by Lee Smolin
Nonlocality: Any phenomenon which does not satisfy the principle of locality, and so involves influences transmitted between systems separated in space.
Operationalism: An approach to instrumentalism in which one specifies for a physical system a set of operations which include how it is to be prepared and how it is to be measured.
Past or causal past: For a particular event, all other events that could have influenced it by sending energy or information to it.
Photon: A quantum of the electromagnetic field, which carries an amount of energy proportional to the frequency of the field.
Pilot wave theory: The first realist approach to quantum mechanics, invented by Louis de Broglie in 1927 and reinvented by David Bohm in 1952. A complete description of an individual system is given by both a wave and a particle, where the particle is guided by the wave.
Planck’s constant: The fundamental quantity specifying the scale at which the effects of quantum physics depart from those of Newtonian physics. Usually represented as h. It comes into the relationships between the energy of a quantum and the frequency of the related wave.
Planck energy: A unit of energy constructed by multiplying Planck’s constant, h, Newton’s gravitational constant, G, and the speed of light, c, together in the right combination to give an energy. It is equal to the energy in one hundred-thousandth of a gram.
Planck length: The unit of length so constructed; it is roughly twenty powers of ten smaller than an atomic nucleus.
Planck mass: The unit of mass so constructed, about one hundred-thousandth of a gram.
Quanta (n., pl.): The particle side of the wave-particle duality.
Quantize (v.): To follow an algorithm that takes as input a classical or Newtonian theory and outputs a corresponding quantum theory. It is known that any such algorithm is highly non-unique.
Quantum Bayesianism: An approach to quantum foundations according to which all uses of probability in quantum mechanics are subjective, betting probabilities.
Quantum cosmology: The theory that attempts to describe the whole universe in the language of quantum theory.
Quantum equilibrium: In a hidden variable theory such as pilot wave theory, the statistical distribution of particles in an ensemble of systems is arbitrary. When it is equal to the square of the wave function, as is specified in Born’s rule, the system is said to be in quantum equilibrium.
Quantum field theory: A quantum theory of fields such as the electric and magnetic fields. These are challenging because they must incorporate special relativity and also because they have an infinite number of degrees of freedom.
Quantum gravity: The theory which combines general relativity and quantum physics.
Quantum mechanics: The theory of atoms and light as developed in the 1920s.
Quantum state: A complete description of an individual system according to quantum mechanics.
Realism: The belief that there is an objective physical world whose properties are independent of what human beings know or which experiments we choose to do. Realists also believe that there is no obstacle in principle to our obtaining complete knowledge of this world.
Relationalism: The philosophy that all the properties of elementary objects or events arise from interactions between pairs or larger sets of them, and hence measure shared properties.
Relational quantum theory: An interpretation of quantum theory according to which the quantum state of a particle, or of any subsystem of the universe, is defined not absolutely, but only in a context created by the presence of an observer, and by a division of the universe into a part containing the observer and a part containing that part of the universe from which the observer can receive information. Relational quantum cosmology is an approach to quantum cosmology which asserts that there is not one quantum state of the universe, but as many states as there are such contexts.
Relativity, the general theory of: Einstein’s 1915 theory of gravitation in which the gravitational force is replaced by the dynamics of the spacetime geometry.
Relativity, the special theory of: Einstein’s 1905 theory of motion and light in the absence of gravity.
Retrocausality: Hypothetical processes in which the order of causes runs backward relative to the global direction of time.
Rule 0: The basic dynamical equation of quantum gravity, which expresses the absence of a global or universal time. Also called the Wheeler-DeWitt equation.
Rule 1: The basic dynamical equation of quantum mechanics that describes how quantum states evolve with respect to time as measured by clocks outside the quantum system. Also called the Schrödinger equation. Rule 1 explains that given the quantum state of an isolated system at one time, there is a law that will predict the precise quantum state of that system at any other time.
Rule 2: The law that prescribes how a quantum state responds to a measurement, which is to collapse immediately into a state within which the measured quantity has a precise value, the value that the measurement produced. Rule 2 explains that the outcome of a measurement can only be predicted probabilistically. But afterward, the measurement changes the quantum state of the system being measured, by putting it in the state corresponding to the result of the measurement. This is called collapse of the wave function.
