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Matter and Energy


  1. 1 Part One. Matter and Energy
    1. 1.1 Division I. Atoms: Atomic Nuclei and Elementary Particles
      1. 1.1.1 Section 111.         The Structure and Properties of Atoms
        1. A. The atomic nature of matter
        2. B. Atomic weights
        3. C. Atomic spectra and the electronic structures of the atom
        4. D. X rays and atomic structure
        5. E. The concept of antimatter
        6. F. The fundamental physical constants: dimensional and dimensionless constants
      2. 1.1.2 Section 112.         The Atomic Nucleus and Elementary Particles
        1. A. The structure of the atomic nucleus and general nuclear phenomena
        2. B. Isotopes: atomic species with the same atomic number but with different atomic masses
        3. C. Radioactive nuclei: their properties and their radiations
        4. D. The neutron as a component of the nucleus and in nuclear reactions
        5. E. Reactions of atomic nuclei
        6. F. The splitting of atomic nuclei by nuclear fission
        7. G. The fusion of atomic nuclei
        8. H. Subatomic, or elementary, particles
        9. I. Effects of the passage of nuclear, or elementary, particles, nuclear radiations, or ionizing radiation through matter
    2. 1.2 Division II.          Energy, Radiation, and the States and Transformation of Matter
      1. 1.2.1 Section 121.         Chemical Elements: Periodic Variation in Their Properties
        1. A. The systematic classification of the elements on the basis of their chemical and physical properties and atomic structures: the periodic law of the elements
        2. B. The groups of the chemical elements in the long form of the periodic table: their occurrence, history, physical and chemical properties, principal compounds, production, and uses
        3. C. Other classifications of the elements or groups of them
        4. D. The origin of the elements and their relative abundances in nature
      2. 1.2.2 Section 122.         Chemical Compounds: Molecular Structure and Chemical Bonding
        1. A. The theory of molecular structure: its history and development
        2. B. Experimental and theoretical procedures for the determination of molecular structures
        3. C. Spectra of molecules
        4. D. The theory of chemical bonding: its development and experimental bases
        5. E. Systems of classification of chemical compounds or substances
        6. F. Inorganic compounds
        7. G. Organic compounds
      3. 1.2.3 Section 123.         Chemical Reactions
        1. A. General considerations of chemical reactions
        2. B. Energy changes in chemical reactions
        3. C. Rates of chemical reactions
        4. D. Mechanisms of chemical reactions
        5. E. Acid–base reactions and equilibria
        6. F. Oxidation—reduction reactions
        7. G. Photochemical reactions
        8. H. Chemical reactions and chemical theory in the synthesis of chemical compounds
      4. 1.2.4 Section 124.         Heat, Thermodynamics, and the Nonsolid States of Matter
        1. A. The principles of thermodynamics
        2. B. The gaseous state of matter
        3. C. The liquid state of matter
        4. D. Solutions and solubility
        5. E. Physical effects at surfaces
        6. F. The plasma state of matter: completely ionized gases interacting with magnetic and electric fields
        7. G. The properties of matter at extreme conditions
        8. H. Transport phenomena
      5. 1.2.5 Section 125.         The Solid State of Matter
        1. A. Crystals and crystallography
        2. B. The theory of the crystalline solid state
        3. C. Ionic crystals
        4. D. Metals
        5. E. Semiconductors and insulators
        6. F. The glassy or amorphous state of matter
      6. 1.2.6 Section 126.         Mechanics of Particles, Rigid Bodies, and Deformable Bodies: Elasticity, Vibrations, and Flow
        1. A. The principles of classical mechanics
        2. B. Celestial mechanics
        3. C. Relativistic mechanics in inertial systems of reference
        4. D. The stress dynamics of elastic materials
        5. E. Vibrations of elastic bodies
        6. F. Fluid mechanics, including gas dynamics
        7. G. Rheological phenomena: deformation and flow
      7. 1.2.7 Section 127.         Electricity and Magnetism
        1. A. The static electric charge
        2. B. Moving charges and electric currents
        3. C. Magnetism
        4. D. The theory of fields in physics
        5. E. The electromagnetic field and the theory of electromagnetic radiation
        6. F. Relativistic electrodynamics
      8. 1.2.8 Section 128. Waves and Wave Motion
        1. A. General wave phenomena and the theory of wave motion
        2. B. Electromagnetic waves
        3. C. Light waves
        4. D. The focusing and imaging of light waves
        5. E. Sound waves
    3. 1.3 Division III.         The Universe: Galaxies, Stars, the Solar System
      1. 1.3.1 Section 131.         The Cosmos
        1. A. The structure and properties of the universe
        2. B. Gravitation: a universal force of mutual attraction that is postulated as acting between all matter
        3. C. Celestial mechanics
        4. D. Properties of the space–time continuum: the astronomical implications of relativity theory
        5. E. The origin and development of the universe
      2. 1.3.2 Section 132.         Galaxies and Stars
        1. A. Galaxies in general
        2. B. The Galaxy: the Milky Way system
        3. C. Star clusters and stellar associations
        4. D. Stars
      3. 1.3.3 Section 133.         The Solar System
        1. A. A survey of the solar system
        2. B. The Sun
        3. C. The planets and their satellites
        4. D. The Earth as a planet
        5. E. The Moon

Introduction to Part One:


The Universe of the Physicist, the Chemist, and the Astronomer

by Nigel Calder


"Give me matter and I will build a world from it." For 200 years since the philosopher Immanuel Kant uttered it, physicists, chemists, and astronomers have striven to make good that boast. That they can now tell an almost unbroken story of events from the birth of the universe to the origin of life on Earth is the cumulative result of many lifetimes spent in careful observation and experiment. Yet even amid this success in updating the first verses of Genesis, new questions nag. Why does familiar matter adopt the forms it does? Are the laws of nature that are known to us enforced throughout the vast, tumultuous universe? What unimaginable worlds of fire or blackness can nature conjure up, quite different from our own?

When men presume to take the fire of the Sun and put it experimentally in a bottle, they forfeit all hope of certainty and repose. Yet the great quest for control over nature starts gently enough. A child at play with building blocks or sand or a rubber ball is a human mind engaged in discovering how matter behaves. Experiments with the rubber ball, for example, reveal laws of reflection. The child finds that the ball will come back to him only if he projects it accurately at a right angle to a flat surface (wall or floor); otherwise it bounces away from him and another child may grab it and interrupt the research program.

If all grown-up children had abandoned this kind of play, the human species would still believe that the Earth was at the centre of the universe, that the planets were propelled by angel-power, and that thunder was the voice of God. But some adults retained the boundless inquisitiveness of the young. Isaac Newton, not the most modest of discoverers, likened himself to a child playing on the seashore. Critics nowadays refer scathingly to the "expensive toys" of the physicists who want many millions of dollars to build a particle accelerator. Not unfairly—a particle accelerator, for all its awesome complexity and cost, is simply a modern way of continuing the experiments with the rubber ball, to see what happens when the ball is very small and travels almost at the speed of light.

By strange paths, play leads to far-reaching results. After the discovery that an electric current creates magnetism, Michael Faraday made a note to look for electricity from magnetism. He played repeatedly with magnets and wires until, ten years later, he discovered electromagnetic induction. Today, giant turbogenerators confirm his discovery 60 times a second, as they feed electric power to our factories and kitchens. In James Clerk Maxwell's hands, Faraday's ever-changing electric currents transformed themselves into mathematical equations predicting the existence of waves that traveled at the speed of light—indeed were light and invisible radiations of a similar kind, including radio waves. Other researchers who were unwittingly taking atoms to pieces came up with a beam of electrons, which inventors turned into a magic pencil; today those waves and electrons enable lesser men to preen themselves on television screens in 260,000,000 homes.

In this latter part of the 20th century, a word-association test for physicist may very well evoke bomb. By coincidence, investigators of the nature of matter and energy stumbled upon a way of breaking open the storehouse of energy in the nucleus of the atom just at the time the human species was entering a period of unprecedented warfare. The swarms of nuclear-powered submarines that cruise with nuclear-tipped, city-killing missiles are a grim enough outcome of the "game." The fact remains that the heart of physics itself is not directed to any such purpose but is an open, cooperative effort by scientists of all nations to understand the material universe we live in.

We inhabit an electric world. It is true that gravity stops us from falling headfirst into the abyss of space; true also that the daylight that powers all life comes from the nuclear reactor that we call the Sun. But of the great set of natural forces known to the physicist—gravitational, nuclear, and electromagnetic—the last, electromagnetism, is the chief governor of events on Earth.

It operates so discreetly, though, that when men started rubbing amber on their sleeves and found it attracted dust, or considered the seeming magic of the north-pointing lodestone, nothing suggested that these were more than curiosities. There was laughter when Benjamin Franklin said that lightning was electric—until he proved it. Nothing suggested that the colour, quality, and chemical behaviour of all familiar matter would be explained by research in electricity and magnetism. But that is in the nature of physics: you ponder the falling of an apple and realize what holds the planets in their courses; you look to see what happens when you pass electric currents through a gas and, in due course, you find out what holds a stone together and why grass is green.

A series of discoveries in the late 19th and early 20th centuries illuminated the hidden mechanisms of our electric world like star shells on a dark night. Diligent work by chemists had shown that all matter was composed of vast numbers of atoms, different for each chemical element and capable of combining in predictable ways to make molecules and crystals. Indeed there was a remarkable pattern in the so-called "periodic table": when the chemical elements were listed by weight, it turned out that elements 3, 11, and 19 . . . all had similar properties; 4, 12, and 20 . . . were also very much alike, and so on.

This pattern made sense only when the physicists discovered the construction of atomic matter. An atom consists of a heavy nucleus surrounded by a number of lightweight electrons exactly neutralizing the electric charge on the nucleus. The electrons group themselves around the nucleus in "shells," like the layers of an onion, each shell being capable of accommodating a definite number of electrons. The outward face of the atom, its outermost shell of electrons, is crucial in determining its chemical behaviour. The number of electrons to be fitted in depends on the charge on the nucleus. In some elements, the metals, there are only one or two easily detachable electrons in the outermost shell. Other elements, the most reactive nonmetals, fall short by only one or two electrons in having a complete outermost shell. These "surplus" and "missing" electrons create a supply-and-demand situation in which atoms combine chemically by exchanging or sharing electrons. The repetition of chemical properties throughout the periodic table arises as one shell of electrons is completed and the next one begins to fill.

The mechanisms sketched in these last few sentences account for almost all the chemical behaviour of all the matter on Earth. The electrical and magnetic behaviour of materials also depends on the arrangements of electrons in their atoms and, in some cases, on the combined effects of many atoms packed together in a crystal. The strength of the chemical bonds formed by electrons, and the related forces between molecules, determine whether materials are solids, liquids, or gases; and they help to fix the strength and flexibility of solids, but in this case the explanations are complicated by the invisible flaws that exist in all materials. The colour of materials is explicable by the "jumps," from one position to another in the vicinity of an atom, which the rules allow an electron to make as the atom, molecule, or crystal absorbs or emits light of particular energy, or colour. Make the same electrons in vast numbers of atoms "jump" the same way simultaneously and you have a very intense laser beam.

Light and its invisible counterparts—radio waves, infrared, ultraviolet, and X-rays—are the purest form of energy. These "electromagnetic radiations" are created by the jerking of electrons, sometimes quite gently, as in a radio antenna, and sometimes very fiercely, as when a beam of fast-moving electrons is suddenly halted by the target in an X-ray tube. The normal "jumps" of electrons in atoms are of intermediate intensity. All these radiant forms of energy can travel through empty space, for example from the Sun to the Earth.

But energy can readily change from one form to another. Sunlight captured by green leaves is converted into the chemical energy of plant-stuff. Coal is plant-stuff buried millions of years ago when continents collided, and a boiler can convert the chemical energy of coal into a scalding jet of steam that turns the blades of a turbine—these are forms of kinetic energy, the energy of directed movement. Using Faraday's trick, the turbine can generate electrical energy. At the end of this chain of transformations, you can switch on the electrical energy and reconvert it to light energy, thereby enjoying the benefits of sunlight after the Sun has set.

