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The Grand Design

Page 13

by Stephen Hawking


  Alternative histories • a formulation of quantum theory in which the probability of any observation is constructed from all the possible histories that could have led to that observation.

  Anthropic principle • the idea that we can draw conclusions about the apparent laws of physics based on the fact that we exist.

  Antimatter • each particle of matter has a corresponding anti-particle. If they meet, they annihilate each other, leaving pure energy.

  Apparent laws • the laws of nature that we observe in our universe—the laws of the four forces, and the parameters such as mass and charge that characterize the elementary particles—in contrast to the more fundamental laws of M-theory that allow for different universes with different laws.

  Asymptotic freedom • a property of the strong force that causes it to become weaker at short distances. Hence, although quarks are bound in nuclei by the strong force, they can move within nuclei almost as if they felt no force at all.

  Atom • the basic unit of ordinary matter, consisting of a nucleus with protons and neutrons, surrounded by orbiting electrons.

  Baryon • a type of elementary particle, such as the proton or neutron, that is made of three quarks.

  Big bang • the dense, hot beginning of the universe. The big bang theory postulates that about 13.7 billion years ago the part of the universe we can see today was only a few millimeters across. Today the universe is vastly larger and cooler, but we can observe the remnants of that early period in the cosmic microwave background radiation that permeates all space.

  Black hole • a region of space-time that, due to its immense gravitational force, is cut off from the rest of the universe.

  Boson • an elementary particle that carries force.

  Bottom-up approach • in cosmology, an idea that rests on the assumption that there’s a single history of the universe, with a well-defined starting point, and that the state of the universe today is an evolution from that beginning.

  Classical physics • any theory of physics in which the universe is assumed to have a single, well-defined history.

  Cosmological constant • a parameter in Einstein’s equations that gives space-time an inherent tendency to expand.

  Electromagnetic force • the second strongest of the four forces of nature. It acts between particles with electric charges.

  Electron • an elementary particle of matter that has a negative charge and is responsible for the chemical properties of elements.

  Fermion • a matter-type elementary particle.

  Galaxy • a large system of stars, interstellar matter, and dark matter that is held together by gravity.

  Gravity • the weakest of the four forces of nature. It is the means by which objects that have mass attract each other.

  Heisenberg uncertainty principle • a law of quantum theory stating that certain pairs of physical properties cannot be known simultaneously to arbitrary precision.

  Meson • a type of elementary particle that is made of a quark and an anti-quark.

  M-theory • a fundamental theory of physics that is a candidate for the theory of everything.

  Multiverse • a set of universes.

  Neutrino • an extremely light elementary particle that is affected only by the weak nuclear force and gravity.

  Neutron • a type of electrically neutral baryon that with the proton forms the nucleus of an atom.

  No-boundary condition • the requirement that the histories of the universe are closed surfaces without a boundary.

  Phase • a position in the cycle of a wave.

  Photon • a boson that carries the electromagnetic force. A quantum particle of light.

  Probability amplitude • in a quantum theory, a complex number whose absolute value squared gives a probability.

  Proton • a type of positively charged baryon that with the neutron forms the nucleus of an atom.

  Quantum theory • a theory in which objects do not have single definite histories.

  Quark • an elementary particle with a fractional electric charge that feels the strong force. Protons and neutrons are each composed of three quarks.

  Renormalization • a mathematical technique designed to make sense of infinities that arise in quantum theories.

  Singularity • a point in space-time at which a physical quantity becomes infinite.

  Space-time • a mathematical space whose points must be specified by both space and time coordinates.

  String theory • a theory of physics in which particles are described as patterns of vibration that have length but no height or width—like infinitely thin pieces of string.

  Strong nuclear force • the strongest of the four forces of nature. This force holds the protons and neutrons inside the nucleus of an atom. It also holds together the protons and neutrons themselves, which is necessary because they are made of still tinier particles, quarks.

  Supergravity • a theory of gravity that has a kind of symmetry called supersymmetry.

  Supersymmetry • a subtle kind of symmetry that cannot be associated with a transformation of ordinary space. One of the important implications of supersymmetry is that force particles and matter particles, and hence force and matter, are really just two facets of the same thing.

  Top-down approach • the approach to cosmology in which one traces the histories of the universe from the “top down,” that is, backward from the present time.

  Weak nuclear force • one of the four forces of nature. The weak force is responsible for radioactivity and plays a vital role in the formation of the elements in stars and the early universe.

