 |
Subjects | Fact sheet | Samples
Science and technology: Sample concise biographies
Baird, John Logie (1888–1946)
Scottish electrical engineer who pioneered television. In 1925 he gave the first public demonstration of television, transmitting an image of a recognizable human face. The following year, he gave the world's first demonstration of true television before an audience of about 50 scientists at the Royal Institution, London. By 1928 Baird had succeeded in demonstrating colour television.
Baird used a mechanical scanner which temporarily changed an image into a sequence of electronic signals that could then be reconstructed on a screen as a pattern of half-tones. The neon discharge lamp Baird used offered a simple means for the electrical modulation of light at the receiver. His first pictures were formed of only 30 lines repeated approximately 10 times a second. The results were crude but it was the start of television as a practical technology.
By 1927, Baird had transmitted television over 700 km/435 mi of telephone line between London and Glasgow and soon after made the first television broadcast using radio, between London and the SS Berengaria , halfway across the Atlantic Ocean. He also made the first transatlantic television broadcast between Britain and the USA when signals transmitted from the Baird station in Coulson, Kent, were picked up by a receiver in Hartsdale, New York.
Baird's black-and-white system was used by the BBC in an experimental television service in 1929. In 1936, when the public television service was started, his system was threatened by one promoted by Marconi-EMI. The following year the Baird system was dropped in favour of the Marconi electronic system, which gave a better definition.
Baird was born in Helensburgh Dunbartonshire on 13 August 1888. He was educated at Larchfield Academy and later took an engineering course at the Royal Technical College, Glasgow. He then studied at Glasgow University, but World War I interrupted his final year there. Rejected as physically unfit for military service, Baird became a superintendent engineer with the Clyde Valley Electrical Power Company. In 1918 he gave up engineering because of ill-health and set himself up in business, marketing successfully such diverse products as patent socks, confections and soap in Glasgow, London and the West Indies. Persistent ill health, leading to a complete physical and nervous breakdown in 1923, forced him to retire.
On his retirement, Baird concentrated on solving the problems of television. Having little money, his first apparatus was crude and makeshift, set up on a washstand in his attic room. A tea-chest formed the base of his motor, a biscuit tin housed the projection lamp, and cheap cycle-lamp lenses were incorporated into the design. The whole contraption was held together by darning needles, pieces of string and scrap wood. Yet within a year he had succeeded in transmitting a flickering image of the outline of a Maltese cross over a distance of a few metres and was able to make his successful demonstration the year after that.
Despite his bitter disappointment at having his system passed over in favour of the Marconi system, Baird continued his experimental work in colour television. By 1939 he had demonstrated colour television using a cathode-ray tube which he had adapted as the most successful method for producing a well-defined and brilliant image. Baird's inventive and engineering abilities were widely recognized. In 1937, he became the first British subject to receive the Gold Medal of the International Faculty of Science. The same year, he was elected Fellow of the Royal Institute of Edinburgh, where a plaque was erected to commemorate his demonstration of true television in 1926. Baird also became an Honorary Fellow of the Royal Society of Edinburgh, Fellow ofthe Physical Society and Associate of the Royal Technical College.
He continued his research on stereoscopic and large screen television until his death.
Bohr, Niels Henrik David (1885–1962)
Danish physicist who was awarded the Nobel Prize for Physics in 1922 for his discovery of the structure of atoms and the radiation emanating from them. He pioneered quantum theory by showing that the nuclei of atoms are surrounded by shells of electrons, each assigned particular sets of quantum numbers according to their orbits. He explained the structure and behaviour of the nucleus, as well as the process of nuclear fission. Bohr also proposed the doctrine of complementarity, the theory that a fundamental particle is neither a wave nor a particle, because these are complementary modes of description.
