the cambridgedictionary of

SCIENTISTSsecond edition

David, Ian, John & Margaret Millar

P U B L I S H E D B Y T H E P R E S S S Y N D I C A T E O F T H E U N I V E R S I T Y O F C A M B R I D G E

The Pitt Building, Trumpington Street, Cambridge, United Kingdom

C A M B R I D G E U N I V E R S I T Y P R E S S

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© David Millar, Ian Millar, John Millar, Margaret Millar 1996, 2002

This book is in copyright. Subject to statutory exceptionand to the provisions of relevant collective licensing agreements,

no reproduction of any part may take place withoutthe written permission of Cambridge University Press.

First published 1996Second edition 2002

Printed in the United Kingdom at the University Press, Cambridge

Typeface Swift 8/9 pt System Quark XPress

A catalogue record for this book is available from the British Library

Library of Congress Cataloguing in Publication dataThe Cambridge dictionary of scientists/David Millar . . . [et al.].

p. cm.Includes index.

ISBN 0-521-80602-X (hardback). – ISBN 0-521-00062-9 (paperback)1. Scientists–Biography–Dictionaries. 2. Science–History.

I. Millar, David.Q141.C128 1996

509.2’2–dc20 95-38471 CIP

ISBN 0 521 80602 X hardbackISBN 0 521 00062 9 paperback

v

List of Panels vi

About the Authors viii

Preface to the Second Edition ix

Preface to the First Edition x

Symbols and Conventions xi

A–Z Dictionary 1

Chronology 390

Nobel Prizewinners in Science 408

Winners of the Fields Medalfor Mathematics 412

Index 413

Contents

vi

The exploration of space 13

Global warming 16

Napoleon and science 35

The entry of women into astronomy 61

The exploration of Australia 75

The history of astronomy 78

Telescopes 95

The history of nuclear and particle physics 107

Pheromones 116

The history of mathematics 121

The Darwin/Wedgwood/Galton relationships 135

Mnemonics 147

The geological timescale 148

Science and the First World War (1914–18) 153

The history of medicine 162

Scientific societies 180

The entry of women into medicine 192

The different forms of carbon 208

The quest for human origins 218

A history of agriculture in the developed world 224

Chaos 231

Superheavy chemical elements: a limit to the periodic table? 239

Periodic table of the chemical elements 249

The history of genetics 251

AIDS and HIV 260

Long-range communication 262

Science and the Second World War (1939–45) 276

The history of the heat engine 278

A strange biochemical: nitric oxide 295

Antarctica: the continent for science 307

The entry of women into chemistry in Britain 329

The entry of women into the biological sciences 334

Panels

vii

The development of photography 342

The Internet and international scientific collaboration 350

The origin of life on Earth: an unsolved problem 357

The development of the computer 363

Human inherited disease and the Human Genome Project 368

The history of aeronautics 384

List of panels

Abel, Neils Henrik [ahbel] (1802–29) Norwegianmathematician: pioneer of group theory; provedthat no algebraic solution of the general fifth-degree equation exists.

Abel was the son of a Lutheran minister. In 1821he went to Oslo to study at the university, but hisfather’s death forced him to give this up in order tosupport the large family of which he was the eldest;he was extremely poor throughout his life. In 1825he visited Germany and France and with LeopoldCrelle (1780–1855) founded Crelle’s Journal in whichmuch of his work was published, since Abel couldnot persuade the French Académie des Sciences todo so. Having failed to find a university post inGermany, and with his health failing due to tuber-culosis, he returned to Norway, where he diedshortly afterwards aged 26. Two days later a letterfrom Crelle announced that the professorship ofmathematics at Berlin, one of the most prestigiousposts in the world, had been awarded to him.

Despite his tragically early death Abel largelyfounded the theory of groups, and in particularcommutative groups, which were later known asAbelian groups. He also showed that the generalfifth-degree equation is not solvable algebraically(ironically Gauss threw this proof away unreadwhen Abel sent it to him). He revolutionized theimportant area of elliptic integrals with his theoryof elliptic and transcendental functions, and contributed to the theory of infinite series.

Adams, John Couch (1819–92) British astronomer:predicted existence of Neptune.

As the son of a tenant farmer, Adams had financialproblems in entering Cambridge, but his career wassuccessful and he remained there throughout his life.

By 1820 it had become apparent to astronomersthat the motion of Uranus could not be explained byNewton’s law of gravitation and the influence ofthe known planets alone, since a small but increas-ing perturbation in its orbit had been observed.While still an undergraduate, Adams proved thatthe deviation had to be due to the influence of aneighth, undiscovered, planet. He sent his predictionfor its position to Airy, the Astronomer Royal, whowas sceptical of its value and ignored it. Only whenLeverrier, in France, announced similar results 9months later did Airy initiate a search by JamesChallis (1803–82) at the Cambridge Observatory,based on Adams’s prediction. The planet, nownamed Neptune, was however found first by JohannGalle (1812–1910) in Berlin in 1846, using Leverrier’sfigures. A bitter controversy about the credit for theprediction soon developed. Adams’s precedence waseventually recognized, despite his taking no part inthe debate. He turned down the subsequent offers ofa knighthood and the post of Astronomer Royal.

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Abbe, Ernst [abuh] (1840–1905) German physicistand developer of optical instruments.

Abbe was professor of physics and observatorydirector at Jena. He worked on optical theory andwith Carl Zeiss (1816–88), an instrument maker,and Otto Schott (1851–1935), a glass maker, wasable to improve several devices. These include theAbbe condenser for converging light on microscopespecimens; the achromatic lens, which is free fromcolour distortion (1886); and the Abbe refractome-ter. From 1888 he was the sole owner of the Zeisscompany, whose optical instruments were of thehighest standard. In 1893 he patented the now-familiar prismatic binocular.

Abegg, Richard [abeg] (1869–1910) German physi-cal chemist.

Abegg’s Rule (for which he is best remembered)states that each element has a positive valence anda negative valence, whose sum is 8. This ideareflects in primitive form the ‘octet rule’, ie thetrend shown by most elements of the second andthird (short) periods to attain an outer octet of elec-trons, but even as a mnemonic it applies only to ele-ments of the fourth to seventh periodic groups.

Abel, Sir Frederick (Augustus) [aybel] (1827–1902) British chemist: expert on military explosives.

An early pupil of Hofmann at the Royal College of Chemistry, he became chemist to the WarDepartment in 1854. He showed that guncotton(obtained by nitrating cotton) could be made safeby removing traces of acid, which, if not removed,led to instability. In 1889 with Dewar he invented‘cordite’, a mixture of guncotton and nitroglyceringelatinized with propanone and petroleum jelly,which became the standard British military propel-lant. It produces little smoke on firing, an impor-tant advantage on a battlefield.

Abel, John Jacob [aybel] (1857–1938) US bio-chemist: detected adrenalin, and crystallizedinsulin; isolated amino acids from blood.

An Ohio farmer’s son, Abel studied very widely in Europe before returning to Johns HopkinsUniversity equipped with a wide knowledge ofchemistry, biology and medicine, as professor ofpharmacology. He studied the adrenal hormonenow known as adrenalin (epinephrine); and in 1926first crystallized insulin and showed it was a proteinand contained zinc. He was the first to isolate aminoacids from blood, in 1914. He did this by passingblood from an artery through a cellophane tubeimmersed in saline; the amino acids dialysedthrough the tube and the blood was returned to avein of the animal. The proof that amino acids arepresent in blood is fundamental in animal bio-chemistry and the method used led the way towardsdialysis in the treatment of kidney disease.

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Adams, Walter Sydney

thermionic diode amplifiers to reliably recordnerve impulses in a single nerve fibre, and to showthat they do not change with the nature or strengthof the stimulus, confirming work by his friend KLewis (1881–1945) in 1905 on this ‘all or none’ law.He went on to show that a nerve transmits infor-mation to the brain on the intensity of a stimulusby frequency modulation, ie as the intensity risesthe number of discharges per second (perhaps10–50) in the nerve also rises – a fundamental dis-covery. He then worked on the brain, using the discovery by Berger in 1924 that electrical ‘brain-waves’ can be detected.

From 1934 he studied these brainwave rhythms,which result from the discharge of thousands ofneurones and which can be displayed as an elec-troencephalogram (EEG). Within a few years themethod was widely used to diagnose epilepsy cases,and later to locate lesions, eg those due to tumoursor injury.

Adrian was linked with Trinity College Cambridgefor nearly 70 years and did much to advance neuro-physiology. He was a very popular figure; as a stu-dent he was a skilful night roof-climber and anexcellent fencer, and he sailed and rock-climbeduntil late in life. He helped to organize a famoushoax exhibition of modern pictures in 1913. He wasnever solemn, moved very quickly and claimed hisown brainwaves were as rapid as a rabbit’s; as amotorist his quick reflexes alarmed his passengers.When in a hurry he would use a bicycle in the longdark basement corridors of the PhysiologicalLaboratory. He shared a Nobel Prize in 1932.

Agassiz, Jean Louis Rodolphe [agasee] (1807–73)Swiss–US naturalist and glaciologist: proposedformer existence of an Ice Age.

Agassiz owed much of his scientific distinction tothe chance of his birth in Switzerland. He studiedmedicine in Germany, but zoology was his keeninterest. He studied under Cuvier in Paris and thenreturned home and worked with enthusiasm onfossil fishes, becoming the world expert on them(his book describes over 1700 ancient species of fish).

Holidaying in his native Alps in 1836 and 1837, heformed the novel idea that glaciers are not static,but move. He found a hut on a glacier which hadmoved a mile over 12 years; he then drove a straightline of stakes across a glacier, and found theymoved within a year. Finding rocks which had beenmoved or scoured, apparently by glaciers, he con-cluded that in the past, much of Northern Europehad been ice-covered. He postulated an ‘Ice Age’ inwhich major ice sheets had formed, moved andwere now absent in some areas – a form of cata-strophism, in contrast to the extreme uniformitar-ianism of Lyell. We now know that a series of iceages has occurred.

In 1846 Agassiz was invited to the USA to lecture,enjoyed it and stayed to work at Harvard. He foundevidence of past glaciation in North America; it toohad undergone an Ice Age. His studies on fossil ani-mals could have been used to support Darwin’sideas on evolution, but in fact Agassiz was America’s

Adams, Walter Sydney (1876–1956) US astronomer:discovered first white dwarf star.

Adams was born in Syria, where his American par-ents were missionaries, but he returned with themwhen he was 9 and was educated in the USA and inEurope.

Adams’s work was principally concerned with thespectroscopic study of stars. He showed how dwarfand giant stars could be distinguished by their spec-tra, and established the technique of spectroscopicparallax to deduce a star’s distance. In 1915 heobserved the spectrum of Sirius B, the faint compan-ion of Sirius, and discovered it to be an exceptionallyhot star. Since it is only 8 light years distant he real-ized that it must therefore be very small (otherwise itwould be brighter), and hence of very high density.Sirius B proved to be a ‘white dwarf’ and the first of anew class of stellar objects; such stars are the finalstage in the evolution of stars of similar mass to theSun, which have collapsed to form extremely denseobjects.