The vibrations of sound and the gravitational energy of water about to cascade down a mountainside are other forms of energy. Sooner or later, though, a shout dies away, water comes to rest, the light from your electric bulb is absorbed in the wallpaper. Where has the energy gone? It has been taken up in those random motions of atoms and molecules that we call heat. All energy degrades to meaningless heat eventually.

Unless there were continuous supplies of new energy, life and indeed all interesting activity in the universe would quickly cease. For example, your brain is kept functioning by food—chemical energy produced by sunlight just in the past few months. Those new supplies of energy come from the transformation of matter into energy.

The Sun is a very ordinary star, lying in the suburbs of a galaxy consisting of about 100,000,000,000 stars; we see the rather flat cross section of the galaxy as the Milky Way, a brushstroke of light across the night sky. There is nothing special, even, about our Galaxy; it is just one of vast numbers of galaxies scattered like ships in a great ocean of space.

The universe is a battleground between gravity and nuclear forces. To make a star, gravity sweeps together a mass of hydrogen gas; it becomes hot and nuclear reactions begin. The nuclei of hydrogen atoms combine together to make heavier elements almost, but not quite, as heavy as the sum of the hydrogen nuclei that went into them. The little bit of matter that is lost is converted into a relatively immense amount of energy. It would blow the star apart but for the strenuous restraint of gravity. A balance is struck, and the size and brightness of a star depends on its mass and on how much of its nuclear fuel has been burned. Fortunately, our star, the Sun, is a slow-burner; nevertheless, inexorable physical changes billions of years from now will make the Sun grow to fill the whole of our sky and swallow the Earth.

In a star more massive than the Sun, this "burning" of nuclear fuel proceeds faster and culminates in a vast explosion called a supernova. In the explosion, nuclear reactions proceed apace and make all the different chemical elements. The diverse atoms, heavier than hydrogen, of which our own bodies are constructed, were made in stars that exploded before the Sun was formed. Some of the heavy material was left swirling around the newborn Sun and made the Earth. Radioactive energy stored in some of the elements provided an internal source of heat for the Earth that accounts for volcanoes, earthquakes, and the slow movements of continents. Sunlight stirred the materials on the surface of the Earth into chemical activity. Eventually this activity became organized in peculiar ways, and life began.

So far, so good. But there are new mysteries that are "out of this world," in the sense that matter and energy are involved in events far more violent than anything normally encountered on the Earth or even in the Sun. The paramount questions with which physicists are now wrestling can be paraphrased as follows: Why is hydrogen the raw material of the universe? Experiments with the nucleus of the hydrogen atom—the proton—are undertaken in the big accelerators that transform the stuff of the atomic nucleus into bizarre, short-lived particles. These particles have properties, similar to electric charge, called the hypercharge and the baryon number. For example, the proton itself has, besides an electric charge of +1, a hypercharge of +1 and a baryon number of 1. However the particles may transform themselves in violent interactions, the totals of charge, hypercharge, and baryon number do not change.

Attempting to find out why this partial order remains amid the confused varieties of nuclear matter, theorists are led to the idea that the particles we see consist of combinations of other, quite different particles that they have named quarks. An early success of this theory was the prediction of the existence of a new combination, a particle called the omega minus that eventually turned up in 1964 during an experiment with the big machine at the Brookhaven National Laboratory, Long Island, N.Y. The quarks themselves have not been discovered at the time of writing.

The next big leap in understanding may well come when the theory of how small pieces of matter behave is blended with the theory of gravity, which at present concerns the huge pieces of matter that make up our universe of galaxies, stars, and planets. With such a "unified" theory physicists may at last be able to answer that question about the raw material of the universe—why hydrogen? At the same time, we shall perhaps come to understand why matter was formed in the "big bang," with which (as many astronomers now suppose) the universe came into existence some 10,000,000,000 years ago, or why the "big bang" was not merely a "big flash."

Even so fundamental an advance would not exhaust the opportunity for fresh discovery in the physical sciences. Another set of pregnant problems results from very strange objects recently discovered in the sky, namely "hot" galaxies, quasars and pulsars. The quasars, in particular, are compact objects of such extraordinary energy that existing laws of physics seem scarcely able to account for them. The pulsars, which flash many times a minute, are also very odd, but less baffling. They are evidently remnants of exploded stars that have collapsed to the enormous density of the material of the atomic nucleus. If an ocean liner were compressed to the density of a pulsar, it would be no bigger than a grain of sand.

The evidence of the pulsars encourages a further idea—one of the strangest in the whole history of man's study of matter and energy. In a pulsar, nuclear forces prevent collapse to even greater densities. But if the collapsed star were even more massive, gravity would be stronger and it would overwhelm even the nuclear forces. Then there would be nothing to stop the process until the whole star had collapsed to smaller than a peanut. Through the intense gravitational field thus set up, no light could escape, and the star would in effect disappear from the universe. Only its gravity would remain, like the grin of the Cheshire Cat in Alice in Wonderland, and, if a space traveler ran into one of these "black holes," he too would be drawn to the same invisible kernel, there to disappear forever—or at least until the laws of physics change.

The possibility that such black holes exist holds out a hope of explaining the quasars as objects of this kind from which material somehow "bounces" out. But that is only a little comfort when scientists have now to reexamine the theory of gravity, which they thought Einstein had cleared up 60 years ago, and to work out the implications of a universe peppered with black holes where the familiar laws of nature are unlikely to apply. There is even the uncomfortable suggestion that our whole universe may be just a big black hole in someone else's universe! Physics, the master science, cannot evade these new battles of the mind.


Part One. Matter and Energy


Three points should be noted about the scope of Part One and its relations to other parts.

The sciences of physics, chemistry, and astronomy have themselves been the object of historical and analytical studies regarding their nature, scope, methods, and interrelations. Part Ten, on the branches of knowledge, is concerned with such studies. The outline in Section 10/32 of Part Ten deals with the sciences of physics, chemistry, and astronomy and treats their history, their nature and scope, and their principal problems and interrelations.

The design and operation of observational and experimental instruments are important in the development of the physical sciences. The treatment of scientific instrumentation is placed in Section 723 of Part Seven, on technology.

Accounts of the several kinds of mathematics used in observation and experiments, and in the derivation and application of physical theories, are set forth in Division II of Part Ten.

The three increasingly complementary physical sciences of physics, chemistry, and astronomy house the knowledge and the organizing theories about matter in all its dimensions, from subatomic particles to the cosmos, about all the states of matter, all the forms of energy, and all the interrelations of matter and energy.


Division I. Atoms: Atomic Nuclei and Elementary Particles

Division II. Energy, Radiation, and the States and Transformation of Matter

Division III. The Universe: Galaxies, Stars, the Solar System


Division I. Atoms: Atomic Nuclei and Elementary Particles


The outlines in the two sections of Division I deal with subatomic and atomic physics.

Section 111. The Structure and Properties of Atoms

Section 112. The Atomic Nucleus and Elementary Particles


Section 111.         The Structure and Properties of Atoms


A. The atomic nature of matter

     1. The atom as consisting of the nucleus surrounded by electrons, the arrangement and behaviour of which determine atomic interactions

     2. Early philosophical speculations on the possible atomic nature of matter

     3. The scientific evidence for the existence and the nature of atoms

          a. Developments in chemistry

          b. The development of spectroscopy and the discovery of atomic spectra

          c. The discovery of the electron as a particle and as a component of all matter

          d. The discovery of X rays

          e. The discovery of the radioactive transformation of one element into another

          f. The Brownian movement of suspended particles

          g. The development of mass spectrometry

          h. The development of scattering and resonance studies with atomic and molecular beams

     4. Models of atomic structure

          a. The Rutherford model of the atom

          b. The Bohr–Sommerfeld model

          c. The wave-mechanical theory of the electronic structure of the atom


B. Atomic weights

     1. Variations in atomic weight as a result of variations in isotopic composition

     2. Significance of atomic weights in chemistry

     3. Atomic weight scales

     4. Methods used for determining atomic weights: chemical methods, physical methods


C. Atomic spectra and the electronic structures of the atom

     1. Atomic spectra: their significance and interpretation

          a. The spectrum of the hydrogen atom

          b. The emission spectra of singly and multiply ionized atoms

          c. Atomic absorption spectra

          d. The effects of magnetic fields and the effects of electric fields on atomic spectra

          e. Intensities, isotope shifts, and fine and hyperfine structures of atomic spectral lines as related to atomic structure

     2. Theories of the origin of atomic spectra in quantized electronic transitions: the classical Bohr theory, wave-mechanical interpretations


D. X rays and atomic structure

     1. General X-ray phenomena

     2. The theory of X rays and their spectra

          a. The structure of the atom as related to the emission of characteristic X rays, absorption edges, fluorescence yield, mesic atoms

          b. Continuous X rays and bremsstrahlung; i.e., the radiation produced by the sudden retardation of a fast-moving charged particle in an intense electrical field

     3. Detection and measurement of X rays

     4. Applications of X rays in biological, medical, industrial, and scientific fields

[see 423.B. and 723.G.81]

     5. Diffraction of X rays by crystals

[see 125.A.2.]


E. The concept of antimatter

     1. General properties of antimatter

     2. Production of antiparticles in high-energy collisions

     3. Invariance of the laws of physics under charge conjugation, an operation in relativistic mechanics that transforms every particle into its antiparticle

     4. Speculations about the possible existence and role of antimatter in the universe


F. The fundamental physical constants: dimensional and dimensionless constants

     1. Measurement of the physical constants

     2. Interrelationships among the constants

     3. Standards of measurement


Suggested reading in the Encyclopedia Britannica:

MACROPAEDIA: Major articles dealing with the structure and properties of atoms

Analysis and Measurement, Physical and Chemical

Atoms: Their Structure, Properties, and Component Particles Physical Science, Principles of

Physical Sciences, The

Micropaedia: Selected entries of reference information


See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above


Section 112.         The Atomic Nucleus and Elementary Particles


A. The structure of the atomic nucleus and general nuclear phenomena

     1. General properties of atomic nuclei

          a. Mass

          b. Charge: atomic number

          c. Radius

          d. Spin

          e. Magnetic moment: nuclear magnetic resonance phenomena

          f. Electric quadrupole moment

     2. Components of atomic nuclei

          a. Neutrons

[see D., below]

          b. Protons

          c. Other possible short- and long-lived components

     3. Isotopes: atomic species with the same atomic number but with different atomic masses

[see B., below]

     4. Systematic relationships between nuclear masses and nuclear binding energies

     5. Nuclear models and the properties of nuclear states

     6. Theories of nuclear structure and nuclear binding force

     7. General nuclear phenomena and reactions

[see C. and E., below]

     8. The formation and evolution of the atomic nuclei in the universe


B. Isotopes: atomic species with the same atomic number but with different atomic masses

     1. Classification of isotopes or nuclides

     2. Isotopic composition of the elements

     3. Formation of isotopes by nuclear reactions

[see E., below]

     4. Effects of isotopic substitution on physical and chemical properties of substances

     5. Chemical and physical separation of isotopes

          a. Mass spectrometry

          b. Other methods of separation; e.g., diffusion, centrifugal separation, thermal diffusion

     6. Applications of radioactive and stable isotopes

[see 242.D.2. and 723.G.8.]


C. Radioactive nuclei: their properties and their radiations

     1. The phenomenon of radioactivity

     2. Types of radioactivity

     3. Sources of radioactivity: naturally occurring radioactive elements, particle bombardment

     4. Interaction of radiation with matter

[see I., below]

     5. The energy release associated with radioactive decay

     6. Nuclear models used to explain nuclear binding: the liquid drop model, the shell model, the unified model

     7. Rates of radioactive transitions

          a. Exponential decay law

          b. Alpha decay

          c. Beta decay

          d. Gamma decay

     8. Applications of radioactivity

[see 723.G.8.]

