DIRECTORY
From its roots with individuals or small groups working mostly in isolation, often in pursuit of quasi-religious goals, science has been transformed into a practical activity that is central to the working of modern society. Today, many projects are highly collaborative in nature, and it can be hard – and indeed invidious – to pick out particular figures. More areas of research exist than ever before, and the boundaries between disciplines are becoming blurred. Mathematicians provide solutions to the problems of physics and physicists explain the nature of chemical reactions, while chemists delve into the mysteries of life and biologists turn their attention to artificial intelligence. Here, we list just some of the figures who have added to our understanding of the world.
PYTHAGORAS
Little is known for certain about the life of the Greek mathematician Pythagoras, who did not leave behind any written work. He was born on the Greek island of Samos, but left some time before 518 BCE for Croton in southern Italy, where he founded a secretive philosophical and religious society called the Pythagoreans. The society’s inner circle called themselves mathematikoi, and held that reality, at its deepest level, is mathematical in nature. Pythagoras believed that the relations between all things could be reduced to numbers, and his group set about discovering these relations. Among his many contributions to science and mathematics, Pythagoras studied the harmonics of vibrating strings, and probably provided the first proof of the theorem that now bears his name: that the square of the hypotenuse on a right-angled triangle is equal to the sum of the squares of the other two sides.
See also: Archimedes
XENOPHANES
Xenophanes of Colophon was an itinerant Greek philosopher and poet. His wide-ranging interests reflected the knowledge he gained from careful observations made on his extensive travels. He identified the energy of the Sun that heats the oceans to create clouds as the driving force behind physical processes on Earth. Xenophanes thought that clouds were the origin of heavenly bodies: the stars were burning clouds, while the Moon was made of compressed cloud. On discovering the fossilized remains of sea creatures far inland, he reasoned that Earth alternated between periods of flood and drought. Xenophanes produced one of the earliest accounts of natural phenomena that did not invoke divine forces to explain them, but his works were largely neglected in the centuries after his death.
See also: Empedocles • Zhang Heng
ARYABHATA
Working in Kusumapura, a centre of learning in India’s Gupta empire, the Hindu mathematician and astronomer Aryabhata wrote a short treatise that was to prove highly influential among later Islamic scholars. Written in verse when he was just 23 years old, the Arabhatiya contains sections on arithmetic, algebra, trigonometry, and astronomy. It includes an approximation of pi (π, the ratio of a circle’s circumference to its diameter) as 3.1416, which is accurate to four decimal places, and of Earth’s circumference as 39,968km (24,835 miles) – very close to the current accepted figure of 40,075km (24,902 miles). Aryabhata also suggested that the apparent movement of the stars was due to the rotation of Earth and that the orbits of the planets were ellipses, but appears to have fallen short of proposing a heliocentric model of the Solar System.
See also: Nicolaus Copernicus • Johannes Kepler
BRAHMAGUPTA
The Indian mathematician and astronomer Brahmagupta introduced the concept of zero into the number system, defining it as the result of subtracting a number from itself. He also detailed the arithmetic rules for dealing with negative numbers. He wrote his major work in 628, while living and working in Bhillamala, the capital city of the Gurjara-Pratihara dynasty. Called Brahma-sphuta-siddhanta (The Correct Treatise of the Brahma), the work contained no mathematical symbols but included a full description of the quadratic formula, a means of solving quadratic equations. The work was translated into Arabic in Baghdad the following century and was a major influence on later Arab scientists.
See also: Alhazen
JABIR IBN-HAYYAN
The Persian alchemist Jabir Ibn-Hayan, also known by the latinized name Geber, was a practical, experimental scientist, who outlined detailed methods for, among other things, making alloys, testing metals, and fractional distillation. Almost 3,000 different books have been attributed to Jabir, but many were probably written in the century after his death. Few of Jabir’s works were known to medieval Europe, but a work attributed to him, called Summa Perfectionis Magisterii (The Sum of Perfection), appeared in the 13th century. It became the best-known book on alchemy in Europe, but was probably written by the Franciscan monk Paul of Taranto. At the time, it was common practice for an author to adopt the name of an illustrious predecessor.
