science and scientists, vol.1, abstract algebra - global warming

Abstract AlgebraAbstract Algebra The Science: Ernst Steinitz’s studies of the algebraic theory of ics provided the basic solution methods for polynomial roots, initiatingthe methodology

and Scientists

and Scientists

Volume 1

Abstract Algebra – Global Warming

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MAGILL’S C H O I C E

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Some essays originally appeared in Great Events from History: Science

and Technology Series (1991), The Twentieth Century: Great Events: 1900-2001

(2002), Great Events from History II: Science & Technology (1991), Great Events

from History: The Ancient World, Prehistory-476 c.e (2004), Great Events from

History: The Middle Ages, 477-1453 (2005), Great Events from History: The

Re-naissance & Early Modern Era, 1454-1600 (2005), Great Events from History:

The Seventeenth Century, 1601-1700 (2006) New material has been added.

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Publisher’s Note ix

Contributors xi

Alphabetical List of Contents xvii

Abstract Algebra 1

AIDS 5

Alpha Decay 9

Amino Acids 14

Anesthesia 18

Antisepsis 23

Artificial Intelligence 27

Aspirin 31

Atmospheric Circulation 35

Atmospheric Pressure 39

Atomic Nucleus 42

Atomic Structure 47

Atomic Theory of Matter 50

Australopithecus 55

Axiom of Choice 59

Ballistics 64

Bell Curve 69

Big Bang 74

Binomial Classification 80

Black Holes 84

Blood Circulation 89

Blood Groups 95

Blue Baby Surgery 99

Boolean Logic 103

Bourbaki Project 108

Boyle’s Law 112

Brahe’s Supernova 118

Buckminsterfullerene 122

Calculus 126

Carbon Dioxide 131

Cassini-Huygens Mission 136

Cell Theory 141

v

Celsius Temperature Scale 146

Cepheid Variables 151

Chandrasekhar Limit 155

Chaotic Systems 160

Chlorofluorocarbons 163

Chromosomes 167

Citric Acid Cycle 171

Cloning 175

Compton Effect 179

Conductivity 183

Contagion 187

Continental Drift 192

Copernican Revolution 196

Cosmic Microwave Background Radiation 201

Cosmic Rays 206

Cro-Magnon Man 209

D’Alembert’s Axioms of Motion 213

Dead Sea Scrolls 217

Decimals and Negative Numbers 223

Definite Proportions Law 227

Diffraction 232

Diphtheria Vaccine 236

DNA Fingerprinting 241

DNA Sequencing 248

Double-Helix Model of DNA 251

Earth Orbit 256

Earth’s Core 261

Earth’s Structure 265

Electric Charge 268

Electrodynamics 273

Electromagnetism 277

Electron Tunneling 283

Electrons 286

Electroweak Theory 292

Euclidean Geometry 296

Evolution 300

Exclusion Principle 306

Expanding Universe 310

Extrasolar Planets 315

vi

Science and Scientists

Fahrenheit Temperature Scale 318

Falling Bodies 322

Fermat’s Last Theorem 327

Fossils 329

Fractals 333

Galactic Superclusters 336

Galaxies 340

Galen’s Medicine 345

Galileo Probe 350

Game Theory 355

Gamma-Ray Bursts 359

Gene-Chromosome Theory 363

Genetic Code 368

Geologic Change 373

Geomagnetic Reversals 379

Germ Theory 382

Global Warming 387

vii

Contents

Publisher’s Note

Lucan’s famous dictum that those standing on the shoulders of giantssee farther than the giants themselves applies to no human endeavor morethoroughly than to the “pure” sciences: astronomy, chemistry, biology, ge-ology, mathematics, physics, and the many subdisciplines they have

spawned The three volumes of Science and Scientists documents 245 of the

most important breakthroughs in the history of science, cross-referenced tolink those that built on others, from ancient times to the present day Theseessays are accompanied by biographical sidebars on many of the giants be-hind the discoveries, as well as charts and schematics illustrating many ofthe basic concepts

The disciplines covered here are broad, including Anthropology, chaeology, Astronomy and Cosmology, Biology, Chemistry, Computer Sci-ence, Earth Science, Environmental Science, Evolution, Genetics, Mathe-

Psychology, and Space Science Arranged alphabetically, these essays dress the most important breakthroughs in these fields, ranging from Ab-stract Algebra to Quantum Mechanics, from the Big Bang to X-Ray Astron-omy, from Antisepsis to Viruses

ad-Accompanying the essays are 125 sidebars highlighting the scientistsand their accomplishments An additional 62 charts, diagrams, and draw-ings illustrate the scientific concepts presented It is important to note thattechnological advances and inventions—such as the telephone, the lightbulb, and the airplane—are not addressed here but are covered in the com-

panion Magill’s Choice set Inventions and Inventors (2 vols., 2002)

