The Physics
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Opus in profectus

Physical Constants

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Reference

Physical constants (exact, computed, measured) Sources: exact, BIPM; measured, NIST, *NASA
symbol name value
c
speed of light in a vacuum
 
299,792,458 m/s
G
gravita­tional constant
 
6.67430 × 10−11 N m2/kg2
h
Planck constant
 
6.62607015 × 10−34 J s
4.1356676969 × 10−15 eV s
hc
h c
 
1.986445857 × 10−25 J m
1,239.841984 eV nm
ℏ =  h
h bar,
reduced Planck constant,
Dirac constant
1.054571817 × 10−34 J s
6.582119570 × 10−16 eV s
fCs
hyperfine transition of 133Cs
 
9,192,631,770 Hz
e
elementary charge
 
1.602176634 × 10−19 C
ε0 electric constant,
permit­ivitty of free space,
vacuum permitivitty
8.8541878128 × 10−12 C2/N m2
μ0 magnetic constant,
permeab­ility of free space,
vacuum permeability
1.25663706212 × 10−6 T m/A
NA
Avogadro constant
 
6.02214076 × 1023  1/mol
k
Boltz­mann constant
 
1.380649 × 10−23 J/K
R = NAk
gas constant
 
8.314462618 J/mol K
σ =  5k4
15h3c2

Stefan-Boltz­mann constant
 
5.670374419 × 10−8 W/m2K4
b
Wien displace­ment constant
 
2.897771955 mm K
58.78925757 GHz/K
mu
atomic mass constant
 
1.66053906660 × 10−27 kg
931.49410242 MeV/c2
1 u
me
electron mass
 
9.1093837015 × 10−31 kg
0.51099895000 MeV/c2
5.48579909065 × 10−4 u
mp
proton mass
 
1.67262192369 × 10−27 kg
938.27208816 MeV/c2
1.007276466621 u
mn
neutron mass
 
1.67492749804 × 10−27 kg
939.56542052 MeV/c2
1.00866491595 u
Kcd
luminous efficacy
 
683 lm/W
H0
hubble constant*
 
69.3 km/s/Mpc
2.25 × 10−18 1/s