See also: John Dalton
IBN-SINA
Also known as Avicenna, the Persian physician Abu ‘Ali al-Husayn Ibn-Sina was a child prodigy who had memorized the whole of the Qur’an by the age of 10. He wrote widely on topics including mathematics, logic, astronomy, physics, alchemy, and music, producing two major works: the Kitab al-shifa (The Book of Healing), a huge encyclopedia of science; and Al-Qanun fi al-Tibb (The Canon of Medicine), which was to remain in use as a university textbook into the 17th century. Ibn-Sina outlined not only medical cures but also ways to stay healthy, stressing the importance of exercise, massage, diet, and sleep. He lived through a period of political upheaval and often found his studies interrupted by the need to stay on the move.
See also: Louis Pasteur
AMBROISE PARÉ
Ambroise Paré spent 30 years working as a military surgeon in the French army, during which time he developed many new techniques, including the use of ligatures to tie arteries after amputation of a limb. He studied anatomy, developed artificial limbs, and produced one of the first medical descriptions of the condition known as “phantom limb”, in which the patient feels sensation in a limb after it has been amputated. He also made artificial eyes from gold, silver, porcelain, and glass. Paré examined the internal organs of people who had died violent deaths and wrote the first legal medical reports, marking the beginning of modern forensic pathology. Paré’s work raised the previously low social status of surgeons, and he acted as personal surgeon to four French kings. Les Oeuvres (The Works), a book detailing his techniques, was published in 1575.
See also: Robert Hooke
WILLIAM HARVEY
English physician William Harvey produced the first accurate description of the circulation of blood, showing that it flows rapidly through the body in one system pumped by the heart. Previously, there were thought to be two blood systems: the veins carried purple blood full of nutrients from the liver, while the arteries carried scarlet “life-giving” blood from the lungs. Harvey demonstrated blood flow in numerous experiments, and studied the heartbeats of various animals. However, he was opposed to the mechanical philosophy of Descartes, and believed that blood had its own life force. Initially resisted, by the time of his death, Harvey’s theory of circulation was widely accepted. Smaller capillaries linking the arteries and veins were discovered under new microscopes in the late 17th century.
See also: Robert Hooke • Antonie van Leeuwenhoek
MARIN MERSENNE
The French monk Marin Mersenne is best remembered today for his work on prime numbers, showing that if the number 2n–1 is prime, then n must also be prime. He also carried out extensive studies in many scientific fields, including harmonics, in which he worked out the laws that govern the frequency of vibrations of a stretched string. Mersenne lived in Paris, where he collaborated with René Descartes, and corresponded extensively with Galileo, whose works he translated into French. He strongly advocated experiment as the key to scientific understanding, stressing the need for accurate data and criticising many of his contemporaries for their lack of rigour. In 1635, he founded the Académie Parisienne, a private scientific association with more than 100 members across Europe, which would later become the French Academy of Sciences.
See also: Galileo Galilei
RENÉ DESCARTES
The French philosopher René Descartes was a key figure in the Scientific Revolution of the 17th century, travelling widely across Europe and working with many of the prominent figures of his day. He helped European scientists to finally overcome Aristotle’s non-empirical approach by applying a thorough scepticism to assumed knowledge. Descartes produced a four-pronged method of scientific enquiry, based on mathematics: accept nothing as true unless it is self-evident; divide problems into their simplest parts; solve the problems by moving from the simple to the complex; and, lastly, check your results. He also developed the Cartesian system of coordinates – with x, y, and z axes – to represent points in space using numbers. This allowed shapes to be expressed as numbers and numbers to be expressed as shapes, founding the mathematical field of analytical geometry.
See also: Galileo Galilei • Francis Bacon
HENNIG BRAND
Little is known about the early life of German chemist Hennig Brand. We do know that he fought in the Thirty Years’ War and dedicated himself to alchemy on leaving the army, searching for the elusive philosopher’s stone that would turn base metal into gold. In 1669, Brand produced a waxy, white material by heating the residue of boiled-down urine. He called this material “phosphorus” (“light-carrier”) because it glowed in the dark. Phosphorus is highly reactive and never found as a free element on Earth, and this marked the first time that such an element had been isolated. Brand kept his method secret, but phosphorus was discovered independently by Robert Boyle in 1680.
