### Database: universal.ddb

 Name(s) Value Units Description elementary_charge e q 1.60217648740e-19 coulomb The elementary charge is a fundamental constant and is the absolute value of the electron charge. It is usually denoted by e (in physics) or q (for engineers). electron_mass m_e 9.1093821545e-31 Kg An electron is a subatomic particle carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. vacuum_impedance Z_0 376.730313461 Ohm The impedance of vacuum is not a measured value, it is a defined one that relates the magnitudes of the electric and magnetic fields of electromagnetic radiation travelling through free space. electric_constant vacuum_permittivity epsilon_0 8.854187817e-12 Farad/meter Constant that connects the magnetic constant and the speed of light. It is defined (in latex syntax) as frac{1}{mu_0 \times c_0^{2}}. magnetic_constant mu_0 12.566370614e-7 Newton/Ampere^2 This parameter (called vacuum permeability, permeability of free space or magnetic constant) is a constant used in connection with the rationalized metre-kilogram-second (rmks) system of electromagnetic equations. This equation system is also called the metre-kilogram-second-ampere (mksa) system. newtonian_constant gravitation_constant G 6.67428e-11 meter^3/(Kg*sec^2) The gravitational constant, denoted G, is an empirical physical constant involved in the calculation of the gravitational attraction between objects with mass. It appears in Newton's law of universal gravitation and in Einstein's theory of general relativity. See also http://en.wikipedia.org/wiki/Gravitational_constant. planck_constant h 6.62606896e-34 Joule*sec The Planck constant (denoted h), also called Planck's constant, is a physical constant used to describe the sizes of quanta in quantum mechanics. It is named after Max Planck, one of the founders of quantum theory. The Planck constant is the proportionality constant between energy (E) of a photon and the frequency of its associated electromagnetic wave. reduced_planck_constant hbar 1.054571628e-34 Joule*sec The Planck constant divided by 2xPI planck_length l_P 1.616252e-35 meter In physics, the Planck length is a unit of length, equal to 1.616252(81)×10−35 meters. It is a base unit in the system of Planck units. The Planck length can be defined from three fundamental physical constants: the speed of light in a vacuum, Planck's constant, and the gravitational constant. Current theory suggests that one Planck length is the smallest distance or size about which anything can be known. planck_mass m_P 2.17644e-8 kg In physics, the Planck mass (mP) is the unit of mass in the system of natural units known as Planck units. The name honors Max Planck, who was the first to propose it. planck_temperature Temp_P TP 1.416785e32 Kelvin In physics, the Planck temperature (TP) is the unit of temperature in the system of natural units known as Planck units. Its name honors the German physicist Max Planck, who proposed it. planck_time time_P 5.39124e-44 sec In physics, the Planck time, (tP), is the unit of time in the system of natural units known as Planck units. It is the time required for light to travel, in a vacuum, a distance of 1 Planck length. The unit is named after Max Planck, who was the first to propose it. light_speed speed_of_light c c_0 299792458 meter/sec In physics, the speed of light (usually denoted c) refers to a fundamental physical constant, the speed at which light and all electromagnetic radiation travel in a perfect vacuum, which is 299,792,458 metres per second (about 300,000 kilometres per second or 186,000 miles per second). PI 3.1415926535897932384626433832795 none PI is a mathematical constant whose value is the ratio of any circle's circumference to its diameter in Euclidean space; this is the same value as the ratio of a circle's area to the square of its radius. Avogadro_number Avogadro_constant L N_A 6.0221417930e23 mole^-1 The Avogadro constant is the number of elementary entities (usually atoms or molecules) in one mole, that is, the number of atoms in exactly 12 grams of carbon-12. Euler_number nepero_number e 2.71828182845904523536 none The mathematical constant e is the unique real number such that the value of the derivative of the function exp(x) at the point x equal to 0 is exactly 1. proton_mass m_p 1.67262163783e-27 kg Mass of the proton, a subatomic particle. neutron_mass m_N 1.6749272928e-27 kg Mass of the neutron, a subatomic particle. Coulomb_constant k_e 8.9875517873681764e9 Newton*meter^2/(Coulomb^2) The