Schrödinger’s cat experiment: A thought experiment in which Rule 1 implies that a cat is in a superposition of two distinct macroscopic states: living and dead.
Schrödinger’s equation: See Rule 1.
Second law of thermodynamics: States that the entropy of an isolated system will most probably increase.
Speed: The rate of change of distance with time.
Spin: The angular momentum of an elementary particle which is an intrinsic property of it, independent of its motion.
Spin network: A graph whose edges are labeled by numbers representing spins. In loop quantum gravity each quantum state of the geometry of space is represented by a spin network.
Standard model of particle physics: A quantum field theory which is our best model of the elementary particles and their interactions, except for gravity.
State: In any physical theory, the configuration of a system at a specified moment of time.
String theory: An approach to quantum gravity based on the hypothesis that the fundamental things in the world are one-dimensional.
Symmetry: An operation by which a physical system may be transformed without affecting the fact that its state is a possible state of the system. Two states connected by a symmetry have the same energy.
Uncertainty principle: A principle in quantum theory according to which it is impossible to measure both the position and momentum (or velocity) of a particle.
Velocity: The rate of change of position in time.
Wave function: A representation of the quantum state of a system.
Wave mechanics: A form of quantum mechanics invented by Erwin Schrödinger in 1926. Later shown to be equivalent to matrix mechanics.
Wave-particle duality: A principle of quantum theory according to which one can describe elementary particles as both particles and waves, depending on the context.
FURTHER READING
Popular Books by the Inventors of Quantum Mechanics
Bell, J. S. Speakable and Unspeakable in Quantum Mechanics. 2nd ed. Introduction by Alain Aspect; two additional papers. Cambridge, UK: Cambridge University Press, 2004.
Bohm, David. Wholeness and the Implicate Order. London: Routledge and Kegan Paul, 1980. Reprint, London: Ark / Routledge, 2002.
Bohr, Niels. Atomic Physics and Human Knowledge. New York: Science Editions, 1961. Reprint, Mineola, NY: Dover Publications, 2010.
Bohr, Niels. Atomic Theory and the Description of Nature: Four Essays with an Introductory Survey. Cambridge, UK: Cambridge University Press, 1934, 1961. Reprint, 2011.
Bohr, Niels. “Discussion with Einstein
on Epistemological Problems in Atomic Physics.” In Albert Einstein: Philosopher-Scientist, edited by Paul Arthur Schilpp, 199–242. 3rd ed. Library of Living Philosophers 7. Peru, IL: Open Court Publishing, 1988.
Einstein, Albert. Autobiographical Notes. Translated and edited by Paul Arthur Schilpp. Centennial ed. Peru, IL: Open Court Publishing, 1999.
Einstein, Albert. Ideas and Opinions. Reprint ed. New York: Broadway Books, 1995.
Heisenberg, Werner. Philosophical Problems of Quantum Physics. 2nd ed. Woodbridge, CT: Ox Bow Press, 1979.
Heisenberg, Werner. The Physical Principles of the Quantum Theory. Translated by Carl Eckart and F. C. Hoyt. Mineola, NY: Dover Publications, 1949.
Schrödinger, Erwin. What Is Life? With Mind and Matter and Autobiographical Sketches. Foreword to What Is Life? by Roger Penrose. Cambridge, UK: Canto / Cambridge University Press, 1992.
Books by Contemporary Contributors
Barbour, Julian. The End of Time: The Next Revolution in Our Understanding of the Universe. New York: Oxford University Press, 1999.
Carroll, Sean. The Big Picture: On the Origins of Life, Meaning, and the Universe Itself. New York: Dutton, 2016.
Deutsch, David. The Beginning of Infinity: Explanations that Transform the World. New York: Viking, 2011.
Deutsch, David. The Fabric of Reality: The Science of Parallel Universes—and Its Implications. New York: Penguin Press, 1997.