See also: Robert Boyle
GOTTFRIED LEIBNIZ
The German Gottfrield Leibniz studied law at the University of Leipzig. During his studies, he became increasingly interested in science as he discovered the ideas of Descartes, Bacon, and Galileo, which marked the start of a lifelong quest to collate all human knowledge. He later studied mathematics in Paris under Christiaan Huygens, and it was here that he began to develop calculus – a mathematical means of calculating rates of change that was to prove crucial to the development of science. He developed calculus at the same time as Isaac Newton, with whom he corresponded and then fell out. Leibniz actively promoted the study of science, corresponding with more than 600 scientists across Europe and setting up academies in Berlin, Dresden, Vienna, and St Petersburg.
See also: Christiaan Huygens • Isaac Newton
DENIS PAPIN
As a young man, French-born English physicist and inventor Denis Papin assisted both Christiaan Huygens and Robert Boyle in their experiments on air and pressure, and in 1679, he invented the pressure cooker. Observing how the steam in the cooker tended to raise the lid, Papin then came up with the idea of using steam to drive a piston in a cylinder, and produced the first design for a steam engine. Papin never built a steam engine himself, but in 1709, he constructed a paddle wheel that demonstrated the practicability of using paddles instead of oars in steam-powered ships.
See also: Robert Boyle • Christiaan Huygens • Joseph Black
STEPHEN HALES
English clergyman Stephen Hales carried out a series of pioneering experiments on plant physiology. He measured the water vapour emitted by the leaves of plants in a process called transpiration, and this led him to the discovery that transpiration drives a continuous upwards flow of fluid from the roots that carries dissolved nutrients around the whole plant. Sap moves from an area of high pressure in the roots to areas of lower pressure where water vapour is transpiring. Hales published his results in 1727 in the book Vegetable Staticks. In addition, he carried out extensive experiments with animals, particularly dogs, measuring blood pressure for the first time. Hales also invented the pneumatic trough, an apparatus used to collect the gases given off during chemical reactions.
See also: Joseph Priestley • Jan Ingenhousz
DANIEL BERNOULLI
Daniel Bernoulli was perhaps the most gifted in a remarkable family of Swiss mathematicians – his uncle Jakob and father Johann both did important work in developing calculus. In 1738, he published Hydrodynamica, in which he examined the properties of fluids. He formulated Bernoulli’s principle, that a fluid’s pressure decreases as its velocity increases. This principle is key to understanding how the wings of an aeroplane produce lift. He realized that a moving fluid must exchange some of its pressure for kinetic energy in order not to violate the principle of the conservation of energy. As well as mathematics and physics, Bernoulli studied astronomy, biology, and oceanography.
See also: Joseph Black • Henry Cavendish • Joseph Priestley • James Joule • Ludwig Boltzmann
GEORGES-LOUIS LECLERC, COMTE DE BUFFON
From 1749 to the end of his life, French aristocrat and naturalist the Comte de Buffon worked tirelessly on his monumental work Histoire Naturelle (Natural History). His aim was to collate all knowledge in the fields of natural history and geology. The encyclopedia spanned 44 volumes when it was finally completed by his assistants 16 years after his death. Buffon constructed a geological history of Earth, suggesting that it was much older than previously assumed. He charted the extinction of species and suggested a common ancestor of humans and apes, predating Charles Darwin by a century.
See also: Carl Linnaeus • James Hutton • Charles Darwin
GILBERT WHITE
British parson Gilbert White was an unmarried curate who lived a quiet life in the small Hampshire village of Selborne. His 1789 book, The Natural History and Antiquities of Selborne, was a compilation of letters written to his friends. In his letters, White laid out a record of his systematic observations of nature and developed his ideas about the inter-relationships of living things. He was, in effect, the first ecologist. White recognized that all living things have a role to play in what we would now call the ecosystem, noting of earthworms that they “seem to be the great promoters of vegetation, which would proceed but lamely without them”. White’s methods, including taking recordings in the same places over many years, were highly influential on subsequent biologists.
