Varying speed of light | Wikipedia audio article
Channel: wikipedia tts
Date: 2019-06-05

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Variable_speed_of_light


00:01:27 1 Historical proposals
00:01:37 1.1 Einstein's early proposal (1911)
00:04:48 1.2 Einstein's updated proposals (1905–1915)
00:08:44 1.3 Dicke's proposal (1957)
00:11:01 1.4 Subsequent proposals
00:12:18 2 Modern VSL theories as an alternative to cosmic inflation
00:17:40 3 Various other VSL occurrences
00:17:52 3.1 Virtual photons
00:18:39 3.2 Varying photon speed
00:19:57 3.3 Varying ic/i in quantum theory
00:21:36 4 Relation to other constants and their variation
00:21:48 4.1 Gravitational constant iG/i
00:22:50 4.2 Fine structure constant iα/i
00:24:40 5 Criticisms of various VSL concepts
00:24:52 5.1 Dimensionless and dimensionful quantities
00:26:55 5.2 Relation to relativity and definition of  ic/i
00:28:28 5.3 General critique of varying ic/i cosmologies
00:28:40 6 References
00:29:46 7 External links



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SUMMARY
=======
A variable speed of light (VSL) is a feature of a family of hypotheses stating that the speed of light in vacuum, usually denoted by c, may in some way not be constant, e.g. varying in space or time, or depending on frequency.
A variable speed of light occurs in some situations of classical physics as equivalent formulations of accepted theories, but also in various alternative theories of gravitation and cosmology, many of them non-mainstream.
Notable attempts to incorporate a variable speed of light into physics have been made by Einstein in 1911, by Robert Dicke in 1957, and by several researchers starting from the late 1980s.
The speed of light in vacuum instead is considered a constant, and defined by the SI as 299792458 m/s. Variability of the speed of light is therefore equivalent with a variability of the SI  meter and/or the SI second.
VSL should not be confused with faster than light theories; nor should it be confused with the fact that the speed of light in a medium is slower than the speed of light in vacuum depending on the medium's  refractive index.