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A003678 Decimal expansion of the SI unit c (speed of light in vacuum), c = 299792458 meters/second.
(Formerly M1912)
2, 9, 9, 7, 9, 2, 4, 5, 8 (list; constant; graph; refs; listen; history; text; internal format)



Since 1983, the speed of light has been defined to be exactly 299792458 m/s.

From Stanislav Sykora, Jun 16 2012: (Start)

General context: Within current metrological systems (SI + IAU definitions), several physics constants have been "assigned" immutable values. They thus became metrological reference points, no longer subject to experimental assessment. These should not be confused with "conventional" values of some empirical quantities (such as Josephson's constant) used in applied metrology, but not assigned, and therefore subject to possible future revisions.

Assigned metrological constants and some of their combinations that appear in the OEIS include the speed of light (this sequence) and its square, cube, and 4th power (A182999, A183000, and A183001, respectively); magnetic permeability of vacuum (A019694); electric permittivity of vacuum (A081799); characteristic impedance of vacuum (A213610); standard gravity acceleration (A072915), standard atmosphere (A213611), Julian year (A213612), Gregorian year (A213613) and the light-year (A213614), all in basic SI units.


Prime factors of this number are 2^1, 7^1, 73^1, 293339^1. - John W. Nicholson, Jun 15 2014

Also decimal expansion of the speed of gravity. - Omar E. Pol, Jun 23 2017

In the 2019 SI system of units (see the second BIPM link, and A322415) one of the seven defining constants is c = 299792458 m/s. - Wolfdieter Lang, Feb 12 2019 [corrected by Ivan Panchenko, May 20 2019]


CRC Handbook for Chemistry and Physics, 75th edition, (1994-1995), Page 1-1.

H. J. Fischbeck and K. Fischbeck, Formulas. Facts and Constants, Springer-Verlag, NY, 2nd ed., 1987.

R. F. Fox and T. P. Hill, An exact value for Avogadro's number, American Scientist, 95 (No. 2, 2007), 104-107.

K. R. Lang, Astrophysical Data: Planets and Stars, Springer-Verlag, NY, 1991.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


Table of n, a(n) for n=9..17.

BIPM, Bureau International des Poids et Mesures, the historic home of SI units (works jointly with NIST).

BIPM, On the revision of the International System of Units (SI), BIPM, Nov 13-16 2018.

G. Bonnet, La vitesse de la lumiere (Text in French).

IAU, International Astronomical Union has accepted SI and added a few definitions of its own.

P. J. Mohr, B. N. Taylor and D. B. Newell, CODATA recommended values of the fundamental physical constants: 2006, Rev.Mod.Phys. 80, 2008, 633-730. DOI: 10.1103/RevModPhys.80.633. (This is the hard-core source of what became CODATA 2010.)

NIST, speed of light in vacuum.

S. Sykora, Constants of Physics and Mathematics, extensive constant-at-a-glance tables.

Eric Weisstein, World of Physics, Speed of Light.

Wikipedia, Speed of gravity.

Wikipedia, Speed of light.

Wikipedia, 2019 redefinition of SI base units


c = 299792458 m/s (equals 299792.458 km/s).


IntegerDigits[299792458] (* Michael De Vlieger, Jun 23 2017 *)


Cf. A224236, A224237, A224238, A070058, A070059, A070060, A070062, A070063, A070064, A322415.

More assigned constants: A003676 (h), A230458 (Δν_{Cs}), A081823 (e), A322578 (N_A), A070063 (k), A322578 (N_A), A182999, A019694, A081799, A213610, A072915, A213611, A213612, A213613, A213614.

Sequence in context: A305308 A087042 A266274 * A201683 A331369 A197394

Adjacent sequences:  A003675 A003676 A003677 * A003679 A003680 A003681




N. J. A. Sloane


Additional comments from Ron Marcinski (ronmarcinski(AT)hotmail.com), Apr 18 2002



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Last modified April 22 19:11 EDT 2021. Contains 343177 sequences. (Running on oeis4.)