How-ever, a few “crossover” achievements—such as the Personal Computer, theInternet, and Vaccination—are included in these pages for having had asgreat an impact on the “pure” sciences as on everyday life The coreachievements in space science also appear here, from the Apollo Moonlanding to the International Space Station

Each essay opens with a brief definition of the topic and a summary ofits significance, followed by a list of the central scientific figures The text ofeach essay is broken into sections with concise subheads “See also” cross-references to other essays in these volumes follow, and each essay endswith a listing of core resources for “Further Reading.” All essays were writ-ten by scholars of history or the sciences

At the end of the third volume students and general readers will find alist of the Nobel Prize winners in science (Chemistry, Medicine, and Phys-ics) and a list of useful Web Sites Indexes arrange the essays by Category,list Personages discussed, and end with a comprehensive Subject Index

ix

Lucy Jayne Botscharow

Northeastern Illinois University

Northeast State Community College

David Wason Hollar, Jr

Rockingham Community College

John Panos Najarian

William Paterson College

Marilyn Bailey Ogilvie

Oklahoma Baptist University

Western Washington University

Glenn Ellen Starr Stilling

Appalachian State University

University of Southern Louisiana

Cassandra Lee Tellier

Alphabetical List of Contents

Compton Effect, 179Conductivity, 183Contagion, 187Continental Drift, 192Copernican Revolution, 196Cosmic Microwave BackgroundRadiation, 201

Cosmic Rays, 206Cro-Magnon Man, 209D’Alembert’s Axioms of Motion, 213Dead Sea Scrolls, 217

Decimals and Negative Numbers,223

Definite Proportions Law, 227Diffraction, 232

Diphtheria Vaccine, 236DNA Fingerprinting, 241DNA Sequencing, 248Double-Helix Model of DNA, 251Earth Orbit, 256

Earth’s Core, 261Earth’s Structure, 265Electric Charge, 268Electrodynamics, 273Electromagnetism, 277Electron Tunneling, 283Electrons, 286

Electroweak Theory, 292Euclidean Geometry, 296Evolution, 300

Exclusion Principle, 306Expanding Universe, 310Extrasolar Planets, 315Fahrenheit Temperature Scale, 318Falling Bodies, 322

Fermat’s Last Theorem, 327Fossils, 329

Fractals, 333xvii

Geologic Change, 373Geomagnetic Reversals, 379Germ Theory, 382

Global Warming, 387

Volume 2

Contents, xxvii

Alphabetical List of Contents, xxxi

Gran Dolina Boy, 393

Grand Unified Theory, 397

Kinetic Theory of Gases, 555Lamarckian Evolution, 560Langebaan Footprints, 566Lascaux Cave Paintings, 568Lasers, 572

Lightning, 576Linked Probabilities, 581Liquid Helium, 586Longitude, 590Lucy, 595Magnetism, 600Manic Depression, 604Mars Exploration Rovers, 607Mass Extinctions, 612Mathematical Logic, 616Mayan Astronomy, 620Medieval Physics, 624Mendelian Genetics, 628Microfossils, 633Microscopic Life, 637Mid-Atlantic Ridge, 641Mitosis, 645

Moon Landing, 649Mössbauer Effect, 654Neanderthals, 658Nebular Hypothesis, 662Neurons, 664

Neutron Stars, 671xviii

Science and Scientists

Plutonium, 769Polio Vaccine: Sabin, 773Polio Vaccine: Salk, 777Polynomials, 781Pompeii, 784Population Genetics, 789

Schrödinger’s Wave Equation, 890

Scientific Method: Aristotle, 894

Scientific Method: Bacon, 899

Scientific Method: Early Empiricism,905

Seafloor Spreading, 910Smallpox Vaccination, 914Solar Wind, 918

Space Shuttle, 922Spectroscopy, 927Speed of Light, 932Split-Brain Experiments, 936Spontaneous Generation, 940Stellar Evolution, 944Stem Cells, 950Stonehenge, 955Stratosphere and Troposphere, 960Streptomycin, 965

String Theory, 969Superconductivity, 972Superconductivity at HighTemperatures, 975Thermodynamics: First and SecondLaws, 979

Thermodynamics: Third Law, 983Troy, 986

Uniformitarianism, 991Van Allen Radiation Belts, 995Very Long Baseline Interferometry,998

Viruses, 1002Vitamin C, 1005xix

Alphabetical List of Contents

Science and Scientists

and Scientists

Abstract Algebra

Abstract Algebra

The Science: Ernst Steinitz’s studies of the algebraic theory of ics provided the basic solution methods for polynomial roots, initiatingthe methodology and domain of abstract algebra

mathemat-The Scientists:

Ernst Steinitz (1871-1928), German mathematician

Leopold Kronecker (1823-1891), German mathematician

Heinrich Weber (1842-1913), German mathematician

Kurt Hensel (1861-1941), German mathematician

Joseph Wedderburn (1882-1948), Scottish American mathematician Emil Artin (1898-1962), French mathematician

