Time, Topology, and the Twin Paradox

Jean‐Pierre Luminet

in The Oxford Handbook of Philosophy of Time

Published in print April 2011 | ISBN: 9780199298204
Published online September 2011 | | DOI:

Series: Oxford Handbooks in Philosophy

Time, Topology, and the Twin Paradox

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This chapter notes that the twin paradox is the best-known thought experiment associated with Einstein's theory of relativity. An astronaut who makes a journey into space in a high-speed rocket will return home to find he has aged less than his twin who stayed on Earth. This result appears puzzling, as the homebody twin can be considered to have done the travelling with respect to the traveller. Hence, it is called a “paradox”. In fact, there is no contradiction, and the apparent paradox has a simple resolution in special relativity with infinite flat space. In general relativity (dealing with gravitational fields and curved space-time), or in a compact space such as the hypersphere or a multiply connected finite space, the paradox is more complicated, but its resolution provides new insights about the structure of space–time and the limitations of the equivalence between inertial reference frames.

Keywords: twin paradox; thought experiment; Einstein's relativity; special relativity; general relativity; hypersphere; inertial reference frames

Article.  6579 words. 

Subjects: Philosophy ; Metaphysics ; Philosophy of Science

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