class dotdict
electron_mass = {'citation': '|search_for=universal_in!', 'name': 'Electron Rest Mass', 'subscript': 'e', 'symbol': 'm', 'units': 'mega electron*volts/c^2', 'url': '', 'value': 0.51099891}

The mass of the electron.

planck_constant = {'citation': '|search_for=universal_in!', 'name': 'Planck Constant', 'subscript': '', 'symbol': 'h', 'units': 'joule*seconds', 'url': '', 'value': 6.62606957e-34}

Planck’s constant.

standard_gravity = {'citation': '|search_for=universal_in!', 'name': 'Standard Gravity', 'subscript': '', 'symbol': 'g', 'units': 'meters/(seconds^2)', 'url': '', 'value': 9.80665}

Earth’s gravity at the surface.

vacuum_impedance = {'citation': '|search_for=universal_in!', 'name': 'Characteristic Impedance of a Vacuum', 'subscript': '0', 'symbol': 'Z', 'units': 'ohms', 'url': '', 'value': 376.730313461}

The impedance of a perfect vacuum.

vacuum_permeability = {'citation': '|search_for=universal_in!', 'name': 'Vacuum Permeability', 'subscript': '0', 'symbol': 'µ', 'units': 'Newton/Ampere^2', 'url': '', 'value': 1.2566370614e-06}

The permeability of a perfect vacuum.

vacuum_permittivity = {'citation': '|search_for=universal_in!', 'name': 'Vacuum Permittivity', 'subscript': '0', 'symbol': 'ε', 'units': 'farad/meters', 'url': '', 'value': 8.854187817e-12}

The permittivity of a perfect vacuum.