Nineteenth Century Background

Before 1900, algebra and most other mathematical disciplines focusedalmost exclusively on solving specific algebraic equations, employing onlyreal, and less frequently complex, numbers in theoretical as well as practi-cal endeavors One result of the several movements contributing to the so-called abstract turn in twentieth century algebra was not only the much-increased technical economy through introduction of symbolic operationsbut also a notable increase in generality and scope

Although the axiomatic foundationalism of David Hilbert is rightly ognized as contributing the motivation and methods to this generalization

rec-by outlining how many specific algebraic operations could be reconstructedfor greater applicability using new abstract definitions of elementary con-cepts, the other “constructivist” approaches—of Henri-Léon Lebesgue,Leopold Kronecker, Heinrich Weber, and especially Ernst Steinitz—had

an equally concrete impact on the redevelopment and extensions of ern algebra

mod-Kronecker’s Contributions

Kronecker had unique convictions about how questions on the tions of mathematics should be treated in practice In contrast to RichardDedekind, Georg Cantor, and especially Karl Weierstrass, Kronecker be-lieved that every mathematical definition must be framed so as to be tested

founda-by mathematical constructional proofs involving a finite number of steps,whether or not the definitions or constructions could be seen to apply toany given quantity In the older view, solving an algebraic equation more

Abstract Algebra / 1

or less amounted only to determining its roots tangibly via some formula

or numerical approximation In Kronecker’s view, the problem of finding

an algebraic solution in general was much more problematic in principlesince Évariste Galois’s discoveries about (in)solvability of quartic andhigher-order polynomials For Kronecker, it required constructions of “al-gorithms,” which would allow computation of the roots of an algebraicequation or show why this would not be possible in any given case.Group and Field Theory

The question of finding algebraic roots in general had been of mental import since the prior work of Galois, Niels Henrick Abel, and CarlFriedrich Gauss In particular, these efforts led Abel and Sophus Lie to for-mulate the first ideas of what is now known as the “theory of groups.”Later, Dedekind introduced the concept of “field” in the context of deter-mining the conditions under which algebraic roots can be found Kro-necker was the first to employ the idea of fields to prove one of the basictheorems of modern algebra, which guarantees the existence of solutionroots for a wider class of polynomials than previously considered.The novelty of the field approach is seen from the introduction toWeber’s contemporaneous paper “Die allgemeinen Grundlagen derGalois’chen Gleichungstheorie” (the general foundations of Galois the-ory) Weber first proved an important theorem stated by Kronecker, whichrelates the field of rational numbers to so-called cyclotomic, or Abelian,groups, a subsequently important area of the development field theory.Weber also established the notion of a “form field,” being the field of all ra-tional functions over a given base field F, as well as the crucial notion of theextension of an algebraic field Although the main part of Weber’s paperinterprets the group of an algebraic equation as a group of permutations ofthe field of its algebraic coefficients, Weber’s exposition is complicated bymany elaborate and incomplete definitions, as well as a premature attempt

funda-to encompass all of algebra, instead of only polynomials In his noted 1893

textbook on algebra, Weber calls F(a) an algebraic field when a is the root of

an equation with coefficients in F, equivalent to the definition given by

Kronecker in terms of the “basis” set for F(a) over a.

A central concern of Weber and other algebraists was that of extendingthe idea of absolute value, or valuation, beyond its traditional usage Forexample, if F is the field of rational numbers, the ordinary absolute value

|a| is the valuation The theory of general algebraic valuations was

origi-nated by Kronecker’s student Kurt Hensel when he introduced the concept

of p-adic numbers In his paper “Über eine neue Begründung der

alge-2 / Abstract Algebra

braischen Zählen” (1899; on a new foundation of the algebraic numbers),Weierstrass’s method of power-series representations for normal algebraicfunctions led Hensel to seek an analogous concept for the newer theory of

algebraic numbers If p is a fixed rational prime number and a is a rational

field of rational numbers For every prime number p, there corresponds a number field that Hensel called the p-adic field, where every p-adic num-

ber can be represented by a sequence

At this time, the American mathematician Joseph Wedderburn was dependently considering similar problems In 1905, he published “A Theo-rem on Finite Algebra,” which proved effectively that every algebra withfinite division is a field and that every field with a finite number of ele-ments is commutative under multiplication, thus further explicating theclose interrelations between groups and fields

in-Steinitz on Algebraic Fields

Two years after Hensel’s paper, Steinitz published his major report,

“Algebraische Theorie der Körper” (1909; theory of algebraic fields), whichtook the field concepts of Kronecker, Weber, and Hensel much further.Steinitz’s paper explicitly notes that it was principally Hensel’s discovery

of p-adic numbers that motivated his research on algebraic fields In the early twentieth century, Hensel’s p-adic numbers were considered (by the

few mathematicians aware of them) to be totally new and atypical matical entities, whose place and status with respect to then-existing math-ematics was not known Largely as a response to the desire for a general,

mathe-axiomatic, and abstract field theory into which p-adic number fields would

also fit, Steinitz developed the first steps in laying the foundations for ageneral theory of algebraic fields

