Physical Constants | |||

Quantity or phenomenon | Symbol | SI unit value | Alternate unit value |

astronomical unit | AU | 1.4959787 x 10^{11}meters | 1.4959787 x 10^{8}kilometers |

atomic mass unit | amu | 1.67377 x 10^{-27}kilogram | 1.67377 x 10^{-24}gram |

Avogadro constant | N, L | 6.022169 x 10^{23} | 6.022169 x 10^{23} |

Bohr magneton | µ_{B} | 9.274 x 10^{-24}joule per tesla | 9.274 x 10^{-28}joule per gauss |

Bohr radius | a_{o} | 5.29177 x 10^{-11}meter | 5.29177 x 10^{-9}centimeter |

Boltzmann's constant | k | 1.3807 x 10^{-23}joule per kelvin | 1.3807 x 10^{-16}erg per kelvin |

characteristic impedance of free space | Z_{o} | 377 ohms | -- |

Compton wavelength of electron | _{ce} | 2.4263 x 10^{-12}meter | 2.4263 x 10^{-10}centimeter |

Compton wavelength of proton | _{cp} | 1.3214 x 10^{-15}meter | 1.3214 x 10^{-13}centimeter |

Compton wavelength of neutron | _{cn} | 1.3196 x 10^{-15}meter | 1.3196 x 10^{-13}centimeter |

Earth's mass | m_{earth} | 5.974 x 10^{24}kilograms | 5.974 x 10^{27}grams |

Earth's mean orbital speed | v_{earth} | 30 kilometers per second | 18.5 miles per second |

Earth's mean radius | r_{earth} | 6.371 x 10^{6}meters | 6371 kilometers |

electron radius | r_{e} | 2.81794 x 10^{-15}meter | 2.81794 x 10^{-13}centimeter |

electron rest mass | m_{e} | 9.10956 x 10^{-31}kilogram | 9.10956 x 10^{-28}gram |

elementary charge | e | 1.60 x 10^{-19}coulomb | -- |

Euler's constant | 0.577216 | 0.577216 | |

Faraday constant | F | 9.65 x 10^{4}coulombs per mole | -- |

fine structure constant | 0.007297 | 0.007297 | |

first radiation constant | c_{1} | 4.9926 x 10^{-24}joule-meter | 4.9926 x 10^{-15}erg-centimeter |

gas constant | R | 8.3145 joules per kelvin per mole | 8.3145 x 10^{7}ergs per kelvin per mole |

gravitational acceleration at Earth's surface | g | 9.8067 meters per second squared | 980.67 centimeters per second squared |

gravitational constant | G | 6.67 x 10^{-11}newton meter squared per kilogram squared | -- |

Hartree energy | E_{h} | 4.3597 x 10^{-18}joule | 4.3597 x 10^{-11}erg |

Moon's mass | m_{moon} | 7.348 x 10^{22}kilograms | 7.348 x 10^{25}grams |

Moon's mean radius | r_{moon} | 1.738 x 10^{6}meters | 1738 kilometers |

natural logarithm base | e | 2.718282 | 2.718282 |

neutron radius | r_{n} | * | * |

neutron rest mass | m_{n} | 1.67492 x 10^{-27}kilogram | 1.67492 x 10^{-24}gram |

nuclear magneton | µ_{n} | 5.051 x 10^{-27}joule per tesla | 5.051 x 10^{-31}joule per gauss |

permeability of free space | µ_{o} | 1.257 x 10^{-6}henry per meter | 1.257 microhenrys per meter |

permittivity of free space | _{o} | 8.85 x 10^{-12}farad per meter | 8.85 picofarads per meter |

pi | 3.14159 | 3.14159 | |

Planck's constant | h | 6.626176 x 10^{-34}joule-second | 6.626176 x 10^{-27}erg-second |

proton radius | r_{p} | 2 x 10^{-16} meter * | 2 x 10^{-14} centimeter * |

proton rest mass | m_{p} | 1.67261 x 10^{-27}kilogram | 1.67261 x 10^{-24}gram |

Rydberg constant | R or R_{H} | 1.097 x 10^{7}per meter | 1.097 x 10^{5}per centimeter |

second radiation constant | c_{2} | 0.014388 meter-kelvin | 1.4388 centimeter-kelvin |

speed of light | c | 2.99792 x 10^{8}meters per second | 2.99792 x 10^{10}centimeters per second |

speed of sound in air | v_{sound} | 331.4 meters per second | 1087 feet per second |

Stefan-Boltzmann constant | 5.67 x 10^{-8}watt per meter squared per kelvin to the fourth | -- | |

Sun's mass | m_{sun} | 1.989 x 10^{30}kilograms | 1.989 x 10^{33}grams |

Sun's mean radius | r_{sun} | 6.970 x 10^{8}meters | 6.970 x 10^{5}kilometers |

Wien's constant | _{w} | 2.898 x 10^{-3}meter-kelvin | 0.2898 centimeter-kelvin |

All values are approximations, accurate to the number of significant digits shown.

*Value depends on environment.

*This was last updated in*September 2005

*Posted by:*Margaret Rouse

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