to found Quantum Theory, although he disagreed with some of the later work on this subject.

From : Wiki

Edison, Thomas Alva (1847-1931)

2008-09-17T21:48:00.000+08:00

Thomas Alva Edison was responsible for over 1000 inventions. He was born in Milan, Ohio, in the United States.
When he was only ten years old, he setup his own chemistry laboratory in his basement.
In the 1860s he worked as a Telegraph operator in the united States and Canada.
In 1876, the profits he made from selling telegraphic printers he had invented, enabled him to set up a laboratory.
A year later, he invented the phonograph, a type of record player that used wax cylinders instead of discs.
He first recording was of himself saying the rhyme 'mary had a little lamb'.
In 1879, he demonstrated the first successful electric Light Bulb.
He discovered that electricity would flow from the bulb's glowing filament onto a metal plate inside the bulb.
This is known as the 'Edison Effect'. It later led to the invention by other people of the radio tube, or valve.

From : Wiki

James Watson (1928 - )and Francis Crick (1916 - )

2008-09-15T21:46:00.000+08:00

James Watson (1928- )and Francis Crick (1916- )
In 1953, They discovered the structure of DNA (deoxyribonucleic acid)the substance that transmits genetic information from one generation to the next.
They showed the shape of the molecule and worked out how the individual components of DNA were joined together.
Watson and Crick won a Nobel Prize for their work, which changed the science of genetics.

From Wiki James Watson - Francis Crick

Descartes, Rene (1596-1650)

2008-09-13T21:44:00.000+08:00

Rene Descartes was a French philosopher, mathematician and natural scientist who invented analytical Geometry and
was the first philosopher to describe the Universe as he saw it in term of mind and matter. He worked out laws of motion.
Descartes rejected the idea that everything we observe is false or a dream by saying that, because we have thoughts, we exist
His Latin Motto, 'cogito,ergo sum' (i thing, there fore i am), is famous. It means that because we have thoughts, we exist.
Descartes' approach to science was to question everything. He worked out thing for himself from the beginning.
Born at La Haye, in France, Descartes was brought up as a Jesuit, travelled widely, and fought in several wars.
From 1628 to 1649 he lived in the Netherlands. He died on a visit to Sweden in 1650.

From: Wiki

Davy, Sir Humphry (1778-1829)

2008-09-11T21:42:00.000+08:00

Sir Humphry Davy (1778-1829)was and English scientist, best remembered for his invention of the miner's safety lamp in 1815.
His lamp prevented the explosion of air containing methane, or fire-damp, a gas common in coal mines.
The lamp's flame was protected by a fine wire mesh to separate it from the explosive gases.
Davy was born and educated in Cornwall, England. When he left school, he went to work for a doctor.
He gave this up and took charge of a laboratory in Bristol Where he studied the effects of gases on people.
He discovered that nitrous oxide (laughing gas ) could be used as an anesthetic.
Later, in London, he studied how electricity is stored in batteries.
He also discovered that materials could be separated into their Elements by passing an electric current through them.

From : Wiki

Darwin, Charles

2008-09-09T21:40:00.000+08:00

Charles Darwin was born in England in 1809 and became one of the world's most famous naturalists.
He was the first person to give a workable explanation of Evolution.
During a five-year voyage around the world, he studied animals and plants in many countries and he was impressed by their great variety.
He observed what he called the struggle for existence, with each organism struggling to get food and avoid being eaten,
and he realized that only those individuals best fitted or suited to their surroundings could survive.
Here was an explanation for the great variety of plant and animal life throughout the world:
conditions vary enormously from place to place and living things have gradually changed to suit these different conditions and habitats.
On his return home, he set about collecting more evidence and in 1859 he published his ideas in his famous book called
On the Origin of Species by Means of Natural Selection.
Darwin's ideas met a lot of opposition at first, but were gradually accepted by most people and are still the basis of the theory of evolution today.
Darwin died in 1882 and was buried in Westminster Abbey, in London.

(The Theory of Evolution)
Darwin Developed the theory of evolution gradually.
His observations during the voyage on HMS Beagle and other expeditions contributed to his ideas.
He published his theory in On the Origin of Species in 1859.
At first the theory met with great opposition - especially among religious leaders and Darwin was ridiculed in cartoons
because people mistakenly thought he had said that human beings are descended from monkeys.

from wiki

Fred Hoyle (1915 - )

2008-09-07T21:38:00.000+08:00

Fred Hoyle A British cosmologist who with other proposed the steady state theory.
This states that the Universe has always existed and that new matter is constantly being created to fill the space left as the Universe expands.
Hoyle also writes science fiction.