See also: Alexander von Humboldt • James Lovelock
NICÉPHORE NIEPCE
The oldest surviving photograph was taken in 1825 by French inventor Nicéphore Niepce of the buildings around his country estate in Saint-Loup-de-Varennes. Niepce had been experimenting for several years to find a technique to fix the image projected onto the back of a camera obscura. In 1816, he produced a negative image using paper coated with silver chloride, but the image disappeared when exposed to daylight. Then around 1822, he came up with a process he called heliography, which used a plate of glass or metal coated with bitumen. The bitumen hardened when it was exposed to light, and when the plate was washed with lavender oil, only the hardened areas remained. It took eight hours of exposure to fix the images. Near the end of his life, Niepce collaborated with Louis Daguerre on ways to improve the process.
See also: Alhazen
ANDRÉ-MARIE AMPÈRE
On hearing of Hans Christian Ørsted’s accidental discovery of the link between electricity and magnetism in 1820, French physicist André-Marie Ampère set about formulating a mathematical and physical theory that explained their relationship. In the process, he formulated Ampère’s law, which states the mathematical relation of a magnetic field to the electric current that produces it. Ampère published his results in 1827, and his book, Memoir on the Mathematical Theory of Electrodynamic Phenomena, uniquely deduced from experience, gave a name to this new scientific field – electrodynamics. The standard unit of electric current, the ampere (or amp), is named after him.
See also: Hans Christian Ørsted • Michael Faraday
LOUIS DAGUERRE
The first practical photographic process was invented by the French painter and physicist Louis Daguerre. From 1826, Daguerre collaborated with Nicéphore Niepce on his heliographic process, but this needed at least eight hours of exposure. Following Niepce’s death in 1833, Daguerre developed a process in which an image on an iodized silver plate was developed by exposure to mercury fumes and fixed using saline. This reduced the exposure time required to 20 minutes, making it practical to take photographs of people for the first time. Daguerre wrote a full description of his process, called the daguerreotype, in 1839, and it made him a fortune.
See also: Alhazen
AUGUSTIN FRESNEL
French engineer and physicist Augustin Fresnel is best known as the inventor of the Fresnel lens, which allows the light from a lighthouse to be seen over greater distances. He studied the behaviour of light, building on the double-slit experiments of Thomas Young, with whom he corresponded. Fresnel carried out a great deal of important theoretical work on optics, producing a set of equations describing how light is refracted or reflected as it passes from one medium to another. The importance of much of his work was only recognized after his death.
See also: Alhazen • Christiaan Huygens • Thomas Young
CHARLES BABBAGE
British mathematician Charles Babbage conceived the first digital computer. Appalled by the number of errors in printed mathematical tables, Babbage designed a machine to calculate the tables automatically, and in 1823 hired engineer Joseph Clement to build it. His “Difference Engine” was to be an elegant contraption of brass cogwheels, but Babbage got only as far as a prototype before running out of money and energy. In 1991, scientists at London’s Science Museum built a Difference Engine to Babbage’s specification, using only technology that would have been available at the time, and it worked, though it tended to jam after a minute or two. Babbage also dreamed of a steam-powered “Analytical Engine”, which would take instructions on punched cards, hold data in a “store”, carry out calculations in the “mill”, and print out the results. This might have been a real computer in the modern sense. His protégée Ada Lovelace (the daughter of poet Lord Byron) wrote programs for it, and has been called the world’s first computer programmer. However, the Analytical Engine project never got off the ground.
See also: Alan Turing
SADI CARNOT
Nicolas-Léonard-Sadi Carnot was an officer in the French army who semi-retired on half-pay to Paris in 1819 to devote himself to science. Hoping to see France catch up with Britain in the Industrial Revolution, Carnot set about designing and building steam engines. His investigations led to his only publication, in 1824, Reflections on the Motive Power of Fire, in which he noted that the efficiency of a steam engine depends principally on the temperature difference between the hottest and coldest parts of the engine. This pioneering work on thermodynamics was later developed by Rudolf Clausius in Germany and William Thomson, Lord Kelvin in Britain, but was largely ignored in Carnot’s lifetime. He died in relative obscurity during a cholera epidemic, aged just 36.