Quantum theory and atomic structure
Bohr's first model of the atom was developed working in Manchester, England, with Ernest Rutherford, who had proposed a nuclear theory of atomic structure from his work on the scattering of alpha rays in 1911. It was not, however, understood how electrons could continually orbit the nucleus without radiating energy, as classical physics demanded. In 1913, Bohr developed his theory of atomic structure by applying quantum theory to the observations of radiation emitted by atoms. Ten years earlier, Max Planck had proposed that radiation is emitted or absorbed by atoms in discrete units, or quanta, of energy. Bohr postulated that an atom may exist in only a certain number of stable states, each with a certain amount of energy, in which electrons orbit the nucleus without emitting or absorbing energy. He proposed that emission or absorption of energy occurs only with a transition from one stable state to another. When a transition occurs, an electron moving to a higher orbit absorbs energy and an electron moving to a lower orbit emits energy. In so doing, a set number of quanta of energy are emitted or absorbed at a particular frequency.
The liquid-droplet model
In 1939, Bohr proposed his liquid-droplet model for the nucleus, in which nuclear particles are pulled together by short-range forces, similar to the way in which molecules in a drop of liquid are attracted to one another. In the case of uranium, the extra
energy produced by the absorption of a neutron causes the nuclear particles to separate into two groups of approximately the same size, thus breaking the nucleus into two smaller nuclei – a process called nuclear fission. The model was vindicated when Bohr correctly predicted the differing behaviour of nuclei of uranium-235 and uranium-238 from the fact that the numbers of neutrons in the two nuclei is odd and even respectively.
Bohr was born and educated in Copenhagen. In 1911, he went to the UK to study at the Cambridge atomic research laboratory under J J Thomson, but moved in 1912 to Manchester to work with Rutherford. He returned to Denmark as a lecturer at the University of Copenhagen in 1913, where he developed his theory of atomic structure. He moved back to Manchester to take up a lectureship offered by Rutherford, but the authorities in Denmark enticed him back, making him a professor in 1916 and then building the Institute of Theoretical Physics, where he was director from 1920. Leading physicists from all over the world developed Bohr's work at the institute, resulting in the more sophisticated quantum mechanics that more fully explained the behaviour of electrons and other elementary particles. During World War II, he took part in work on the atomic bomb in the USA, after which he became a passionate advocate for the control of nuclear weapons. In 1952, Bohr was instrumental in creating the European Centre for Nuclear Research (CERN), now at Geneva, Switzerland. In addition to his scientific papers, Bohr published three volumes of essays: Atomic Theory and the Description of Nature (1934), Atomic Physics and Human Knowledge (1958), and Essays 1958–1962 on Atomic Physics and Human Knowledge (1963).
Fibonacci, Leonardo (c. 1170–c. 1250)
also known as Leonardo of Pisa
Italian mathematician. He published Liber abaci/The Book of the Calculator in Pisa in 1202, which was instrumental in the introduction of Arabic notation into Europe. From 1960, interest increased in Fibonacci numbers, in their simplest form a sequence in which each number is the sum of its two predecessors (1, 1, 2, 3, 5, 8, 13, ...). They have unusual characteristics with possible applications in botany, psychology, and astronomy (for example, a more exact correspondence than is given by Bode's law to the distances between the planets and the Sun).
In 1220, Fibonacci published Practica geometriae, in which he used algebraic methods to solve many arithmetical and geometrical problems.
Fibonacci was born in Pisa. He learned mathematics in Algeria and travelled extensively in the Mediterranean region. Returning to Pisa in about 1200, he began his mathematical writings. In 1225 he won a mathematical competition in Pisa in the presence of Holy Roman Emperor Frederick II. A marble tablet dated 1240 is thought to refer to Fibonacci as being awarded an annual pension for his accountancy services to the state.
Liber abaci was a thorough treatise on algebraic methods and problems in which he strongly advocated the introduction of the Indo-Arabic numeral system, comprising the figures 1 to 9, and the innovation of the 'zephirum' – the figure 0 (zero). Dealing with operations in whole numbers systematically, he also proposed the idea of a bar (solidus) for fractions.
Hubble, Edwin (Powell) (1889–1953)
US astronomer. He discovered the existence of galaxies outside our own, and classified them according to their shape. His theory that the universe is expanding is now generally accepted.