Source : Wiki

Nicolaus Copernicus (1473-1543)

2008-09-05T21:36:00.001+08:00

Nicolaus Copernicus
A Polish canon or priest, proposed that the SUN and not the Earth is at the centre of the Universe.
This was dangerous teaching at a time when the Bible was believed to prove that the Earth is the central and most important body of all.
Like Aristarchus 1800 years earlier, it made him unpopular.
He published his theory in a book which very few people bought or read, but the fact that it existed was enough to start others discussing the theory.
However,proof did not come until the century after Copernicus died. His theory was not completely accurate.
First, He believed that the planets move in circles instead of ellipses.
Second, he thought that the stars are dim objects not much farther off than the outermost planet then known, Saturn.
In other words he thought that the Sun was really at the centre of the Universe instead of being an average star in a huge Galaxy.

Source : Wiki

Gustav R. Kirchhoff (1824-1887)

2008-09-03T21:33:00.002+08:00

Kirchhoff was a German physicist. in 1845, he worked out a set of laws called Kirchhoff's laws.
These laws made it possible to work out the amount of current flowing at any point in a network of electric conductors.
He also showed that alternating current in an electric conductor with no resistance travels at the speed of light.
With the German chemist Robert Bunsen he developed the modern spectroscope.
They used the spectroscope and a prism specially designed by Kirchhoff to analyse substances.
In 1860, they showed that when metal compounds are heated in a flame, each gives off a spectrum particular to the metal.
It was by using this technique that Kirchhoff and Bunsen discovered the elements caesium and rubidium.
From laws he developed about the emission and absorption of radiation, he suggested the concept of the black body.
This was a key step in the development of the branch of physics known as quantum mechanics.

Source :Wiki

William Harvey (1578-1657)

2008-08-29T20:44:00.001+08:00

Harvey was an English physician. He was the first to accurately describe the circulation of the blood.
He showed that blood moves around the body in only one direction along arteries and veins.

Complete here

August Weismann (1834-1914)

2008-08-27T20:41:00.001+08:00

Weismann was one of the founders of the science of genetics.
He realized that something in the germ cells, contained in the sexual organs,
was passed on to the next generation controlling their heredity. He found that in born characteristics of both parents,
such as height and eye colour, were combined in their offspring but that acquired characteristics were not inherited.
He showed that offspring of mice which had
Had their tails cut off were born with normal tails.

Complete Here

Thomas Hunt Morgan (1866-1945)

2008-08-25T20:38:00.001+08:00

Thomas Hunt Morgan
An American zoologist and geneticist, he won the Nobel prize for Physiology in 1930 for his work linking.
Chromosomes and heredity. His experiments with the fruit fly Drosophila showed that the genes,
the units of heredity, were carried on the chromosome.
He later showed that the position of the genes on the chromosome controlled inherited characteristics.

Complete here

Antoine Lavoisier (1743-1794)

2008-08-23T20:35:00.001+08:00

Lavoisier was a French chemist. He correctly explained the role of oxygen in combustion.
By carefully weighing and analyzing materials after burning,
he showed that burned materials are heavier than unburned materials.
This was because of the addition of a gas , discovered by scheele and Priestley. Lavoisier named it oxygen.

Complete here

Robert boyle (1627-1691)

2008-08-21T20:33:00.001+08:00

Boyle was an Irish scientist. He founded the study of chemistry as a separate science and aimed to 'improve natural knowledge by experiment'.
He is known for his experiments on gases and was the first chemist to isolate and collect a gas.
He formulated Boyle's law:
A Volume of gas at a constant temperature varies inversely with the pressure applied to the gas.
He showed that air is absorbed in the process of combustion and that only one part of air, oxygen, is necessary for breathing.

Complete here

William crookes (1832-1919)

2008-08-19T20:30:00.001+08:00

Crookes was a British physicist and chemist. In 1861, he discovered the element thallium.
His studies on electrical discharges in vacuum tubes resulted in the Crookes tube, an early cathode ray tube,
in 1880 he found that 'cathode rays' cast shadows and traveled in straight lines, which could be deflected by a magnet.
He believed that cathode rays were made up of negatively charged particles (electrons).