Greene, Brian. The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos. New York: Alfred A. Knopf, 2011.
Penrose, Roger. The Emperor’s New Mind: Concerning Computers, Minds, and The Laws of Physics. Reprint ed., with a new preface by the author. Oxford and New York: Oxford University Press, 1999.
Penrose, Roger. Shadows of the Mind: A Search for the Missing Science of Consciousness. Oxford and New York: Oxford University Press, 1994.
Rovelli, Carlo. The Order of Time. New York: Riverhead Books, 2018. // L’ordine del tempo. Milan: Adelphi Edizioni, 2017.
Rovelli, Carlo. Reality Is Not What It Seems: The Journey to Quantum Gravity. New York: Riverhead Books, 2017. // La realtà non è come ci appare: La struttura elementare delle cose. Milan: Raffaello Cortina Editore, 2014.
Rovelli, Carlo. Seven Brief Lessons on Physics. New York: Riverhead Books, 2016. // Sette brevi lezioni di fisica. Milan: Adelphi Edizioni, 2014.
Tegmark, Max. Our Mathematical Universe: My Quest for the Ultimate Nature of Reality. New York: Alfred A. Knopf, 2014.
Biographies of Key Figures
Byrne, Peter. The Many Worlds of Hugh Everett III: Multiple Universes, Mutual Assured Destruction, and the Meltdown of a Nuclear Family. Oxford and New York: Oxford University Press, 2010.
Farmelo, Graham. The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom. New York: Basic Books, 2009.
Gribbin, John. Erwin Schrödinger and the Quantum Revolution. Hoboken, NJ: John Wiley and Sons, 2013.
Hoffmann, Banesh, with Helen Dukas. Albert Einstein: Creator and Rebel. New York: Viking Press, 1973.
Klein, Martin J. Paul Ehrenfest. Vol. 1: The Making of a Theoretical Physicist. New York: American Elsevier, 1970.
Overbye, Dennis. Einstein in Love: A Scientific Romance. New York: Penguin, 2000.
Pais, Abraham. Niels Bohr’s Times: In Physics, Philosophy, and Polity. Oxford, UK, and New York: Clarendon Press / Oxford University Press, 1991.
Pais, Abraham. Subtle is the Lord: The Science and the Life of Albert Einstein. Oxford, UK, and New York: Oxford University Press, 1982. Reprint ed., with a new foreword by Roger Penrose, 2005.
Peat, F. David. Infinite Potential: The Life and Times of David Bohm. Reading, MA: Addison-Wesley, 1997.
Histories of Quantum Physics
Bacciagaluppi, Guido, and Antony Valentini. Quantum Theory at the Crossroads: Reconsidering the 1927 Solvay Conference. Cambridge, UK, and New York: Cambridge University Press, 2009.
Baggott, Jim. The Quantum Story: A History in 40 Moments. Oxford, UK, and New York: Oxford University Press, 2011.
Baggott, Jim. Beyond Measure: Modern Physics, Philosophy, and the Meaning of Quantum Theory. Oxford, UK, and New York: Oxford University Press, 2004.
Forman, Paul. “Weimar Culture, Causality, and Quantum Theory, 1918–1927: Adaptation by German Physicists and Mathematicians to a Hostile Intellectual Environment.” Historical Studies in the Physical Sciences, Vol. 3 (1971): 1–115. Forman expanded on his original argument in: Forman, Paul. “Kausalität, Anschaulichkeit, and Individualität, or How Cultural Values Prescribed the Character and the Lessons Ascribed to Quantum Mechanics.” In Society and Knowledge: Contemporary Perspectives in the Sociology of Knowledge and Science, edited by Nico Stehr and Volker Meja, 333–47. New Brunswick, NJ: Transaction Books, 1984.
Gefter, Amanda. Trespassing on Einstein’s Lawn: A Father, a Daughter, the Meaning of Nothing, and the Beginning of Everything. New York: Bantam Books, 2014.
Gilder, Louisa. The Age of Entanglement: When Quantum Physics Was Reborn. New York: Alfred A. Knopf, 2008.