His data on the speed at which galaxies were receding (based on their red shifts) were used to determine the portion of the universe that we can never come to know, the radius of which is called the Hubble radius. Beyond this limit, any matter will be travelling at the speed of light, so communication with it will never be possible. The ratio of the velocity of galactic recession to distance has been named the Hubble constant.
Hubble discovered Cepheid variable stars in the Andromeda galaxy in 1924, proving it to lie far beyond our own Galaxy. In 1925 he introduced the classification of galaxies as spirals, barred spirals, and ellipticals. In 1929 he announced Hubble's law, stating that the galaxies are moving apart at a rate that increases with their distance from each other.
Hubble was born in Marshfield, Missouri, and studied at the University of Chicago, Illinois, graduating in 1910, and then at Oxford University, where he gained a degree in law in 1912. He was also an athlete and a heavyweight boxer. He returned to America 1913 and briefly practised law in Louisville, Kentucky, but his real interest was in astronomy, and he went to the Yerkes Observatory, Williams Bay, Wisconsin, as a graduate student in astronomy in 1914. He was awarded a PhD 1917 for a thesis on the photography of faint nebulae. After serving with the American Expeditionary Force in World War I, he joined the staff at Mount Wilson Observatory, near Pasadena, California, 1919 and carried out research on galactic and extragalactic nebulae. During World War II he was chief of ballistics and director of the Supersonic Wind Tunnel Laboratory at the Aberdeen Proving Ground, Maryland. Afterwards he returned to what was to become the Mount Wilson and Palomar observatories, and was one of the first to use the new 508-cm/200-in Hale Telescope that was installed in 1948.
Nearly all Hubble's work related to nebulae, which he was the first to show were extragalactic, that is, located outside our own Galaxy. It has been said that Hubble opened up the observable region of the universe in the same way that the Italian astronomer and physicist Galileo opened up the Solar System in the 17th century, and British astronomers William and John Herschel opened up the Milky Way in the 18th and 19th centuries. He gave an account of some of his researches in The Realm of the Nebulae (1936).
Humboldt, (Friedrich Wilhelm Heinrich) Alexander (1769–1859)
Baron von Humboldt
German geophysicist, botanist, geologist, and writer who, with French botanist Aimé Bonpland (1773–1858), explored the regions of the Orinoco and Amazon rivers in South America 1800–04, and gathered 60,000 plant specimens. He was a founder of
ecology.
Humboldt aimed to erect a new science, a 'physics of the globe', analysing the deep physical interconnectedness of all terrestrial phenomena. He believed that geological phenomena were to be understood in terms of basic physical causes (for example, terrestrial magnetism or rotation).
One of the first popularizers of science, he gave a series of lectures later published as Kosmos/Cosmos 1845–62, an account of the relations between physical environment and flora and fauna.
Humboldt was born in Berlin and studied at Göttingen and the Mining Academy, Freiburg. He travelled widely in Europe before the expedition to South and Central America. Surveying, mapping, and gathering information, Humboldt covered some 9,600 km/6,000 mi. The accounts of his travels were written over the next 20 years.
In meteorology, he introduced isobars and isotherms on weather maps, made a general study of global temperature and pressure, and instituted a worldwide programme for compiling magnetic and weather observations. His studies of American volcanoes demonstrated they corresponded to underlying geological faults; on that basis he deduced that volcanic action had been pivotal in
geological history and that many rocks were igneous in origin. In 1804, he discovered that the Earth's magnetic field decreased from the poles to the Equator.
Mendel, Gregor Johann (1822–1884)
Austrian biologist who founded genetics. His experiments with successive generations of peas gave the basis for his theory of particulate inheritance rather than blending, involving dominant and recessive characters. His results, published 1865–69, remained unrecognized until the early 20th century.
Mendel formulated two laws now recognized as fundamental laws of heredity: the law of segregation and the law of independent assortment of characters. Mendel concluded that each parent plant contributes a 'factor' to its offspring for determining a particular trait. These are what we now recognize as genes or alleles. He showed that the pairs of factors in the offspring do not give rise to a blend of traits.
Much of his work was performed on the edible pea Pisum, which he grew in the monastery garden. He carefully self-pollinated and wrapped (to prevent accidental pollination by insects) each individual plant, collected the seeds produced by the plants, and studied the offspring of these seeds. Seeing that some plants bred true and others not, he worked out the pattern of inheritance of various traits.