     9. Measurement and characterization of radioactivity

[see I 4., below]


D. The neutron as a component of the nucleus and in nuclear reactions

     1. Properties of neutrons

     2. Sources of neutrons

     3. Manipulation and control of neutrons

     4. Nuclear reactions produced by neutrons

     5. Neutron detection based on the secondary effects of nuclear reactions


E. Reactions of atomic nuclei

     1. The classification of nuclear reactions

          a. The types of nuclear reactions classified according to the kind of bombarding radiation or particles

          b. The types of nuclear reactions classified according to the nuclear processes involved or according to their products

     2. The energy relationships of nuclear reactions

     3. Theories and models of nuclear reactions


F. The splitting of atomic nuclei by nuclear fission

     1. Phenomena of nuclear fission

          a. Spontaneous and induced fission reactions

          b. Products of nuclear fission

          c. The energy released in fission

     2. Fission chain reactions: the critical mass

          a. Nuclear explosions: nuclear, or atomic, bombs

          b. Controlled nuclear fission

     3. Nuclear models and theories of nuclear fission: liquid drop model, adiabatic models, statistical models


G. The fusion of atomic nuclei

     1. Phenomena of nuclear fusion

     2. Nuclear fusion reactions

          a. General types of fusion reactions

          b. The energy released in fusion reactions

          c. Requirements for intensive fusion reactions

     3. Occurrence of thermonuclear reactions

          a. Thermonuclear reactions in the Sun and the stars

          b. Thermonuclear explosions: the hydrogen, or thermonuclear, bomb

     4. Basic conditions required for a thermonuclear reactor

          a. The formation of a suitable plasma

          b. The confinement and control of high-temperature plasma

     5. The possible approaches to controlled fusion: prospects for the future


H. Subatomic, or elementary, particles

     1. Development of the concept of subatomic particles as the fundamental units of matter and energy

          a. The discovery of the various particles

          b. Yukawa mesons and the theory of nuclear forces

          c. Advances in quantum field theory: renormalization theory, dispersion theory

          d. The known elementary particles

     2. The fundamental forces associated with particle interactions

     3. Systems for classifying the elementary particles

          a. According to the forces that influence them

          b. According to the kind of statistics they follow

          c. According to their particle–antiparticle symmetries

          d. According to stability

          e. According to charge multiplets

          f. According to unitary symmetry, or the SU(3) classification

          g. According to charged-hypercharge multiplets

     4. Elementary particles and the laws of conservation and symmetry

          a. The theory of subatomic particles and the quantum mechanical symmetry operations

          b. Dynamic symmetries: space and time inversion

          c. Violation of conservation laws: charge conjugation, time reversal, parity

          d. Internal symmetries

     5. Sources of the unstable elementary particles

          a. Formation of resonances in high-energy accelerators

          b. Production by cosmic ray interactions

     6. Relations of the weak interactions to strong and electromagnetic interactions described by conserved current and algebra of current

     7. Other particles suggested by contemporary theoretical ideas

     8. Reactions of elementary particles with atoms

     9. Theories of nuclear structure and nuclear forces involving the elementary particles


I. Effects of the passage of nuclear, or elementary, particles, nuclear radiations, or ionizing radiation through matter

     1. The fundamental processes involved when energetic particles or radiations interact with or pass through matter

          a. The passage of electromagnetic waves and their interaction with atomic structure

          b. The passage of particles or radiations through matter

     2. Secondary and tertiary effects of radiation: physical effects, molecular activation and related phenomena, chemical effects, biological effects

     3. Utilization of high-energy radiation in biological, medical, and technological fields

     4. The use of fundamental processes of interaction between radiation and matter for the detection and characterization of nuclear and elementary processes

          a. Mechanisms of detection systems: ionization and charge collection, conversion of the distributed energy of the primary ionizing particle into light

          b. Properties of ionization media

          c. Major types of radiation detectors: scintillation counters, ionization detectors, spark chambers, cloud chambers, bubble chambers

[see 723.F.7.]

          d. Applications of radiation detectors in science, technology, and industry

[see 723.G.8.]


Suggested reading in the Encyclopaedia Britannica:

MACROPAEDIA: Major articles dealing with the atomic nucleus and elementary particles

Analysis and Measurement, Physical and Chemical


See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above


Division II.          Energy, Radiation, and the States and Transformation of Matter


[For Part One headnote see page 21.]


Division I deals with modern advances in subatomic and atomic physics.

The outlines in the first three sections of Division II treat, respectively, chemical elements, chemical compounds, and chemical reactions. The last five sections of this division are concerned with heat, thermodynamics, and the nonsolid states of matter; with the solid state of matter: with the mechanics of particles, rigid bodies, and deformable bodies; with electricity and magnetism; and with waves and wave motion.


Section 121. Chemical Elements: Periodic Variation in Their Properties

Section 122. Chemical Compounds: Molecular Structure and Chemical Bonding

Section 123. Chemical Reactions

Section 124. Heat, Thermodynamics, and the Nonsolid States of Matter

Section 125. The Solid State of Matter

Section 126. Mechanics of Particles, Rigid Bodies, and Deformable Bodies: Elasticity, Vibrations, and Flow

Section 127. Electricity and Magnetism

Section 128. Waves and Wave Motion


Section 121.         Chemical Elements: Periodic Variation in Their Properties


A. The systematic classification of the elements on the basis of their chemical and physical properties and atomic structures: the periodic law of the elements


B. The groups of the chemical elements in the long form of the periodic table: their occurrence, history, physical and chemical properties, principal compounds, production, and uses

     1. Hydrogen, its forms, isotopes, and compounds: water, its structure, forms, and physical and chemical properties

     2. The alkali metals, or the Group Ia elements of the periodic table: lithium, sodium, potassium, rubidium, cesium, francium

     3. The alkaline-earth metals, or the Group Ila elements of the periodic table: beryllium, magnesium, calcium, strontium, barium, radium

     4. The boron group of the elements, or the Group Ilia elements of the periodic table: boron, aluminum, gallium, indium, thallium

     5. The carbon group of the elements, or the Group IVa elements of the periodic table: carbon, silicon, germanium, tin, lead

     6. The nitrogen group of the elements, or the Group Va elements of the periodic table: nitrogen, phosphorus, arsenic, antimony, bismuth

     7. The oxygen group of the elements, or the Group Via elements of the periodic table: oxygen, sulfur, selenium, tellurium, polonium

     8. The halogen elements, or the Group VIIa elements of the periodic table: fluorine, chlorine, bromine, iodine, astatine

     9. The noble gases, or the Group 0 elements of the periodic table, formerly called the inert gases: helium, neon, argon, krypton, xenon, radon

     10. The zinc group elements, or the Group IIb elements of the periodic table: zinc, cadmium, mercury

     11. The transition elements: elements with partly filled d or J. orbitals occupying the middle portion of the periodic table

          a. Individual elements of the first transition series: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper

          b. Individual elements of the second and third transition series: zirconium and hafnium, niobium and tantalum, molybdenum and tungsten, technetium and rhenium, ruthenium and osmium, rhodium and iridium, palladium and platinum, silver and gold

          c. The lanthanide elements

[see B.I2., below]

          d. The actinide elements

[see B.13.. below]

     12. The rare-earth, or lanthanide. elements of the periodic table: scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium

[see also 724.C.3.u.]

     13. The actinide elements of the periodic table: actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, lawrencium

     14. The transactinide elements of the periodic table: unnilquadium (or rutherfordium), unnilpentium (or hahnium), unnilhexium, unnilseptium, unniloctium, unnilennium; heavier elements which have yet to be discovered but whose existence is extrapolated based on the periodic law


C. Other classifications of the elements or groups of them

     1. Metals; semimetals, or metalloids; nonmetals

     2. Stable and radioactive elements

     3. Native and combined elements

     4. Noble metals, including the platinum group of metals

     5. Synthetic elements: transuranium elements

     6. Biologically active or essential elements

[see 335.A.3.[

     7. Technologically significant elements

[see 724.0.3.]


D. The origin of the elements and their relative abundances in nature

     1. On Earth

          a. In the crust

[see also 2I4.C.]

          b. In the hydrosphere

[see also 222.B. and C.]

          c. In the atmosphere

[see also 221.A.I.]

          d. In the biosphere

     2. In the solar system

[see also 133.A.]

     3. In the stars

[see also 132.D.7.b.]

     4. In the rest of the universe

[see also 131.A.I.a.]


Suggested reading in the Encyclopaedia Britannica:

MACROPAEDIA: Major articles dealing with chemical elements: periodic variation in their properties

Chemical Compounds Chemical Elements    


MICROPAEDIA: Selected entries of reference information

magnesium      nitrogen group ytterbium                     nickel

radium             element                        yttrium                                    niobium

strontium         phosphorus      synthetic elements,      osmium

boron group:    noble gases:     including the               palladium

aluminum        argon               transuranium               platinum

boron               helium             elements:                     rhenium

boron group     krypton                        americium                    rhodium

element                        neon                berkelium                    ruthenium

gallium                        noble gas         californium                  silver

indium             radon               curium                         tantalum

thallium                       xenon              einsteinium                  technetium

carbon group:  oxygen group: fermium                                   titanium

carbon             oxygen                        lawrencium                  transition element

carbon group   oxygen group  mendelevium               tungsten

element                        element                        neptunium                   vanadium

germanium      polonium         nobelium                     zirconium

lead                 selenium          plutonium                    zinc group:

silicon              sulfur               promethium                 cadmium

tin                    tellurium          technetium                  mercury

halogen elements:        rare-earth elements:     transuranium   zinc

astatine                        cerium             element                                    zinc group

bromine                       dysprosium      unnilennium                element

chlorine                       erbium             unnilhexium                other:

fluorine                        europium         unniloctium                 allotropy

halogen                        gadolinium      unnilpentium   Aufbau principle

iodine              holmium          unnilquadium  chemical element

hydrogen and its         lanthanum       unnilseptium    chemical symbol

isotopes:          lutetium           transition elements:     group

deuterium        neodymium     chromium        lanthanide

hydrogen         praseodymium cobalt              contraction

tritium             promethium     copper             metal

nitrogen group:            rare-earth metal           gold                 metalloid

antimony         samarium         hafnium                       nonmetal

arsenic             scandium         iridium             nucleosynthesis

bismuth                       terbium                        iron                  periodic law

nitrogen                       thulium                        manganese      




See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Section 122.         Chemical Compounds: Molecular Structure and Chemical Bonding


A. The theory of molecular structure: its history and development

     1. Early concepts of molecular structure

     2. Quantum mechanical and electrostatic approaches to the theory of molecular structure

     3. Molecular bonds and shapes

          a. Spatial arrangement of atoms: chains, rings, chelates, polymers

          b. Isomers: structural isomers, stereoisomers

     4. Time-dependency properties of molecules

     5. Molecular structure and its relation to the properties of bulk matter

          a. The physical properties of matter as affected by molecular size, shape, and interactions, and interactions of molecules with radiations and fields

          b. The chemical behaviour of matter as determined by the nature of molecular bonds

          c. The chemical, physical, and biochemical properties of a substance inferred from its known or postulated molecular structure


B. Experimental and theoretical procedures for the determination of molecular structures

     1. The separation, isolation, and purification of chemical substances based on chemical equilibria and rate phenomena

          a. By volatility differences: distillation, sublimation, evaporization

          b. By chromatography: liquid phase, gas phase, thin layer

          c. By solubility differences: precipitation, crystallization, zone melting, solvent extraction

          d. By ion-exchange reactions

          e. By electrophoresis and electrolytic methods

          f. By mechanical methods: filtration, sedimentation, sieving, flotation, centrifugation

     2. Classical methods of qualitative and quantitative analysis

     3. Instrumental methods used to identify functional groups, molecular sub-units, and structural features

          a. Spectrochemical methods: microwave, infrared, ultraviolet, Raman spectroscopy, colorimetry, atomic absorption spectroscopy

          b. Mass spectrometry

          c. Magnetic resonance spectrometry

          d. Thermometric methods: thermogravimetry, calorimetry, cryoscopy

          e. Radiochemical methods: radiometric analysis, activation analysis, isotopic dilution

          f. Electrochemical methods: potentiometry, polarography, electrodeposition, oscillometry