proportionality constant ke in Coulomb's law is called Coulomb's constant. Fermi_constant Fermi_coupling_constant G_F 1.166371e-5 GeV^-2 The strength of Fermi's interaction is given by the Fermi coupling constant G_F. Bohr_magneton Bohr_Procopiu_magneton mu_B 9.2740091523e-24 Joule/Tesla The Bohr magneton is a physical constant of magnetic moment of electrons. conductance_quantum G0 G_0 12.9 kOhm The conductance quantum is the quantized unit of conductance. Josephson_constant K_J 483597.9e9 Hz/Volt The Josephson constant is the inverse of the quantum of magnetic flux. magnetic_flux_quantum phi_0 Phi0 2.06783366752e-15 Weber The magnetic flux quantum is the quantum of magnetic flux passing through a superconductor. nuclear_magneton mu_N 5.0507832413e-27 Joule/Tesla The nuclear magneton is the natural unit for expressing magnetic dipole moments of heavy particles such as nucleons and atomic nuclei. von_Klitzing_constant R_K 25 812.807 557 Ohm This constant gives the inverse value of one quantum of electrical conductance. Bohr_radius a0 a_0 0.52917720859e-10 meter In the Bohr model of the structure of an atom, put forward by Niels Bohr in 1913, electrons orbit a central nucleus. The model says that the electrons orbit only at certain distances from the nucleus, depending on their energy. In the simplest atom, hydrogen, a single electron orbits, and the smallest possible orbit for the electron, that with the lowest energy, is most likely to be found at a distance from the nucleus called the Bohr radius. classical_electron_radius Lorentz_radius Thomson_scattering_length re r_e 2.817940289458e-15 meter The classical electron radius is roughly the size the electron would need to have for its mass to be completely due to its electrostatic potential energy - not taking quantum mechanics into account. Fermi_coupling_constant G_F GF 1.166371e-5 GeV^-2 The strength of Fermi's interaction is given by the Fermi coupling constant G_F. fine_structure_constant alpha 7.2973525705e-3 none The fine-structure constant (usually by the Greek letter alpha) is a fundamental physical constant, namely the coupling constant characterizing the strength of the electromagnetic interaction. hartree_energy EH E_H 4.3597441775e-18 Joule A hartree is the atomic unit of energy. circulation_quantum 3.63694755024e-4 meter^2/sec quantum of circulation Rydberg_constant R_infinity 10973731.56852573 meter^-1 The Rydberg constant represents the limiting value of the highest wavenumber (the inverse wavelength) of any photon that can be emitted from the hydrogen atom, or, alternatively, the wavenumber of the lowest-energy photon capable of ionizing the hydrogen atom from its ground state. Thomson_cross_section sigma_e sigmae 0.6652458558e-28 meter^2 not specified weak_mixing_angle Weinberg_angle theta_W thetaW 0.2221576 not specified not specified Boltzmann_constant K_B KB k 1.380650388238137546253272195613524e-23 Joule/Kelvin The Boltzmann constant is the physical constant relating energy at the particle level with temperature observed at the bulk level. Faraday_constant F 96485.3399 Coulomb/mole The Faraday constant is the magnitude of electric charge per mole of electrons. first_radiation_constant c1 c_1 3.7417711819e-16 W/meter^2 not specified Loschmidt_constant n0 n_0 2.6867774e25 1/meter^3 The Loschmidt constant is the number of particles (atoms or molecules) of an ideal gas in a given volume (the number density). gas_constant R 8.31447215 Joule/(Kelvin*mole) The gas constant is equivalent to the Boltzmann constant, but expressed in units of energy per kelvin per mole molar_Planck_constant 3.99031271627e-10 Joule*sec/mole not specified molar_volume V_m Vm 24.78959842e-6 meter^3/mole The molar volume is the volume occupied by one mole of a substance (chemical element or chemical compound) at a given temperature and pressure. The value provided here is at room temperature, i.e. 25 Celsius. Sackur_Tetrode_constant S0/R -1.151704744 not specified The Sackur–Tetrode equation is an expression for the entropy of a monatomic classical ideal gas which uses quantum considerations to arrive at an exact formula. The provided value is for 1 K and 100 kPa. second_radiation_constant c2 c_2 1.438775225e-2 meter*Kelvin not specified Stefan_Boltzmann_constant sigma 5.670400e-8 W*m^-2*K^-4 The Stefan–Boltzmann constant, a physical constant denoted by the Greek letter σ, is the constant of proportionality in the Stefan–Boltzmann law. Wien_displacement_constant 2.897768551e-3 meter*Kelvin not specified