Adams also searched for the relativistic spectralshift expected from a heavy star’s presumed intensegravitational field. This he succeeded in finding in1924, thereby proving his hypothesis about thenature of Sirius B and strengthening the case forEinstein’s general relativity theory as well. Adamsspent most of his working life at the Mount WilsonObservatory in southern California, and was itsdirector from 1923 until 1946.

Addison, Thomas (1793–1860) British physician: afounder of endocrinology.

A graduate in medicine from Edinburgh andLondon, his early work included the first cleardescriptions of appendicitis, lobar pneumonia andthe action of poisons on the living body. In 1855 hissmall book On the Constitutional and Local Effects ofDisease of the Supra-renal Capsules described two newdiseases: one is ‘pernicious’ anaemia; the other,also an anaemia, is associated with bronzing of theskin and weakness, and is known as Addison’s dis-ease. He found that cases of the latter showed post-mortem changes in the suprarenal capsules (one ontop of each kidney). Later, physiological studies byothers showed that the suprarenal capsules areglands, now known as the adrenal glands, whichproduce a complex group of hormones. Addison’sdisease was the first to be correctly attributed toendocrine failure (ie disorder of the ductless glandsof internal secretion).

Adrian, Edgar Douglas, Baron Adrian (1889–1977) British neurophysiologist: showed frequencycode in nerve transmission.

Adrian began his research in physiology inCambridge before the First World War, but in 1914he speedily qualified in medicine and tried to get to France. In fact he was kept in England workingon war injuries and his later work was a mixture of ‘pure’ research and applications to medical treatment.

In the 1920s he began his best-known work.Already, crude methods were available for detec-ting electrical activity in nerve fibres. Adrian used

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main opponent to Darwin’s view that species hadevolved.

Agnesi, Maria Gaetana [anyayzee] (1718–99)Italian mathematician and scholar: remembered inthe naming of the cubic curve ‘the Witch of Agnesi’.

Born in Milan, Maria was one of the 24 children ofa professor of mathematics at the University ofBologna. With his encouragement she spoke sevenlanguages by the age of 11, and by the age of 14 shewas solving problems in ballistics and geometry.Her interests covered logic, physics, mineralogy,chemistry, botany, zoology and ontology; herfather arranged her public debates. From this timeshe suffered a recurring illness in which convul-sions and headaches were symptoms. Her fatheragreed that she should in future lead a quiet lifefree from social obligations. Maria thereafter de-voted herself to the study of new mathematicalideas. Her Instituzioni analitiche ad uso della gioventù(1748, Analytical Institutions) was published as ateaching manual. In 1750, she was appointed to thechair of mathematics and philosophy at Bologna.Maria Agnesi’s work was one of promise ratherthan fulfilment: she made no original discoveriesand her major work was written as a guide to students. The cubic curve named the Witch ofAgnesi was formulated by Fermat. A mistranslationcaused the use of ‘witch’ for ‘curve’.

Agricola, Georgius (Lat), Georg Bauer (Ger)[agrikola] (1494–1555) German mineralogist, geolo-gist and metallurgist: described mining and metal-lurgical industries of 16th-c.

Born in Saxony, Agricola trained in medicine inLeipzig and in Italy. The link between medicine andminerals led to his interest in the latter, and hiswork as a physician in Saxony put him in idealplaces to develop this interest and to extend it tomining and metal extraction by smelting, andrelated chemical processes. His book De natura fos-silium (1546, On the Nature of Fossils) classifies min-erals in perhaps the first comprehensive system.Later he wrote on the origin of rocks, mountainsand volcanoes. His best-known book, De re metallica(1556, On the Subject of Metals) is a fine illustratedsurvey of the mining, smelting and chemical tech-nology of the time. An English edition (1912) wasprepared by the American mining engineer H CHoover (who became president of the USA,1929–33) and his wife.

Airy, Sir George Biddell [ayree] (1801–92) Britishgeophysicist and astronomer: proposed model ofisostasy to explain gravitational anomalies.

Airy was successful early in life, his talent andenergy leading to his appointment as AstronomerRoyal in 1835, a post he held for 46 years. He muchextended and improved the astronomical measure-ments made in Britain. Airy’s researches were inthe fields of both optics and geophysics. He experi-mented with cylindrical lenses to correct astigma-tism (a condition he suffered from himself); and hestudied the Airy discs in the diffraction pattern of apoint source of light.

In geophysics he proposed that mountain ranges

Alembert, Jean le Rond d’

3

acted as blocks of differing thickness floating inhydrostatic equilibrium in a fluid mantle, ratherlike icebergs in the sea. He was thus able to explaingravitational anomalies that had been observed inthe Himalayas as due to the partial counteractionof the gravitational attraction of the topographyabove sea level with that of a deep ‘root’ extendinginto the mantle. His model of isostasy satisfactorilyexplains the gravity field observed over mountainousterrain in much of the world.

Airy was arrogant and unlucky in his failings, nowalmost better known than his successes. He failed to exploit Adams’s prediction of a new planet,Neptune; he was against Faraday’s idea of ‘lines offorce’ (a fruitful intuition, in fact); and although heexpended great effort to ensure precise measure-ments of the transits of Venus, observed in 1874 and1882, the results failed to give accurate measure-ments of the scale of the solar system because Venus’satmosphere makes the timing of its apparent contactwith the Sun’s disc uncertain. An ingenious inventorof laboratory devices, he was remarkably precise, tothe extent of labelling empty boxes ‘empty’.

Alembert, Jean le Rond d’ [dalãbair] (1717–83)French mathematician: discovered d’Alembert’sprinciple in mechanics.

D’Alembert’s forename comes from that of thechurch, St Jean le Rond, on whose steps he wasfound as a baby. He was probably the illegitimateson of a Parisian society hostess, Mme de Tenzin,and the chevalier Destouches; the latter paid for hiseducation while he was brought up by a glazier andhis wife. He studied law, and was called to the barin 1738, but then flirted briefly with medicinebefore choosing to study mathematics and to liveon his father’s annuity.

Early research by d’Alembert clarified the conceptof a limit in the calculus and introduced the idea ofdifferent orders of infinities. In 1741 he was admittedto the Académie des Sciences and 2 years later pub-lished his Traité de dynamique (Treatise on Dynamics),which includes d’Alembert’s principle, thatNewton’s Third Law of Motion holds not only forfixed bodies but also for those free to move. A widevariety of new problems could now be treated, suchas the derivation of the planar motion of a fluid. Hedeveloped the theory of partial differential equationsand solved such systems as a vibrating string and thegeneral wave equation (1747). He joined Euler, A IClairault (1713–65), Lagrange and Laplace in apply-ing calculus to celestial mechanics and determinedthe motion of three mutually gravitating bodies. Thisthen allowed many of the celestial observations to beunderstood; for example, d’Alembert explainedmathematically (1754) Newton’s discovery of preces-sion of the equinoxes, and also the perturbations inthe orbits of the planets.

D’Alembert was then persuaded by his friend,Denis Diderot (1713–84), to participate in writinghis encyclopedia, contributing on scientific topics.This project was denounced by the Church afterone volume, and d’Alembert turned instead to pub-lishing eight volumes of abstruse mathematical

Alferov, Zhores

only the difficulties, and on his return he realizedthat the caliph would probably ensure an unpleas-ant death for him. To avoid this, he pretended to bemad, and maintained this successfully until thecaliph died in 1021. Alhazen then considered study-ing religion, before turning fully to physics inmiddle age. His mathematical and experimentalapproach is the high point of Islamic physics, andhis work in optics was not surpassed for 500 years.

Al-Khwarizmi [al-khwahrizmee] (c.800–c.850) Persianmathematician: introduced modern number notation.

Little is known of al-Khwarizmi’s life; he was amember of the Baghdad Academy of Science andwrote on mathematics, astronomy and geography.His book Algebra introduced that name, althoughmuch of the book deals with calculations. However,he gives a general method (al-Khwarizmi’s solution)for finding the two roots of a quadratic equation

ax2 + bx + c= 0 (where a ≠ 0);he showed that the roots are

x1 = [– b + (b2 – 4ac)�� ]/2aand x2 = [– b – (b2 – 4ac)�� ]/2a

In his book Calculation with the Hindu Numerals hedescribed the Hindu notation (misnamed ‘Arabic’numerals) in which the digits depend on their posi-tion for their value and include zero. The term‘algorithm’ (a rule of calculation) is said to benamed after him. The notation (which came intoEurope in a Latin translation after 1240) is of hugepractical value and its adoption is one of the greatsteps in mathematics. The 10 symbols (1–9 and 0)had almost their present shape by the 14th-c, in surviving manuscripts.

Allen, James (Alfred) Van see Van AllenAlpher, Ralph Asher (1921– ) US physicist: (with

Robert Herman) predicted microwave backgroundradiation in space; and synthesis of elements inearly universe.

studies. Shortly before his death J H Lambert (1728–77) wished to name his ‘newly discovered moon ofVenus’ after d’Alembert, but the latter was suffi-ciently acute to doubt (correctly) from calculationsthat it existed, and gently declined the offer.

Alferov, Zhores (1930– ) Russian physicist: devisedimproved transistors, and semiconductor lasers.

Alferov and Herbert Kroemer (1928– ) werejointly awarded the Nobel Prize for physics in 2000,together with KILBY. Alferov was born in Belorussiain 1930, graduating from the ElectrotechnicalInstitute in Leningrad in 1952. Kroemer obtainedhis doctorate in theoretical physics from Göttingenin the same year, and five years later he wasemployed by RCA in New Jersey. Both men wereinterested in semiconductor heterostructures.These used sandwiches (stacked layers) of differentsemiconductors, such as arsenides, giving a smallerband gap than in conventional semiconductors.Kroemer showed that the reduced band gap makesfor a smaller energy barrier for electrons in tran-sistors made of these materials, allowing highergain and speed. Then in 1963 both he and Alferovindependently suggested building semiconductorlasers using heterostructures. Alferov designed,patented and built the first such laser able to workat room temperature, by using gallium arsenideand aluminium arsenide. Thereafter commercialapplications took off rapidly, and it became a keyelement of the current information revolution. Thelasers are used in CD players, laser printers andfibre optic communications.

Alfvén, Hannes Olof Gösta [alfvayn] (1908–95)Swedish theoretical physicist: pioneer of plasmaphysics.

Educated at Uppsala, Alfvén worked in Swedenuntil 1967, when he moved to California. Much ofhis work was on plasmas (gases containing positiveand negative ions) and their behaviour in magneticand electric fields. In 1942 he predicted magneto-hydrodynamic waves in plasmas (Alfvén waves)which were later observed. His ideas have beenapplied to plasmas in stars and to experimentalnuclear fusion reactors. He shared a Nobel Prize in1970 for his pioneering theoretical work on mag-netohydrodynamics.