See also: Joseph Fourier • James Joule
JEAN-DANIEL COLLADON
Swiss physicist Jean-Daniel Colladon demonstrated that light could be trapped by total internal reflection inside a tube, allowing it to travel along a curved path – a core principle behind modern-day optical fibres. In experiments carried out on Lake Geneva, Colladon demonstrated that sound travels four times more quickly through water than through air. He transmitted sound through water over a distance of 50km (30 miles), and proposed using this method as a means of communicating across the English Channel. He also carried out important work in the field of hydraulics, studying the compressibility of water.
See also: Léon Foucault
JUSTUS VON LIEBIG
The son of a chemical manufacturer in Darmstadt, Germany, Justus von Liebig carried out his first chemistry experiments as a child in his father’s laboratory. He grew up to become a charismatic professor of chemistry whose laboratory-based teaching methods were hugely influential. Von Liebig discovered the importance of nitrates to plant growth and developed the first industrial fertilizers. He was also interested in the chemistry of food and developed a manufacturing process to produce beef extracts. The company he founded, the Liebig Extract of Meat Company, would later produce the trademarked Oxo stock cubes.
See also: Friedrich Wöhler
CLAUDE BERNARD
French physiologist Claude Bernard was a pioneer in experimental medicine. He was the first scientist to study the internal regulation of the body, and his work was to lead to the modern concept of homeostasis – the mechanism by which the body maintains a stable internal environment while the external environment changes. Bernard studied the roles of the pancreas and liver in digestion, and described how chemicals are broken down into simpler substances only to be built up again into the complex molecules needed to make body tissues. His major work, An Introduction to the Study of Experimental Medicine, was published in 1865.
See also: Louis Pasteur
WILLIAM THOMSON
Born in Belfast, physicist William Thomson became professor of natural philosophy at Glasgow University at the age of 22. In 1892, he was ennobled, and became Baron Kelvin, after the river that runs through Glasgow University. Kelvin viewed physical change as fundamentally a change in energy, and his work produced a synthesis of many areas of physics. He developed the second law of thermodynamics and established the correct value for “absolute zero”, the temperature at which all molecular movement ceases, at –273.15°C (–459.6°F). The Kelvin scale, which starts at 0 at absolute zero, is named after him. He invented the mirror galvanometer to receive faint telegraph signals, and presided over the laying of the trans-Atlantic cable in 1866. He also invented an improved mariner’s compass and a tide-predicting machine. Lord Kelvin often courted controversy, rejecting Darwin’s theory of evolution and making many bold statements – including the prediction that “no aeroplane will ever be practically successful”, made one year before the Wright brothers’ first flight in 1903. However, a quote widely attributed to Lord Kelvin stating that “there is nothing new to be discovered in physics now” is almost certainly apocryphal.
See also: James Joule • Ludwig Boltzmann • Ernest Rutherford
JOHANNES VAN DER WAALS
Dutch physicist Johannes van der Waals made a significant contribution to the field of thermodynamics with his 1873 doctoral thesis, in which he showed that there is a continuity between a liquid and gaseous state at a molecular level. Van der Waals showed not only that these two states of matter merge into one another, but also that they should be considered as essentially of the same nature. He postulated the existence of forces between molecules, which are now called the van der Waals forces, and which explain properties of chemicals such as their solubility.
See also: James Joule • Ludwig Boltzmann • August Kekulé • Linus Pauling
ÉDOUARD BRANLY
A physics professor at the Paris Catholic Institute, Édouard Branly was a pioneer in wireless telegraphy. In 1890, he invented a radio receiver known as the Branly coherer. The receiver was a tube with two electrodes inside it spaced a little apart, and metal filings in the space between the electrodes. When a radio signal was applied to the receiver, the resistance of the filings was reduced, allowing an electric current to flow between the electrodes. Branly’s invention was used in later experiments on radio communication by Italian Guglielmo Marconi, and widely used in telegraphy up to 1910, when more sensitive detectors were developed.
See also: Alessandro Volta • Michael Faraday
IVAN PAVLOV
The son of a priest, Russian Ivan Pavlov abandoned plans to follow in his father’s footsteps in order to study chemistry and physiology at the University of St Petersburg. In the 1890s, Pavlov was studying salivation in dogs when he noticed that his dogs would salivate whenever he entered the room, even if he had no food with him. Pavlov realized that this must be a learned behaviour, and started 30 years of experiments into what he called “conditioned responses”. In one experiment, he would ring a bell every time he fed the dogs. He found that after a period of learning (conditioning), the dogs would salivate just on hearing the bell. In this work, Pavlov laid the groundwork for the scientific study of behaviour, although physiologists today consider his explanations to be oversimplified.