Steinitz constructed the roots of algebraic equations with coefficientsfrom an arbitrary field, in much the same fashion as the rational numbers

are constructable from the integers (a X = b), or the complex numbers from

ques-tion of the structure of what are called inseparable extension fields, whichWeber had proposed but not clarified Many other innovative but highlytechnical concepts, such as perfect and imperfect fields, were also given.Perhaps most important, Steinitz’s paper sought to give a constructive def-inition to all prior definitions of fields, therein including the first system-atic study of algebraic fields solely as “models” of field axioms Steinitzshowed that an algebraically closed field can be characterized completely

Abstract Algebra / 3

by two invariant quantities: its so-called characteristic number and its scendence degree One of the prior field concepts was also clarified.

tran-Impact

Although Steinitz announced further investigations—including cations of algebraic field theory to geometry and the theory of functions—they were never published Nevertheless, the import and implications ofSteinitz’s paper were grasped quickly It was soon realized that general-ized algebraic concepts such as ring, group, and field are not merely for-mally analogous to their better-known specific counterparts in traditionalalgebra In particular, it can be shown that many specific problems of mul-tiplication and division involving polynomials can be simplified greatly bywhat is essentially the polynomial equivalent of the unique-factorization-theorem of algebra, developed directly from field theory in subsequentstudies

appli-In 1913, the concept of valuation was extended to include the field ofcomplex numbers An American algebraist, Leonard Dickson (1874-1957),further generalized these results to groups over arbitrary finite fields Per-haps most notably, the French and German mathematicians Emil Artinand Otto Schreier in 1926 published a review paper, which in pointing outpathways in the future development of abstract algebra, proposed a pro-gram to include all of extant algebra in the abstract framework of Steinitz

In 1927, Artin introduced the notion of an ordered field, with the important

if difficult conceptual result that mathematical order can be reduced tionally to mathematical computation This paper also extended Steinitz’sfield theory into the area of mathematical analysis, which included the firstproof for one of Hilbert’s twenty-three famous problems, using the theory

opera-of real number fields

As noted by historians of mathematics, further recognition and tion of the growing body of work around Steinitz’s original publicationcontinued Major texts on modern algebra, such as that by Bartel Leendertvan der Waerden in 1932, already contained substantial treatment ofSteinitz’s key ideas As later pointed out by the “structuralist” mathemati-cians of the French Nicolas Bourbaki group, the natural boundaries be-tween algebra and other mathematical disciplines are not so much ones ofsubstance or content, as of approach and method, resulting largely fromthe revolutionary efforts of Steinitz and others such as Emmy Noether.Thus, the theory of algebraic fields after the 1960’s is most frequently pre-sented together with the theory of rings and ideals in most textbooks.The theory of algebraic fields is not only an abstract endeavor but also,

adop-4 / Abstract Algebra

since the late 1940’s, has proven its utility in providing practical tional tools for many specific problems in geometry, number theory, thetheory of codes, and data encryption and cryptology In particular, the use-fulness of algebraic field theory in the areas of polynomial factonizationand combinatorics on digital computers has led directly to code-solvinghardware and software such as maximal length shift registers and signa-ture sequences, as well as error-correcting codes Together with Noether’stheory of rings and ideals, Steinitz’s field theory is at once a major demar-cation between traditional and modern theory of algebra and a strong linkconnecting diverse areas of contemporary pure and applied mathematics.

computa-See alsoAxiom of Choice; Bell Curve; Boolean Logic; Bourbaki Project;Calculus; Chaotic Systems; D’Alembert’s Axioms of Motion; Decimals andNegative Numbers; Euclidean Geometry; Fermat’s Last Theorem; Fractals;Game Theory; Hilbert’s Twenty-Three Problems; Hydrostatics; Incom-pleteness of Formal Systems; Independence of Continuum Hypothesis; In-tegral Calculus; Integration Theory; Kepler’s Laws of Planetary Motion;Linked Probabilities; Mathematical Logic; Pendulum; Polynomials; Proba-bility Theory; Russell’s Paradox; Speed of Light

Further Reading

Artin, Emil Algebraic Numbers and Algebraic Functions New York: New

York University Press, 1951

Budden, F J The Fascination of Groups Cambridge, England: Cambridge

The Scientists:

James W Curran (b 1944), epidemiologist

AIDS / 5

Joel Weisman (b 1928), physician who, with Dr Michael Gottlieb,

identified the first cases of AIDS

Grete Rask (d 1977), Danish surgeon practicing in Zaire who became

the first documented European to be infected with the AIDS virus

A Mysterious Affliction

In 1976, people in a village along the Ebola River on the border of theSudan and Zaire (later renamed Congo) experienced a virulent and horri-fying disease that came suddenly A trader from the nearby village ofEnzara, suffering from fever and profuse and uncontrollable bleeding, wasadmitted to the teaching hospitals in Moridi Within days of his admission,