Alhazen, Abu al-Hassan ibn al Haytham (Arabic)[alhazen] (c.965–1038) Egyptian physicist: mademajor advances in optics.

Alhazen rejected the older idea that light wasemitted by the eye, and took the view that light wasemitted from self-luminous sources, was reflectedand refracted and was perceived by the eye. Hisbook The Treasury of Optics (first published in Latin in1572) discusses lenses (including that of the eye),plane and curved mirrors, colours and the cameraobscura (pinhole camera).

His career in Cairo was nearly disastrous. Born inBasra (now in Iraq), he saw in Cairo the annual flood-ing of the Nile and persuaded the caliph al-Hakim tosponsor an expedition to southern Egypt with theobject of controlling the river and providing an irri-gation scheme. Alhazen’s expedition showed him Ralph A Alpher

4

A civilian physicist in the Second World War,Alpher afterwards worked in US universities and inindustry. He is best known for his theoretical workconcerning the origin and evolution of the universe.In 1948, Alpher, together with Bethe and Gamow,suggested for the first time the possibility of explain-ing the abundances of the chemical elements as theresult of thermonuclear processes in the earlystages of a hot, evolving universe. This workbecame known as the ‘alpha, beta, gamma’ theory.As further developed in a number of collaborativepapers with R Herman (1914–97) over the years, andin another important paper with Herman and J WFollin Jr, this concept of cosmological element syn-thesis has become an integral part of the standard‘Big Bang’ model of the universe, particularly as itexplains the universal abundance of helium. Thesuccessful explanation of helium abundance isregarded as major evidence of the validity of themodel. While this early work on forming the ele-ments has been superseded by later detailed stud-ies involving better nuclear reaction data, the ideashad a profound effect on later developments.

Again in 1948, Alpher and Herman suggested thatif the universe began with a ‘hot Big Bang’, then theearly universe was dominated by intense electro-magnetic radiation, which would gradually have‘cooled’ (or red-shifted) as the universe expanded,and today this radiation should be observed ashaving a spectral distribution characteristic of ablack body at a temperature of about 5 K (based onthen-current astronomical data). At that time radioastronomy was not thought capable of detectingsuch weak radiation. It was not until 1964 thatPenzias and R W Wilson finally observed the back-ground radiation. It was realized later that evi-dence for this radiation had been available in 1942in the form of observed temperatures of certaininterstellar molecules. The existence of this back-ground radiation (current observed value 2.73 K),whose peak intensity is in the microwave region ofthe spectrum, is widely regarded as a major cosmo-logical discovery and strong evidence for the valid-ity of the ‘Big Bang’ model, to which Alpher,Gamow and Herman contributed the pioneeringideas.

Alter, David (1807–81) US physicist: contributed tospectral analysis.

A physician and inventor as well as a physicist,Alter was one of the earliest investigators of thespectrum. In 1854 he showed that each elementhad its own spectrum, conclusively proved a fewyears later by Bunsen and Kirchhoff in their pio-neer research on the Fraunhofer lines. He alsoforecast the use of the spectroscope in astronomy.

Altounyan, Roger (Ernest Collingwood)[altoonyan] (1922–87) British medical pioneer;introducer of the anti-asthma drug sodium cromo-glycate.

Of Irish–Armenian and English parentage, he wasalso the grandson of W G Collingwood (1854–1932),the friend and biographer of John Ruskin(1819–1900). Roger Altounyan was born in Syria,

Alvarez, Luis

5

but spent summer holidays sailing in the LakeDistrict with his sisters. Here the family met ArthurRansome (1884–1967) and became the model for hisSwallows and Amazons children’s books. Roger’sasthma, however, was fact as well as fiction. Hestudied medicine, and practised it at the ArmenianHospital in Aleppo run by his father and grandfa-ther. In 1956 he returned to England and joined apharmaceutical company. He was concerned thatasthma was not taken seriously and determined tofind a cure. For the next 10 years he worked in hisown time testing compounds on himself, inducingasthma attacks two or three times a week with abrew of guinea pig hair, to which he was allergic,almost certainly to the detriment of his own health.Compound 670, sodium cromoglycate, has beenmuch used to prevent attacks of allergic asthmaand rhinitis. The Spinhaler device he invented toinhale the drug was based on aircraft propellers; hehad been a pilot and flying instructor during thewar.

Alvarez, Luis (Walter) [alvahrez] (1911–88) USphysicist: developed the bubble-chamber techniquein particle physics.

Alvarez was a student under Compton, and thenjoined Lawrence at the University of California atBerkeley in 1936. He remained there, becoming professor of physics in 1945.

Alvarez was an unusually prolific and diversephysicist. He discovered the phenomenon of orbitalelectron capture, whereby an atomic nucleus ‘cap-tures’ an orbiting electron, resulting in a nuclidewith a lower proton number. In 1939, together withBloch, he made the first measurement of the mag-netic moment of a neutron. During the SecondWorld War he worked on radar, developing suchdevices as microwave navigation beacons and radarlanding approach systems for aircraft, and alsoworked on the American atomic bomb project. In1947 he built the first proton linear accelerator,and later developed the bubble-chamber techniquefor detecting charged subatomic particles, which inturn led to a great increase in the number of knownparticles. For this he received the Nobel Prize forphysics in 1968.

He was ingenious in the application of physics toa variety of problems. He used the X-ray componentof natural cosmic radiation to show that Chephren’spyramid in Egypt had no undiscovered chamberswithin it; and he used physics applied to theKennedy assassination evidence to confirm thatonly one killer was involved. With his son Walter(1940– ), a geologist, he studied the problem ofthe catastrophe of 65 000 000 years ago which killedthe dinosaurs and other fossil species; they con-cluded from tracer analysis that a probable causewas Earth’s impact with an asteroid or comet,resulting in huge fires and/or screening of the Sunby dust. His interest in optical devices led him tofound two companies; one to make variable focusspectacle lenses, devised by him to replace his bifo-cals; the other to make an optical stabilizer, whichhe invented to avoid shake in his cine camera and

Amici, Giovan Battista

inspector-general of the university system byNapoleon, a post he retained until his death.

Ampère was a versatile scientist, interested inphysics, philosophy, psychology and chemistry,and made discoveries in this last field that wouldhave been important had he not been unfortunatein being pre-empted by others on several occasions.In 1820 he was stimulated by Oersted’s discovery,that an electric current generates a magnetic field,to carry out pioneering work on electric currentand electrodynamics. Within months he had madea number of important discoveries: he showed thattwo parallel wires carrying currents flowing in thesame direction attracted one another while whenthe currents ran in opposite directions they wererepelled; he invented the coiled wire solenoid; andhe realized that the degree of deflection of Oersted’scompass needle by a current could be used as a measure of the strength of the current, the basis ofthe galvanometer. Perhaps his most outstandingcontribution, however, came in 1827, when he provided a mathematical formulation of electro-magnetism, notably Ampère’s Law, which relatesthe magnetic force between two wires to the prod-uct of the currents flowing in them and the inversesquare of the distance between them. It may be gen-eralized to describe the magnetic force generated atany point in space by a current flowing along a con-ductor. The SI unit of electric current, the ampere(sometimes abbreviated to amp) is named in hishonour. The ampere is defined as that steady cur-rent which, when it is flowing in each of two infi-nitely long, straight, parallel conductors that havenegligible areas of cross-section and are 1 metreapart in a vacuum, causes each conductor to exert aforce of 2 × 10 –7 N on each metre of the other.

in binoculars. He was an engaging and popular personality.

Amici, Giovan Battista [ameechee] (1786–1868) Italian microscopist: improved the com-pound microscope.

Amici trained as an engineer and architect inBologna; he became a teacher of mathematics butwas soon invited to Florence to head the observa-tory and science museums there. His interest fromhis youth was in optical instruments, especiallymicroscopes. At that time compound microscopeswere inferior to simple types, partly because ofaberrations and also because of the false idea thatenlargement was the dominant target of design.Amici devised in 1818 a catadioptric (mirror) designthat was free of chromatic aberration and used it toobserve the circulation of protoplasm in Chara cells;at once he became distinguished as an optician andas a biologist. By 1837 he had a design with a resolv-ing power of 0.001 mm and a numerical aperture of0.4 that was able to magnify 6000 times. His objec-tives had up to six elements; he invented the tech-nique of immersion microscopy, using oil.

He also much improved telescopes, but his maininterest remained in biology, where he made thenotable discovery of the fertilization of phanero-gams, observing in 1821 the travel of the pollentube through the pistil of the flower.

Amontons, Guillaume [amõtõ] (1663–1705) Frenchphysicist: discovered interdependence of tempera-ture and pressure of gases.

In his teens Amontons became deaf, and his inter-est in mechanics seems then to have begun. He laterimproved the design of several instruments,notably the hygrometer, the barometer and theconstant-volume air thermometer. In 1699 he dis-covered that equal changes in the temperature of afixed volume of air resulted in equal variations inpressure, and in 1703 seemed near to suggestingthat at a sufficiently low temperature the pressurewould become zero. Unfortunately his results wereignored and it was almost a century later beforeCharles rediscovered the relationship. His work onthe thermal expansion of mercury, however, con-tributed to the invention of the mercury ther-mometer by Fahrenheit.

Ampère, André Marie [ãpair] (1775–1836) Frenchphysicist and mathematician: pioneer of electro-dynamics.

Ampère was a very gifted child, combining a pas-sion for reading with a photographic memory andlinguistic and mathematical ability. He was largelyself-taught. His life was disrupted by the FrenchRevolution when, in 1793, his father, a Justice ofthe Peace, was guillotined along with 1500 fellowcitizens in Lyon. For a year Ampère seems to havesuffered a state of shock; he was aged 18. Ten yearslater, his adored young wife died following thebirth of his son. His second marriage, undertakenon the advice of friends, was a disaster. His profes-sional life ran more smoothly.

In 1802 Ampère was appointed to the first of aseries of professorships, and in 1808 was appointed

6

A M Ampère

Anaximander (of Miletus) [anaksimander](611–547 bc) Ionian (Greek) natural philosopher:suggested Earth was a curved body in space.

A pupil of Thales, Anaximander’s writings arenow lost, but he is credited with a variety of novelideas. He was the first Greek to use a sundial (longknown in the Middle East), and with it found thedates of the two solstices (shortest and longest days)and of the equinoxes (the two annual occasionswhen day and night are equal). He speculated onthe nature of the heavens and on the origin of theEarth and of man. Realizing that the Earth’s surfacewas curved, he believed it to be cylindrical (with itsaxis east to west); and he was probably the firstGreek to map the whole known world. He visual-ized the Earth as poised in space (a new idea).

Anderson, Carl David (1905–91) US physicist: dis-covered the positron and the muon.

Anderson, the only son of Swedish immigrants,was educated in Los Angeles and at the CaliforniaInstitute of Technology, where he remained for therest of his career.