     4. Diffraction methods for determining molecular structures: electron, X-ray, and neutron beam diffraction

     5. Physical methods used to determine optical activity, magnetic susceptibility, calorific values, heat of combustion, activation energy, and reaction rates

     6. The synthesis and characterization of derivatives, or specifically modified molecules

     7. The determination of molecular weight based on thermodynamic theory, on transport phenomena, and on known spatial arrangements of atoms in the solid state

     8. The principles of conformational analysis as related to molecular structure

     9. The scattering of molecular beams and its usefulness in the study of molecular interactions


C. Spectra of molecules

     1. The theory of molecular spectra

     2. Types of molecular spectra: microwave, infrared, Raman, visible, and ultraviolet spectra

     3. The interpretation of molecular band spectra in determining molecular structure


D. The theory of chemical bonding: its development and experimental bases

     1. Nonquantum treatments of chemical bonding

          a. Early ideas and concepts of chemical bonding: valence

          b. The early electronic theory of bonding

               i. The nature of ionic bonds: shell theory, ion pairs

               ii. The nature of covalent and coordinate bonds: the octet

          c. Application of the quantum theory to atomic structure

     2. Quantum-mechanical treatment of chemical bonding

          a. Atomic and molecular orbital concepts

          b. Bonding in the hydrogen molecule

          c. Bonding in simple polyatomic molecules

          d. Quantum-mechanical calculations

     3. Other bonding effects: hydrogen bonding; metallic bonds in metals, intermetallic compounds, and coordination compounds; bonds in crystals, in weak associations, and in electron-deficient compounds

     4. Experimental observation of chemical bonding

     5. Anomalous molecular structures, or molecular fragments with apparently anomalous valences: free radicals, carbenes, carbanions, carbonium ions


E. Systems of classification of chemical compounds or substances

     1. By their elemental composition or molecular structure: organic, inorganic, organometallic, and

nonstoichiometric compounds

     2. By their bond type: ionic, covalent, and coordination compounds

     3. By their chemical reactivity: acids, bases, and salts; oxidizing and reducing agents

     4. By their physical state: gas, liquid, and solid

     5. By their origin: natural and synthetic


F. Inorganic compounds

     1. Nomenclature of binary, ternary, and coordination compounds

     2. Structural classification of inorganic compounds

          a. Salts

          b. Oxides, anhydrides, acids, and bases

          c. Coordination compounds

          d. Organometallic compounds

[see G.1.c.. below]

          e. Catenates

          f. Inorganic polymers

          g. Special nonmetallic derivatives

     3. Methods of preparation of inorganic compounds

     4. Reactions of inorganic compounds; e,g., acid—base, substitution, isomerization, oxidation

reduction, addition


G. Organic compounds

     1. The major groups of organic compounds: their nomenclature, chemical and physical properties,

synthesis, occurrence, reactions, and analysis

          a. Hydrocarbons: aliphatic and aromatic

          b. Organic halogen compounds: alkyl, alkenyl, and alkynyl halides; aryl halides

          c. Organometallic compounds

          d. Alcohols, phenols, and ethers

          e. Carboxylic acids and their derivatives

          f. Aldehydes, ketones, and their derivatives

          g. Organic nitrogen compounds

          h. Organic sulfur compounds

          i. Organic phosphorus compounds

          j. Organic silicon compounds

          k. Heterocyclic compounds

          1. Oils, fats, and waxes

          m. Carbohydrates

          n. Amino acids, proteins, and peptides

          o. Isoprenoids and terpenes

          p. Steroids and their derivatives

          q. Nucleotides and nucleosides

          r. Nucleic acids: DNA and RNA

          s. Alkaloids

          t. Dyestuffs and pigments

          u. Organic polymers

     2. Preparation and purification of organic compounds

     3. Physical properties of organic compounds

     4. Reactions of organic compounds: addition, substitution, displacement, hydrolysis, pyrolysis, condensation, polymerization, molecular rearrangement


Suggested reading in the Encyclopedia Britannica:

MACROPAEDIA: Major articles dealing with chemical compounds: molecular structure and chemical bonding

Biochemical Components of Organisms

toluene xylene

inorganic acids and oxides:


carbon dioxide carbon monoxide Dry Ice

hydrogen chloride hydrogen cyanide hydrogen ion nitric acid nitric oxide nitrous acid nitrous oxide oxide

phosphoric acid phosphorous acid rare-earth metal silica gel silicic acid sulfur oxide sulfuric acid water glass

inorganic nitrogen compounds: ammonia ammonium hydroxide


hydrazine hydroxylamine

isoprenoids and terpenes: abietic acid camphor carotene isoprene limonene menthol pinene


methods of chemical analysis: assaying chemical

precipitation chromatography colorimetry countercurrent distribution differential thermal analysis


gas chromatography gel

chromatography gravimetric analysis iodine valuenephelometry and turbidimetry paper

chromatography polarimetry polarography qualitative

chemical analysis quantitative chemical analysis spectrochemical analysis thin-layer chromatography titration



molecular bonds and shapes:

configuration conformation diastereoisomer enantiomorph isomerism optical activity racemate resolution strain theory tautomerism

nucleic acids and their components: adenine

adenosine triphosphate cytosine




nucleic acid nucleoside nucleotide RNA



oils, fats, and waxes: babassu palm castor oil Chinese wax cod-liver oil cohune oil copra

cottonseed essential oil fat

fish oil






phospholipidpine oil

sperm oil spermaceti tallow

triglyceride wax

whale oil

organic halogen compounds: acid halide aldrin

benzene hexachloride carbon tetrachloride chloral hydrate chlordane chlorobenzene chloroform chlorotrifluoroethylene cyanogen halide DDT

dichlorobenzene ethyl chloride ethylene bromide ethylene chloride Freon

halocarbon halon


methyl bromide methyl chloride methylene chloride phosgene polychlorinated biphenyl tear gas

tetrachloroethane tetrachloroethylene tetrafluoroethylene toxaphene trichloroethane trichloroethylene vinyl chloride vinylidene chloride

organic nitrogen,


phosphorus compounds: amide



azo compound benzidine biotin


diazonium salt dimethoate ethanolamine



nitro compound nitrobenzene nitroglycerin nitroso compound oxime


PETN phorate picric acid polysulfide

sulfide sulfonamide sulfonic acid sulfoxide


thiourea urea






Grignard reagent metal carbonyl tetraethyl lead

peroxy compounds: hydrogen peroxide peroxide

peroxy acid

petroleum, gasoline, oil, and coal: gasoline kerosine microcrystalline wax

napalm naphtha

paraffin wax petrochemical petroleum

polymers and resins: balsam


copolymer dammar dragon's blood elastomer frankincense gamboge

initiator latex

Lucite macromolecule mastic

monomer neoprene polyacrylonitrile polychlorotrifluoroethylene

polyester          silver nitrate    resonance,       chemical formula

polyether         soap     theory of         chemical indicator

polyolefin        steroids and their        valence            definite

polystyrene      derivatives:      van der Waals proportions,

polysulfide      aldosterone      forces  law of

polysulfone     cholesterol       water:  excitation

polytetrafluoro-           corticoid          anomalous water         functional group

ethylene           cortisol            deliquescence  homologous series

polyurethane   cortisone          efflorescence   ion-exchange resin

polyvinyl alcohol         ergosterol        hard water       ketene

polyvinyl chloride       sapogenin        heavy water     lecithin

resin     saponin            hydrate            litmus

rubber  steroid ice        molecular sieve

silicone            steroid hormone          steam   molecule

turpentine        testosterone     water   multiple

urea-formaldehyde      theory of chemical      other:   proportions,

resin     bonding:          alicyclic compound     law of

vinyl compound          chemical          alkali    nonstoichiometric

salts:    association       anhydride        compound

alum    chemical bonding        base     phenolphthalein

ammonium      covalent bond carbanion         phosphine

chloride           electronegativity         carbene            quinone

ammonium nitrate       ion       carbon disulfide          radical

lithium carbonate        ion pair            carbonate        

Rochelle salt    ionic bond       carbonium ion

saltpetre           metallic bond  carbonyl group           

silane   orbital  chemical         




See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above


Section 123.         Chemical Reactions


A. General considerations of chemical reactions

     1. Basic concepts involved in the study of chemical reactions: transformation, conservation of mass and energy, law of simple multiple proportions in compounds

     2. Growth of major theories concerning chemical reactions

     3. Classification and nomenclature of the principal kinds of chemical reactions

          a. According to the relationship involved between the starting materials and the final products

i. Decomposition reactions

ii. Polymerization reactions

iii. Chain reactions

iv. Substitution reactions

v. Addition and elimination reactions

vi. Oxidation-reduction reactions

[see F., below]

vii. Acid-base reactions

[see E., below]

          b. According to the energy changes involved

[see B.1., below]

          c. According to the reaction rates or chemical kinetics involved

[see also C., below]

          d. According to the reaction mechanism involved

[see D.4., below]


B. Energy changes in chemical reactions

     1. The classification of chemical reactions according to energy changes involved: exothermic and endothermic

     2. The significance of activation energy in chemical reactions

     3. Thermodynamic relations in chemical reactions: chemical equilibrium, free energy and entropy changes


C. Rates of chemical reactions

     1. Factors that affect the rate or direction of chemical reactions

          a. Solvents

          b. Temperature

          c. Pressure

          d. Catalysts

          e. Collisions

          f. Light

          g. Isotopic substitution

          h. Molecular structure

     2. Factors that affect the kinetic order of chemical reactions: concentration of reactants, mechanism of reaction, conditions of the reaction

     3. Factors that affect the extent of chemical reactions: equilibrium constant

     4. Complex reactions: reactions governed by more than one reaction rate

     5. Experimental methods for studying chemical kinetics

          a. Measurement of reaction rates

          b. Determination of the order of reactions

          c. Relaxation methods

     6. Kinetic studies as a means of elucidating reaction mechanisms


D. Mechanisms of chemical reactions

     1. Factors influencing the course of a reaction: reactants, transition state, solvent, catalysts, products, reaction conditions

     2. Energy changes through single-stage and multi-stage processes

     3. Factors that reveal the mechanisms of a reaction: chemical and stereochemical nature of the reactants, intermediates, and products; kinetics of the reaction

     4. Classification of reaction mechanisms based on the nature of electron pairing in the transition state, on the nature of the attacking species, on the nature of catalysis, on the number of components of the transition state

     5. Mechanisms of the principal types of reactions: nucleophilic and electrophilic substitution, addition and elimination reactions


E. Acid–base reactions and equilibria

     1. General properties of acids and bases

     2. Theoretical approaches to acid–base concepts

          a. The definition of an acid as a substance that gives rise to hydrogen ions and of a base as a substance that gives rise to hydroxyl ions in aqueous solutions

          b. The Bronsted–Lowry concept defining an acid as a proton donor and a base as a proton acceptor

          c. The Lewis electronic theory defining an acid as an electron acceptor and a base as an electron donor

     3. Acid–base reactions

          a. Proton-transfer reactions

          b. Lewis acid reactions

          c. Acid–base catalysis

     4. Quantitative aspects of acid—base equilibria

          a. Equilibria in aqueous solutions

          b. Equilibria in nonaqueous solvents

          c. Equilibria involving Lewis acids

          d. The effect of molecular structure on acid—base equilibria

     5. The experimental study of acid—base reactions and equilibria


F. Oxidation—reduction reactions

     1. Major classes of oxidation—reduction reactions: oxygen atom transfer, hydrogen atom transfer,

electron transfer

     2. Definitions of oxidation and reduction based on the reaction's stoichiometry

     3. Theoretical aspects of oxidation—reduction processes

          a. The concept of oxidation state

          b. Half reactions and the determination of redox potentials

          c. Oxidation—reduction equilibria and reaction rates

          d. Mechanisms of redox reactions

     4. Electrochemical reactions: chemical changes associated with the passage of an electrical current

          a. The electrochemical process: types of reactions

          b. Complex electrochemical reactions

          c. The Nernst and Butler—Volmer equations

     5. Oxidation—reduction reactions in biological systems

     6. Oxidation—reduction reactions in combustion and flames


G. Photochemical reactions

     1. The photochemical process

     2. Experimental methods used in the study of the photochemical process and photochemical


     3. The application of photochemical processes


H. Chemical reactions and chemical theory in the synthesis of chemical compounds

     1. Factors that affect the choice of a specific synthetic path

     2. Factors that affect the choice of reaction conditions

     3. The separation and purification of reaction products

[see 122.B.1.]