40 percent of the nurses and several doctors were stricken By the time theWorld Health Organization officials and U.S Centers for Disease Control(CDC) staff arrived, thirty-nine nurses and two physicians had died fromwhat was being referred to as Ebola fever Later that year, another insidi-ous disease, manifested by malaise, unrelenting pneumonia, skin lesions,and weight loss, was making its rounds in the village of Abumombazi,Zaire, close to the Ebola River

Notable among the first affected in Africa was a Danish surgeon, GreteRask, who had devoted much of her professional life in medical service tothe people of the former Belgian Congo Sterile rubber gloves, disposableneedles and syringes, and adequate blood banking systems were almostnonexistent in the village hospital As the only surgeon in a Zairian villagehospital, Rask often operated on her patients with her bare hands, usingpoorly sterilized equipment

In 1976, Rask developed grotesquely swollen lymph glands, severe tigue, and continuous weight loss and was suffering from diarrhea Later,she labored for each breath and finally decided to return to her native Den-mark to die For months, doctors tested and examined the surgeon butwere unable to explain what was making her sick Doctors could not un-derstand why several health problems were afflicting the frail woman Hermouth was covered with yeast infections, staphylococcus bacteria hadspread in her bloodstream, and her lungs were infected with unknown or-ganisms Serum tests showed her immune system as being almost non-functional She died at the end of 1977

fa-The autopsy revealed that millions of organisms identified as

Pneu-mocystis carinii had caused the rare pneumonia that had slowly ravaged

and suffocated Rask That particular protozoan became the landmark ganism in the identification of the new disease Questions were raised as towhere and how she became infected, but answers were not forthcoming

or-6 / AIDS

About all that was known of this strange new disease was that it depletedthe patient’s immune system, leaving the patient’s body vulnerable to un-usual and rare infections It would soon become known universally as ac-quired immunodeficiency syndrome (AIDS).

Investigating the History of AIDS

Clinical epidemics of cryptococcal meningitis, progressive Kaposi’ssarcoma, and esophageal candidiasis were recognized in Zaire, Zambia,Uganda, Rwanda, and Tanzania This syndrome was termed “slim dis-ease” in these countries because of the sudden unintentional weight loss ofthe affected individuals, resulting in a severely emaciated appearance.Kaposi’s sarcoma, a kind of skin cancer, had become an especially com-mon finding in the affected patients During the same period, similar clini-cal manifestations were noted in the United States, primarily in homosex-

Known AIDS-Related Deaths in the U.S

Source: Statistics are from the U.S Centers for Disease Control, National Center for Health Statistics.

ual males in New York City and San Francisco These men had developedKaposi’s sarcoma of the skin, oral candidiasis, weight loss, fever, andpneumonia.

One of the first identified cases in North America was a Canadian flightattendant, Gaetan Dugas, who would later become known as “patientzero.” In 1978, he developed purplish skin lesions and was informed that

he had Kaposi’s sarcoma and that it was nonmalignant He went about hisregular routines with no further concern After hearing news of more cases

of Kaposi’s sarcoma in the homosexual population, he contacted doctorsAlvin Friedman-Kien and Linda Laubenstein at New York University Hisaffliction then was rediagnosed as malignant cancer In desperation, hewent to bathhouses and engaged in anonymous sex

In Europe, signs of the mysterious disease began to appear among mosexual men who had visited the United States or whose sexual partnershad visited that country The outbreak had also afflicted a number of im-migrant Africans

ho-The CDC embarked on a major investigation to track patients and theirsexual partners in an effort to determine the disease’s causes, its origin, theway it was being spread, and why it was focused on homosexual men.European and African doctors, with assistance from major internationalagencies, were involved, likewise, in the search for answers and to deter-mine why women in Africa were getting sick as fast as the men were

Impact

The virus that causes AIDs would be called the human ciency virus, or HIV, because it attacked the body’s ability to fight infec-tions It was found in the blood and was transmitted through blood trans-fusions It would also be found in the umbilical cord and passed frommother to fetus The virus could be passed through hypodermic needles,endangering the lives of intravenous drug abusers The virus would also

immunodefi-be found in semen and immunodefi-become a threat to the sexual partners of affected dividuals, both men and women In short, the virus with the opportunisticinfections producing AIDS would become the most feared and dreadedepidemic of the twentieth century AIDS came at a time when the priority

in-of the U.S government was to cut spending on domestic affairs

After the first public report of AIDS in 1981, the number of affected viduals began to multiply rapidly Added to the global estimates of per-sons diagnosed with AIDS are an unknown number of dead victims.The virus has now well established itself in the general population, withyoung persons and heterosexual women particularly at risk The estimates

indi-8 / AIDS

of HIV-positive cases worldwide are in the millions Although the number

of persons living longer with HIV in developed countries, where ing drugs are available, has risen, the death toll worldwide has increased,especially in Africa and Eastern Europe The epidemic of infection anddeaths in Africa—where in some nations it is estimated that a third or more

mitigat-of the population has been exposed to the disease—is a grim reminder mitigat-ofhow AIDS can ravage those struggling with ignorance of the disease andlack of access to education and appropriate medical care Even in theUnited States, where mortality from AIDS decreased in the late 1990’s, thedeath toll is again on the rise—a grim reminder that there is no cure, thatavailable therapies do not allow a “normal” lifestyle, and that vigilance isessential to avoid placing oneself, and others, at risk