See also: Konrad Lorenz
HENRI MOISSAN
French chemist Henri Moissan received the 1906 Nobel Prize in Chemistry for his work isolating the element fluorine, which he produced by electrolysing a solution of potassium hydrogen difluoride. When Moissan cooled the solution to –50°C (–58°F), pure hydrogen appeared at the negative electrode, and pure fluorine at the positive one. Moissan also developed an electric-arc furnace that could reach a temperature of 3,500°C (6,300°F), which he used in his attempts to synthesize artificial diamonds. He did not succeed, but his theory that diamonds could be made by putting carbon under high pressure at high temperatures was subsequently proved correct.
See also: Humphry Davy • Leo Baekeland
FRITZ HABER
The scientific legacy of German chemist Fritz Haber is mixed. On the positive side, Haber and his colleague Carl Bosch developed a process for synthesizing ammonia (NH3) from hydrogen and atmospheric nitrogen. Ammonia is an essential ingredient of fertilizers, and the Haber–Bosch process allowed the industrial production of artificial fertilizers, greatly increasing food production. On the negative side, Haber developed chlorine and other deadly gases for use in trench warfare, and personally oversaw their use on battlefields during World War I. His wife Clara, also a chemist, killed herself in 1915 in opposition to her husband’s involvement in the use of chlorine gas at Ypres.
See also: Friedrich Wöhler • August Kekulé
C T R WILSON
Charles Thomson Rees Wilson was a Scottish meteorologist with a particular interest in the study of clouds. To aid his studies, he developed a method of expanding moist air inside a closed chamber to produce the state of supersaturation needed for cloud formation. Wilson found that clouds formed in the chamber much more easily in the presence of dust particles. In the absence of dust, clouds only formed when the saturation of the air passed a critical high point. Wilson believed that clouds were forming on ions (charged molecules) in the air. To test this theory, he passed radiation through the chamber to see whether the resultant ion formation would cause clouds to form. He found that the radiation left a trail of condensed water vapour in its wake. Wilson’s cloud chamber proved crucial for studies in nuclear physics, and won him the Nobel Prize in Physics in 1927. In 1932, the positron was first detected using a cloud chamber.
See also: Paul Dirac • Charles Keeling
EUGÈNE BLOCH
French physicist Eugène Bloch carried out studies in spectroscopy, and produced evidence in support of Albert Einstein’s interpretation of the photoelectric effect using the idea of quantized light. During World War I, Bloch worked on military communications, developing the first electronic amplifiers for radio receivers. In 1940, he fell victim to the anti-Jewish laws of the Vichy government and was dismissed from his post as a professor of physics at the University of Paris. He fled to unoccupied southern France, but was captured by the Gestapo in 1944 and deported to Auschwitz, where he was killed.
See also: Albert Einstein
MAX BORN
In the 1920s, German physicist Max Born, while professor of experimental physics at the University of Göttingen, collaborated with Werner Heisenberg and Pascual Jordan to formulate matrix mechanics, a mathematical means of dealing with quantum mechanics. When Erwin Schrödinger formulated his wavefunction equation to describe the same thing, Born was the first to suggest the real-world meaning of Schrödinger’s mathematics – it described the probability of finding a particle at a specific point on the space-time continuum. In 1933, Born and his family left Germany when the Nazis dismissed Jews from academic posts. He settled in Britain, becoming a British citizen in 1939. He was awarded a Nobel Prize in Physics for his work on quantum mechanics in 1954.
See also: Erwin Schrödinger • Werner Heisenberg • Paul Dirac • J Robert Oppenheimer
NIELS BOHR
One of the leading early theorists of quantum physics, Dane Niels Bohr’s first major contribution to the quantum revolution was to refine Ernest Rutherford’s model of the atom. In 1913, Bohr added the idea that electrons occupy specific quantized orbits around the nucleus. In 1927, Bohr collaborated with Werner Heisenberg to formulate an explanation of quantum phenomena that came to be known as the Copenhagen interpretation. A concept central to this interpretation was Bohr’s complementarity principle, which states that a physical phenomenon, such as the behaviour of a photon or an electron, may express itself differently depending on the experimental set-up used to observe it.