     4. The identification, characterization, and analysis of reaction products

[see 122.B.2. through 9.]


Suggested reading in the Encyclopedia Britannica:

MACROPAEDIA: Major articles dealing with chemical reactions

Chemical Reactions


chemical          oxidation and  preparative      others:

equilibrium      reduction:        procedures:      chemical reaction

chemical          antioxidant      alkylation        equivalent weight

intermediate    combustion      asymmetric      Hess's law of heat

collision theory            oxidation-reduction    synthesis          summation

initiator            reaction           chemical synthesis       heterogeneous

inversion          spontaneous    condensation   reaction

isotopic            combustion      reaction           homogeneous

fractionation    photochemistry:          hydrogenation reaction

Markovnikov rule        actinometer     hydrolysis        reaction, heat of

mass action, law of     photochemical ion-exchange  

microscopic     equivalence law           reaction          

reversibility,    photochemical isomerization  

principle of      reaction           polymerization           

reaction rate    photolysis        sulfation         

relaxation        photosensitization                  






See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Section 124.         Heat, Thermodynamics, and the Nonsolid States of Matter


A. The principles of thermodynamics

     1. The description of physical phenomena based on the concepts of system, state of a system, and changes of state

     2. The first law of thermodynamics

     3. The second law of thermodynamics

     4. Stable equilibrium

          a. Equations relating properties of systems that are in, or are passing through, stable equilibrium states

          b. Temperature considered as the potential governing the flow of energy between systems

          c. Heat

            i. The definition of heat as a form of energy transferred from one body to another under the influence of a difference in temperature

            ii. Theories of heat: the phlogiston theory, the caloric theory, the kinetic molecular theory

            iii. Heat transfer in matter: heat conductivity in solids, convection in liquids and gases, heat transfer in boiling liquids, evaporation and condensation

            iv. Technical applications of heat energy

[sec 72I.B.7. and 725.A.5.a.]

            v. Heat and its relation to entropy, work, and change of energy

     5. Thermodynamic relations in simple systems

          a. The Carnot cycle

          b. Maxwell's equations relating entropy to pressure, volume, and temperature for closed systems that assume only stable equilibrium states

          c. Phase changes and equilibria

          d. Simple one-component systems: processes at constant volume and at constant pressure; the equation of state, which relates pressure, volume, and temperature for stable equilibrium states

          e. Simple multicomponent systems: the Maxwell relations, Dalton's law for mixture of gases, Raoult's law and Henry's law for ideal solutions

          f. Bulk flow

          g. Equilibrium in chemical reactions

[see 123.B.31

     6. The third law of thermodynamics

     7. The effects of applied force fields on simple systems

     8. Steady rate processes; e.g., systems approaching stable equilibrium, flow of a substance through a barrier

     9. Statistical thermodynamics

          a. The laws of thermodynamics that consider the detailed microscopic structure of physical systems and the states of such systems

          b. Statistics of grand systems


B. The gaseous state of matter

     1. The nature and properties of a gas

     2. The thermodynamic approach to gases: the macroscopic view that deals with bulk measurable properties

          a. The simple gas laws

          b. The thermal equation of state for perfect gases

          c. Empirical equations of state for real gases

     3. The particle-description approach to gases

          a. The distribution function

          b. The Boltzmann transport equation and the single-particle distribution function

          c. The N-particle distribution function and the thermodynamic-equilibrium properties and transport properties of dense gases

          d. The behaviour of a gas at the hydrodynamic and thermal relaxation stages


C. The liquid state of matter

     1. The behaviour and properties of liquids at equilibrium

     2. The molecular structure of liquids based on distribution functions, which measure the probable distribution of some property of molecules through the liquid

     3. Properties of liquids

          a. Transport properties

          b. Acoustic properties: propagation of sound waves

          c. Electrical and magnetic properties

          d. Thermodynamic properties

          e. Optical properties

          f. Surface tension


D. Solutions and solubility

     1. General classes of solutions: electrolytes and nonelectrolytes, solutions of weak electrolytes, endothermic and exothermic solutions

     2. Properties of solutions

          a. Composition ratios: molarity, molality, mole fraction

          b. Equilibrium properties: correlation of the vapour pressure of a solution to its composition

          c. Colligative properties: rise in boiling point, decrease in freezing point, osmotic pressure

          d. Transport properties: viscosity, thermal conductivity, diffusivity

     3. Thermodynamic and molecular aspects of solvent and solute interactions

          a. Energy considerations: entropy, enthalpy, Gibbs free energy

          b. Effects of molecular structure and weak intermolecular forces

          c. Effects of chemical interactions; e.g., hydrogen bonding, chemical combinations

     4. General theories of solution: the prediction of solubility and solution properties

          a. Solutions of nonelectrolytes: Raoult's law and Henry's law for ideal solutions; theoretical expressions for the excess properties of regular athermal, associated, and solvated solutions

          b. Solutions of electrolytes: Debye—Hfickel theory and modifications, Arrhenius dissociation theory

     5. Effects of temperature and pressure on the solubility of solids and gases


E. Physical effects at surfaces

     1. Surface tension and surface energy: cohesion and adhesion

     2. Adsorption on liquid and solid surfaces

     3. Tribological phenomena, the mechanical and physical effects at interfaces: friction, wear, lubrication

     4. Colloids: the kinds of dispersions and their properties and preparation

          a. Irreversible colloidal systems: lyophobic sols, emulsions, foams, pastes, gels

          b. Reversible colloidal systems: solutions of polymers and proteins, solutions of soaps and dyes


F. The plasma state of matter: completely ionized gases interacting with magnetic and electric fields

     1. Basic plasma properties and parameters: electrical quasineutrality, electron density, kinetic temperature, particle velocities, magnetic and electric field strengths

     2. Elastic and inelastic collisions of plasma particles

     3. Radiation from plasmas; e.g., X rays, synchrotron radiation, excitation radiation

     4. The formation of plasmas

     5. The behaviour of plasmas in magnetic and electric fields

     6. The determination of plasma variables

     7. Fluidlike behaviour in plasmas

     8. Applications of plasmas; e.g., power production, jet propulsion

[see I12.G.4., 72I.B.8.a., and 721.C.31

     9. The existence of plasmas in nature: in the extraterrestrial medium, in the Sun and stars, on Earth


G. The properties of matter at extreme conditions

     1. Properties of matter at low temperatures

          a. Effects of low temperature on entropy, heat capacity, magnetic properties, and conductivity

          b. Special physical phenomena at very low temperatures: superconductivity, superfluidity

          c. Special methods for obtaining and characterizing low temperatures: adiabatic cooling, adiabatic dilution

     2. Special properties of matter at high temperatures

     3. Effects of high pressure on the physical, chemical, electronic, and magnetic properties of matter


H. Transport phenomena

     1. The kinetic molecular theory of the transport properties of gases, liquids, suspensions, and polymers

     2. Phenomenological expressions of transport

     3. Hydrodynamic aspects of transport phenomena

     4. Transport phenomena in macrosystems


Suggested reading in the Encyclopaedia Britannica:

MACROPAEDIA: Major articles dealing with heat, thermodynamics, and the nonsolid states of matter

Matter: Its Properties, States, Varieties, and Behaviour Physical Sciences, The

Thermodynamics, Principles of


MICROPAEDIA: Selected entries of reference information General subjects

colloids.•         caloric theory  phase rule        heat capacity

aerosol convection       thermal fusion internal energy

colloid heat transfer    vaporization    Lagrangian

dialysis            thermal            solutions and   function

emulsion          conduction      solubility:        Maxwell's demon

foam    liquid state of matter:  amalgam          Rankine cycle

gel       capillarity        Arrhenius theory         reversibility

gaseous state of           detergent         exsolution        specific heat

matter: diffusion         Henry's law     temperature

Avogadro's law           fluid    ideal solution   thermodynamics

Boyle's law      glass    saturation        other:

Dalton's law    liquid   solid solution   adsorption

degenerate gas            osmosis            solution           cohesion

diffusion         superfluidity    thermodynamics          friction

fluid    surface-active  and statistical  liquid crystal

gas       agent   mechanics:       plasma

kinetic theory of          surface tension            absolute zero   Stefan

gases    phase changes and      canonical         Boltzmann law

Maxwell–        equilibria:        ensemble         thermal expansion

Boltzmann       boiling point    carnot cycle     transport

distribution law           condensation   energy,            phenomenon

mean free path            critical point    equipartition of           tribology

perfect gas       distillation       enthalpy          wear

van der Waals eutectic            entropy

forces  freezing point  free energy

heat transfer in            latent heat       freedom, degree of

matter: melting point   Hamiltonian

adiabatic          phase   function

demagnetization          phase diagram heat



See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above


Section 125.         The Solid State of Matter


A. Crystals and crystallography

     1. Patterns of atoms in crystals

          a. The three-dimensional periodic arrangement of atoms in crystals: crystal planes and their notation

          b. Symmetry considerations in the classification of crystal systems

     2. Diffraction of X rays, electrons, and neutrons by crystal structures

     3. Processes of crystal growth

          a. Theoretical aspects of crystal growth: energy considerations, growth of eutectics, constitutional supercooling, nucleation

          b. Preparation of crystals: monocomponent and polycomponent crystal growth

     4. Imperfections and dislocations in crystalline materials and their effects on the properties of the crystals

     5. Effects of temperature, pressure, and alloying on the strength and hardness of crystals


B. The theory of the crystalline solid state

     1. The classification of solids according to their electronic structure and bonding: ionic solids, covalent solids, metallic solids, molecular solids, hydrogen-bonded solids

     2. The arrangement of atoms in crystalline solids

[see Ala., above]

     3. The elastic and plastic properties of solids

     4. The thermal and thermodynamic properties of solids: specific heat, thermal conductivity

     5. The electronic structure of solids

          a. The nature and mobility of electrons in conductors, insulators, and semiconductors

          b. Electron emission: thermionic emission, photoelectric emission, field emission

          c. The nearly free electron approximation

          d. The energy-band theory of the solid state

     6. The principal types of magnetic behaviour exhibited by solids: paramagnetism, diamagnetism, ferromagnetism

     7. The interaction of light with solids

          a. The behaviour of solids illuminated with radiation: reflection, absorption, or transmission of photons

          b. The generation of electromagnetic radiation from the energy supplied to the solid

          c. The photoelectric effect


C. Ionic crystals

     1. Bonding in ionic crystals

     2. The structure of ionic crystals

          a. Perfect ionic crystals

          b. Defects in ionic crystals: Frenkel defect, Schottky defect, colour centres

     3. Properties of ionic crystals

          a. Vibrational and electronic properties

          b. Thermal properties

          c. Polarizing and diffusion properties and the nature of ionic conduction

          d. Optical properties


D. Metals

     1. Structural aspects of metals and alloys

     2. Elementary description of metals: the use of the free electron model to explain thermal and electrical conductivity of metals

     3. The electronic structure of metals and related effects

          a. The interaction between the periodic lattice and the conduction electrons: the weak pseudopotential

          b. Electron motion in a magnetic field and conduction-related effects

     4. Band structure and properties of metal groups: alkali metals, semimetals, noble metals, transition metals

     5. Lattice vibrations: interaction between ions; interaction between electrons, phonons, and dispersion

     6. Metal surface phenomena: thermionic and field emission of electrons, electron tunnelling, photoemission, free carrier absorption and interband transitions

     7. Many-body effects: plasma oscillations, spin waves, Fermi liquid theory, dynamic effects and shake-off electrons

     8. Superconductivity in metals

          a. Thermal properties of superconductors: transition temperature, specific heat and thermal conductivity, energy gaps

          b. Magnetic and electromagnetic properties of superconductors: critical field, Meissner effect, phase coherence effects

