 # Physical Constants

In Physics there are many constants. These relate the real universe (or the bits we think we understand!) to the human-invented scales of measurement.

Name Value Equation/notes
Atomic mass unit 1 u = 1.661 x 10-27 kg = 931.5 MeV c-2
Avogadro constant NA = 6.02 x 1023 mol-1
Boltzmann constant k = 1.38 x 10-23 J K-1
Coulomb's law constant 1/(4πε0) = 8.99 x 109 N m2 C-2
Electric permittivity ε0 = 8.85 x 10-12 N-1 m-2 C2
Gravitational constant G = \$6.67 x 10^{-11} N⋅(m/{kg})^2\$
Magnetic permeability \$μ_0 = 4π x 10^{-7} T m A^{-1}\$
Electron charge e = 1.60 x 10-19 C
Electron mass me = 9.11 x 10-31 kg = 5.49 x 10-4 u = 0.511 MeV c-2
Neutron mass mn = 1.675 x 10-27 kg = 1.008 665 u = 940 MeV c-2
Proton mass mp = 1.673 x 10-27 kg = 1.007 276 u = 938 MeV c-2
Planck constant h = 6.63 x 10-34 J s
Speed of light (vacuum) c = 3.00 x 108 m s-1
Stefan-Boltzmann constant σ = 5.67 x 10-8 W m-2 K-4
Universal gas constant R = 8.31 J mol-1 K-1

## Site Index

### Latest Item on Science Library:

The most recent article is:

Trigonometry

View this item in the topic:

Vectors and Trigonometry

and many more articles in the subject:

### Mathematics

Mathematics is the most important tool of science. The quest to understand the world and the universe using mathematics is as old as civilisation, and has led to the science and technology of today. Learn about the techniques and history of mathematics on ScienceLibrary.info. ### Great Scientists

#### Lynn Margulis

1938 - 2011

Lynn Margulis was an American biologist who is considered one of the leading figures in the study of symbiosis in biological evolution.  ### Quote of the day... I do not say think as I think, but think in my way. Fear no shadows, least of all in that great specter of personal unhappiness which binds half the world to orthodoxy. 