Complete here

Tycho Brahe (1546-1601)

2008-08-17T20:27:00.001+08:00

Tycho Brahe
A Danish astronomer, lived before the telescope was invented and made the most accurate observations with the naked eye ever known.
Like most astronomers of the time, he was employed by his king as an astrologer who had to cast horoscopes,
but his real interest was the movement of the planets.
He believed that the planets orbit the sun , but he also thought that the sun orbits the earth,
and that our planet was the center of the universe.
Brahe set out to prove this by observing the positions of the planet
After His death the observations reached the hands of Johannes Kepler, who was studying the same problem.
Brahe's naked-eye observations helped Kepler prove that the earth also revolves around the sun,
and that the planets move in ellipses, not circles.

Complete Here

Linus Pauling (1901- 1994 )

2008-08-15T20:22:00.002+08:00

Linus Pauling A united states chemist, Linus Pauling won the 1954 Nobel Prize for chemistry for his work on chemical bonding
He Calculated the energies needed to bind atoms in a molecule,
the distance between the atoms and the angles at which bonds form .
Also he won the Nobel prize for Peace in 1962

Complete Here

DR Stephen Hawking (1942- )

2008-08-13T20:17:00.001+08:00

Hawking is a British theoretical physicist.
He is best known for his theories about black holes, which are invisible bodies in space with strong gravitational forces.
He has shown that they give off particles and radiation until they explode and disappear.
Hawking is generally thought to have made some of the most important finds about gravity since Einstein's theory of general relativity.
He is currently working on combining gravity and a branch of physics known as quantum mechanics in a single theory that can explain the origin and structure of the universe.
He holds the post of lucasian professor of physics at Cambridge University,
a post Sir Isaac Newton once held. Hawking has suffered from an incurable disease of the nervous system since the 1960s.

Complete Here

Alexander Graham Bell (1847-1922)

2008-08-11T20:13:00.001+08:00

Alexander Graham Bell Was born and educated in Scotland but lived for most of his life in the United States of America.
Before he left Scotland, Bell began teaching deaf children using a code of symbols invented by his father.
His interest in the human voice, and the realization that speech produces around waves vibrating in air,
led him to become the first person to successfully transmit speech by means of electrified wire .
In 1876, he announced the world's first workable Telephone. It had certain disadvantages;
it had to be moved quickly from mouth to earand the sound was very faint even when the speaker shouted.
The American inventor Edison soon produced a much more powerful and successful telephone.
In 1880, Bell brought out the Gramophone which was an improved version of Edison's phonograph,
a machine which recorded speech and played it back
Though Bell will always be associated with the invention of the telephone,
he would rather have been remembered as a teacher of the deaf.

Complete here

Evangelista Torricelli (1608-1647)

2008-08-09T20:11:00.001+08:00

Torricelli was an Italian mathematician and physicist.
He discovered the principle of the barometer.
He put a long Mercury-filled glass tube, closed at one end, upside-down in a cup of mercury.
The air pressure on the surface of the mercury in the cup held the column of mercury in the tube at a height of 760 mm.
The weight of the column of mercury was equal to the pressure of the atmosphere.

Complete here

Baird, John Logie (1888-1946)

2008-08-07T20:07:00.002+08:00

Baird was a Scottish engineer.
In 1924 he became the first person ever to transmit a television picture by radio waves.
He was also the first to transmit a picture across the Atlantic (in 1928),
and in the same year he transmitted colour television picture.
Baird's first television apparatus, set up in his attic workshop at Hastings, England,
included a tea chest, a biscuit tin, the front lenses from a number of bicycle lamps, bits of wood,
darning needles, string, and sealing-wax.
This crude camera transmitted a blurred image of a cross to a receiver at the other end of the attic.
Despite improvements made by Baird,
in 1937 the British Broadcasting Corporation chose for its broadcasts a rival system that used a Cathode Ray Tube.

Complete Here

Charles Babbage (1792-1871)

2008-08-05T20:04:00.001+08:00

Charles Babbage
Resigned as professor of Mathematics at Cambridge to work on designing a mechanical calculating machine.
Despite the invention of logarithms, the need for accurate and complicated calculations had outgrown the existing simple machines,
such as the Abacus.
Babbage's aim was to use sets of gears that moved each other to produce columns of figures.
These figures would then be printed out automatically.
His difference Engine, as he called it, was never finished,
but the beautifully-machined parts can be seen in the Science Museum, London.
He abandoned it for the Analytical Engine, Which was intended to solve algebraic problems as well as do direct calculations,
but he could not find enough money to complete it. He is now respected as a computing pioneer born before his time.