See also: Ernest Rutherford • Erwin Schrödinger • Werner Heisenberg • Paul Dirac
GEORGE EMIL PALADE
Romanian cell biologist George Emil Palade graduated in medicine from the University of Bucharest in 1940. He emigrated to the USA at the end of World War II, and carried out his most important work at the Rockefeller Institute in New York. Palade developed new techniques for tissue preparation that allowed him to examine the structure of cells under an electron microscope, and this work greatly advanced the understanding of cellular organization. His most important achievement was the discovery in the 1950s of ribosomes – bodies inside cells that were previously thought to be fragments of mitochondria, but are in fact the primary sites of protein synthesis, linking together amino acids in a specific sequence.
See also: James Watson and Francis Crick • Lynn Margulis
DAVID BOHM
American theoretical physicist David Bohm advanced an unorthodox interpretation of quantum mechanics. He postulated the existence of an “implicate order” to the Universe that is a more fundamental order of reality than the phenomena we experience as time, space, and consciousness. He wrote: “an entirely different sort of basic connection of elements is possible, from which our ordinary notions of space and time, along with those of separately existent material particles, are abstracted as forms derived from the deeper order.” Bohm worked with Albert Einstein at Princeton University until the early 1950s, when his Marxist political views led him to leave the USA – first for Brazil and later London, where he was a professor of physics at Birkbeck College from 1961.
See also: Erwin Schrödinger • Hugh Everett III • Gabriele Veneziano
FREDERICK SANGER
British biochemist Frederick Sanger is one of four scientists to have won two Nobel prizes, both in Chemistry. He won his first prize in 1958 for determining the sequence of amino acids that make up the protein insulin. Sanger’s work on insulin provided a key to understanding the way that DNA codes for making proteins, by showing that each protein has its own unique sequence of amino acids. Sanger’s second prize was awarded in 1980 for his later work sequencing DNA. Sanger’s team sequenced human mitochondrial DNA – a set of 37 genes found on mitochondria that is inherited only from the mother. The Sanger Institute, now one of the world’s leading centres of genomic research, was established in his honour near his home in Cambridgeshire, Britain.
See also: James Watson and Francis Crick • Craig Venter
MARVIN MINSKY
American mathematician and cognitive scientist Marvin Minsky was an early pioneer in artificial intelligence, co-founding in 1959 the AI laboratory at the Massachusetts Institute of Technology (MIT), where he spent the rest of his career. His work focused on the generation of neural networks – artificial “brains” that can develop and learn from experience. In the 1970s, Minsky and his colleague Seymour Papert developed the “Society of Mind” theory of intelligence, investigating the way in which intelligence can emerge from a system made solely of non-intelligent parts. Minsky defines AI as “the science of making machines do things that would require intelligence if done by men”. He was an advisor on the film 2001: A Space Odyssey, and has speculated as to the possibility of extraterrestrial intelligence.
See also: Alan Turing • Donald Michie
MARTIN KARPLUS
Increasingly, modern science is conducted using computers to model results. In 1974, American-Austrian theoretical chemist Martin Karplus and his colleague, American-Israeli Arieh Warshel, produced a computer model of the complex molecule retinal, which changes shape when exposed to light and is crucial to the working of the eye. Karplus and Warshel used both classical physics and quantum mechanics to model the behaviour of electrons in the retinal molecule. Their model greatly improved the sophistication and accuracy of computer modelling for complex chemical systems. Karplus and Warshel shared the 2013 Nobel Prize in Chemistry with British chemist Michael Levitt for their achievement in this field.
See also: Augus Kekulé • Linus Pauling
ROGER PENROSE
In 1969, British mathematician Roger Penrose collaborated with physicist Stephen Hawking to show how matter in a black hole collapses into a singularity. Penrose subsequently worked out the mathematics to describe the effects of gravity on the space-time surrounding a black hole. Penrose has turned his attention to a wide range of topics, proposing a theory of consciousness based on quantum mechanical effects operating at a subatomic level in the brain, and more recently a theory of a cyclic cosmology, in which the heat death (end state) of one universe becomes the Big Bang of another, in an endless cycle.