Anderson discovered the positron accidentally in1932 (its existence had been predicted by Dirac in1928). As a result, Dirac’s relativistic quantummechanics and theory of the electron were rapidlyaccepted and it became clear that other antiparti-cles existed. Anderson shared the 1936 Nobel Prizefor physics with V F Hess for this discovery.

Anderson discovered the positron while studyingcosmic rays, which he did by photographing theirtracks in a cloud chamber in order to find theenergy spectrum of secondary electrons producedby the rays. A lead plate divided the chamber so thatthe direction of movement of the particles could bededuced (they are slowed or stopped by the lead).Also, a magnetic field was applied to deflect parti-cles in different directions according to theircharge and by an amount related to their mass.Many positive particles were seen which were notprotons; they were too light and produced too littleionization. Anderson identified their mass as aboutthat of an electron, concluding that these were pos-itive electrons, or positrons. The discovery was con-firmed by Blackett and Occhialini the followingyear.

Anderson discovered another elementary particlewithin the same year, again by observing cosmic raytracks. It had unit negative charge and was 130times as heavy as an electron, and seemed a possibleconfirmation of Yukawa’s theory of a particle com-municating the strong nuclear force (now called api-meson or pion). However a series of experimentsby Anderson in 1935 revealed that it was not and therole of this mu-meson (or muon), as it is now called,remained unclear. The true pi-meson was firstfound by Powell in 1947. Positrons are inherentlystable, but as they are antiparticles of electrons thetwo annihilate each other. Mesons are intrinsicallyunstable and decay rapidly. (Portrait on p. 170)

Anderson, Elizabeth, née Garrett (1836–1917)British physician; pioneered the acceptance ofwomen into British medical schools.

Anderson, Elizabeth

7

Elizabeth Garrett was born in London, where herfather had a pawnbroker’s shop. He later built anexpanding business malting grain at Snape inSuffolk. Educated by a governess at home, followedby boarding school in London, she settled to theduties of daughter at home, helping to run the largehousehold. She joined the Society for Promotingthe Employment of Women, whose aim was toimprove the status of women through educationand employment. Elizabeth Blackwell, the firstwoman to graduate in medicine in America (1849)gave a lecture on ‘Young Women Desirous ofStudying Medicine’, which impressed ElizabethGarrett and her friend Emily Davies (1830–1921)who decided that Elizabeth should work to openthe medical profession in England to women andthat Emily Davies would pursue higher educationfor women (she founded Girton College, Cam-bridge). As she was the youngest, Elizabeth’s sisterMillicent (Fawcett) was to work for the vote forwomen.

After graduation in New York Elizabeth Blackwellwas inscribed on the British Medical Register. TheMedical Council decided in future to exclude allholders of foreign degrees. To practise medicine inBritain Elizabeth Garrett had to gain admission to aBritish medical school.

With the financial support of her father shebecame an unofficial medical student at theMiddlesex Hospital in 1860. Although she had theapproval of the Dean, students and staff objected andshe had to leave. No medical school or university inGreat Britain would admit a woman, so she applied tothe Society of Apothecaries, which provided a mini-mum qualification in medicine. After taking coun-sel’s opinion, the Society was unable to refuse herapplication because of the wording of its Charter, anopening closed soon after her success. She attended acourse by T H Huxley on natural history and physiol-ogy and John Tyndall’s course on physics at theRoyal Institution, at their invitation. Only privatetuition for the Apothecaries’ medical course wasopen to her and she found tutors at the medicalschools at St Andrews, Edinburgh and London. Shepassed the Apothecaries’ Hall examination in 1865,becoming the first woman to complete a recognizedcourse of medical training with legal qualificationsin Britain.

As a woman Elizabeth Garrett was barred fromany hospital appointment and was unacceptable asan assistant in general practice. She was dependenton an allowance from her father for some time. Shebecame a consultant physician to women and chil-dren from her home in London. Although willing toattend male patients she feared that to do so mightcreate a scandal. In 1865, just before a cholera epi-demic reached London, she opened the St Mary’sDispensary for Women and Children in a poor areaof London and became visiting medical officer to achildren’s hospital in East London.

The Sorbonne in Paris admitted women in 1868and in 1870 Elizabeth Garrett became the firstwoman MD from that university. In 1871 she

Anderson, Philip Warren

collection of their fossils; and he found evidence ofvery early human life in central Asia.

Andrews, Thomas (1813–85) British physicalchemist: showed existence of critical temperatureand pressure for fluids.

The son of a Belfast merchant, Andrews studiedchemistry and medicine in Scotland. In Paris hestudied chemistry under Dumas and at Giessen hestudied under Liebig. In Belfast he first practisedmedicine and later became professor of chemistry.He proved that ‘ozone’ is an allotrope of oxygen (iea different form of the element; ozone was latershown to be O3; ordinary oxygen is O2). He was a fineexperimenter and is best known for his work on thecontinuity of the liquid and gaseous states ofmatter (1869). Using carbon dioxide, he showedthat above its ‘critical temperature’ (31°C) it cannotbe liquefied by pressure alone. This example sug-gested that at a suitably low temperature, any gascould be liquefied, as was later demonstrated byCailletet.

Anfinsen, Christian (Boehmer) (1916–95) US bio-chemist: made discoveries related to the shape andactivity of enzymes.

Educated at Swarthmore and Harvard, Anfinsenafterwards worked at Harvard and from 1950 at theNational Institutes of Health in Bethesda, MD. In1960 Moore and W H Stein (1911–80) found thesequence of the 124 amino acids which make upribonuclease and it became the first enzyme forwhich the full sequence was known. However, itwas clear that enzymes owe their special catalyticability not only to the sequence of amino acid unitsbut also to the specific shape adopted by the chain-like molecule. Anfinsen showed that, if this shape isdisturbed, it can be restored merely by putting themolecule into the precise environment (of temper-ature, salt concentration, etc) favourable for it,when it spontaneously takes up the one shape (outof many possibilities) that restores its enzymicactivity. He deduced that all the requirements forthis precise three-dimensional assembly must bepresent in the chain sequence; and he showed thatother proteins behaved similarly. He shared theNobel Prize for chemistry with Moore and Stein in1972.

Ångström, Anders (Jonas) (1814–74) Swedishspectroscopist: detected hydrogen in the Sun.

Ångström was educated at Uppsala and taughtphysics at the university there until his death. Hewas an early spectroscopist and deduced in 1855that a hot gas emits light at the same wavelengthsat which it absorbs light when cooler; this wasproved to be so in 1859 by Kirchhoff. From 1861 hestudied the Sun’s spectrum, concluding that hydro-gen must be present in the Sun, and mapping about1000 of the lines seen earlier by Fraunhofer. A non-SI unit of length, the ångström (Å) is 10 –10 m; it wasused by him to record the wavelength of spectrallines.

Anning, Mary (1799–1847) British palaeontologist.Mary Anning had the good fortune to be born in

Lyme Regis in Dorset, a place of great geological

married James Skelton Anderson (died 1907) andcombined family life with her work. The LondonSchool of Medicine for Women, which was initiatedby Sophia Jex-Blake, opened in 1874 and ElizabethGarrett Anderson served on the ExecutiveCommittee, taught in the school and worked forthe students to be admitted to the University ofLondon’s examinations. In 1883 she was electedDean, the same year that Mary Scharlieb and EdithShove became the first women to gain medicaldegrees from London University. The Schoolbecame a college of the University of London. From1886 Elizabeth Garrett Anderson was concernedwith the New Hospital for Women which served asthe teaching hospital for the London School ofMedicine for Women. In 1908 she was electedmayor of Aldeburgh, the first woman mayor inEngland. It was due to the efforts of ElizabethGarrett Anderson that medical education and medical science was opened to women in Britain.

Anderson, Philip Warren (1923–95) US physicist:discovered aspects of the electronic structure ofmagnetic and disordered systems.

Anderson studied at Harvard, doing doctoralresearch with Van Vleck and spending 1943–45involved in antenna engineering at the NavalResearch Laboratory. Anderson’s career was largelywith Bell Telephone Laboratories, but he becameprofessor of physics at Princeton in 1975, and healso held a visiting professorship at Cambridge, UK(1967–75). Under Van Vleck, Anderson worked onpressure broadening of spectroscopic lines. In 1958he published a paper on electronic states in disor-dered media, showing that electrons would be con-fined to regions of limited extent (Andersonlocalization) rather than be able to move freely. In1959 he calculated a model explaining ‘superex-change’, the way in which two magnetic atoms mayinteract via an intervening atom. In 1961 he pub-lished important work on the microscopic origin ofmagnetism in materials. The Anderson model is aquantum mechanical model that describes local-ized states and their possible transition to freelymobile states. This model has been used widely tostudy magnetic impurities, superconducting tran-sition temperatures and related problems. Also,during his work on superconductivity and super-fluidity, Anderson worked on the possible super-fluid states of helium-3. For these investigations ofelectronic properties of materials, particularlymagnetic and disordered ones, Anderson sharedthe 1977 Nobel Prize for physics.

Andrews, Roy Chapman (1884–1960) US natural-ist and palaeontologist.

Andrews’s career was mostly spent with theAmerican Museum of Natural History, New York,and with its expeditions (especially to Asia) to col-lect specimens. His more dramatic finds includedthe fossil remains of the largest land mammal yetfound, Paraceratherium, a relative of the rhinowhich stood 5.5 m high; and the first fossil dinosaureggs. He had a special interest in whales and othercetaceans (aquatic mammals) and built up a fine

8

interest and, when a year old, to survive a lightningstrike. Her nurse sheltered with her beneath a treeduring a thunderstorm with two others; only Marysurvived.

Her father, a cabinetmaker, supplemented hisincome by selling local fossils to summer visitors. He died when Mary was 11 years old andshe, apparently well trained by him, continued tohelp the family income by the same means. Herbrother discovered the head of a marine reptile inthe cliffs between Lyme Regis and Charmouth in1811 and Mary carefully excavated the completeremains, named Ichthyosaurus in1817; she sold it toa collector for £23. This was the beginning of a life-time’s fruitful fossil-hunting; her value to palaeon-tologists was in her local knowledge, her skill inrecognition and the care she took to present herfinds in an uninjured state. In 1823 she discoveredthe complete skeleton of an little-known saurian,named Plesiosaurus by William Conybeare(1787–1857) and described by him at a meeting ofthe Geological Society in London in 1824. Anothermajor discovery of hers at Lyme was described asPterodactylus macronyx by William Buckland(1784–1856) in 1829; this fossil of a strange flyingreptile attracted much attention.

Mary Anning supplied fossils to palaeontologists,collectors and museums, as well as to the visitors toher shop in Lyme Regis and attracted the generalpublic to fossil-collecting and to herself, by her suc-cesses. She became both knowledgeable and awareof the significance of her discoveries. She left nopublications and her contribution to the ‘goldenage’ of British geology has been largely neglected;her discoveries were described and collected byothers. In her later years she was assisted by a smallgovernment grant awarded by the prime minister,Lord Melbourne, at the prompting of Buckland andthe Geological Society of London. When she diedher work was acknowledged by the president of theSociety in his anniversary address. Later a stained-glass window to her memory was placed by theFellows in the parish church at Lyme Regis.

