The Elegant Universe - Brian Greene [226]
Product. The result of multiplying two numbers.
Proton. Positively charged particle, typically found in the nucleus of an atom, consisting of three quarks (two up-quarks and one down-quark).
Quanta. The smallest physical units into which something can be partitioned, according to the laws of quantum mechanics. For instance, photons are the quanta of the electromagnetic field.
Quantum chromodynamics (QCD). Relativistic quantum field theory of the strong force and quarks, incorporating special relativity.
Quantum claustrophobia. See quantum fluctuations.
Quantum determinism. Property of quantum mechanics that knowledge of the quantum state of a system at one moment completely determines its quantum state at future and past moments. Knowledge of the quantum state, however, determines only the probability that one or another future will actually ensue.
Quantum electrodynamics (QED). Relativistic quantum field theory of the electromagnetic force and electrons, incorporating special relativity.
Quantum electroweak theory. See electroweak theory.
Quantum field theory. See relativistic quantum field theory.
Quantum fluctuation. Turbulent behavior of a system on microscopic scales due to the uncertainty principle.
Quantum foam. See spacetime foam.
Quantum geometry. Modification of Riemannian geometry required to describe accurately the physics of space on ultramicroscopic scales, where quantum effects become important.
Quantum gravity. A theory that successfully mergers quantum mechanics and general relativity, possibly involving modifications of one or both. String theory is an example of a theory of quantum gravity.
Quantum mechanics. Framework of laws governing the universe whose unfamiliar features such as uncertainty, quantum fluctuations, and wave-particle duality become most apparent on the microscopic scales of atoms and subnuclear particles.
Quantum tunneling. Feature of quantum mechanics showing that objects can pass through barriers that should be impenetrable according to Newton's classical laws of physics.
Quark. A particle that is acted upon by the strong force. Quarks exist in six varieties (up, down, charm, strange, top, bottom) and three "colors" (red, green, blue).
Radiation. The energy carried by waves or particles.
Reciprocal. The inverse of a number; for example, the reciprocal of 3 is 1/3, the reciprocal of 1/2 is 2.
Relativistic quantum field theory. Quantum-mechanical theory of fields, such as the electromagnetic field, that incorporates special relativity.
Resonance. One of the natural states of oscillation of a physical system.
Riemannian geometry. Mathematical framework for describing curved shapes of any dimension. Plays a central role in Einstein's description of spacetime in general relativity.
Schrödinger equation. Equation governing the evolution of probability waves in quantum mechanics.
Schwarzschild solution. Solution to the equations of general relativity for a spherical distribution of matter; one implication of this solution is the possible existence of black holes.
Second law of thermodynamics. Law stating that total entropy always increases.
Second superstring revolution. Period in the development of string theory beginning around 1995 in which some nonperturbative aspects of the theory began to be understood.
Singularity. Location where the fabric of space or spacetime suffers a devastating rupture.
Smooth, Smooth space. A spatial region in which the fabric of space is flat or gently curved, with no pinches, ruptures, or creases of any kind.
Space-tearing flop transition. See flop transition.
Spacetime. A union of space and time originally emerging from special relativity. Can be viewed as the "fabric" out of which the universe is fashioned; it constitutes the dynamical arena within which the events of the universe take place.
Spacetime foam. Frothy, writhing, tumultuous character of the spacetime fabric on ultramicroscopic scales, according to a conventional point-particle perspective.