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Speed of light

The speed of light is the speed of electromagnetic waves. Light travels at slower speed inside materials like glass or water; its highest speed is in a vacuum. The speed of light in vacuum is a universal physical constant denoted c (in ISO and IEC standards c 0 {\displaystyle c_{0}} ), exactly equal to 299792458 m⋅s−1. It is exact because, by…

History, Standards & Measurement

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across the Milky Way
87400 years
astronomical units per day
173[Note 1]
Distance
Time
from geostationary orbit to Earth
119 ms
from Moon to Earth
1.3 s
from Sun to Earth (1 AU)
8.3 min

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Overview

Notation

In unit systems

Fundamental role in physics

Faster-than-light observations and experiments

Propagation of light

Practical effects of finiteness

Determination

History

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Map overview Semantic statistics

Speed of light

Nodes286
Edges285
Triples285
Avg. degree1.99
Density0.006993
Components1

How this topic connects Entity context

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Speed of light

Top relations

measured by · 36
Speed of light → Accademia, According, Assuming, Because, Boyer, Christiaan Huygens, Cimento, Deep Space Network, Earth, Earth's, Earth-based, Florence, From, Galileo, Galileo Galilei, Galileo's, Global Positioning System, GPS, He, Historically
related to External links · 35
Speed of light → Albert, Applet, BBC Radio, BIPM, Data Gallery, Definition, Greg Egan, Illustrations, In Our Time, International Bureau, Light, Live-Counter, Measures, Michelson, Michelson Speed, Mile Long Vacuum Tube, National Institute, Nicholson, NIST, Nottingham Department
related to history · 30
Speed of light → Abū Rayhān, Alexandria, Alhazen, Also, Arabic, Aristotelian, Aristotle, Based, BCE, Book, Bīrūnī, Early Islamic, Einstein's, Empedocles, Euclid, European, Greece, Greeks, Haytham, He
related to Increased accuracy of c and redefinition of the metre and second · 15
Speed of light → As, Boulder, Colorado, General Assembly, General Conference, In, Louis Essen, Measures, Radio-Scientific Union, Standards, The, These, This, US National Bureau, Weights
related to Connections with electromagnetism · 14
Speed of light → Earth, Fizeau, Gustav Kirchhoff, Hippolyte Fizeau, His, In, Leyden, Léon Foucault, Maxwell, Philosophical Transactions, Rudolf Kohlrausch, The, Weber/Kohlrausch, Wilhelm Eduard Weber
related to Notation · 14
Speed of light → Celeritas, Einstein, German-language, Historically, In, Isaac Asimov, James Clerk Maxwell, Latin, Leonhard Euler, Max Abraham, Rudolf Kohlrausch, Sometimes, The, Wilhelm Eduard Weber
related to "Luminiferous aether" · 12
Speed of light → After Maxwell's, Albert, Beginning, Earth, Edward, In, Michelson, Modern, Morley, Some, The, Thomas Young
related to Cavity resonance · 11
Speed of light → Another, As, By, Essen, Gordon-Smith, If, In, Louis Essen, One, The, The Essen
related to Upper limit on speeds · 11
Speed of light → An, Analysis, As, If, In, Lorentz, More, One, Such, The, This
related to Defined as an explicit constant · 10
Speed of light → As, CGPM, General Conference, Improved, In, Measures, SI, They, To, Weights

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Important terminology

light speed vacuum time travel value second earth distance velocity used theory electromagnetic metre frequency waves relativity one faster constant

Entity relationships Subject–Predicate–Object triples

SubjectPredicateObjectConfidenceSrc
Speed of lightacross the Milky Way87400 years1.00infobox
Speed of lightastronomical units per day173[Note 1]1.00infobox
Speed of lightDistanceTime1.00infobox
Speed of lightfrom geostationary orbit to Earth119 ms1.00infobox
Speed of lightfrom Moon to Earth1.3 s1.00infobox
Speed of lightfrom Sun to Earth (1 AU)8.3 min1.00infobox
Speed of lightfrom the Andromeda Galaxy to Earth2.5 million years1.00infobox
Speed of lightfrom the nearest galaxy to Earth70000 years1.00infobox
Speed of lightfrom the nearest star to Sun (1.3 pc)4.2 years1.00infobox
Speed of lightkilometres per hour10800000001.00infobox
Speed of lightmetres per second299792458‍1.00infobox
Speed of lightmiles per hour6710000001.00infobox
Speed of lightmiles per second1860001.00infobox
Speed of lightone foot1.0 ns1.00infobox
Speed of lightone light-year1.0 year1.00infobox
Speed of lightone metre3.3 ns1.00infobox
Speed of lightone parsec3.26 years1.00infobox
Speed of lightparsecs per year0.307[Note 2]1.00infobox
Speed of lightthe length of Earth's equator134 ms1.00infobox
Speed of lightis aspeed of electromagnetic waves0.90text
Speed of lightis aupper limit for the speeds of objects with positive rest mass0.90text

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