  THE UNIVERSE HAS A DESIGN, and so does a book. But unlike the universe, a book does not appear spontaneously from nothing. A book requires a creator, and that role does not fall solely on the shoulders of its authors. So first and foremost we’d like to acknowledge and thank our editors, Beth Rashbaum and Ann Harris, for their near-infinite patience. They were our students when we required students, our teachers when we required teachers, and our prodders when we required prodding. They stuck with the manuscript, and did it in good cheer, whether the discussion centered around the placement of a comma or the impossibility of embedding a negative curvature surface axisymmetrically in flat space. We’d also like to thank Mark Hillery, who kindly read much of the manuscript and provided valuable input; Carole Lowenstein, who did so much to help with the interior design; David Stevenson, who guided the cover to completion; and Loren Noveck, whose attention to detail has saved us from some typos we would not like to have seen committed to print. To Peter Bollinger: much gratitude for bringing art to science in your illustrations, and for your diligence in ensuring the accuracy of every detail. And to Sidney Harris: Thank you for your wonderful cartoons, and your great sensitivity to the issues facing scientists. In another universe, you could have been a physicist. We are also grateful to our agents, Al Zuckerman and Susan Ginsburg, for their support and encouragement. If there are two messages they consistently provided, they were “It’s time to finish the book already,” and “Don’t worry about when you’ll finish, you’ll get there eventually.” They were wise enough to know when to say which. And finally, our thanks to Stephen’s personal assistant, Judith Croasdell; his computer aide, Sam Blackburn; and Joan Godwin. They provided not just moral support, but practical and technical support without which we could not have written this book. Moreover, they always knew where to find the best pubs.

  Air, discovery of

  Almagest (Ptolemy)

  Alternative histories. See also Quantum physics/quantum theory

  Feynman diagrams and

  Feynman’s sum over histories and

  the past and

  quantum vs. Newtonian worlds and

  universe and

  Anaximander

  Anthropic principle

  strong anthropic principle

  weak anthropic principle

  Antimatter

  Anti-quarks (pi mesons)

  Anti
-realists

  Apparent laws of nature

  Aquinas, Thomas

  Archimedes

  Aristarchus

  Aristotle

  creation as deliberate design

  four-element theory

  on no exceptions to natural laws

  rate of falling objects theory

  reason for principles of nature

  use of reason instead of observation

  Asymptotic freedom

  Atomism

  Atoms

  hydrogen, Lamb shift and

  quarks, protons, and neutrons

  strong nuclear force and

  Augustine of Hippo, St.

  Babylonians

  Baryon

  Berkeley, George

  Beryllium

  Big bang theory

  CMBR and

  evidence of

  irregular universe and inflation

  as spontaneous quantum event

  when it happened

  Black hole

  Boshongo people

  Boson

  Brain

  laws of science and

  model building of

  Buckyballs

  buckyball soccer

  particle paths

  Buoyancy, law of

  Caenorhabditis elegans

  Carbon

  as basis for life

  creation of, in primordial universe

  triple alpha process and

  in universe

  Carroll, John W.

  Cathode rays

  CERN, Geneva

  Chemistry

  Chinese philosophy and mythology

  God as Creator

  tale of the ten suns

  Christianity

  creation as deliberate design

  John XXI’s list of heresies, science and

  miracles

  natural laws as obedient to God

  notion of free will and purpose

  Ptolemaic model adopted by Roman Catholic Church

  rejection of indifferent natural laws

  Roman Catholic Church acknowledges wrong to Galileo

  Clepsydra

  Conway, John

  Copernicus

  Corpuscle theory

  Cosmic microwave background radiation (CMBR)

  evidence of inflation and

  Cosmological constant

  Cosmology. See also Universe

  “bottom up” approach

  grand design and

  laws of nature as “fine-tuned”

  number of dimensions in the universe

  predictions in

  “top down” approach

  Crater Lake, Oregon

  Creation. See also Life; Universe

  account in Genesis

  big bang theory

  empirical evidence of

  God as Creator

  as godless

  of life

  M-theory and

  myths

  origin of the universe

  spontaneous quantum creation of the universe

  Curvature/curved spaces

  geodesics

  great circle

  Darwin, Charles

  Davisson, Clinton

  Davy, Sir Humphrey

  Delayed-choice experiments

  Democritus

  De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres [Copernicus])

