Physical constants
==================

Contains useful physical constants. Fundamental constants can be also found in `sympy.physics.units`_ module.

.. _sympy.physics.units: https://github.com/sympy/sympy/blob/b6376e085a047b8bada988ff57fbb79a62546842/sympy/physics/units/definitions/unit_definitions.py#L245

.. py:currentmodule:: symplyphysics.quantities

.. py:data:: standard_conditions_temperature

    Zero Celsius degrees. The :attr:`~symplyphysics.symbols.thermodynamics.temperature` at which water freezes.
    It is also temperature for Standard Temperature and Pressure (STP)

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Standard_temperature_and_pressure>`__.

Symbol:
    :code:`T_std`

Latex:
    :math:`T_\text{std}`

Dimension:
    :code:`temperature`


.. py:data:: standard_laboratory_temperature

    Approximately :math:`25` degrees Celsius. Commonly used :attr:`~symplyphysics.symbols.thermodynamics.temperature` for tabulation purposes.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Room_temperature#Definitions_in_science_and_industry>`__.

Symbol:
    :code:`T_lab`

Latex:
    :math:`T_\text{lab}`

Dimension:
    :code:`temperature`


.. py:data:: electron_rest_mass

    :attr:`~symplyphysics.symbols.basic.mass` of stationary electron.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Electron_mass>`__.

Symbol:
    :code:`m_e`

Latex:
    :math:`m_\text{e}`

Dimension:
    :code:`mass`


.. py:data:: bohr_radius

    The Bohr radius is the radius of the electron orbit of the hydrogen atom closest
    to the nucleus in the atomic model proposed by Niels Bohr.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Bohr_radius>`__.

Symbol:
    :code:`a_0`

Latex:
    :math:`a_0`

Dimension:
    :code:`length`


.. py:data:: hydrogen_ionization_energy

    The ionization energy is the smallest energy required to remove an electron from
    a free atom in its basic energy state to infinity.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Ionization_energy#Bohr_model_for_hydrogen_atom>`__.

Symbol:
    :code:`IE_h`

Latex:
    :math:`\mathrm{IE}_\text{H}`

Dimension:
    :code:`energy`


.. py:data:: solar_mass

    The solar :attr:`~symplyphysics.symbols.basic.mass` is a standard unit of mass in astronomy approximately equal to the mass
    of the Sun. The relative uncertainty of the measurement is :math:`4 \cdot 10^{-5}`.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Solar_mass>`__.

Symbol:
    :code:`M_Sun`

Latex:
    :math:`M_\odot`

Dimension:
    :code:`mass`


.. py:data:: earth_mass

    The Earth :attr:`~symplyphysics.symbols.basic.mass` is a standard unit of mass in astronomy equal to the mass of the planet 
    Earth. The relative uncertainty of the measurement is :math:`10^{-4}`.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Earth_mass>`__.

Symbol:
    :code:`M_Earth`

Latex:
    :math:`M_\oplus`

Dimension:
    :code:`mass`


.. py:data:: boltzmann_constant

    The Boltzmann constant is the proportionality factor that relates the average relative thermal energy of particles
    in a gas with the thermodynamic temperature of the gas.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Boltzmann_constant>`__.

Symbol:
    :code:`k_B`

Latex:
    :math:`k_\text{B}`

Dimension:
    :code:`energy/temperature`


.. py:data:: molar_gas_constant

    The gas constant is the constant of proportionality that relates the energy scale in physics to the temperature
    scale and the scale used for amount of substance.
    It is molar equivalent to the :attr:`~boltzmann_constant`.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Gas_constant>`__.

Symbol:
    :code:`R`

Latex:
    :math:`R`

Dimension:
    :code:`energy/(amount_of_substance*temperature)`


.. py:data:: speed_of_light

    The speed of light in vacuum is a universal physical constant that is exactly equal to :math:`299 \, 792 \, 458` metres per second.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Speed_of_light>`__.

Symbol:
    :code:`c`

Latex:
    :math:`c`

Dimension:
    :code:`velocity`


.. py:data:: vacuum_permittivity

    Vacuum permittivity, also known as permittivity of free space or the electric constant, is the value of the absolute
    dielectric permittivity of classical vacuum.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Vacuum_permittivity>`__.

Symbol:
    :code:`epsilon_0`

Latex:
    :math:`\varepsilon_0`

Dimension:
    :code:`capacitance/length`


.. py:data:: vacuum_permeability

    Vacuum permeability, also known as permeability of free space of the magnetic constant, is the value of the absolute
    permeability of classical vacuum.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Vacuum_permeability>`__.

Symbol:
    :code:`mu_0`

Latex:
    :math:`\mu_0`

Dimension:
    :code:`force/current**2`


.. py:data:: elementary_charge

    **Elementary charge** is a fundamental physical constant defined as the electric charge carried by a single proton
    or, equivalently, the magnitude of the negative charge carried by a single electron.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Elementary_charge>`__.