Apollonius (of Perga) [apawlohneeuhs] (c.260–190tbc) Greek mathematician: wrote classic treatiseon conic sections.

Apollonius was a student in Alexandria and latertaught there, specialising in geometry. Of his books,one survives, On Conic Sections. It deals with thecurves formed by intersecting a plane through adouble circular cone (see diagram). These are thecircle, ellipse, parabola and hyperbola (the lastthree were named by Apollonius). Much of the bookon the properties of conics is original; it representsthe high point of Greek geometry and, although atthe time the work appeared to have no uses, Kepler1800 years later found that the planets moved inellipses and the curves now have many applicationsin ballistics, rocketry and engineering.

Apollonius was also interested in astronomy andespecially in the Moon, and proposed a theory ofepicycles to describe the sometimes apparently retrograde motions of the outer planets.

Appleton, Sir Edward

Appert, Nicholas-François [apair] (c.1749–1841)French chef: devised an improved method of foodpreservation.

As a innkeeper’s son, Appert was familiar withfood preparation and he became a chef and confec-tioner. A government prize was offered forimproved methods of preserving food, especiallyfor military use, and from 1795 Appert experi-mented with sealing food into glass jars usingwaxed cork bungs. Using heat-sterilization of thevessel and contents he was successful and in 1810he claimed the 12t000 franc prize. He used auto-claves (pressure cookers) to give a temperature alittle above the boiling point of water. Tinplate canscame into use in England after 1810 and weresealed by soldering. Appert’s work was highlypraised, but he died in poverty. Pasteur’s work,which rationalized Appert’s success, came in the1860s.

Appleton, Sir Edward (Victor) (1892–1965)British physicist: pioneer of ionospheric physics;discovered reflective layers within the ionosphere.

Appleton studied physics at Cambridge, but it wasservice in the First World War as a signals officerwhich led to his interest in radio. In 1924 he wasappointed professor of experimental physics atKing’s College, London. In 1939 he was appointedsecretary of the Department of Scientific andIndustrial Research, and later became vice-chancellorof Edinburgh University.

In 1901 Marconi had transmitted radio signalsacross the Atlantic, to the astonishment of many inthe scientific community who believed that, sinceelectromagnetic radiation travels in straight linesand the Earth’s surface is curved, this was not pos-sible. Shortly afterward, A E Kennelly (1861–1939)and Heaviside proposed a reflecting layer of chargedparticles in the atmosphere as the explanation. In aclassic experiment in 1925, Appleton became thefirst to demonstrate beyond doubt the existence ofsuch a reflecting layer within the ionosphere. Hetransmitted signals between Bournemouth andCambridge (a distance of 170 km); and by slowly

(1)

v v v

(2) (3)

(4)

v

(5)

v

(6)

v

Conic sections – Cone (sometimes double) cut by a planeto give (1) a single point (2) a pair of straight lines (3) ahyperbola (4) a parabola (5) a circle (6) an ellipse

9

Arago, Dominique François Jean

cation. The school had a Science Club to whichEthel Sargant, who had also attended the school,gave talks on botany. After taking degree examina-tions at University College, London, and NewnhamCollege, Cambridge, Agnes Robertson became aresearch assistant to Ethel Sargant at her privatelaboratory and worked on seedling structures.From 1903–08 she returned to London to take upresearch on gymnosperms.

After her marriage in 1909 she worked at theBalfour Laboratory in Cambridge until 1927 andthereafter in her own laboratory at home. For thenext 50 years her researches were mainly con-cerned with the anatomy and morphology of mono-cotyledonous plants and her researches weregathered into book form. She published Herbals,Their Origin and Evolution (1912), Water Plants: A Studyof Aquatic Angiosperms (1920), and Monocotyledons(1925). She also produced in the CambridgeBotanical Handbook series The Gramineae: A Study ofCereal, Bamboo, and Grass (1934). In 1946 she waselected to the fellowship of the Royal Society; shewas the third woman to receive the honour. Afterthe Second World War she turned more to philoso-phy and wrote The Natural Philosophy of Plant Form(1950), The Mind and the Eye (1954) and The Manifoldand the One (1957).

Archer, Frederick (Scott) (1813–57) British inven-tor of the wet collodion photographic process.

Orphaned early in life, Archer was apprenticed toa London silversmith. This led him first to studycoins and then to design them and to work as a por-trait sculptor. To obtain likenesses for this he beganin 1847 to use the primitive photographic methodsof the time. He experimented to improve them andtried collodion (a solution of nitrocellulose inether), on paper and then on glass, as part of thesensitive material. In 1851 he published hismethod: collodion containing iodide was flowedover a glass plate. This was followed by silver nitratesolution. The moist plate was quickly exposed inthe camera and then developed, fixed and washedto give a glass negative from which positive paperprints could be made. The moist plate was muchmore sensitive to light than its predecessors andallowed exposures to be reduced to 2–20 s.

Archer was diffident, poor, generous and un-worldly. Talbot claimed (falsely) that the wholeprocess was covered by his patents, but by 1854 hisattempts to prevent the use of collodion by legalinjunctions had failed and, as the daguerrotypepatents had lapsed in 1853, the public could takeup photography without restraint and did soenthusiastically. Despite the need to carry a tentand portable laboratory, the wet collodion processquickly supplanted all others and was widely usedby amateurs and professionals until 1880, when themore convenient gelatine dry plate was introduced.

Archer died poor and unappreciated, and hisfamily received niggardly provision from Govern-ment and professional photographers who hadprofited by use of his unpatented methods. Onlyafter many years was his contribution recognized.

varying the frequency and studying the receivedsignal he showed that interference was occurringbetween the part of the signal that travelled in a straight line from transmitter to receiver (thedirect, or ground, wave) and another part that was reflected by the ionosphere (the sky wave).Measurement of the interference caused by the dif-ferent path lengths enabled him to measure theheight of the reflecting layer, about 70 km. This wasthe first radio distance measurement. This layer isnow known as the Heaviside layer or E layer.Further work revealed a second layer above thefirst, which is now called the Appleton layer or Flayer . The E layer is more effective after dark, sincethe Sun’s ultraviolet rays interact with the ionos-phere, which is why distant radio stations are morereadily picked up at night. For his achievementsAppleton received the Nobel Prize for physics in1947.

Arago, Dominique François Jean [aragoh](1786–1853) French physicist.

Beginning his career as a secretary at the Bureaude Longitudes, Arago went with Biot to Spain in1806 to complete the geodetic measurements of anarc of the meridian. The return journey was event-ful as the ship was wrecked and he was almostenslaved at Algiers. He made distinguished researchesin many branches of physics, and in 1838 suggesteda crucial experiment to decide between the particleand wave theories of light, by measuring its speed inair and in water. The experiment was tried byFoucault in 1850 and pointed to the wave theory.

Arago was the first to discover that substancesother than iron have magnetic properties. He dis-covered in 1820 the production of magnetism byelectricity; a piece of iron, surrounded by a coil ofwire, was briefly magnetized by passing a currentfrom either a capacitor or a voltaic cell through thecoil.

The device called Arago’s disc consists of a hori-zontal copper disc with a central vertical spindle;the disc can be spun by a belt and pulley. Above it,and separately mounted, is a pivoted compassneedle. When the disc is spun, the needle follows it;if the rotation of the plate is reversed, the needleslows, stops and also reverses. The effect is due toeddy currents in the disc, although Arago did notknow this. The value of his experiments in electric-ity and magnetism is that they later inspiredFaraday to make his major discoveries.

Arago was a close friend of Humboldt for half acentury; the latter wrote of Arago as ‘one giftedwith the noblest of natures, equally distinguishedfor intellectual power and for moral excellence’.

Arber, Agnes, née Robertson (1879–1960) Britishbotanist: her careful investigations of plant struc-ture made a lasting contribution to botanicalknowledge.

Agnes Robertson became an enthusiastic studentof botany while attending the North LondonCollegiate School for Girls. The school was unusu-ally good in its teaching of science and it was therethat she learned about plant anatomy and classifi-

10

Archimedes (of Syracuse) [ah(r)kimeedeez](c.287–212 bc) Sicilian Greek mathematician andphysicist: pioneer of statics and hydrostatics.

A member of a wealthy noble family, Archimedesstudied in Alexandria but returned to Syracuse inSicily, whose king Hieron II was a relative.Archimedes was the finest scientist and mathe-matician of the ancient world but little is firmlyknown of his life, although legends exist. He isknown to have used experiments to test his theo-ries, which he then expressed mathematically. Hedevised weapons against the Roman fleet when itattacked Syracuse in 215 bc; the Romans took thecity in 212 bc and Archimedes was killed. Cicerofound and restored his tomb in 75 bc.

In mathematics, Archimedes used geometricalmethods to measure curves and the areas and volumesof solids (e.g. the volume of a sphere, 4πr3/3); he used aclose approximation for π (he showed it to be between223/71 and 220/70) and developed his results withoutthe use of the calculus (which came nearly 2000 yearslater). He used a new notation to deal with very largenumbers, described in his book Sand-Reckoner.

In applied mathematics, he created mechanics;his innovations ranged from the directly practical(eg the compound pulley and the Archimedianscrew) to derivations of the theory of levers and cen-tres of gravity, forming the basic ideas of statics. Hefounded hydrostatics, contributing ideas whichincluded specific gravity and the Archimedes prin-ciple: this states that when a body is wholly orpartly immersed in a fluid, it experiences a buoyantforce (upthrust) which shows itself as an apparentloss of weight, equal to the weight of fluid dis-placed. (The fluid can be liquid or gas.)

Archimedes’ water-screw for moving water up aslope has been claimed to be the helical device fromwhich screws of all kinds developed: screw deviceswere certainly known to Hero, who was thought byPliny, incorrectly, to have originated the idea ofthis invaluable mover and fixer. The place of thehelix in molecular biology was unknown until over2000 years later.

Gauss thought that Archimedes had onlyNewton as a mathematical equal.

Aristarchus (of Samos) [aristah(r)kuhs] (c.320–c.250tbc) Greek astronomer: proposed heliocentriccosmology; and made first estimate of astro-nomical distances.

Although little is known of the life of Aristarchus,he was perhaps the first to propose that the Earthmoved around the Sun, in contrast to the acceptedthinking of his day. He also attempted to estimatethe relative distances of the Sun and the Moon,using the fact that when the Moon is exactly halflight and half dark it forms a right angle with theEarth and the Sun. Although his result was wildlyinaccurate, it was the first experimental attempt atmeasuring an astronomical distance. His workmakes him the most original of the Greek astrono-mers and in the modern view the most successful.His heliocentric scheme was made precise byCopernicus in the 16th-c.

Armstrong, Edwin Howard

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Aristotle [aristotl] (384–322 bc) Athenian (Greek)philosopher and naturalist: provided philosophicalbasis of science which proved dominant for 18 cen-turies.

