Ask the Experts   Physics Job Board   University Departments   Einstein eGreetings   Science eStore Local in California? Visit one of our retail stores. XUMP - Science Toys      Fundamental Physical Constants Values given below are from the CODATA 1998 recommended by the National Institute of Standards and Technology of United States (NIST). Values contain the (uncertainty) in the last two decimal places given in brackets. Values that do not have this uncertainty listed are exact. For example: mu = 1.66053873(13) x 10-27 kg mu = 1.66053873 x 10-27 kg Uncertainty in mu = 0.00000013 x 10-27 kg Name Symbol Value Atomic Mass Unit mu 1.66053873(13) x 10-27 kg Avogadro's Number NA 6.02214199(47) x 1023 mol-1 Bohr Magneton B 9.27400899(37) x 10-24 J T-1 Bohr Radius ao 0.5291772083(19) x 10-10 m Boltzmann's Constant k 1.3806503(24) x 10-23 J K-1 Compton Wavelength c 2.426310215(18) x 10-12 m Deuteron Mass md 3.34358309(26) x 10-27 kg Electric Constant o 8.854187817 x 10-12 F m-1 Electron Mass me 9.10938188(72) x 10-31 kg Electron-Volt eV 1.602176462(63) x 10-19 J Elementary Charge e 1.602176462(63) x 10-19 C Faraday Constant F 9.64853415(39) x 104 C mol-1 Fine Structure Constant 7.297352533(27) x 10-3 Hartree Energy Eh 4.35974381(34) x 10-18 J Hydrogen Ground State 13.6057 eV Josephson Constant Kj 4.83597898(19) x 1014 Hz V-1 Magnetic Constant o 4 x 10-7 Molar Gas Constant R 8.314472(15) J K-1 mol-1 Natural Unit of Action 1.054571596(82) x 10-34 J s Newtonian Constant of Gravitation G 6.673(10) x 10-11 m3 kg-1 s-2 Neutron Mass mn 1.67492716(13) x 10-27 kg Nuclear Magneton n 5.05078317(20) x 10-27 J T-1 Planck Constant h 6.62606876(52) x 10-34 J s h = 2 Planck Length lp 1.6160(12) x 10-35 m Planck Mass mp 2.1767(16) x 10-8 kg Planck Time tp 5.3906(40) x 10-44 s Proton Mass mP 1.67262158(13) x 10-27 kg Rydberg Constant RH 10 9.73731568549(83) x 105 m-1 Stefan Boltzmann Constant 5.670400(40) x 10-8 W m-2 K-4 Speed of Light in Vacuum c 2.99792458 x 108 m s-1 Thompson Cross Section e 0.665245854(15) x 10-28 m2 Wien Displacement Law Constant b 2.8977686(51) x 10-3 m K Source: CODATA Recommended Values of the Fundamental Physical Constants: 1998 by Peter J. Mohr and Barry N. Taylor National Institute of standards and Technology, Gaithersburg, MD 20899-8401 Related Websites NIST Fundamental Constants AMAZING! International System of Units In-depth information on the SI, the modern metric system Uncertainty of Measurement Results Guidelines for the expression of uncertainty in measurement eFunda - Online Reference for Engineers eFunda provides extensive Unit Conversion, Equations, and Material Data of value to engineers.    'There comes a time when the mind takes a higher plane of knowledge but can never prove how it got there. All great discoveries have involved such a leap. The important thing is not to stop questioning.' Albert Einstein (1879- 1955) Related Books CRC Handbook of Chemistry and Physics (Student Edition) by David R. Lide CRC Handbook of Chemistry and Physics on CD-ROM, 2000 Version by David R. Lide CRC Handbook of Chemistry and Physics, 81st Edition by David R. Lide

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