Symbol:
    :code:`e`

Latex:
    :math:`e`

Dimension:
    :code:`charge`


.. py:data:: hbar

    **Reduced Planck constant** is a modified version of the Planck constant used in the description of
    Quantum Mechanics.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Planck_constant#Reduced_Planck_constant>`__.

Symbol:
    :code:`hbar`

Latex:
    :math:`\hbar`

Dimension:
    :code:`action`


.. py:data:: planck

    The **Planck constant** is a fundamental physical constant of foundational importance in quantum mechanics.
    It is the constant of proportionality between a photon's energy and frequency.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Planck_constant#>`__.

Symbol:
    :code:`h`

Latex:
    :math:`h`

Dimension:
    :code:`action`


.. py:data:: avogadro_constant

    The **Avogadro constant** is an SI defining constant defined as the number of constituent particles
    per mole.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Avogadro_constant>`__.

Symbol:
    :code:`N_A`

Latex:
    :math:`N_\text{A}`

Dimension:
    :code:`1/amount_of_substance`


.. py:data:: acceleration_due_to_gravity

    A conventional standard value of the gravitational acceleration at Earth's surface.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Standard_gravity>`__.

Symbol:
    :code:`g`

Latex:
    :math:`g`

Dimension:
    :code:`acceleration`


.. py:data:: stefan_boltzmann_constant

    The **Stefan—Boltzmann constant** is the constant of proportionality between radiant exitance and black body's temperature
    in the Stefan—Boltzmann law.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law#>`__.

Symbol:
    :code:`sigma`

Latex:
    :math:`\sigma`

Dimension:
    :code:`energy/(length**2*temperature**4*time)`


.. py:data:: richardson_constant

    Constant of proportionality proposed by Richardson to describe the law of thermionic emission.

    **Links:**

    #. `Richardson's law <https://en.wikipedia.org/wiki/Thermionic_emission#Richardson's_law>`__.

Symbol:
    :code:`a`

Latex:
    :math:`a`

Dimension:
    :code:`current/(length**2*temperature**2)`


.. py:data:: rydberg_frequency

    In spectroscopy, the **Rydberg constant** is a physical constant relating to the electromagnetic spectra of an atom.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Rydberg_constant#Rydberg_frequency>`__.

Symbol:
    :code:`R_H`

Latex:
    :math:`R_\text{H}`

Dimension:
    :code:`frequency`


.. py:data:: wien_displacement_constant

    A constant of proportionality in *Wien's displacement law*.

    **Links:**

    #. `Wien's displacement law <https://en.wikipedia.org/wiki/Wien%27s_displacement_law>`__.

Symbol:
    :code:`b`

Latex:
    :math:`b`

Dimension:
    :code:`action*temperature*velocity/energy`


.. py:data:: gravitational_constant

    The **gravitational constant** is a physical constant used in calculating the gravitational
    attraction between two objects.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Gravitational_constant>`__.

Symbol:
    :code:`G`

Latex:
    :math:`G`

Dimension:
    :code:`length**3/(mass*time**2)`


.. py:data:: hubble_constant

    The **Hubble's constant** is the proportionality constant between the recessional velocity and
    the proper distance between the galaxy and the observer in the Hubble's law. Its exact value
    is up to debate, however, the fundamental theory gives the number :math:`7%` per billion years.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Hubble%27s_law>`__.

Symbol:
    :code:`H`

Latex:
    :math:`H`

Dimension:
    :code:`1/time`


.. py:data:: zero_point_luminosity

    **Zero-point luminosity** is a constant defined relative to a star for calibrating perposes. The
    value given here has been defined by the International Astronomical Union (IAU).

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Zero_point_(photometry)#Bolometric_magnitude_zero_point>`__.

Symbol:
    :code:`L_0`

Latex:
    :math:`L_0`

Dimension:
    :code:`power`


.. py:data:: sun_luminosity

    :attr:`~symplyphysics.symbols.astronomy.luminosity` of the Sun.

Symbol:
    :code:`L_Sun`

Latex:
    :math:`L_\odot`

Dimension:
    :code:`power`


.. py:data:: faraday_constant

    The **Faraday constant** represents the amount of electric charge carried by one mole,
    or Avogadro's number, of electrons.

    **Links:**

    #. `TechTarget <https://www.techtarget.com/whatis/definition/Faraday-constant>`__.

Symbol:
    :code:`F`

Latex:
    :math:`\mathfrak{F}`

Dimension:
    :code:`charge/amount_of_substance`


.. py:data:: vacuum_impedance

    The **impedance of free space** is a physical constant relating the magnitudes of the
    electric and magnetic fields of electromagnetic radiation travelling through free space.
    A common appoximation of its value is :math:`120 \pi \, \Omega`.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Impedance_of_free_space>`__.

Symbol:
    :code:`Z_0`

Latex:
    :math:`Z_0`

Dimension:
    :code:`impedance`