Son of the court physician at Macedon, Aristotlewas orphaned early and moved to Athens, where hebecame Plato’s finest pupil. In 342tbc he returnedto Macedon as tutor and then adviser to Philip II’sson Alexander, who became Alexander the Great.Later he became a public teacher in Athens, using agarden he owned (the Lyceum). His collected lec-tures cover most of the knowledge of the time in science, and some other fields such as logic andethics (but not mathematics), and include much ofAristotle’s own work in zoology and anatomy. Hewas a first-class naturalist and marine biologist,whereas his record of older views in physics andcosmology contained many misguided, althoughdefensible, ideas. Aristotle’s books survived in theArab world, and re-entered Christian Europe inLatin translation in the 12th and 13th-c. It was nofault of the writer that his books were accordedalmost divine authority, and some of the erroneousideas were not easily displaced (eg that bodies ‘outside the sphere of the Moon’ are perfect andunchanging). His status as a major figure in philos-ophy has never changed.

Armstrong, Edwin Howard (1890–1954) US radioengineer.

Many teenagers build radio receivers; Armstrongwas unusual in also making a transmitter before hebecame a student of electrical engineering atColumbia. Then, during the First World War, heworked on the problem of locating aircraft bydetecting the stray radio emission from their igni-tion systems; a side-result was his development of thesuperheterodyne circuit, which made radio tuningmuch easier and helped make radio popular. From

Aristotle: from a bas-relief found in the collection ofFulvius Ursinus.

Armstrong, Neil

Arrhenius, Svante (August) [arayneeus] (1859–1927) Swedish physical chemist: proposed theory of ionic dissociation; he foresaw the greenhouseeffect in 1896.

Arrhenius came from a family of farmers, and hisfather was an estate manager and surveyor. Heattended Uppsala University and did very well inphysical science, and then moved to Stockholm towork for a higher degree on aqueous solutions ofelectrolytes (acids, bases and salts); he concludedthat such solutions conduct a current because theelectrolyte exists in the form of charged atoms orgroups of atoms (positive cations and negativeanions), which move through the solution when acurrent is applied. He obtained good evidence forthis during the 1880s but his theory was only slowlyaccepted, especially in Sweden. (Since then, furtherevidence has substantially confirmed his views,and has also shown that salts are largely ionic evenin the solid state.) In 1903 he was awarded theNobel Prize for chemistry. His work was surpris-ingly varied and included immunology, cosmicphysics and the first recognition of the ‘greenhouseeffect’ (heat gain by the atmosphere due to carbondioxide). He also studied the effect of temperatureon the rates of chemical reactions, and showed that

k = A exp (– E/RT)where k is the rate constant for the reaction, A is

the frequency factor, E is the activation energy forthe reaction, R is the gas constant and T the Kelvintemperature (this is the Arrhenius equation).

Aston, Francis William (1877–1945) British chemi-cal physicist: invented mass spectrograph.

After graduating in chemistry in Birmingham,Aston worked for 3 years as a chemist in a nearbybrewery. In his leisure at home he designed andmade an improved vacuum pump and in 1903 heturned to physics as a career, working on dischargetubes in Birmingham and, from 1909, in Cambridgeas J J Thomson’s assistant. They worked on the ‘pos-itive rays’ which Thomson had found to be gener-ated within one part of a vacuum tube throughwhich an electric discharge is passed. Aston andThomson believed that their experiments on posi-tive rays from tubes containing neon gas showed itto contain atoms with masses of about 20 and 22units. Proof of this, and extension of the work, wasinterrupted by the First World War.

Aston’s war work at the Royal Aircraft Establish-ment linked him with a talented group of physicists,including Lindemann, Taylor, Adrian, G P Thomsonand H Glauert (1892–1934). Soon after the war hedevised a mass spectrograph which was able to sepa-rate atoms of similar mass and measure these massesaccurately (his third spectrograph to 1 in 105; 1 in 109

is now easily available on commercial machines). Aston showed clearly that over 50 elements consistedof atoms of similar but different relative atomic mass(eg for S; 32, 33 and 34) but the same atomic number(ie nuclear charge). The Aston rule is that the massesare approximately integers; the apparent deviationsof relative atomic masses of the elements from integers results from the presence of these isotopes.

1934 he taught electrical engineering at Columbiaand by 1939 he had devised a major advance inradio transmission: FM.

Previously, radio signals conveyed speech or musicby changes in the amplitude of the carrier radiowaves (amplitude modulation, AM). The snag of thisis that electrical storms and appliances introducerandom noise (static). Armstrong’s method was tovary the carrier signal by changes in frequency (fre-quency modulation, FM) which is largely free frominterference. This requires use of high frequenciesthat have only a limited range, but it has become thepreferred mode for radio and TV use.

Armstrong, Neil (Alden) (1930– ) US astronaut:the first man to walk on the Moon.

This most dramatic act of manned explorationoccurred on 20 July 1969 and represented success ina curious international contest. In 1957 the USSRhad placed an unmanned spacecraft (Sputnik) intoorbit, and this blow to national self-esteem in theUSA led to President Kennedy in 1961 committinghis country to a manned moon-landing within thedecade.

The Manned Spacecraft Centre, at Houston, TX,worked for this result and success came with theApollo 11 flight commanded by Armstrong. He hadserved as a naval aviator in the Korean War andlater studied aeronautical engineering at PurdueUniversity, IN, and the University of SouthernCalifornia before joining the organization whichbecame NASA (the National Aeronautics and SpaceAdministration) in 1955. By 1969 he was wellequipped to land a spacecraft on the Moon, underhis manual control. The scientific results of thevisit were limited and were exceeded by the resultsfrom unmanned space probes. Armstrong leftNASA in 1971 and, after a period as professor ofaeronautical engineering at Cincinnati, OH,became a businessman from 1980.

Neil Armstrong lands on the Moon in 1969 from Apollo11, with Edwin ‘Buzz’ Aldrin who is holding the edge ofthe US flag.

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Panel: The exploration of space

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THE EXPLORATION OF SPACE

To transform dreams of space travel into reality andto explore space directly, rockets are needed: theirpower overcomes the force of gravity which pulls allobjects towards the centre of the Earth.

Konstantin Edvardovich Tsiolkovsky (1857–1935)was the first to suggest multistage rockets. He alsosuggested the use of liquid hydrogen and liquidoxygen as propellants, burned in a combustionchamber. Independently, GODDARD successfully maderockets fuelled by gasoline (petrol) and liquid oxygen.In 1937, one of these reached a height of about 2.5km/1.6 mi. Hermann Oberth (1894–1990) consideredrocket propulsion and guidance systems theoreti-cally. His work led to the ethanol/liquid-oxygen-fuelled German V2 rocket that was perfected by VON

BRAUN during the Second World War.After the war von Braun worked in the USA, devel-

oping rockets that could carry instruments into theuppermost part of the Earth’s atmosphere. In 1954 heproposed using the Redstone rocket, similar in designto the V2, to put a satellite weighing 2 kg into orbitaround the Earth. In the event, the first US satellite,the 14 kg Explorer 1, was launched by a Jupiter Crocket early in 1958. Using Geiger counters aboard it,VAN ALLEN discovered the radiation belts of energetic,charged particles that surround the Earth, and whichnow carry his name.

The first Earth-orbiting satellite was the 84 kgSoviet Sputnik 1. This was launched on 4 October1957, using kerosene (paraffin oil)/liquid-oxygenfuel. The rocket engines were designed by a team ledby Sergei Pavolvich Korolev (1907–66). His rocketsalso powered the first manned space flight on 29April 1961 by Yuri Gagarin (1934–68), whose flight inthe Vostok 1 capsule (4.7 tonnes) around the Earthlasted 108 minutes. Furthermore, Korolev’s rocketslaunched the first space probe, Venera 3, to land onthe planet Venus.

With the Soviet Luna programme and the USRanger programme, television pictures of the Moon’s surface were sent back to Earth before thespacecraft crashed into the Moon. Later, the softlandings of Surveyor spacecraft were a prelude toAmerica’s Apollo programme. It was during theApollo 11 mission that NEIL ARMSTRONG became thefirst human being to set foot on the Moon, on 20 July1969, speaking the now famous prepared words‘that’s one small step for man; one giant leap formankind’. The other Apollo 11 astronauts wereMichael Collins (1930– ) and Edwin E (Buzz) Aldrin(1930– ).

For the Apollo programme, the gigantic 110 m-tallSaturn V rocket was developed by von Braun’s team.It had to send 40 tonnes towards the Moon at aspeed exceeding 11 km s–1. It was needed to meet US

President John F Kennedy’s objective, stated in 1961,‘that this nation should commit itself to achieving thegoal, before this decade is out, of landing a man onthe Moon and returning him safely to Earth’. In suc-cessfully accomplishing this, scientists also investi-gated samples of lunar material, and studied theMoon’s gravitational, magnetic, and seismic proper-ties. The Apollo 15 mission, with David R Scott(1932– ), Alfred M Worden (1932– ) and James BIrwin (1930– ), was the first to use a battery-powered lunar rover to travel up to 103 km/63 mifrom the landing site. The Apollo missions, throughthe rock samples they provided, led to the generalacceptance, from 1984, of a novel theory of theMoon’s origin, as due to impact on the early Earth ofa Mars-sized planetesimal, the resulting debris coa-lescing to form the Moon.

Also during the 1960s, many Soviet cosmonautsand American astronauts orbited the Earth. The firstAmerican astronaut to do so was John H Glenn(1921– ), later a senator and by virtue of his secondspaceflight in October 1998, the oldest astronaut. InFebruary 1962 he travelled three times round theworld in less than 5 hours in his Mercury Friendship 7capsule, which was launched by an Atlas rocket.Confidence was building up as L Gordon Cooper(1927– ) survived in space for more than 24 hoursaboard the Mercury Faith 7 capsule during May 1963.Aboard Vostok 6, Valentina Tereshkova (1937– ) was the first woman in space, in June1963. In March 1965, Aleksei Leonov donned aspacesuit to emerge from Voskhod 2, a three-manspacecraft, and to walk in space for the first time.Edward H White (1930–67) became the firstAmerican to walk in space 3 months later, this timefor 21 min. In 1965 and 1966, 10 two-man Geminimissions were launched by Titan 2 rockets, withArmstrong on Gemini 8, Michael Collins on Gemini10, and Buzz Aldrin on Gemini 12. The Gemini pro-gramme demonstrated that humans could surviveand operate in space for at least 2 weeks, and thatone space vehicle could rendezvous and dock withanother. Both astronauts and flight control crews onthe ground gained valuable experience for the Apollo programme.

Polar-orbiting satellites were used during the1960s for research on both the Earth’s atmosphereand the near-Earth space environment. Clouds wereobserved from the Tiros satellites, leading toimproved weather forecasts. The Transit navigationalsatellite and Echo telecommunications satellite pro-grammes commenced in 1960. Remote sensing of theEarth’s surface for a variety of resource studies wassuccessfully begun in 1972 with Landsat 1. Onimages taken from the Ikonos satellite, launched inSeptember 1999, objects with a size of only 1m or socan be picked out.

