# Physics and Astronomical Constants and Errata

Written: 1998.08.01
Last Revised: 1998.08.29

## Physics Constants and Errata

SI Units (fundamental)

 Length m (metre) Mass kg (kilogram) Time s (second) Electrical Current A (ampere) Thermodynamic Temperature K (kelvin) Amount of matter mol (mole)

SI Units (derived)

 Area m² Volume m³ Frequency Hz (hertz, 1/s) Density kg/m³ Speed, Velocity v (m/s) Angular Velocity v (rad/s) Acceleration a (m/s²) Angular Acceleration a (rad/s²) Force N (newton, kg·m/s²) Pressure Pa (pascal, N/m²) Work, Energy J (joule, N·m) Power W (watt, N·m/s) Specific Heat Capacity cp (J/(kg·K)) Thermal Conductivity k (W/(m·K)) Electrical potential difference V (volt, W/A) Magnetic flux Wb (weber, V·s) Magnetic flux density T (tesla, Wb/m²) Unified Atomic Mass Unit u (1.660565E-27 kg) Electron-volt eV (1.602E-19 J)

SI Prefixes

 E (exa) 1018 P (peta) 1015 T (tera) 1012 G (giga) 109 M (mega) 106 k (kilo) 103 iso 100 m (milli) 10-3 m (micro) 10-6 n (nano) 10-9 p (pico) 10-12 f (femto) 10-15 a (atto) 10-18
Physics Constants
Speed of light in vacuum c = 3E8 m/s
Electron rest mass me = 5.49E-4 u
Neutron rest mass mn = 1.0087 u
Proton rest mass mp = 1.0072 u
Hydrogen atom rest mass m1H = 1.0078 u
Deuterium atom rest mass m2H = 2.0141 u
Carbon atom rest mass m1C = 12.0000 u (exact; 1u is defined as 1/12 the mass of Carbon-12)
Universal gas constant R = 8.31 J/mol·K
Avogadro constant NA = 6.02E23 atoms/mol
Stefan-Boltzmann constant s = 5.67E-8 W/(m²·K4)
Gravitational constant G = 6.6726E-11 m³/(s²·kg)
Bohr radius rB (hydrogen atom radius) = 5.29E-11 m
Proton radius = 1.2E-15 m
Proton magnetic moment mp = 1.41E-26 J/T
Light-year = 9.46E15 m
Planck constant = 6.626E-34 J·s
Mass Density
White dwarf star core ~ 1010 kg/m³
Uranium nucleus ~ 3·1017 kg/m³
Neutron star core ~ 1017 to 1018 kg/m³
Black hole ~ 1019 kg/m³
Energy Density (at 100% efficiency)
Matter/antimatter annihilation = 9E16 J/kg
Deuterium fusion = 6.2E14 J/kg
Uranium-235 fission = 8.9E13 J/kg
Hydrogen burning = 1.2E8 J/kg
Methane gas burning = 5.0E7 J/kg
Coal burning ~ 2.3E7 J/kg (depending on grade of coal)
TNT detonation = 4.2E6 J/kg
Power Intensities
Power intensity at surface of Sun ~ 6E7 W/m²
Power intensity of oxy-acetylene torch ~ 1E7 W/m²
Power intensity of largest modern lasers built to date ~ 1E19 W/m²
Temperatures
Laboratory or fusion reactor plasma = 5E7 K
Shock wave in atmosphere at Mach 20 = 2.5E4 K
Luminous nebulae = 1E4 K
Freezing temperature of water (0°C) = 273.15 K
Specific Heats
Aluminum = 960 J/kg·K
Carbon (graphite) = 710 J/kg·K
Iron = 420 J/kg·K
Air = 994 J/kg·K
Hydrogen = 14200 J/kg·K
Pure water = 4180 J/kg·K
Miscellaneous
Energy required to ionize hydrogen = 13.58 eV/atom (1.3 GJ/kg)
Energy required to split deuterium nuclei into neutrons and protons = 2.2 MeV/atom (105 TJ/kg)

## Astronomical Constants and Errata

The Milky Way Galaxy
Mass ~ 2.2E41 kg
Radius ~ 50,000 light years
Number of stars ~ 100 billion
Density of interstellar space ~ 1E-18 to 1E-21 kg/m³
The Sun (Sol)
Radius = 6.96E8 m
Mass = 1.989E30 kg
Surface temp = 5800 K
Surface temp = 3800 K in sunspots
Core density = 1.6E5 kg/m³
Core temp = 15.6 million
Corona temp ~ 1 million K
Power output = 3.827E26 W
Orbital radius around the centre of the galaxy ~ 3E20 m
The Earth
Radius = 6.371E6 m
Depth of crust = 40 km
Depth of mantle = 2700 km
Mass = 5.974E24 kg
Core density = 9.5E3 kg/m³
Crust density = 2.8E3 kg/m³
Mass of ocean water ~ 1.4E21 kg
Orbital radius around Sol = 149.6 million km (1 AU)
The Moon
Radius = 1.738E6 m
Mass = 7.348E22 kg
Orbital radius around Earth = 382,000 km  This website is owned and maintained by Michael Wong
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