See alsoHuman Immunodeficiency Virus; Immunology; Oncogenes;Viruses

Further Reading

Check, William A AIDS New York: Chelsea House, 1988.

Drotman, D Peter, and James W Curran “Epidemiology and Prevention

of Acquired Immunodeficiency Dyndrome (AIDS).” In Public Health

and Preventive Medicine, edited by Kenneth Fuller Maxey 12th ed East

Norwalk, Conn.: Appleton-Century-Crofts, 1985

Gottlieb, Michael S., et al CDC Mortality and Morbidity Weekly Review—June

5, 1981 Atlanta, Ga.: Atlanta HHS Publication, 1981.

Ma, Pearl, and Donald Armstrong, eds AIDS and Infections of Homosexual

Men 2d ed Stoneham, Mass.: Butterworth, 1989.

Medical World News—The News Magazine of Medicine—November 23, 1987.

San Francisco, Calif.: Miller Freeman, 1987

Shilts, Randy And the Band Played On: Politics, People, and the AIDS

Epi-demic New York: St Martin’s Press, 1987.

—Margaret I Aguwa, updated by Christina J Moose

Alpha Decay

Alpha Decay

The Science: George Gamow applied the newly developed quantum chanics to the atomic nucleus to explain alpha decay and founded thefield of nuclear physics

me-Alpha Decay / 9

The Scientists:

George Gamow (1904-1968), Russian American physicist

Fritz Houtermans (1903-1966), Austrian physicist

Ernest Rutherford (1871-1937), British physicist

Mysteries of the Atom

In 1911, Ernest Rutherford’s experiments, in which he bounced alphaparticles off the atoms of a very thin gold foil, showed that all the positivecharge and more than 99 percent of the mass of atoms is concentrated in atiny central region of the atom called the “nucleus.” The diameter of thenucleus is one one-hundred-thousandth of the diameter of the atom By

1913, Niels Bohr had developed a model of the atom in which the tively charged electrons orbited the nucleus in specific allowed orbits.Bohr’s model explained Rutherford’s results and accurately predicted cer-tain atomic spectra

nega-Bohr’s theory left an unanswered question: Why are electrons allowedonly in certain orbits? Answering this question showed that electrons mustbehave sometimes like waves and sometimes like particles The laws ofphysics that govern objects that behave like waves and particles at thesame time are called quantum mechanics

In 1928, physicists had just developed mathematical techniques for ing calculations using the newly developed rules of quantum mechanics

do-In major European universities, young physicists eagerly applied tum physics to the behavior of atoms in emitting light and in forming mol-ecules The university at Göttingen in Germany was the center of this activ-ity Waiters in local cafés had standing instructions not to send tablecloths

quan-to the laundry until someone had checked quan-to see that no valuable tions were written on them Study at Göttingen became essential to anystudent who hoped to become a theoretical physicist

equa-The Nuclear Valley

George Gamow came to Göttingen with a quick mind and a formidablesense of humor He already understood the basic principles of quantummechanics and was fascinated by its power to predict atomic behavior Anindividualist to his toes, however, Gamow disliked working in crowded,fashionable fields of physics Since most of Göttingen was working on theapplication of quantum mechanics to atoms, he looked for a new problem.Unlike the atom, the nucleus had been little studied Physicists realizedthat it had positive charge and mass Certain nuclei also spontaneously