Panel: The exploration of space

From Earth-orbiting satellites in highly eccentricorbits, Norman F Ness (1933– ) discovered andinvestigated the magnetopause, the boundarybetween the Earth’s magnetic field and the inter-planetary medium. This had been postulated byCHAPMAN in 1931. Konstantin Gringauz (1918–93)found the plasmapause, the outer boundary of theEarth’s topside ionosphere, in 1963, and Lou A Frank(1938– ) observed the rings of auroral light aroundthe Earth’s magnetic poles from the DynamicsExplorer 1 satellite.

Realizing the 1945 idea of CLARKE, a Syncom 2telecommunications satellite was launched into geo-stationary orbit in July 1963. At an altitude of 36 000km/22 370 mi above the equator, the orbital period isone day, and so the satellite always remains above acertain geographical position. With at least threesuch satellites, point-to-point communications arepossible anywhere in the world (except for the polarregions). The geostationary orbit is also invaluablefor making continuous meteorological observationsover most of the Earth.

From 1970s onwards, the USA explored the planetsof the solar system with Mariner, Pioneer, Viking andVoyager spacecraft. Striking photographs wereobtained and many scientific investigations pursued.The USSR concentrated on carrying out detailedstudies of Mars and Venus. Detailed knowledge of theplanets was vastly increased by these programmes.

During 1973, several American scientists workedfor weeks at a time in Skylab, an orbiting laboratory.First they corrected several mechanical problems with their equipment. Their subjects of study rangedfrom stellar astronomy and solar physics, to thebehaviour of substances under almost weightlessconditions, and the physiological effects of space onastronauts. From 1967, the then USSR conductedsome 60 manned space flight missions, the longestlasting more than a year. In the Salyut or Cosmosspacecraft and, after 1986, the Mir space station,they accumulated a wealth of practical experienceacross many scientific and technological disciplines.Svetlana Savitskaia (1948– ) worked outside theSalyut 7 space station for nearly 4 hours in July 1984,the first time that a woman performed extravehicularactivity (EVA). The first British cosmonaut, HelenSharman (1963– ), worked aboard Mir for a weekin 1991, and the second, Michael Foale (1957– )aboard the US Space Shuttle in 1992 and 1999, andMir in 1997.

The US Space Shuttle flew for the first time in April1981. It is a recoverable and reusable launch vehiclerather than an expendable rocket. During launch itsthree main engines, fuelled by liquid hydrogen andliquid oxygen, are supplemented by two solid fuel(polybutadiene) rocket boosters. The Shuttle’s cargo

bay is vast, 18 m/59 ft long and 4.56 m/15 ft diameter.Once in space, the cargo of satellites can be launched.Alternatively, the cargo bay can house a laboratory,such as the European Spacelab, in which experimentsare performed during the mission, which typicallylasts 10 days. Ulf Merbold (1941– ) was the firstEuropean astronaut aboard Spacelab at the end of1983. The Soviets used a rather similar space shuttle,called Buran (‘Snowstorm’). This was launched for thefirst and only time in November 1988.

European, Chinese, Japanese and other nationalspace programmes developed since the 1960s to complement the superpowers’ space programmes.The Ariadne, Long March and Lambda or Mu rocketslaunched a wide variety of both civil and militarysatellites with scientific or technological payloads. Forexample, both Europe and Japan sent spacecraft(Giotto, and Suisei and Sakigake, respectively) as wellas the Soviet Vega probes, to study HALLEY’S cometwhen it neared the Sun in 1986. The European SPOT(Satellite pour l’observation de la terre) satellites haveexcellent spatial resolution and colour discriminationfor geological and cartographic remote-sensing inves-tigations of our planet. Besides downward-lookinginstruments to investigate such phenomena as theozone hole and volcanoes, telescopes can view out-wards to investigate space across the electromagneticspectrum at wavelengths where the atmosphereabsorbs radiation. New insights into the universe, andits origin, are obtained. Although initially plagued byan instrumental defect, the shuttle-launched Hubblespace telescope, when repaired in orbit in 1994, gavesuperb observations.

The space nations are currently working towardsan International Space Station and are consideringthe benefits of a manned mission to the Moon and/orMars. The USA is forging ahead with its internationalspace station, Freedom, and is considering the bene-fits of a manned mission to the Moon and/or to Mars,as well as smaller satellites dedicated to solving par-ticular scientific problems. International collabora-tion will undoubtedly be the hallmark of future spaceexploration.

For the future, tele-communications satellites will transfer Internet traffic, and constellations of low Earth-orbiting satellites may be introduced.Europe is developing a satellite system for navi-gation, known as Galileo. There are hopes that new technologies will lead to very much cheaperaccess to space – that is the key to its future commercialization. Perhaps the most exciting futuremissions are to Mars, with launches planned everytwo years, investigating whether or not life everexisted there.

Prof M J Rycroft, CAESAR Consultancy, Cambridge

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Aston found that isotopic masses are not exactlyintegral (by about 1%) and he related the discrepancy(the ‘packing fraction’) to the force binding thenucleus together. Atomic energy generation fromnuclear reactions, on Earth or in the stars, can be cal-culated from packing fractions.

The modern mass spectrograph has played a cen-tral part in nuclear physics and radiochemistry,and more recently in exact analysis in organicchemistry. Aston was a ‘one device’ investigator,but he chose a device whose value has beenimmense.

He was a shy man, a poor teacher, with a passionfor sports and for sea travel. He won the Nobel Prizefor chemistry in 1922.

Atiyah, Sir Michael (Francis) [atty-ah] (1929– )British mathematician.

Atiyah, the son of a Lebanese father and a Scottishmother, attended schools in Cairo and Manchesterbefore his military service and then became a student, and later a fellow, of Trinity College,Cambridge. Further work at Princeton and Oxfordfollowed, and led to professorships at both.

In 1963 he developed the Atiyah–Singer indextheorem, and his subsequent publications in topol-ogy and algebra have contributed to a variety ofareas in pure mathematics. He developed furtherthe theory of complex manifolds, which hadstarted with the Riemann surface (a multilayeredsurface) being used to understand multivaluedfunctions of a single complex variable. Atiyah con-sidered what happened when there was more thanone complex variable. He received the Fields Medalin 1966 primarily for his work on topology.

The Fields Medal is awarded every four years totwo, three or four mathematicians under the age of40 and having outstanding distinction and promisein mathematics. The Canadian mathematicianJohn Fields initiated, and provided money for, thisinternational medal for high mathematical ability.The first medals were awarded in Oslo in 1936; andit is recognized as the mathematical equivalent of aNobel Prize. Later Atiyah renewed interest inquaternions (see Hamilton) by showing their rela-tionship with string theory, now widely used inmathematical physics. From Oxford he returned toCambridge as Master of Trinity College and directorof the Isaac Newton Institute for MathematicalSciences, in 1990.

Atkins, Anna, née Children (1799–1871) Britishbotanist: the first to use photography to illustratescientific studies.

Anna was the only child of J G Children, a Fellowof the Royal Society whose wife had died shortlyafter Anna’s birth. Her father was a friend of theHerschel family and Anna knew John Herschelfrom childhood. She had a close relationship withher father and shared his scientific interests. Nodoubt this position helped her acceptance in themale scientific circle. She was a skilled illustratorand provided over 200 drawings for her father’stranslation of Lamarck’s book The Genera of Shells,published in 1823. Anna married J P Atkins in 1825;

Auerbach, Charlotte

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there were no children and she continued her sci-entific interests and collaboration with her father.Children chaired the Royal Society meeting at whichTalbot announced his ‘calotype’ photographicprocess, and father and daughter took up the processenthusiastically. In the same year she became anactive member of the Botanical Society of London.

The calotype process was difficult (partly becauseTalbot’s information was inadequate), but in 1842Herschel described his ‘cyanotype’ process. To illus-trate her large collection of algae Anna Atkinsturned to photography. As she explains in her pref-ace ‘The difficulty of making accurate drawings ofobjects as minute as many of the Algae andConfervae, has induced me to avail myself of SirJohn Herschel’s beautiful process of Cyanotype, toobtain impressions of the plants themselves.’ Shemade contact photograms of algae, totalling 389pages of illustration and 14 of handwritten text,and making more than a dozen copies of the whole,which were sent to scientific friends and institu-tions. And so with her Photographs of British Algae:Cyanotype Impressions (3 vols, 1843–53) she becamethe first to apply photography to illustrate scien-tific studies, predating Talbot’s Pencil of Nature(1844–46), although the latter includes pho-tographs made with a camera. Atkins’s work is bothpermanent and suited to its subject, with seaweedsshown as paler images on a rich blue background.

Auerbach, Charlotte [owerbakh] (1899–1994)German–British geneticist: discoverer of chemicalmutagenesis.

Lotte Auerbach, born in Germany and the daugh-ter and grand-daughter of scientists, herself stud-ied science at four German universities and thentaught in schools in Berlin until, in 1933, all Jewishteachers were dismissed. She escaped to Edinburgh,followed by her mother, worked for a PhD andobtained a lowly job at the Institute of AnimalGenetics there, becoming a lecturer in 1947.

Discussions with the geneticist H J Müller led herto study mutation in animal cells (a mutation is achange, spontaneous or induced, in a gene or a

Elizabeth Anderson

Panel: Global warming

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GLOBAL WARMING

Before the industrial revolution (roughly pre-1800)there had been large regional or global changes inclimate: notably a series of ice ages. The last ice ageended about 20 000 years ago, and we now live in aninterglacial period. These pre-1800 changes, resultingfrom causes such as change in solar radiation, or dustand gas from volcanoes, owe nothing to human activ-ity. However, since the mid-19th-c human activity hasplayed an increasing part. Over a century before thiswas considered, the idea of the ‘greenhouse effect’ wasborn. FOURIER, in 1827, recognized that the Earth’satmosphere acts somewhat like the glass of a green-house in raising the temperature, and TYNDALL about1860 showed that water vapour and carbon dioxide(CO2) are important in the matter. The Sun’s radiation ispartly reflected by clouds before it reaches the Earth,but the solar energy that arrives warms it; nearly 300 W m–2 on average. The Earth in turn re-radiates energy,but mainly in the longer wavelength infrared region;this radiation is strongly absorbed by water vapour andCO2 (0.03% of the atmosphere) and so the atmosphereabsorbs the radiation and re-emits much of it back toEarth. The net result is that the atmosphere has a blan-keting effect akin to glass. It keeps the Earth some 20˚ Cwarmer than it would be without the effect. The mainconstituents of air, nitrogen and oxygen, do not absorbin the infrared.

In 1896 ARRHENIUS calculated that doubling the atmospheric CO2 content would increase the globalaverage temperature by between 5 and 6˚ C; a resultclose to modern values based on more refined calcula-tion. In 1940 G S Callendar calculated the warming dueto a smaller increase in CO2, which he estimated asarising from burning fossil fuels (coal and oil). Neitherof these calculations aroused very much general interest at the time.

