For the book by David J. Griffiths, see Introduction to Quantum Mechanics (book).
This article is a non-technical introduction to the subject. For the main encyclopedia article, see Quantum mechanics.
Part of a series of articles about
Quantum mechanics
Schrödinger equation
Introduction
Glossary
History
Background
Classical mechanics
Old quantum theory
Bra–ket notation
Hamiltonian
Interference
Fundamentals
Complementarity
Decoherence
Entanglement
Energy level
Measurement
Nonlocality
Quantum number
State
Superposition
Symmetry
Tunnelling
Uncertainty
Wave function
Collapse
Experiments
Bell's inequality
Davisson–Germer
Double-slit
Elitzur–Vaidman
Franck–Hertz
Leggett–Garg inequality
Mach–Zehnder
Popper
Quantum eraser
Delayed-choice
Schrödinger's cat
Stern–Gerlach
Wheeler's delayed-choice
Formulations
Overview
Heisenberg
Interaction
Matrix
Phase-space
Schrödinger
Sum-over-histories (path integral)
Equations
Dirac
Klein–Gordon
Pauli
Rydberg
Schrödinger
Interpretations
Bayesian
Consistent histories
Copenhagen
de Broglie–Bohm
Ensemble
Hidden-variable
Local
Superdeterminism
Many-worlds
Objective collapse
Quantum logic
Relational
Transactional
Von Neumann–Wigner
Advanced topics
Relativistic quantum mechanics
Quantum field theory
Quantum information science
Quantum computing
Quantum chaos
EPR paradox
Density matrix
Scattering theory
Quantum statistical mechanics
Quantum machine learning
Scientists
Aharonov
Bell
Bethe
Blackett
Bloch
Bohm
Bohr
Born
Bose
de Broglie
Compton
Dirac
Davisson
Debye
Ehrenfest
Einstein
Everett
Fock
Fermi
Feynman
Glauber
Gutzwiller
Heisenberg
Hilbert
Jordan
Kramers
Lamb
Landau
Laue
Moseley
Millikan
Onnes
Pauli
Planck
Rabi
Raman
Rydberg
Schrödinger
Simmons
Sommerfeld
von Neumann
Weyl
Wien
Wigner
Zeeman
Zeilinger
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Quantum mechanics is the study of matter and its interactions with energy on the scale of atomic and subatomic particles. By contrast, classical physics explains matter and energy only on a scale familiar to human experience, including the behavior of astronomical bodies such as the moon. Classical physics is still used in much of modern science and technology. However, towards the end of the 19th century, scientists discovered phenomena in both the large (macro) and the small (micro) worlds that classical physics could not explain.[1] The desire to resolve inconsistencies between observed phenomena and classical theory led to a revolution in physics, a shift in the original scientific paradigm:[2] the development of quantum mechanics.
Many aspects of quantum mechanics are counterintuitive[3] and can seem paradoxical because they describe behavior quite different from that seen at larger scales. In the words of quantum physicist Richard Feynman, quantum mechanics deals with "nature as She is—absurd".[4] Features of quantum mechanics often defy simple explanations in everyday language. One example of this is the uncertainty principle: precise measurements of position cannot be combined with precise measurements of velocity. Another example is entanglement. In certain circumstances, two particles with a shared history may become mutually 'entangled', in which case a measurement made on one particle (such as an electron that is measured to have spin up) will be statistically correlated with the outcome of an equivalent measurement on the other particle (that the other will be more likely to be found to have spin down). This applies even though the particles may be so far apart that it is impossible for the result of the first measurement to have been transmitted to the second particle before the second measurement takes place.
Quantum mechanics helps us understand chemistry, because it explains how atoms interact with each other and form molecules. Many remarkable phenomena can be explained using quantum mechanics, like superfluidity. Liquid helium in a container, cooled to a temperature near absolute zero spontaneously flows up and over the rim of its container, an effect which cannot be explained by classical physics.
^"Quantum Mechanics". National Public Radio. Retrieved 22 June 2016.
^Kuhn, Thomas S. The Structure of Scientific Revolutions. Fourth ed. Chicago; London: The University of Chicago Press, 2012. Print.
^"Introduction to Quantum Mechanics". Socratease. Archived from the original on 15 September 2017.
^Feynman, Richard P. (1988). QED : the strange theory of light and matter (1st Princeton pbk., seventh printing with corrections. ed.). Princeton, NJ: Princeton University Press. pp. 10. ISBN 978-0691024172.
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