See also: Georges Lemaître • Subrahmanyan Chandrasekhar • Stephen Hawking
FRANÇOIS ENGLERT
In 2013, Belgian physicist François Englert shared the Nobel Prize in Physics with Peter Higgs for independently proposing what is now known as the Higgs field, which gives fundamental particles their mass. Working with fellow Belgian Robert Brout, Englert first suggested in 1964 that “empty” space might contain a field that confers mass to matter. The Nobel Prize was awarded as a result of the detection in 2012 at CERN of the Higgs boson – the particle associated with the Higgs field – which confirmed Englert, Brout, and Higgs’ predictions. Brout had died in 2011, and so missed out on the Nobel Prize, which is not awarded posthumously.
See also: Sheldon Glashow • Peter Higgs • Murray Gell-Mann
STEPHEN JAY GOULD
American palaeontologist Stephen Jay Gould’s specialized area of research concerned the evolution of land snails in the West Indies, but he wrote widely about many aspects of evolution and science. In 1972, Gould and colleague Niles Eldredge proposed the theory of “punctuated equilibrium”, which proposed that, rather than being a constant, gradual process as Darwin had imagined, the evolution of new species took place in rapid bursts over periods as short as a few thousand years, which were followed by long periods of stability. To back up their claim, they cited evidence from the fossil record, in which patterns of evolution in various organisms support their theory. In 1982, Gould coined the term “exaptation” to describe the way in which a particular trait may be passed on for one reason, and then later come to be coopted for a very different function. His work widened understanding of the mechanisms by which natural selection takes place.
See also: Charles Darwin • Lynn Margulis • Michael Syvanen
RICHARD DAWKINS
British zoologist Richard Dawkins is best known for his popular science books, including The Selfish Gene (1976). His most significant contribution to his field is his concept of the “extended phenotype”. An organism’s genotype is the sum of the instructions contained in its genetic code. Its phenotype is that which results from the expression of that code. While individual genes may simply code for the synthesis of different substances in an organism’s body, the phenotype should be considered to be everything that results from that synthesis. For example, a termite mound may be considered to be part of a termite’s extended phenotype. Dawkins views the extended phenotype as the means by which genes maximize their chances of survival to the next generation.
See also: Charles Darwin • Lynn Margulis • Michael Syvanen
JOCELYN BELL BURNELL
In 1967, while working as a research assistant at Cambridge University, British astronomer Jocelyn Bell was monitoring quasars (distant galactic nuclei) when she discovered a strange series of regular radio pulses coming from space. The team she was working with jokingly called the pulses LGM (Little Green Men), referring to the remote chance that they were an attempt at extraterrestrial communication. They later determined that the sources of the pulses were rapidly spinning neutron stars, which were dubbed pulsars. Two of Bell’s senior colleagues were awarded the 1974 Nobel Prize in Physics for the discovery of pulsars, but Bell missed out because she was only a student at the time. Many leading astronomers, including Fred Hoyle, objected publicly to her omission.
See also: Edwin Hubble • Fred Hoyle
MICHAEL TURNER
American cosmologist Michael Turner’s research focuses on understanding what happened directly following the Big Bang. Turner believes that the structure of the Universe today, including the existence of galaxies and the asymmetry between matter and antimatter, can be explained by quantum-mechanical fluctuations that took place during the rapid burst of expansion called cosmic inflation, which occurred moments after the Big Bang. In 1998, Turner coined the term “dark energy” to describe the hypothetical energy that permeates the whole of space and explains the observation that the Universe is expanding in all directions at an accelerating rate.
See also: Edwin Hubble • Georges Lemaître • Fritz Zwicky
TIM BERNERS-LEE
Few living scientists have had as much impact on everyday life as British computer scientist Tim Berners-Lee, who invented the World Wide Web. In 1989, Berners-Lee was working at CERN, the European Organization for Nuclear Research, when he had the idea of establishing a network of documents that could be shared across the world via the Internet. A year later, he wrote the first web client and server, and in 1991, CERN built the first website. Today, Berners-Lee campaigns for open access to the Internet, free from government control.
See also: Alan Turing