In 1957 R Revelle (1909– ) and H E Suess (1909– ) of the Scripps Institute of Oceanography, CA, notedthat mankind’s ever-increasing contribution of CO2 tothe atmosphere constituted a global climatic experi-ment, whose progress and outcome needed study.Measurement of atmospheric CO2 levels began in thatyear at Mauna Kea in Hawaii, and other studies followed.

Water and CO2 are the main natural greenhousegases. The former is outside human control, as issome CO2 emission (eg from volcanoes). But muchCO2 emission is now man-made, by burning of fuels.Of course CO2 is absorbed by green plants for photo-synthesis, a process diminished by human deforesta-tion, especially in the tropics; CO2 is also absorbed by the oceans. Historically, atmospheric CO2 hassteadily increased since 1800, as shown by the graph(Figure 1).

Another important greenhouse gas is methane,

CH4, ‘marsh gas’. As the last name implies it is gener-ated by bacterial action on wet organic matter in lakes,peatland, and increasingly in man-made landfillrubbish sites, and reservoirs. It is also released in thecoal and oil extraction industries, and from termites,and both ends of cattle by enteric fermentation of theirdiet. Itself a potent greenhouse gas, it is ultimatelyconverted to CO2 in the atmosphere by oxidation.

From about 1980 the Earth as a whole has seenmany unusually warm years and a high incidence ofextreme climatic events – droughts, floods and storms.Figure 2 shows temperatures from 1860 to 2000; andwhen allowance is made for natural variations in solarenergy reaching the Earth’s surface, the trend roughlycorrelates with the increase in CO2. Sophisticatedstudies led the IPCC in 2000 to conclude that man-made additions to the atmosphere, the ‘enhancedgreenhouse effect’, provides the dominant cause ofthis global warming.

The IPCC conclusion is that on present trends theglobal average temperature will rise by about 5˚ C. Thecertain and probable effects of this will be dramatic,but difficult to predict in detail. Positive and negativefeedback, and interactions between many of theprimary effects of climate change make the overall cli-matic change a complex case for modelling.

For example, Europe in general will become warmerby 2100, but for the UK the position is less certain: ifchange in ocean currents diverts the Gulf Stream(which makes Britain’s climate milder than its latitudewould imply) this greatly affects prediction. However,some major effects are clearly foreseeable. Agriculturalpractices will need to change over large areas; diseasepatterns will alter, as will the availability of fresh water.

A dramatic and predictable effect will be that onsea level. This will rise in part because of simple expan-sion of water with rise in temperature; and alsobecause of melting of glaciers and mountain ice caps,and of polar ice, notably the Antarctic continent. Sealevel is predicted to rise between 60 cm and 1 m by2100. Worldwide, half of humanity lives in coastalareas. Some islands will be inundated, as will much of

Fig. 1. The increase of atmospheric carbon dioxide since1700 showing measurements from ice cores in Antarctica(squares) and, since 1957, direct measurements from theMauna Loa observatory in Hawaii (triangles).

Panel: Global warming

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Bangladesh, the Nile delta in Egypt, and large areas inthe USA and China. The Netherlands has at least theadvantage of experience, and should be able toenhance existing technology and use experience notavailable in other areas, where population surges willresult from inability to control land loss.

Attempts to alleviate these huge global problemshave led to calls for reduction of CO2 emissions world-wide, or at least (and more realistically) reduction of therate of CO2 increase. The burning of fossil fuels (coaland gas) for domestic heating, industrial power use,and transport are clear targets for reduction: the indus-trialized northern hemisphere emits most CO2 but thedevelopment of industry in Russia, China and India willworsen the problems. More efficient usage, and betterinsulation, can only slightly reduce CO2 emissions. Soalso will contributions of renewable ‘clean’ (ie CO2-free) power from hydroelectricity, geothermal, tide,wind and wave power, despite the enthusiasm of theirsupporters. More substantial help can come from wideruse of nuclear fission power (as in France) but publicconfidence in nuclear safety has been disturbed by theChenobyl disaster and the UK and Germany seemunwilling to follow this path. Nuclear fusion, the sourceof the Sun’s power, has yet to prove itself as a practicalearthly power source. If photovoltaic (solar) power togenerate electricity can be further developed, it showsreal promise: it could, for example, be used not only tomeet static needs, but also for all forms of transport.Unless storage batteries can be made much lighter thanexisting types, it is possible that a ‘hydrogen economy’will develop. In this scheme photovoltaic current isused to decompose water to give hydrogen, which isthen liquefied and distributed much as petrol and dieselnow is – but requiring high refrigeration (it boils at–252˚ C). In a vehicle, the hydrogen would feed a fuelcell, re-generating electricity to power a motor. Theonly exhaust product in the cycle would be water. A

full-scale trial in Iceland from 2002 of part of thisscheme, although valuable, is limited in so far asIceland has a small population (276 000) and abundanthydroelectric power to generate hydrogen.

Alternative and very different ideas have also beenput forward; for example TELLER’S group believe thatreflective particles in the upper atmosphere, to reduceincoming solar radiation, could be cost-effective.Another philosophy is offered by the US economistFrances Cairncross (1944– ), who has argued that it ishopeless to try to prevent a massive rise in CO2 emis-sion from the developing world. There at present thefuel consumption is only the equivalent of 1 to 2barrels of oil per person annually, compared with 10for Europeans and 40 for Americans. Her view is thathumanity in the past has adapted to and survivedgreat climatic changes, and can do so again; and thatother globe-wide problems (eg water pollution)‘deserve greater priority than global warming’.

Global warming has become essentially a politicalproblem. For the wealthy and democratic Westernworld and Japan, making the social and economicchanges needed to deal with the foreseeable climaticchange would be political suicide. Good general inten-tions conflict with national interests. Internationalagreements made at Kyoto and elsewhere are limitedin scope and are unlikely to be fulfilled. Fossil fuelinterests, notably in the USA, argue that causes otherthan human activities are responsible for the climaticchanges that are already discernible; and that actionshould be delayed until further evidence is available.But the weight of scientific opinion is clearly different, and scientists generally are dismayed by governmental delay and complacency.

Moving away from high dependency on fossil fuelswould reduce the influence of OPEC on worldeconomies, and defer the not-too-distant date whenfossil fuel supplies become exhausted. IM

Fig. 2. Changes in global average surface temperature (surface air temperatureover land and sea surface temperatures combined) from 1860 to 2000 relative to theperiod 1961–90. The solid curve represents smoothing of the annual values to suppress sub-decadal timescale variations.

Auger, Pierre Victor

sure, contain the same number of smallest particles’.There is now ample evidence that he was right; insome cases (eg the noble gases) the smallest particlesare atoms; for most other gases, they are combina-tions of atoms (molecules). The law gives a directmethod of finding the molecular formula of a gas,and such a formula in turn gives the relative atomicmasses of the elements present in it. Avogadro’s Lawshows that the simple gases hydrogen and oxygenare diatomic (H2 and O2) and that water is H2O (andnot HO as Dalton believed). However, the law waslargely rejected or ignored for 50 years (althoughAmpère accepted it) until Cannizzaro in 1860 con-vinced a Chemical Congress at Karlsruhe of its value.

The SI base unit of amount of substance is themole (which is related to Avogadro’s Law). The moleis defined as containing as many elementary enti-ties (usually atoms or molecules, and specified foreach case) as there are atoms in 0.012 kg of carbon-12. Thus for a compound, 1 mole has a mass equalto its relative molecular mass in grams. Thenumber of entities in a mole, the Avogadro con-stant, NA, is 6.022 × 1023 mol –1; and 1 mole of anyideal gas, at STP (standard temperature and pres-sure), has a molar volume of 22.415 dm3.

For example: since the relative atomic masses(‘atomic weights’) of carbon and oxygen are 12 and16 respectively, a mole of carbon dioxide (CO2) willweigh 12 + (2 × 16) = 44 g, and will have a volume atSTP close to 22.4 dm3.

Ayrton, Hertha, née (Phoebe) Sarah Marks(1854–1923) British electrical engineer; the firstwoman to present a paper to the Royal Society.

Sarah Marks (she later adopted the name Hertha)was the daughter of a Polish Jew who fled toEngland following persecution under the Tsarist

chromosome; such a change in the hereditarymaterial leads to an abrupt alteration in the char-acteristics of an organism). Müller had shown thatX-rays produced mutations: Lotte Auerbach firstshowed that mustard gas ([CH2CH2Cl]2S, used in theFirst World War) did so in the fruit fly, Drosophila.She became an authority on such chemical muta-tions, which have been of great value in researchand in cancer treatment, and she directed theMedical Research Council Mutagenesis ResearchUnit ‘for as long as she could conceal her age fromher employers’, not retiring until 1969. She waselected a Fellow of the Royal Society in 1957.

Auger, Pierre Victor [ohzhay] (1899–1993) Frenchphysicist: discovered the Auger effect.

Auger was educated at the École Normale Supé-rieure and subsequently became professor ofphysics at the University of Paris. After the SecondWorld War he held a succession of posts in Frenchand European science administration and wasdirector general of the European Space andResearch Organization at his retirement.

Auger is remembered for his discovery in 1925 ofthe Auger effect, in which an atom absorbs energyin the form of an X-ray photon, and loses it by emit-ting an electron. Auger spectroscopy uses the effectto yield information about the electronic structureof atoms, particularly if they form part of a crystal.

Avery, Oswald (Theodore) [ayveree] (1877–1955)US bacteriologist: showed that the genetic materialof bacterial chromosomes is DNA.

Born in Canada, Avery went to New York when hewas 10 and remained there for his working life; hequalified in medicine at Columbia in 1904, andfrom 1913 researched in bacteriology at theRockefeller Institute Hospital. His special interestwas pneumococci (the bacteria causing pneumo-nia). In 1928 he was intrigued by the claim of theBritish microbiologist F Griffith (1881–1941) that anon-virulent, ‘rough’ (ie unencapsulated) pneumo-coccus could be transformed into the virulent,smooth (capsulated) form in the mouse by the merepresence of some of the dead (heat-killed) smoothbacteria.

Avery found this so strange that he repeated thework, and also showed in 1944 that the substancethat caused the transformation is deoxyribonucleicacid (DNA). Prudently, he did not go on to surmisethat genes are simply DNA, which was surprisingenough to be accepted only slowly after 1950 andformed the basic idea of molecular biology.

Avogadro, (Lorenzo Romano) Amedio (Carlo)[avohgadroh] (1776–1856) Italian physicist: proposeda method for finding molecular formulae of gases.

Trained in law like his forefathers and working asa lawyer for some time, after 1800 he turned to sci-ence and held professorships in physics for much ofhis life. His fame now rests on one brilliant andimportant idea. He considered Gay-Lussac’s Law ofcombining volumes and with little evidence offereda daring explanation for it in 1811. His idea,Avogadro’s Law, was that ‘equal volumes of all gases,under the same conditions of temperature and pres-

Amedio Avogadro

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