He reported his findings in 'Experiments with Plant Hybrids' (1866), but the importance of his work was not recognized at the time, even by the eminent botanist Karl Wilhelm von Naegeli, to whom Mendel sent a copy of his paper. It was not until 1900, when his work was rediscovered by Hugo De Vries, Carl Erich Correns, and Erich Tschermak von Seysenegg, that Mendel achieved fame – 16 years after his death.
Biography
Mendel was born in Heinzendorf (now Hyncice in the Czech Republic), and entered the Augustinian monastery in Brünn, Moravia (now Brno, Czech Republic) in 1843. Later he studied at Vienna. In 1868 he became abbot of the monastery. His experiments breeding peas gave the basis for his theory of particulate inheritance rather than blending inheritance.
Mendel's experiments
Seeing that some plants bred true (always produced identical offspring, identical to the parent plant) Mendel decided to investigate the results of crossing two varieties with different characteristics, for example tall and dwarf pea varieties. Having carefully self-pollinated and wrapped each individual plant, collected the seeds produced by the plants, and studied the plants that grew from these seeds, he found that dwarf plants produced only dwarf offspring and that the seeds produced by this second generation also produced only dwarf offspring. With tall plants, however, he found that both tall and dwarf offspring were produced and concluded that there were two types of tall plants, those that bred true and those that did not.
Next he cross-bred dwarf plants with true-breeding tall plants and found that all the offspring in the first generation were tall but that the offspring from subsequent generations were a mixture: one-quarter true-breeding dwarf plants, one-quarter true-breeding tall plants, and one-half non-true-breeding tall plants.
Mendel also studied other characteristics in pea plants, such as flower colour, seed shape and flower position, finding that, as
with height, simple laws governed the inheritance of these traits.
Mendeleyev, Dmitri Ivanovich (1834–1907)
Russian chemist who framed the periodic law in chemistry in 1869, which states that the chemical properties of the elements depend on their relative atomic masses. This law is the basis of the periodic table of the elements, in which the elements are arranged by atomic number and organized by their related groups.
Mendeleyev was the first chemist to understand that all elements are related members of a single ordered system. From his table he predicted the properties of elements then unknown, of which three (gallium, scandium, and germanium) were discovered in his lifetime. Meanwhile Lothar Meyer in Germany presented a similar but independent classification of the elements.
Mendeleyev was born in Tobol'sk, Siberia, and studied at St Petersburg and in Germany at Heidelberg. He became professor at the Technical Institute in St Petersburg 1864. But in 1890, for supporting a student rebellion, he was retired from the university and became controller of the Bureau for Weights and Measures.
Mendeleyev was convinced that the future held great possibilities for human flight, and in 1887 he made an ascent in a balloon to observe an eclipse of the Sun.
His textbook Principles of Chemistry 1868–70 was widely adopted.
Pavlov, Ivan Petrovich (1849–1936)
Russian physiologist who was awarded a Nobel Prize for Physiology or Medicine in 1904 for his discovery of the physiology of digestion. Pavlov studied conditioned reflexes in animals. His work had a great impact on behavioural theory and learning theory.
Pavlov was born in Ryazan and studied in St Petersburg at the university and the Imperial Medical Academy, where he became professor in 1890.
Studying the physiology of the circulatory system and the regulation of blood pressure, Pavlov devised animal experiments such as the dissection of the cardiac nerves of a living dog to show how the nerves that leave the cardiac plexus control heartbeat strength.
Pavlov's work relating to human behaviour and the nervous system also emphasized the importance of conditioning. He deduced that the inhibitive behaviour of a psychotic person is a means of self-protection. The person shuts out the world and, with it, all damaging stimuli. Following this theory, the treatment of psychiatric patients in Russia involved placing a sick person in completely calm and quiet surroundings.
Pavlov summarized his Nobel prize-winning work in Die Arbeit der Verdauungsdrüsen/Lectures on the Work of the Principal Digestive Gland (1897).
|