10 / Alpha Decay

Alpha Decay / 11

George Gamow: Physicist, Cosmologist, Geneticist

Born March 4, 1904, in Odessa, Russia, George Gamow started his

scientific career as a boy, when his father gave him a telescope for his

thirteenth birthday Little did his father know that his son would one

day become one of the greatest scientists of the twentieth century

After graduating from the University of Leningrad in 1926, Gamow

went to Göttingen, a center for the study of the new quantum

mechan-ics At this time, natural radioactivity was the focus of research of many

of the great physicists of the day, from the Curies to Lord Rutherford,

and Gamow was particularly interested in

its relationship to the atomic nucleus In

1928, he made his first great contribution

when he described quantum tunneling of

alpha particles to explain the radioactive

process of alpha decay His investigation of

the atomic nucleus would take him to

Co-penhagen, where he worked under Niels

Bohr laying the theoretical groundwork for

nuclear fusion and fission

During the 1930’s, Gamow taught at

uni-versities in Copenhagen, Leningrad,

Cam-bridge, Paris, and the United States In

Washington, D.C., he and Edward Teller

worked on the theory of beta decay He also

turned his attention to astrophysics and the

origin of the elements This work led to his

1948 proposal of the “big bang” theory of

the universe, for which he is best known

Gamow was more than a theoretical

physicist, however: Known for his sense of humor and revered by his

students, he was also devoted to education His “Mr Tompkins” series

used science fiction to explain difficult science in a way that anyone—

including Tompkins, whose attention span was notoriously short—

could understand In 1954, inspired by the Watson-Crick DNA model,

he theorized that the order of the DNA molecules determined protein

structure The problem, as he saw it, was to determine how the

four-letter “alphabet” of nucleic acid bases could be formed into “words.”

His “diamond code” paved the way for Marshall W Nirenberg to

crack the genetic code in 1961

In 1956, Gamow settled in Boulder to teach at the University of

Col-orado That year, he received UNESCO’s Kalinga Prize for his

popular-ization of science, and two years later he was married (a second time)

to Barbara “Perky” Perkins, who initiated the George Gamow Lecture

Series after his death, in 1968

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emitted nuclear radiation of various kinds One kind of emission, alphaparticles, had been extensively studied by Rutherford and his collabora-tors They had shown that alpha particles are the nuclei of helium atomsand that they carry two units of positive charge Although it is impossible

to predict when any given nucleus will emit an alpha, the rate at which asample of a particular kind of nucleus emits alphas is characteristic All thealphas emitted from one type of nucleus have a unique energy Further-more, the rate at which alphas are emitted increases as the energy of the al-pha particle increases

Gamow recognized that the large positive charge of the nucleus meansthat an alpha particle is electrically repelled by the nucleus The only waythat alphas can stay inside a nucleus is if they are held in place by a verystrong nuclear force that is not in effect beyond the edge of the nucleus Thesituation is analogous to that of a ball trapped in a valley that rolls up oneside of the hills that trap it Unless it has enough energy to go over the top

of the hill, the ball rolls up hillside and rolls back down If, however, theball could suddenly dig a tunnel through the hill, it would be free of thevalley and would roll down the other side of the hill and out into the coun-tryside The alpha particle is the ball trapped in the nuclear valley by thehills of the nuclear force The electrical repulsion is the other side of the hilldown which the alpha coasts, gathering speed as it goes

Alpha Tunneling

Quantum mechanics predicts that the wave nature of certain particlesallows them to penetrate regions of space where an ordinary particle is ex-tremely unlikely to go In the case of an alpha particle bouncing back andforth inside a nuclear valley, Gamow realized, each time the alpha collidedwith the nuclear energy wall, there was a small probability that its wavenature would allow it to penetrate the nuclear energy wall and escape fromthe nucleus down the electrical hill The probability of penetration in-creased as the energy of the alpha particle increased Gamow put numbersinto this quantum model of the nucleus and predicted the rate at whichalphas were emitted and the way that rate should increase as the energy ofthe alpha increased Like the atom, the nucleus obeyed the laws of quan-tum mechanics

Impact

Gamow’s explanation of alpha decay triggered an idea in the mind ofanother Göttingen physics student, Fritz Houtermans Houtermans asked

12 / Alpha Decay

himself the following question: If alphas can escape from nuclei by ing through the energy wall of the nucleus, cannot nuclei be built fromlighter nuclei when alphas tunnel into heavy nuclei? He realized not onlythat the alpha could be absorbed into the nucleus but also that energywould be emitted in the process At the very high temperatures insidestars, this process could provide a tremendous source of energy and liter-ally make the stars shine It also determined the types of elements thatwere formed from hydrogen and deuterium in stellar interiors Thus,Gamow’s mechanism helped to determine the overall structure of the uni-verse.

tunnel-Gamow’s success in using quantum mechanics to explain alpha decayopened the field of nuclear physics because it showed that nuclei could betreated by the logic of quantum physics The fact that one nucleus emitted

a lighter nucleus indicated that there must be a complex inner structure tothe nucleus Modern physicists are still working to understand that struc-ture

See alsoAtomic Nucleus; Atomic Structure; Atomic Theory of Matter;Compton Effect; Cosmic Rays; Electron Tunneling; Electrons; ElectroweakTheory; Exclusion Principle; Grand Unified Theory; Heisenberg’s Uncer-tainty Principle; Isotopes; Neutrons; Nuclear Fission; Photoelectric Effect;Plutonium; Quantized Hall Effect; Quantum Chromodynamics; QuantumMechanics; Quarks; Radioactive Elements; Wave-Particle Duality of Light;

X Radiation; X-Ray Crystallography; X-Ray Fluorescence

Further Reading

Boorse, Henry A., and Lloyd Motz, eds The World of the Atom Vol 2 New

York: Basic Books, 1966

Born, Max My Life: Recollection of a Nobel Laureate New York: Charles

Scribner’s Sons, 1978

_ Physics in My Generation 2d rev ed New York: Springer-Verlag,

1969

Gamow, George Mr Tompkins Explores the Atom Cambridge, England:

Cambridge University Press, 1944

_ My World Line: An Informal Autobiography New York: Viking

Heisenberg, Werner Nuclear Physics New York: Methuen, 1953.