Complete Here

Amedeo Avogadro (1776-1856)

2008-08-03T19:57:00.002+08:00

Amedeo Avogadro
Was an Italian physicist.
He is famous for his gas law, known as Avogadro's law,
Which states that when each one of a set of identical glass jars is filled with a different Gas,
at the same temperature and pressure, they each contain the same number of molecules of gas.
To discover the actual number of molecules requires the use of Avogadro's number.
It is usually written as 6.0220 X 10²³ which is a short way of writing
602,200,000,000,000,000,000,000. This is about the number of molecules of any gas,
including AIR, that would be contained in 22.4 litres.

For Complete Here

Jons Berzelius (1779-1848)

2008-08-01T19:49:00.002+08:00

Berzelius was a Swedish chemist. He classified different substances by calculating their atomic weights.
By 1818 he had accurately calculated the atomic weights of 45 elements and suggested a new way of naming the elements
by using the first letter or letters of their names, O = oxygen
Combinations of elements are represented by putting the letters together CO2 = Carbon dioxide, one carbon atom joined to two oxygen atoms.

Source : Wikipedia

History of science 1961 –

2008-07-25T16:29:00.002+08:00

Assassination of J.F. Kennedy 1963
Chernobyl explosion 1986
Re- unification of East and West Germany 1990
First hole in Ozone layer indentified
First human heart transplant
Smallpox wiped out by vaccination
Developments in genetic engineering
Gell-Mann suggested existence of quarks
Quarks revealed
Development of microchips and micro-computers
Revolutionized production of all kinds of machines
Quasars observed
First Moon Landings
Hawking developed his theory of black holes
Soviet astronauts complete one year in space
A computer is used to solve a problem set by Archimedes

Laser c. 1960
Silicon chip c. 1961
Microprocessor c. 1971
Space shuttle c. 1981
Superconductors c. 1987

History of science 1921 – 1960

2008-07-21T16:22:00.004+08:00

World War 2 1939-1945
First atomic bomb explodes 1945
Edmund Hilary first to climb Everest 1953
Discovery of paleomagnetism
Salk produces polio vaccine
Watson and Crick reveal the structure of DNA
Chadwick discovers neutrons
Bohr discovers structure of atom
Transistor invented first integrated circuit is made, start of microelectronics
Tombaugh discovers Pluto
Habble discovers Universe is Expanding

Electron microscope c. 1939
Programmable electronic computer c. 1943
Fibre optics c. 1955
Artificial satellite c. 1959

History of science 1881 – 1920

2008-07-17T16:16:00.003+08:00

Amundsen reaches South Pole 1911
World War 1 1914-18
Russian Revolution 1917
Wegener introduces
Continental drift theory
Freud’s psychoanalysis experiments
Fleming discovers penicillin
Ehrlich begins treating disease with chemicals
Becquerel discovers radioactivity
Curies discover radioactivity of radium
Thomson discovers electrons
Rutherford conducts nuclear physics experiments
Einstein presents his theory of relativity
Planck works on radiation
Ambrose fleming produces first vacuum tube, which will be used in the development of radio and television

Petrol engine car c. 1885
Pneumatic tyre c. 1888
Radio c. 1895
Aeroplane c. 1903
Bakelite c 1908

History of science 1841 - 1880

2008-07-13T16:12:00.003+08:00

Marx and Engels publish Communist Manifesto 1848
Lincoln becomes president of USA 1860
Suez Canal opened 1869
Darwin’s observations during the voyage of HMS Beagle confirm Lyell’s theories
Darwin publishes his on the origin of species
Lister begins antiseptic
Medicine and Pasteur shows microbes cause disease
Mendel’s experiments reveal laws of inheritance of genes
Mendeleyev devises periodic table of elements
Bunsen and Kirchhoff design first spectroscope, discover caesium and rubidium with it
Maxwell announces theory of electromagnetic waves
Joule measures amount of heat
Adams and Leverrier pinpoint position of Neptune and Galle finds it with telescope
Mobius discovers a figure with only one side and one edge

Safety pin c. 1849
Passenger lift c. 1852
Refrigerator 1858
Telephone 1875
Light bulb c. 1875