Gribbin, John. In Search of Schrödinger’s Cat: Quantum Physics and Reality. New York: Bantam Books, 1984.
Jammer, Max. The Philosophy of Quantum Mechanics: The Interpretations of Quantum Mechanics in Historical Perspective. New York: John Wiley and Sons, 1974.
Kaiser, David. How the Hippies Saved Physics: Science, Counterculture, and the Quantum Revival. New York: W. W. Norton, 2011.
Kragh, Helge. Quantum Generations: A History of Physics in the Twentieth Century. Princeton: Princeton University Press, 1999. Reprint, 2002.
Kuhn, Thomas S. Black-Body Theory and the Quantum Discontinuity, 1894–1912. Chicago: University of Chicago Press, 1987.
Stone, A. Douglas. Einstein and the Quantum: The Quest of the Valiant Swabian. Princeton: Princeton University Press, 2013.
Collections of Papers
DeWitt, Bryce Seligman, and Neill Graham, eds. The Many Worlds Interpretation of Quantum Mechanics. Princeton Series in Physics. Princeton: Princeton University Press, 1973. Reprint ed.: Princeton Legacy Library, 2015.
Saunders, Simon, Jonathan Barrett, Adrian Kent, and David Wallace, eds. Many Worlds? Everett, Quantum Theory, and Reality. Oxford: Oxford University Press, 2010.
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INDEX
The page numbers in this index refer to the printed version of this book. The link provided will take you to the beginning of that print page. You may need to scroll forward from that location to find the corresponding reference on your e-reader.
academic community, 277
academic life, 94
acceleration, 297
actuality, possibility and, 177–78, 197–98, 200, 243
adjacent possible, 201
Against Method (Feyerbend), 173
Aharonov, Yakir, 118, 216
alternate geometry, 229
American Communist Party, 115n
amplitude, 138
angular momentum, 77, 263n, 297
anti-realism, xxvi, xxix, 8, 26, 94, 117, 175
of Bohr, 106
definition of, 297
electrons and, 85
nature and, xxv
physics and, xxv
quantum mechanics and, xxi
approximations, 192
Arcadia (Stoppard), 15
Aspect, Alain, 45, 46, 49, 220
assumptions, 10
astronomy, 274
atomic bomb, 108
atomic laws, 251–52, 258
atomic scale, xvii, xx, 77, 91
atomic systems, wave function and, 141, 213
atoms, xiv, xv, xvii, 56, 71
behavior of, 129
Bohr on, 93
chemical properties of, 3
communication between, 46–47
&
nbsp; configuration space of, 122–24, 123, 217–18
copies of, 248
decay of, 125
definition of, 297
density of, 73
electrons and, 78, 83
energy and, 77–78
ensemble of, 59
entanglement of, 252
freedom and, 246
gravity and, 74
Heisenberg on, 87
laws of, 251–52, 258
light and, 77–78
location of, 5
matter and, 72
measurement of, 195
molecules and, 3, 246–47
nucleus of, 74
observables of, 27
photons and, 195, 209–10
pilot wave theory and, 122
properties of, xvi, 5, 6–7
quantum mechanics and, 6, 62
quantum states of, 37–38
quantum teleportation, 186
radiation and, 52, 93, 125
realism and, 75
retrocausality, 216–17, 217
solar system and, 74
spacetime, 257–59
spectrum of, 59–60, 78
states of, 49–51, 60–61, 77–78, 146–47, 152
stationary states of, 77
superposition of, 4–5, 6–7, 50, 139–40, 146, 152, 156–57
true theory of, xxi
water and, xv
averages, 62–63
backgrounds
cosmic microwave, 121
definition of, 297
dependence on, 264, 297
independence principle, 229, 264, 267, 297
spacetime and, 269
symmetry and, 264
Barbour, Julian, 201–3, 244
Bateson, Gregory, 191
Bayesian probabilities, 160–61, 163, 297
beables, 26–27, 206–7, 213, 218, 222, 224, 240
beliefs, 164, 205
Bell, John, xxviii, xxix, 26, 39, 41, 45, 47–49, 55, 56, 105, 220