  Descartes, René

  Dicke, Robert

  Double-slit experiment

  buckyball soccer

  delayed-choice experiments

  Feynman’s insight

  particle paths

  two-slit soccer

  “which-path” information

  Dualities

  Earth

  as center of the universe

  cessation of rotation

  Copernican model and

  creation

  curvature of, and geodesics

  eclipse and

  ether (luminiferous ether) and

  gravity and

  as hospitable to life

  laws of nature and

  Mercator projection, world map

  orbit

  planetary system of

  Ptolemaic model and

  seasonal weather patterns

  speed of

  Eccentricity of elliptical orbits

  Eclipse (lunar or solar)

  prediction of

  Economics

  Eddington, Arthur

  Effective theory

  Egyptian creation myth

  Einstein, Albert

  cosmological constant

  on creation of the universe

  expanding universe and

  general relativity

  photoelectric effect

  special relativity

  on time

  on unified theory

  on the universe

  Einstein’s theory of relativity

  general relativity

  GPS satellite navigation systems and general relativity

  space-time and general relativity

  special relativity

  Electromagnetic force

  bosons and

  electroweak force and

  light and

  Maxwell’s equations

  QED and

  speed of electromagnetic waves

  Electrons

  double-slit experiment and

  Feynman diagrams and

  particle paths

  Electroweak force

  three new particles discovered

  Elegance, of models

  Empedocles

  Energy

  constant zero

  of empty space

  of universe

  Epicurus

  Ether (luminiferous ether)

  Euclid

  Evolution

  Faraday, Michael

  Fermion

  Feynman, Richard (Dick)

  Feynman diagrams

  Feynman paths

  QED and

  sum over histories

  van owned by

  FitzGerald, George Francis

  Force fields

  bosons

  fermions

  Fowler, William

  Free will

  Friedmann, Alexander

  Fuller, Buckminster

  Galaxies

  alternative histories and

  cosmological constant and

  expanding universe and

  heavy elements and formation of

  inhomogeneities in universe and

  light from distant

  number of and stars in

  planetary systems of

  quantum fluctuations and formation of

  Galileo

  rate of falling objects theory

  Game of Life

  blinkers

  evolution of a still life

  glider guns

  gliders

  still-life blocks

  Geodesics

  Germer, Lester

  God (or gods)

  as causal in nature

  creation and

  as dice-thrower

  first-cause argument

  Joshua praying for the sun and moon to halt

  as mathematician

  natural laws, human statues and

  natural laws and

  Newton’s belief in God’s intervention

  universe as God’s dollhouse

  what happened before the world existed?

  Grand design

  laws of nature as “fine-tuned” and

  no-boundary condition and

  Grand unified theories (GUTS)

  Gravitational waves

  Gravity

  cosmological constant

  cosmological constant and

  creation of stars, galaxies, planets

  effective theory and

  Einstein’s general relativity and

  galaxies and

  mathematical
formulation of theory

  M-theory and

  Newton’s law of

  orbits and three dimensions

  quantum theory and

  as shaper of space-time

  standard model not applicable

  supergravity theory

  warpage of time and space by

  as weak force

  Great circle

  Greece, ancient

  distinction between human and natural laws lacking

  Ionian science

  laws of nature and

  questions of creation and

  scientific method lacking

  Stoics

  “Grimnismal” (The Elder Edda)

  Harris, Sidney, cartoons by

  Heisenberg, Werner

  Heisenberg uncertainty principle

  empty space, impossibility of, and

  Planck’s constant

  Helium

  big bang theory and

  creation of beryllium, carbon, and

  in primordial universe

  Heraclitus

  Hitchhiker’s Guide to the Galaxy

  Holographic principle

  Hoyle, Fred

  Hubble, Edwin

  Humans. See also Life

  creation of, Biblical

  definition of living beings

  existence relative to cosmic history

  free will and

  natural laws and

  origins of homo sapiens

  psychology as study of will and behavior

  robot vs.

  self-awareness

  soul of

  written language and cultivation begun

  Hume, David

  Hydrogen

  fusion, in stars

  isotopes

  Lamb shift and

  in primordial universe

  Inertia, law of

  Inflation theory

  irregular universe and

  “Initial conditions”

  Intelligent design

  Interference

  constructive

  destructive

  double-slit experiment

  Newton’s rings and

  puddle interference

  “which-path” information and

  Young’s experiment and

  Ionian science

  Johnson, Samuel

  John XXI, Pope

  Kelvin, William Thomson, Lord

 

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