History of science 1800 – 1840

2008-07-11T16:08:00.003+08:00

Napoleon invades Russia 1812
Battle of Waterloo 1815
Introduction of Penny post in England 1840
Lyell publishes his theory of Earth’s development
Schleiden and schwann show that all plants and animals are made up of cells
Dalton develops his atomic theory which is the basis of modern physics and chemistry
Davy isolates sodium and potassium using electrolysis
Faraday conducts experiments with electricity and magnetism
Alessandro Volta invents first electric battery
Wallaston and Fraunhofer discover absorption lines in solar spectrum.
Babbage develops programmable analytical machine

Electric battery c. 1800
Steam Locomotive c. 1804
Camera c. 1822
Electromagnet c. 1825
Telegraph c. 1837

History of science 1700 – 1799

2008-07-09T16:03:00.003+08:00

Cook Discovers Australia 1770
American Declaration of Independence 1776
French revolution 1789
Edward Jenner introduces smallpox vaccinations
Linnaeus classifies 4400
Animals and nearly 8000 plants
Lavoisier produces table of 31 chemical elements
Euler works out mathematics of refraction of light
Benjamin Franklin performs his kite experiment, proving that lightning is electricity
Herschel discovers Uranus

Steam engine c. 1712
Iron smelting c. 1750
Spinning Jenny c. 1764
Power Loom c. 1785

History of science 1600-1699

2008-07-07T15:57:00.003+08:00

Pilgrim fathers sail to America 1620
Louis XIV becomes king of France 1643
Plague kills 70,000 in England 1665
Harvey discovers method of circulation of blood
Malpighi uses microscope to discover the structure of animals and plants
Boyle introduces modern idea of elements
Newton Makes discoveries about light and colourand the laws of gravity and motion
Bacon advocates Experiments for proof of scientific laws
Kepler discovers planets have elliptical orbits –laws of planetary motion
Halley makes observations of comets. They later prove to be bodies with regular orbits (1705)
Calculus invented separately by Newton and liebnitz
Napier develops logarithms
Pascal with fermat develop the mathematics of probability

Telescope c. 1608-09
Submarine c. 1620
Calculating machine c.1643
Steam pump 1698

History of science 1500 – 1599

2008-07-05T15:51:00.002+08:00

Luther begins Reformation 1517
Ferdinand Magellan voyage of circumnavigation 1519-21
England defeats Spanish Armada 1588
Vesalius’s on the Structure of the human body – most accurate anatomy book
John Gerard publishes his comprehensive herbal
Galileo researches the laws
Governing falling bodies and pendulums
Stevinus conducts experiments for understanding gravity.
Copernicus puts forward the theory that the whole Universe circulates around the sun
Galileo first to use a telescope effectively and makes many new discoveries

Leonardo Da Vinci draws vertical take-off flying machine c. 1500
Compound microscope 1590
Thermometer 1592

History of science AD 500 - 1499

2008-07-03T15:47:00.001+08:00

Marco polo visits Asia 1271-95
Black Death kills 1 in 4 in Europe 1334-51
Columbus lands in the Americas 1492
Avicenna writes The Canon of Medicine-most important medical book for centuries
Alchemy comes to Europe from Arabia where its practice has given rise to first known book on chemistry.
Roger Bacon experiments with lenses and discusses
Spectacles for the longsighted
Leonardo da Vinci makes first observation of capillary action
Chinese observe crab supernovas.
Algebra developed by the Arabs.
Arabs introduce Hindu numerals to Europe

Gunpowder c.1000
Magnetic compass c. 1100
Spectacles c. 1280
First gun c. 1288
Printing press c.1440

History of science 1000BC - AD500

2008-07-01T15:42:00.001+08:00

First Olympic Games 776 BC
Roman conquest of Britain ad 43
Vesuvius erupts, destroying Pompeii ad 79
Hippocrates establishes profession of physician and begins to free medicine from superstition.
Chinese develop acupuncture.
Democritus states all matter is made of atoms, solid particles that cannot be divided.
Aristotle develops theory of four basic elements
Archimedes discovers the principle of levers and pulleys
Ptolemy states the Earth is round and is the motionless center of a revolving Universe
Hindus devise a system of numerals.
Euclid writes his Elements. It will be used as a textbook for next 2000 years

Water clocks c.650 BC
Abacus c.500 BC
Archimedes screw c. 200 BC
Paper (for writing) c. 100

History of science 5000 BC – 1000 BC

2008-06-29T15:36:00.003+08:00

Tutankhamen Pharaoh of Egypt c. 1358
Israelites leave Egypt for Canaan c. 1200
Egyptians devise the first calendar and use it to predict the Nile floods.
Babylonians predict solar and lunar eclipses.