     9. Magnetic phenomena in metals: diamagnetism, paramagnetism, ferromagnetism, antiferromagnetism, nuclear magnetic resonance


E. Semiconductors and insulators

     1. General properties of semiconductors and insulators

     2. Mechanisms of conduction: mobility of charged particles and electrons in solids

     3. Electrical conduction in semiconductors

          a. Chemical approach: impurity conduction, hopping process

          b. Physical approach: energy band and gaps, lattice vibrations, statistical properties

          c. Extrinsic and intrinsic semiconductors

          d. Measurement of conductivity and of energy gaps

     4. Principles involved in semiconductor applications

          a. Optical effects: photoelectric effect, photovoltaic effect, luminescence

          b. Electrical and related effects: hot electron effects, thermoelectric effects

          c. Junction effects

          d. Pressure and stress effects


F. The glassy or amorphous state of matter

     1. Effects of temperature and composition on glass properties

     2. The structure of glass

     3. General properties of glasses: mechanical, chemical, optical, and electrical properties


Suggested reading in the Encyclopxdia Britannica:

MACROPAEDIA: Major articles dealing with the solid state of matter

Matter: Its Properties, States, Varieties, and Behaviour



See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Section 126.         Mechanics of Particles, Rigid Bodies, and Deformable Bodies: Elasticity, Vibrations, and Flow


A. The principles of classical mechanics

     1. The fundamental parameters and concepts of classical mechanics: matter, space, motion, time

     2. Statics, the equilibrium of systems at rest: force, friction

     3. Dynamics: motion of systems

          a. Kinematics: motion of particles and rigid bodies without consideration of the forces producing the motion

            i. Velocity and acceleration

            ii. Rotation about a fixed axis

            iii. Motion in a circular path

            iv. Simple harmonic motion

            v. Relative motion

          b. Kinetics: motion of bodies under the action of forces upon them

            i. Newton's laws of motion: the law of inertia, the law of force, the law of action and reaction

            ii. Motion under a constant force

            iii. Ballistics: phenomena and laws of projectiles and their propulsion, flight, and impact

            iv. The motion of the pendulum

            v. Newton's law of universal gravitation

            vi. Kepler's laws of planetary motion

          c. Impulse and momentum

          d. Work and power

          e. Energy

            i. The concepts of energy and energy conservation

            ii. Forms of energy and examples of energy transformations associated with each energy form

            iii. The equivalence of mass and energy

          f. The conservation of momentum

     4. Mechanics of nonrigid bodies

          a. The collision of bodies or particles: centre of mass system, elastic collisions, inelastic collisions

          b. Stiffness in mechanical vibrations

     5. Motion in a rotating frame of reference: inertia forces and Coriolis forces

     6. Mechanics of complex systems

          a. The principle of virtual work

          b. The rotation of spinning tops and gyroscopes

          c. The precession and nutation of rotating bodies

          d. Lagrange's and Hamilton's equations of motion


B. Celestial mechanics

     1. The scope and history of celestial mechanics

     2. The two-body problem and perturbations that cause the orbits of planets and satellites to deviate from ellipses

     3. The three-body problem

     4. The general n-body problem


C. Relativistic mechanics in inertial systems of reference

     1. Mechanical foundations of special relativity

     2. Relativistic kinematics

     3. The relationship between gravitational mass and inertial mass


D. The stress dynamics of elastic materials

     1. The phenomenon of elasticity: stress-strain relationships

     2. Elasticity in viscous and crystalline bodies

     3. Elastic constants

     4. The theory of elasticity: mathematical expressions defining elastic properties


E. Vibrations of elastic bodies

     1. The nature of vibrations: natural or free vibrations, damped and forced vibrations

     2. Vibrators and their sources of energy

     3. Types of vibrational waves: their properties and modes of propagation

     4. The behaviour of materials undergoing vibration

     5. Detection and utilization of vibrations

[see 723.F.6. and 735.K.2.]


F. Fluid mechanics, including gas dynamics

     1. General properties of'fluids, ideal and actual: mechanical and thermodynamic properties

     2. Fluid statics and equilibrium

          a. The basic equation of fluid statics

          b. Fluid forces on plane and curved surfaces: analysis of forces, buoyancy, stability of floating and submerged bodies

     3. Fluids in motion: hydrodynamics and aerodynamics

          a. Frictionless one-dimensional fluid flow

          b. Flow in pipes and channels: laminar flow, turbulent flow, special types of flow

          c. General two- and three-dimensional flow: mathematical conditions, vorticity, boundary layers, drag

          d. Compressible fluid flow: isentropic flow, shock waves


G. Rheological phenomena: deformation and flow

     1. Continuum mechanics

          a. Kinematics of deformation and flow: strain, shear, compression, elongation

          b. Dynamics: balance of forces and torques

     2. Constitutive equations: stress-deformation relations in different media

     3. Yield strength of materials: fracture and fatigue

     4. The application of molecular theories to explain rheological phenomena


Suggested reading in the Encyclopzdia Britannica:

MACROPAEDIA: Major articles dealing with the mechanics of particles, rigid bodies, and deformable bodies: elasticity, vibrations, and flow

Energy Conversion

Matter: Its Properties, States, Varieties, and Behaviour Mechanics: Energy, Forces, and Their Effects

MICROPAEDIA: Selected entries of reference information


General subjects          deformation and         Hooke's law    slip

deformation and                                

elastienv:         flow     plasticity          strain

bulk modulus  elasticity          shear modulus stress





kinetic energy mechanical energy potential energy power


fluid mechanics: Archimedes' principle austausch coefficient Bernoulli's theorem boundary layer capillarity cavitation convergence and divergence eddy


fluid mechanics Froude number hydraulics

laminar flow Mach number Magnus effect Pascal's principle Reynolds number terminal velocity Torricelli's theorem

turbulent flow viscosity

rotarr motion: angular momentum angular velocity centrifugal force Coriolis force couple

inertia, moment of precession

reduced mass torque

uniform circular motion


damping pendulum

periodic motion reduced mass resonance

simple harmonic motion vibration others:



celestial mechanics chaos

density equilibrium equivalence principle escape velocity Kepler's laws of planetary motion pressure

reference frame specific gravity statistical mechanics

tensile strength yield point Young's modulus

elementary classical mechanics: acceleration collision d'Alembert's

principle dynamics


gravity, centre of inertia

kinematics kinetics


mechanics momentum motion


equation of Newton's law of gravitation Newton's laws of motion

position vector



See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Section 127.         Electricity and Magnetism


A. The static electric charge

     1. General phenomena of static electricity

          a. The basic laws of electrostatics that relate the interaction of charged bodies at rest

          b. The electrostatic field

          c. The electric dipole

          d. Electrostatic energy and force

          e. Electricity in the atmosphere

[see also 2I2.C., 221.A.3.b., and 223.B.2.]

     2. Electrostatics of dielectrics and capacitors: polarization

     3. Electrostatic potential

          a. High-voltage phenomena

          b. Electric fields and potential distributions in two and three dimensions

     4. Measurement of electrostatic forces and fields

[see 723.D.I.e.]


B. Moving charges and electric currents

     1. Direct electric current: current that flows in one direction

          a. General phenomena of moving electric charges: definitions of electric quantities and their units

          b. Electromotive force

          c. Behaviour of direct currents in electric circuits: Ohm's law; Kirchhoff's laws; the principles of devices that measure or indicate the presence of current, potential difference, and resistance

     2. The conduction of electricity

          a. The motion of charged particles in an electric field

          b. The mechanisms of the conduction of electricity: in a vacuum, in gases, in liquids and solids, in metals and semiconductors

          c. Thermoelectric effects: phenomena in which electric energy is transformed into thermal energy or vice versa

          d. Electron emission: thermionic emission, secondary emission, photoelectric emission

     3. Alternating electric currents: current that reverses itself with uniform frequency

          a. Faraday's law of electromagnetic induction

          b. The mathematical and graphical representation of alternating currents

          c. Basic laws of alternating current circuits

          d. The detection and measurement of alternating currents and voltages

[see 723.D.I c.]

          e. Parallel resonant circuits

          f. Alternating current bridges for determining impedance

          g. Propagation of electric waves in cables

          h. Filters that select signals

          i. Transient phenomena of alternating circuits

          j. Eddy currents and skin, or surface, effects

          k. Principles of generation and transmission of ac single- and multiphase power

     4. Primary effects and properties of electric fields and currents

          a. Magnetic effects of steady electric currents

[see C2., below]

          b. Magnetic effects of changing currents

[see C.4., below]

          c. Force, energy, and power associated with electromagnetic fields

          d. The generation of electromagnetic radiation by the changing of currents in circuits

     5. Effects of electricity on matter

          a. Piezoelectricity and applications of the phenomenon

          b. Optical effects: electroluminescence, Kerr effect, Stark effect

          c. Thermal effect: resistance heating

          d. Chemical effects: electrolysis, electro-osmosis, electrophoresis

          e. Bioelectric effects: effects associated with nerve, brain, and muscle action in which potential differences occur and can be influenced by applied potential


C. Magnetism

     1. General phenomena of magnetic systems

     2. Magnetic effects of steady electric currents

          a. The magnetic field of steady currents: Ampere's law, the law of Biot and Savart

          b. The magnetic moment of a current loop

          c. The magnetic field of a solenoid

     3. Motion of charged particles in magnetic and electric fields

          a. The force on a moving charge

          b. Motion of charges in uniform flux density

          c. Motion of charges in combined electric and magnetic fields

          d. Magnetic dipole moments: atomic moments, nuclear moments, magnetic resonance

     4. Magnetic effects of varying currents

          a. The laws of electromagnetic induction

          b. Inductance and magnetic energy

     5. Properties of magnetic materials

          a. The classification of magnetic substances

          b. Induced and permanent atomic magnetic dipoles

          c. Magnetism of matter

            i. Diamagnetism

            ii. Paramagnetism

            iii. Ferromagnetism

            iv. Antiferromagnetism

            v. Ferrimagnetism

            vi. Terrestrial magnetism

[see also 212.B.]

          d. Atomic structure and magnetism


D. The theory of fields in physics

     1. The definition of a field in physics: the scope of field theory

     2. Mathematical treatment of fields

     3. Classification of fields: material and nonmaterial fields; scalar, vector, and tensor fields

     4. Examples of scalar, vector, and tensor fields in ordinary space

     5. Fields with distributions in more than three dimensions


E. The electromagnetic field and the theory of electromagnetic radiation

     1. The classical theory of radiation

          a. The development of concepts and theories concerning the nature of light

          b. Semiquantitative treatment of electromagnetic radiation: Maxwell's equations for the electromagnetic nature of light

          c. The electromagnetic spectrum

     2. The quantum theory of radiation

          a. Evidences of the particle nature of electromagnetic radiation: Compton effect, photoelectric effect, Raman effect

          b. The wave–particle duality of the photon

          c. The interaction of electromagnetic radiation with atomic and molecular structures: absorption, emission, and scattering processes

          d. The relation of electromagnetic radiation to quantum theory and relativity

     3. The mathematical formulation of electromagnetic theory

          a. Maxwell's equations for electromagnetic fields and radiation

          h. Transmission of radiation in free space

          c. Wave equations in space bounded by conductors

          d. Scattering of electromagnetic waves

          e. Electromagnetic waves in material media

          f. The functions of antennas


F. Relativistic electrodynamics

     1. Electrodynamics in four-dimensional notation

     2. Applications of relativistic principles in the treatment of electromagnetic and nuclear force fields of relativistic particles


Suggested reading in the EncycloArdia Britannica:

MACROPAEDIA: Major articles dealing with electricity and magnetism

Electricity and Magnetism      Energy Conversion Electromagnetic Radiation


MICROPAEDIA: Selected entries               

General subjects          electricity        ether    magnetism of matter:

stationary electric                               

charges and related     electromotive force     infrared radiation        antiferromagnetism

phenomena:     Faraday's law of          Maxwell's        Barkhausen effect

capacitance      induction         equations         Curie point

Coulomb force            inductance       Michelson-Morley       diamagnetism

dielectric         Joule's law       experiment      ferrimagnetism

dielectric constant       Kirchhoff's circuit       Planck's           ferromagnetism

electret            rules     radiation law   hysteresis

electric charge Lenz's law       polarization     magnet

electric dipole  Ohm's law       Poynting vector           magnetic dipole

electric Peltier effect   radiation          magnetic

displacement   reactance         Raman effect  permeability

electric field    resistance         Stefan-            magnetic pole

electric resistivity         Boltzmann law            magnetic

polarization     Seebeck effect            thermal radiation         susceptibility

electric potential          Thomson effect           ultraviolet        magnetostriction

electric electricity in the          radiation          paramagnetism

susceptibility   atmosphere:     magnetic effects of     other:

electrostatic     ball lightning   electric currents:          electrostriction

induction         lightning          Ampere's law  ferroelectricity

Stark effect     Saint Elmo's fire          Biot-Savart law           Leyden jar

electric currents and    electromagnetic fields displacement   permittivity

related phenomena:     and the theory of        current piezoelectricity

alternating current       electromagnetic           magnetic circuit           Zeeman effect

cathode ray     radiation:         magnetic field

charge carrier   electromagnetic           magnetic force           

direct current   field     magnetism      

electric current            electromagnetic           magnetometer

electrical          radiation                     




See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Section 128. Waves and Wave Motion


A. General wave phenomena and the theory of wave motion

     1. General properties of waves: frequency, amplitude, wavelength, phase

     2. Classification of waves

          a. Waves classified by the medium supporting the transmission of wave motion: water waves, sound waves, electromagnetic waves

          b. Waves classified by the motion of particles in a wave: transverse, longitudinal, torsional, and cylindrical waves

          c. Other classifications: bow waves and shock waves

     3. The theory of waves

          a. General characteristics of vibratory motion: periodicity, group velocity, energy content

          b. The velocity of waves

          c. The wave equation: the space-time description of wave motion

          d. Transport of energy and momentum

     4. The principle of superposition of waves

          a. Standing waves: waves with stationary nodes

          b. Modulation of waves

          c. Pulse and wave trains

     5. The behaviour of waves at boundaries or interfaces: reflection, transmission, refraction

     6. The diffraction and interference of waves

     7. The interaction of waves with matter: absorption, dispersion


B. Electromagnetic waves

     1. Properties and behaviour of electromagnetic waves

     2. Waves of the electromagnetic spectrum and their properties

          a. Radio waves

          b. Microwaves

          c. Infrared radiation

          d. Visible light

[see C., below]

          e. Ultraviolet waves

          f. X rays

[see I I I.D.]

          g. Gamma rays

     3. Sources of incoherent electromagnetic waves

          a. Sources of radio waves: oscillators, antennas, cosmic objects

          b. Sources of microwaves: klystrons, magnetrons, Gunn diodes, tunnel diodes, cosmic sources

          c. Sources of infrared, visible, and ultraviolet waves

            i. Blackbody radiation

            ii. Luminescence, fluorescence, phosphorescence

            iii. The passage of electrical current through a resisting medium

          d. Sources of X rays: X-ray tubes (bremsstrahlung), synchrotron radiation

          e. Sources of gamma rays: radioactive nuclei

     4. Sources of coherent electromagnetic waves: lasers and masers

     5. The transmission of electromagnetic waves: through matter, through space, by wave guides and transmission lines


C. Light waves

     1. Light as a wave motion: the wave theory of light

          a. The properties of light consistent with the wave theory: diffraction, interference, polarization, dispersion

          b. The spectrum of light: the description of colour in terms of wavelengths

     2. The velocity of light and its measurement

     3. Interference of light

     4. Diffraction phenomena

     5. Polarization

          a. Superposition of polarized beams: plane, circularly, or elliptically polarized light

          b. Double refraction: waves in anisotropic media

          c. Characterization of polarized light by Stokes's parameters and Poincarê sphere

     6. Properties and behaviour of light waves based on Maxwell's equations of electromagnetic theory

     7. The interaction of light with matter

          a. Reflection and refraction

          b. Dispersion and scattering

          c. Absorption: mechanical and chemical effects of light

     8. The quantum theory of light: the photon

          a. Observed photon phenomena: photoelectric effect, Compton scattering, Rayleigh scattering

          b. The uncertainty principle in relation to the study of the phenomena of light

          c. The detection and counting of photons

     9. The separation of light into its constituent wavelengths, the analysis of light spectra

10. Sources of light

11. The biological effects of light, including photosynthesis

[see 322.A. and 335.B.]


D. The focusing and imaging of light waves

     1. Geometrical optics: the geometry of light rays and their image-forming properties through optical systems

          a. Theoretical considerations: law of reflection, law of refraction, Lagrange theorem, Gauss theory of lenses

          b. Optical systems: components, applications, lens aberrations, brightness of image formed

     2. Optics and information theory

          a. Optical data processing

          b. Holography: a two-step image-forming process using coherent light


E. Sound waves

     1. The nature and properties of sound waves

     2. Shock waves and their characteristics

     3. Sources of sound waves

     4. The reception of sound

     5. Applications of acoustics

          a. Recording and reproduction

[see 735.F.]

          b. Architectural and acoustical design

[see 733.A.8.]

          c. Speech and music

[see 514.D.1. and 624.B.]

          d. Military acoustical detectors

[see 735.J.2.]

          e. Noise control

[see 733.A.8.]

     6. Physical aspects of musical sound

          a. The special properties of musical sound: pitch, timbre, loudness; fundamentals and overtones

          b. The production of sound waves by musical instruments


Suggested reading in the Encyclopedia Britannica:

MACROPAEDIA: Major articles dealing with waves and wave motion

Colour Optics, Principles of

Electromagnetic Radiation     Sound Light

MICROPAEDIA: Selected entries of reference information


General subjects          amplitude        diffraction       double refraction

behaviour and                        

properties of waves:    beat     dispersion        Faraday effect

absorption       Brewster's law Doppler effect Fermat's principle

frequency        infrared radiation        lens      whistler

Huygens' principle      light     light modulator           white noise

interference     luminescence   magnification  other:

longitudinal wave       phosphor         mirror  aureole

moire pattern   phosphorescence         optical image   Cellini's halo

Newton's rings            radiation          optics   halo

phase   rainbow           periscope         Michelson–Morley

Rayleigh scattering     spectrum          prism   experiment

reflection         thermoluminescence    projection screen         mirage

refraction         ultraviolet        projector          MOssbauer effect

Snell's law       radiation          pupil    Munsell colour

standing wave X ray   relative aperture          system

transverse wave           lasers and masers:        spectroscopy   photoelasticity

wave front       laser     stereoscopy     pleochroism

wave motion   maser   sound waves:  Poynting vector

wave number   optical pumping          combination tone        Stokes lines

wave velocity  stimulated       loudness          wave-particle

wavelength      emission          overtone          duality

Young's           manipulation of light   pitch   

experiment      waves: resonance       

electromagnetic           aberration        resonator        

waves: aperture           shock wave    

chemiluminescence     collimator        siren    

colour  critical angle    sound 

electroluminescence    diffraction grating       sound barrier  

electromagnetic           diopter sound intensity           

radiation          fibre optics      timbre 

ether    Fresnel lens     tone    

gamma ray       holography                 



See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Division III.         The Universe: Galaxies, Stars, the Solar System


[For Part One headnote see page 21.]

The outlines in the three sections of Division III deal with the subject matter of cosmology and cosmogony, of astronomy, and of astrophysics.

Accounts of the complex instrumentation involved in these disciplines are set forth in Section 723 of Part Seven. Historical and analytical studies of the nature and scope of astronomy and astrophysics are set forth in Section 10/32 of Part Ten.


Section 131. The Cosmos

Section 132. Galaxies and Stars

Section 133. The Solar System


Section 131.         The Cosmos


A. The structure and properties of the universe

     1. Basic data for the universe

          a. The estimated chemical composition of the universe [see also 121.D.]

          b. The large-scale structure and behaviour of the universe: evidence that the universe is expanding, Hubble's law and the theory of the red shift

          c. The age of the universe

          d. The clustering of galaxies

          e. Cosmic microwave background radiation

          f. The missing mass problem

          g. Space–time: a four-dimensional continuum used to describe the universe

     2. Cosmological models: theoretical representations of the original behaviour of the universe

[see E.1., below]

     3. The known and postulated components of the universe

          a. Distant galaxies

[see 132.A.]

          b. The Local Group of galaxies

[see 132.A.1.c.]

          c. Quasars and related objects, including such hypothetical phenomena as supermassive black holes at the centres of galaxies

          d. Nebulae

          e. Stars and stellar groups

[see 132.0. and 132.D.]

          f. Planetary systems: solar and extrasolar systems

[see also 133.A.]


B. Gravitation: a universal force of mutual attraction that is postulated as acting between all matter

     1. Development of gravitational theory

          a. Early concepts: the Aristotelian viewpoint, contributions of Kepler and Galileo

          b. Newton's law of gravity

[see also 126.A.3.b.v.]

     2. Interpretation of gravity measurements

          a. Potential theory: mathematical representation of the gravitational fields of irregular mass distributions

[see also 10/22.D.2.c.]

          b. Effects of local mass differences: measurement of small gravity anomalies

     3. Modern gravitational theory and its relation to other aspects of physical theory

          a. Field theories of gravity and their general properties and predictions

          b. Gravitational fields and the general theory of relativity: principles and consequences

[see D.2., below]

     4. Acceleration of gravity on the Earth's surface

[see 212.A.[

     5. The gravitational constant, G: methods of measurement, possible variation in time and space


C. Celestial mechanics

[see 126.B.]


D. Properties of the space–time continuum: the astronomical implications of relativity theory

     1. The special theory of relativity

          a. Historical background: the search for the ether

          b. Relativity of space and time

          c. Consequences of the special theory

     2. The general theory of relativity

          a. Use of relativity to interpret gravitational phenomena

          b. Experimental confirmation of the theory

          c. Implications of general relativity


E. The origin and development of the universe

     1. The development of the universe as a whole

          a. Big-bang versus steady-state models of the universe

          b. Primordial nucleosynthesis

          c. The early universe: extrapolations backward in time to the beginning of the universe

     2. The formation and development of components of the universe: galaxies, stars, the solar system

[see also 132.B., 132.D., and 133.A.]

          a. The origin and development of galaxies: protogalaxies

          b. The formation and development of stars

          c. The origin of the solar system

     3. Time scale of the universe: dating of significant events in the history of the universe

     4. Theories of the possible fate of the universe


Suggested reading in the Encyclopxdia Britannica: MACROPAEDIA: Major articles dealing with the cosmos

Analysis and Measurement, Physical and Chemical Cosmos, The


Physical Sciences, The



MICROPAEDIA: Selected entries of reference information

General subjects          element synthesis:       free-fall           Lorentz-


big-bang model           carbon cycle    gravitation       FitzGerald

cosmology       nucleosynthesis           gravitational radius     contraction

COSMOS       proton-proton  Newton's law of          relativistic mass

expanding universe     cycle    gravitation       relativity

Great Attractor           extraterrestrial life:      weight time dilation

Hubble's constant        Green Bank     weightlessness other:

Mach's principle          equation          relativity:         cosmic ray

Olbers' paradox           Ozma, Project Einstein's mass-           ephemeris

quasar  gravitation:      energy relation            Scorpius X-1

steady-state     Cavendish       equivalence     supernova

theory  experiment      principle         


See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Section 132.         Galaxies and Stars


A. Galaxies in general

     1. Statistical properties

          a. Classification of galaxies

          b. Observational methods of determining the distances to galaxies

          c. Distribution of galaxies

     2. Physical properties: size, mass, luminosity, age, composition

     3. Structural features

     4. Clusters of galaxies

          a. Types and distribution

          b. Interactions between cluster members

     5. Extragalactic radio and X-ray sources

          a. Radio galaxies

          b. X-ray galaxies

          c. Quasars

     6. The origin and evolution of the galaxies

[see also 131.E.21


B. The Galaxy: the Milky Way system

     1. Distance determinations in the Galaxy

     2. Stellar velocities: the motions of stars with respect to the Sun, the motion of the Sun with respect to the Local Standard of Rest (LsR)