Rutherford, Ernest The Newer Alchemy Cambridge, England: Cambridge

The Scientists:

Elso Barghoorn (1915-1984), American paleontologist and member of

the United States National Academy of Sciences

J William Schopf (b 1941), American paleontologist and consultant on

extraterrestrial life to the U.S space program

Keith Kvenvolden (b 1930), American organic geochemist and geologist Stanley Miller (b 1930), American chemist

Life in Ancient Rocks

On November 16, 1967, J William Schopf and Elso Barghoorn of vard University and Keith Kvenvolden of the U.S Geological Survey pre-sented a paper to the National Academy of Sciences summarizing theirsearch for traces of amino acids (the proteins that form the basis of life) inthe oldest known sedimentary rocks This team of scientists had analyzedorganic material leached from pulverized black chert (a type of rock) fromthree formations: the 1-billion-year-old Australian Bitter Springs forma-tion, the 2-billion-year-old Canadian Gunflint chert, and the 3-billion-year-old Fig Tree chert from South Africa The latter was the oldest undeformedPrecambrian sedimentary rock known at the time (The Precambrian erabegan about 4.6 billion years ago and ended about 570 million years ago.)The Gunflint locality had already yielded abundant evidence of earlylife in the form of many examples of structurally preserved microorgan-

Har-isms Gunflint was the subject of a classic 1954 paper in the journal Science

by Barghoorn and Stanley Tyler, which announced the first indisputablereports of early Proterozoic microfossils (The Proterozoic is the later oftwo divisions of Precambrian time.) Well-preserved microorganisms werereported in the Bitter Springs formation by Barghoorn and Schopf in 1965

14 / Amino Acids

The fossil evidence for life in the Fig Tree chert was not as compelling, butSchopf and Barghoorn were in the process of examining this material andsaw bacterial microfossils using an electron microscope; they reportedthese findings in 1966.

The types and quantities of amino acids present in the samples were termined by pulverizing carefully cleaned samples of hard, virtually im-permeable chert and leaching any organic material present with varioussolvents The nature of the organic material was determined by gas chro-matography, a method of separating the individual elements in a chemicalmixture Twenty amino acids were identified in all the samples; a twenty-first occurred only in the Bitter Springs formation Concentrations were ex-tremely low and decreased with increasing geologic age Barghoorn andhis colleagues noted that the concentrations of various amino acids in all

de-Amino Acids / 15

Pseudofossils?

In 2002, paleobiologists Martin D Brasier and Owen R Green of the

University of Oxford published a paper in Nature in which they

ques-tioned the widely accepted view that the oldest

microfossils—evi-dence for microorganisms capable of photosynthesis about 3.465

bil-lion years ago—are located in the Apex chert in Western Australia’s

Warrawoona group If this is true, as many paleobiologists believe,

then oxygen-releasing life would have changed Earth’s atmosphere

during this period, setting the environmental conditions for life ever

since

Brasier and Green described the use of new geochemical and other

techniques that encouraged a reevaluation of previous assumptions

Brasier’s group demonstrated that structures similar to microfossils

can be formed through abiotic (inorganic) reactions involving

amor-phous carbon They postulated that microfossils were actually

“pseudofossils” and that J William Schopf and his colleagues should

reconsider their conclusions According to Brasier, “The shapes are far

too complicated to be bacteria .” It is far more likely, he contends,

that the squiggles thought to be microfossils were really caused when

rocks formed from reactions between the carbon dioxide and

monox-ide released by hot, metal-rich hydrothermal vents These reactions

may even have jump-started the amino acids that are the basis of

ter-restrial life

Schopf’s group countered that, if Brasier were correct, the

microfossils would have been found throughout the world The two

camps are still analyzing their data New studies, on both sides,

under-score that the mysteries of early life still remain to be revealed

three samples corresponded to the distribution of amino acids in living ganisms.

or-Because the amino acids occurred with microfossils in samples high inorganic matter, the scientists concluded that microfossils developed at thesame time that chemical evolution produced life, and that this proved theexistence of life as early as 3 to 3.1 billion years ago This also provided evi-dence that amino acids, the fundamental chemical building blocks of cells,had remained essentially unchanged throughout history

Sample for chemical analysis Electrode

It has been shown many times that organic compounds, the beginnings of life, including amino acids, are produced readily within water in sealed flasks containing reducing gases such as carbon dioxide en- ergized by electrical discharges, ultraviolet light, or even shock waves The most famous of these experi- ments, shown here, was conducted in 1953 by Stanley L Miller and Harold C Urey.