The wheel
Potter’s wheel
Bricks fired in kilns

John Dalton (1766-1844)

2008-06-18T18:03:00.001+08:00

Dalton was an English chemist. He is best known for his atomic theory to explain the structure of matter. It became one of foundations of modern chemistry. He was first to calculate weights of the atoms of several elements. He worked out of table of atomic weights of elements but it was later found to be inaccurate.

Niels Bohr (1885-1962)

2008-06-16T18:00:00.001+08:00

Bohr was Danish physicist who contributed greatly to the development of modern nuclear physics. For his work on the structure of the atom he won the 1922 Nobel Prize for Physics. In 1943 he worked as an advisor to scientist developing the nuclear bomb.

Joseph Lister (1827-1912)

2008-06-14T17:55:00.000+08:00

Lister was a British surgeon who radically changed surgical practice with the introduction of antiseptics. They reduced the risk of bacterial infection during surgery. Lister’s antiseptic solution of carbolic acid was used to clean wounds and surgical cuts and to scrub surgeons’ hands. Lister believed that infection was caused by airborne dust particles, so he also sprayed the air with carbolic acid. The equipment was heated to a high temperature to make it bacteria free. His discoveries met with initial resistance but had become widely accepted by the 1880s when he introduced antiseptic catgut ligatures. Ligatures are the strong threads used to sew surgical wounds together. He also devised new operations and invented several surgical instruments.

Alexander Fleming (1881 - 1955)

2008-06-12T17:45:00.000+08:00

Fleming was a British bacteriologist in 1928. He noticed that a spot of green mould stopped the growth of some bacteria, he was cultivating the antibiotic drug penicillin was developed from the mould. Fleming won the 1945 Nobel prize for medicine which he shared with Howard florey and Ernst chain the scientists who developed the use of the drug.

Lee De Forest (1826 - 1906)

2008-06-10T17:37:00.003+08:00

This American inventor pioneered wireless telegraphy and radio broadcasting.
He invented a vacuum tube that amplified electrical symbol, which was to be significant in the development of radio and television communication.

Andre Ampere (1775 - 1836)

2008-06-08T00:07:00.001+08:00

Ampere was a French physicist. He is famous for his work with electricity and magnetism. Ampere discovered that parallel electric currents attract each other if they move in the same direction and repel each other if they move in opposite directions. He discovered that when electricity produces magnetism and that when electricity is passed through a coiled wire it acts like a magnet. The unit used to measure the size of an electric current was named Ampere or AMP in his honour. ==========>>>

Roger Bacon (1214 - 1292)

2008-06-05T23:57:00.004+08:00

An English monk and Alchemist, Bacon become known as the founder of experimental science. He believed that doing experiments for your self was the way to learn about nature rather than accepting what other people tell you.
His most important work was the opus maius in which he wrote about the scientific method of learning. he did many Experiments. He showed how rainbows are made by the effect of water drops on sunlight, and how lenses could be used to help people with weak sight. More reading

George Washington Carver (1864-1943)

2008-06-05T23:46:00.003+08:00

Carver was an American educator and agricultural scientist. he worked to improve crop production and agricultural methods. he encouraged farmers of the Southern States to grow soil enriching peanuts and sweet potatoes. He discovered many uses for the new crops from peanuts. He made over 300 products including soap and Ink.

Source :Wikipedia

Space Shuttle

2008-05-21T01:17:00.003+08:00

Space Shuttle The main American space transportation system, which uses reusable components. The major part of the system is a delta-winged orbiter, which is about the same size as a medium-range airliner. This carries the astronaut crew and the cargo, which is installed in a huge payload bay measuring about 18.3 x 4.6 m (60 x 15ft).

The orbiter rides into space on an external tank, which carries fuel for its engines. To the sides of the external tank are strapped solid rocket boosters. The boosters fire with the main engines at launch, to Earth to be used again. The external tank is jettisoned just before the orbiter goes into orbit. The orbiter returns from orbit as a glider and lands on an ordinary runway. The first shuttle flight from the Kennedy Space Centre, took place on April 12 1981.
In November the orbiter, Columbia, became the first spacecraft ever to return to space.

Newton's laws of motion

2008-05-13T00:04:00.002+08:00

Newton's laws of motion describe the relationship between the forces acting on a body and the motion they produce.