     3. The stars and star clusters nearest the Sun

     4. The classification of stars according to the Hertzsprung–Russell diagram

     5. The galactic composition

          a. The stellar populations

          b. Emission nebulae: composition and physical characteristics of H II regions

          c. Planetary nebulae

          d. Supernova remnants

          e. Dust clouds

          f. The general interstellar medium: principal components and their distribution throughout the various galactic regions

            i. Grains of interstellar dust

            ii. Interstellar clouds of neutral hydrogen (H I regions)

            iii. Interstellar molecules and radicals

          g. Primary cosmic rays

          h. Interstellar magnetic fields

     6. Structure and dynamics of the Galaxy

          a. The spatial structure of the Galaxy: the dimensions of the Galaxy

          b. Regions of the Galaxy: the nucleus, the central bulge, the dish, the spiral arms, the spherical component, the massive halo

          c. The magnetic field of the Galaxy: its origin and its effects on cosmic rays, radio waves, and light

          d. The rotation of the Galaxy: the differential rotation of stars, gas about the galactic centre

     7. The evolution of the Galaxy

[see also 131.E 2.]

          a. Hydromagnetic and gravitational theories of the formation of spiral structure

          b. Chemical evolution: the problem of the distribution of heavy elements

          c. Star formation: theories concerning the gravitational condensation of galactic dust and gas clouds


C. Star clusters and stellar associations

     1. Globular clusters: systems containing many thousands to a million old stars in a symmetrical, roughly spherical form

     2. Open clusters: systems containing about a dozen to hundreds of stars, usually in an unsymmetrical arrangement

     3. Stellar associations: loose groupings containing dozens to a few hundred stars of similar spectral type and common origin

     4. Relationship of clusters to the Galaxy: the formation and dispersion of clusters and their locations in the Galaxy

     5. Clusters in external galaxies


D. Stars

     1. The identification and nomenclature of the stars

          a. The celestial sphere and celestial coordinate systems

          b. The constellations and other sky divisions

          c. Star names and designations

          d. Modern star maps and catalogs

     2. Observable stellar characteristics

          a. Stellar positions and motions

          b. The apparent brightness or apparent luminosity of the stars: the usv and other systems

          c. Stellar spectra

[see also 11I.C.]

     3. Derived, or calculated, stellar characteristics

          a. Intrinsic stellar brightness: absolute magnitudes, total luminosities

          b. Stellar masses

          c. Stellar diameters

          d. Stellar temperatures

          e. The average characteristics of main-sequence, or dwarf, stars

     4. Stellar variability

          a. Geometric variables; e.g., eclipsing binaries

          b. Intrinsic variables

            i. Pulsating stars; e.g., Cepheid, RR Lyrae, and Beta Canis Majoris variables

            ii. Explosive variables; e.g., novae, supernovae, and novalike variables

     5. Statistics of stars

          a. Correlations between luminosity, spectrum, mass, and radius: the Hertzsprung–Russell diagram and other relations

          b. Statistics of binary star systems

          c. Statistics of special types of stars

     6. Stellar structure

          a. Stellar atmospheres

          b. Internal structure of stars

     7. Stellar evolution

[see also 131.E.2.]

          a. The life history of a typical star

            i. Formation of a protostar by gravitational contraction

            ii. Attainment of the main sequence

            iii. Evolution away from the main sequence

            iv. Estimates of stellar ages

          b. Formation of chemical elements in stars

          c. Probable fates of stars: white dwarfs, neutron stars, black holes


Suggested reading in the Encyclopaedia Britannica: MACROPAEDIA: Major articles dealing with galaxies and stars

Cosmos, The



Physical Sciences, The Stars and Star Clusters

of reference information        


MICROPAEDIA: Selected entries               

General subjects          galaxies:          21-centimetre  nucleosynthesis

astronomical catalogs                         

and instruments:          Andromeda     radiation          Populations I

AG catalog      Galaxy star pairs and groups:  and II

Almagest         Cygnus A        binary star       proton-proton

armillary sphere           galaxy  eclipsing variable         cycle

astronomical map        Maffei I and II            star      white dwarf star

Carte du ciel    Magellanic Cloud        Pleiades           variable stars:

celestial globe  Milky Way Galaxy      star cluster       Cepheid variable

Henry Draper  Seyfert galaxy stellar association        eclipsing variable

Catalogue        Virgo A           stars:    star

Hertzsprung-   nebulae:           Algol   flare star

Russell diagram           Crab Nebula    Alpha Centauri            light curve

Messier catalog           Cygnus Loop  Barnard's star  long-period

New General   Horsehead Nebula      Betelgeuse       variable star

Catalogue of   Lagoon Nebula           Bethlehem, Star of      nova

Nebulae and    nebula  colour index    supernova

Clusters of Stars          North American          Eta Carinae     T Tauri star

star catalog      Nebula Fomalhaut       U Geminorum star

constellations: Orion Nebula  Harvard           variable star

Aquarius          Ring Nebula    classification   other:

Aries    StrOmgren sphere       system degenerate gas

Cancer 30 Doradus     Kepler's Nova galactic coordinate

Capricornus     Trifid Nebula  magnitude       H I region

constellation    radio and X-ray           Mira Ceti         H II region

Crux    emission:         Sirius   infrared source

Gemini            cosmic ray       star      interstellar

Leo      forbidden lines            Sun      medium

Orion   pulsar   Tycho's Nova  light-year

Pisces  radio source     stellar evolution:          limb darkening

Sagittarius       red shift           black hole        parallax

Scorpius          Sagittarius A   carbon cycle    parsec

Taurus Scorpius X-1   Chandrasekhar           

Ursa Major      synchrotron     limit    

Virgo   radiation          giant star        

                        neutron star    



See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above

Section 133.         The Solar System


A. A survey of the solar system

     1. The Sun

[see B., below]

     2. The major planets of the solar system, their surfaces and atmospheres, their satellites

[see C., D., and E., below]

     3. Other constituents of the solar system

          a. Minor planets, or asteroids

          b. Comets

          c. Meteoroids, meteors, and meteorites

          d. The interplanetary medium

     4. Regularities of the solar system: the distances of the planets from the Sun, the distribution of natural satellites

     5. Interactions among various bodies in the solar system: gravitational perturbations, actual physical encounters

     6. Theories of the origin of the solar system: origin by an orderly process, origin by catastrophe

[see also 131.E.2.c.]


B. The Sun

     1. The Sun's surface layers and their features: the quiet Sun

          a. Solar data derived from observations of the photosphere, the visible luminous surface of the Sun

          b. The chromosphere, the relatively transparent layer that forms a transition zone between the Sun's photosphere and corona: the flash spectrum, spicules, supergranulation

          c. The corona, the luminous, high-temperature, rarefied gas envelope of the Sun: form, structure, physical properties; the solar wind

     2. Solar features that occur with increased frequency during the active phase of the solar cycle: the active Sun

          a. Centres of activity: areas of localized strong magnetic fields at the Sun's surface

          b. Sunspots: their physical nature, the sunspot cycle of about 11 years

          c. Other features; e.g., faculae, prominences, flares, corona( condensations

     3. The solar interior: energy generation, the evolution of the Sun

[sec also 132.1.7.]

     4. Solar radiation, including light, radio waves, and particles

     5. Solar-terrestrial relationships and interactions


C. The planets and their satellites

     1. The terrestrial planets

          a. Mercury

          b. Venus

          c. Earth

[see D.. below]

          d. Mars

     2. The minor planets, or asteroids

[see .A.3.a aboN el

     3. The giant planets and Pluto

          a. Jupiter

          b. Saturn

          c. Uranus

          d. Neptune

          e. Pluto


D. The Earth as a planet

     1. The distance of the Earth from the Sun: the astronomical unit and solar parallax

     2. The orbital motion of the Earth around the Sun and the rotation of the Earth on its axis: the year, the day, the precession of the equinoxes

[see also E.7.a., below]

     3. Effects of the Earth's orbital position and speed on astronomical observations

          a. Astronomical parallax

          b. Aberration of light

     4. The Earth's magnetism, temperature, and other physical properties

[see 212]

     5. The structure and composition of the Earth's interior

[sec 213]

     6. The origin of the Earth, its atmosphere, hydrosphere, and surface features

[see 232 and 241]


E. The Moon

     1. The shape, radius, mean density, and varying brightness of the Moon

     2. The motion of the Moon

          a. The apparent motion: the month, or sidereal and synodic periods of the Moon; optical and physical librations

[see 7.a.n., below]

          b. The actual motion

     3. The mass and gravitational field of the Moon

          a. Underlying theory: basic gravitational properties of the Moon

          b. Discovery of lunar mascons: gravity anomalies on the Moon

     4. The physical nature of the Moon

          a. Observations from Earth and from space vehicles: results of remote lunar photography, manned lunar landings, and close-up photography

[see also 738.C.]

          b. The lunar surface features: craters, lineaments (e.g., mare ridges, the lunar grid system, rilles), temporary or transient features

          c. Theories of origin of the Moon's surface features: the volcanic and impact theories

     5. The origin and evolution of the Moon

          a. Probable development of the Moon's orbit

          b. Evidence from the composition and physical properties of the Moon

     6. The chemical nature of the Moon

          a. Surface composition: findings of the chemical analysis of lunar rock samples

          b. Possible zonal variations of the interior

     7. The Sun–Earth–Moon system

          a. Relative motions of the Sun, Earth, and Moon

            i. The geometry of the Sun–Earth–Moon system: the celestial equator, the apparent motion of the Sun along the ecliptic, the inclination of the Earth's axis to its orbit

           ii. Motions of the Sun–Earth–Moon system as the astronomical basis of chronology: the day, month, and year; the Sothic cycle, Metonic cycle, and other complex cycles

          b. Eclipses of the Sun and Moon

          c. Tides in the Earth and in the Moon

[see also 222.G.3.[


Suggested reading in the Encyclopedia Britannica:

MACROPAEDIA: Major articles dealing with the solar system. See also Section 211 of Part Two


Earth, The: Its Properties, Composition, and Structure Eclipse, Occultation, and Transit

Physical Sciences, The

Solar System, The


MICROPAEDIA: Selected entries of reference information General subjects

calendars:        Dionysian period         Gregorian calendar      Julian calendar

Aztec calendar            Egyptian calendar       intercalation    Julian period

calendar           French republican        international date        leap year

Chinese calendar         calendar           line      lunar calendar

day      Greek calendar            Jewish calendar           Mayan calendar


Muslim calendar perpetual calendar Roman republican calendar

solar calendar Tibetan calendar week


comets.. Arend-Roland, Comet comet

Encke's Comet Halley's Comet



Callisto Europa Ganymede

Great Red Spot


Jupiter Mars:

Chryse Planitia Deimos Mars

Olympus Mons Phobos Syrtis Major Tharsis Utopia Planitia

Mercury.. Caloris Mercury

minor planets: asteroid Eros

Icarus Pallas Ra-Shalom

Trojan planets Moon:

Cassini's laws Copernicus libration Linne

Mare Orientale Moon


Neptune: Neptune

Nereid Triton

objects of extraterrestrial origin: achondrite carbonaceous

chondrite chondrite chondrule


meteor shower meteorite meteoritics meteoroid

Orgueil meteorite tektite

Tunguska event

planetary motion:


constant of anomaly conjunction Copernican systemeclipse ecliptic equinox equinoxes, precession of the heliocentric system nutation



orbital velocity parallax phase

Ptolemaic system retrograde motion solstice

synodic period tidal friction


Tychonic system zodiac


Charon Pluto


Dione Enceladus

Iapetus Mimas Phoebe Rhea

Saturn Tethys Titan


chromosphere corona facula

flash spectrumheliopause

limb darkening photosphere solar cycle solar energy solar flare

solar nebula solar

prominence solar radiation solar wind Sun





Oberon Titania Umbriel Uranus


Venus other:

albedo Bode's law

celestial mechanics Forbush effect gegenschein interplanetary medium


planet Planet X planetesimal quadrature



solar system


See Section 10/32 of Part Ten

INDEX: See entries under all of the terms above