The first law, the law of inertia, states that a body remains in the state of rest or in uniform motion in a straight line unless it is acted on by an external force.

The second law states that the rate of change of velocity-that is, the acceleration (a)-- produced by a force is proportional to that force (F) and inversely proportional to the mass (m) of the body:

a = F/m or F = ma.

The third law states that to every action there is an equal and opposite reaction

Wind

2008-05-07T21:51:00.006+08:00

Wind Air in motion. Winds are caused basically by temperature differences over the Earth's surface. A major circulation pattern is set up as air over the equator becomes hot and rises. This creates a low-pressure region, known to early sailors as the doldrums, where the air is still and waters calm for days on and.

As the hot air rises, cool air from polar regions moves in to take its place. The hot air in turn cools and sinks down near the poles. if the earth were not rotating, the winds would blow north-south. But the Earth is rotating, and the winds are deflected by the so-called Coriolis affect. This makes the winds blow towards the equator from the north-east in the northern hemisphere and from the south-east in the southern.

such winds, called the trade winds, blow towards the equator from about the 30th parallels north and south. Between about the 30-60th parallels, by contrast, the winds blow predominantly from the west-from the south-west in the northern hemisphere and from the north-west in the southern. These winds are called the prevailing westerlies.

Kirchoff's Laws

2008-05-01T00:33:00.003+08:00

Kirchhoff's Laws Of electric circuits; in any network of wires the sum of all the currents going into a junction is the same as the sum of all the currents going out (junction theorem). In a closed circuit, or loop, the sum of the emfs is equal to the sum of the voltages across each of the Resistances (loop equation).

Kirchhoff's circuit laws are a pair of laws that deal with the conservation of charge and energy in electrical circuits, and were first described in 1845 by Gustav Kirchhoff. Widely used in electrical engineering, they are also called Kirchhoff's rules or simply Kirchhoff's laws.

Both circuit rules can be directly derived from Maxwell's equations, but Kirchhoff preceded Maxwell and instead generalized work by Georg Ohm.

Source : wikipedia

OHM's Law

2008-04-23T20:07:00.004+08:00

Ohm's Law The potential difference (V) between the ends of a conductor is directly proportional to the current (I) flowing through it. V=IR, Where R is the electrical resistance. Georg Simon Ohm established the law in 1827

See Wikipedia

Inverse square law

2008-04-18T22:25:00.003+08:00

Inverse square law A law in which the effect of something (light intensity, gravity,electrical charge) Varies inversely as the square of its distance away. For example, the light intensity from a source 20 metres away will be only one-quarter that when the source is 10 metres away. The distance is doubled, therefore, the effect is reduced to a ¼ :

½² = ¼

See here for complete.

Seasons

2008-04-11T23:31:00.004+08:00

1 = 2004 Mar 20 9:00:00 pm UT
2 = 2003 Jun 21 9:00:00 pm UT
3 = 2004 Sept 22 9:00:00 pm UT
4 = 2003 Dec 22 9:00:00 pm UT

Seasons Natural divisions of the year, marked by regular changes in the weather and the lengths of the days and nights. The rhythm of the seasons is most evident in temperate regions,where the four seasons : spring - summer - autumn - winter , are most distinct.

The seasons are caused by the inclination (23½°) of the earth's axis to the plane of its orbit around the Sun. This allows a certain point on the earth to receive more solar radiation at some times than at others. It is summer in the northern hemisphere ( winter in the southern) when the north pole is tilted towards (south pole away from) the Sun ; and winter in the northern hemisphere (summer in the southern) when the north pole is tilted away (south pole towards) the Sun. At times in between, when the Earth's axis is tilted nether towards nor away from the Sun, the equinoxes occur. Then day and night are of equal length throughout the worlds.

Equinoxes The two tomes of the year when day and and night are of equal length throughout the worlds. They occur when the Sun lies exactly above the equator, in the spring (spring or vernal equinox) on about March 21 as the Sun is moving north; and in the autumn (autumnal equinox) on about September 23 as the Sun is moving south.

Solstices The times in the year when the Earth's axis is tilted most towards or away from the Sun; or from an observer's point of view, the times when the sun is highest and lowest in the sky at noon. In the northern hemisphere the Sun is highest in the moon sky on about June 21 each year (summer solstice); and lowest on about December 21 (winter solstice). On these dates occur, respectively, the longest and shortest periods of daylight.