====== Measurement ======
SI: Système International (SI) d'unités; International system of units.

===== SI base units =====
^ Quantity ^ Name of unit ^ Symbol of unit ^
| Length | meter | m |
| Time | second | s |
| Mass | kilogram | kg |
| Electric current | [[bn:ampere|ampere]] | A |
| Thermodynamic temperature | [[bn:kelvin|kelvin]] | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |

===== SI derived units =====
<sortable>
^ Quantity ^ Name of unit ^ Symbol ^ Equivalent units ^
| Area | square meter | m$^2$ |
| Volume | cubic meter | m$^3$ |
| Frequency | [[bn:hertz|hertz]] | Hz | s$^{-1}$ |
| Density, mass density | kilogram per cubic meter | kg m$^{-3}$ |
| Speed, velocity | meter per second | m s$^{-1}$ |
| Angular speed, angular velocity | radian per second | rad s$^{-1}$ |
| Acceleration | meter per second squared | m s$^{-2}$ |
| Angular acceleration | radian per second squared | rad s$^{-2}$ |
| Force | [[:bn:newton|newton]] | N | kg m s$^{-2}$ |
| Pressure, mechanical stress | [[:bn:pascal|pascal]] | Pa | N m$^{-2}$ |
| Kinematic viscosity | square meter per second | m$^2$ s$^{-1}$ |
| Dynamic viscosity | newton-second per meter squared | N s m$^{-2}$ |
| Work, energy, quantity of heat | [[bn:joule|joule]] | J | N m |
| Power | [[bn:watt|watt]] | W | J s$^{-1}$ |
| Charge, quantity of electricity | [[bn:coulomb|coulomb]] | C | A s |
| Potential difference, electromotive force | [[bn:volta|volt]] | V | J C$^{-1}$, W A$^{-1}$ |
| Electric field strength | volt per meter | V m$^{-1}$ | N C$^{-1}$ |
| Electric resistance | [[bn:ohm|ohm]] | $\Omega$ | V A$^{-1}$ |
| Capacitance | [[bn:faraday|farad]] | F | A s V$^{-1}$ |
| Magnetic flux | [[bn:weber|weber]] | Wb | V s |
| Inductance | [[bn:henry|henry]] | H | V s A$^{-1}$ |
| Magnetic flux density | [[bn:tesla|tesla]] | T | Wb m$^{-2}$ |
| Magnetic field strength | ampere per meter | A m$^{-1}$ |
| Magnetomotive force | ampere | A |
| Luminous flux | lumen | lm | cd sr |
| Luminance | candela per square meter | cd m$^{-2}$ |
| Illuminance | lux | lx | lm m$^{-2}$ |
| Wave number | one per meter | m$^{-1}$ |
| Entropy | joule per kelvin | J K$^{-1}$ |
| Specific heat capacity | joule per kilogram-kelvin | J kg$^{-1}$ K$^{-1}$ |
| Thermal conductivity | watt per meter-kelvin | W $m^{-1}$ K$^{-1}$ |
| Radiant intensity | watt per steradian | W sr$^{-1}$ |
| Activity, radioactivity | [[bn:becquerel|becquerel]] | Bq | s$^{-1}$ |
| Radiation dose | [[bn:gray|gray]] | Gy | J kg$^{-1}$ |
| radiation dose equivalent | [[bn:sievert|sievert]] | Sv | J kg$^{-1}$ |
| Angle (plane) | radian | rad |
| Solid angle | steradian | sr |
</sortable>

===== Unit prefixes =====
^ Prefix ^^ Base 10 ^ English word ^^
^ Name ^ Symbol ^:::^ Short scale ^ Long scale ^
| yotta | Y | $10^{24}$ | septillion | quadrillion |
| zetta | Z | $10^{21}$ | sextillion | trilliard |
| exa | E | $10^{18}$ | quintillion | trillion |
| peta | P | $10^{15}$ | quadrillion | billiard |
| tera | T | $10^{12}$ | trillion | billion |
| giga | G | $10^9$ | billion | milliard |
| mega | M | $10^6$ | million |  |
| kilo | k | $10^3$ | thousand |  |
| hecto | h | $10^2$ | hundred |  |
| deca | da | $10^1$ | ten |  |
|  |  | $10^0$ | one |  | 
| deci | d | $10^{-1}$ | tenth |  |
| centi | c | $10^{-2}$ | hundredth |  |
| milli | m | $10^{-3}$ | thousandth |  |
| micro | μ | $10^{-6}$ | millionth |  |
| nano | n | $10^{-9}$ | billionth | milliardth |
| pico | p | $10^{-12}$ | trillionth | billionth |
| femto | f | $10^{-15}$ | quadrillionth | billiardth |
| atto | a | $10^{-18}$ | quintillionth | trillionth |
| zepto | z | $10^{-21}$ | sextillionth | trilliardth |
| yocto | y | $10^{-24}$ | septillionth | quadrillionth |

==== Length-scales in the universe ====

===== Numerical constants =====
==== Fundamental physical constants ====
^ Name ^ Symbol ^ Python code \\ ''scipy.constants.'' ^ Value ^
| Speed of light in vacuum | c | ''c'' | $3.0 \times 10^8$ m s$^{-1}$ |
| Magnitude of charge of electron | e | ''e'' | $1.6\times 10^{-19}$ C |
| Gravitational constant | G | ''G'' | $6.7\times 10^{-11}$ N m$^2$ kg$^{-2}$ |
| [[bn:planck|Planck’s]] constant | h | ''h'' | $6.6\times 10^{-34}$ J s |
| [[bn:boltzmann|Boltzmann]] constant | k | ''k'' | $1.4\times 10^{-23}$ J K$^{-1}$ |
| [[bn:avogadro|Avogadro’s]] number | N$_A$ | ''N_A'' | $6.0\times 10^{23}$ mol$^{-1}$ |
| Gas constant | R | ''R'' | $8.3$ J mol$^{-1}$ K$^{-1}$ |
| Mass of electron | m$_e$ | ''m_e'' | $9.1\times 10^{-31}$ kg |
| Mass of proton | m$_p$ | ''m_p'' | $1.7\times 10^{-27}$ kg |
| Mass of neutron | m$_n$ | ''m_n'' | $1.7\times 10^{-27}$ kg |
| Permeability of free space | $\mu_0$ | ''mu_0'' | $1.3 \times 10^{-6}$ T m A$^{-1}$ |
| Permittivity of free space | $\epsilon_0$ | ''epsilon_0'' | $8.9\times 10^{-12}$ C$^2$ N$^{-1}$ m$^{-2}$ |

==== Astronomical data ====
^ Name ^ Symbol ^ Python code ^
| [[:bn:hubble|Hubble]] constant |  |  |
| Age of the universe |  |  |
| 1 astronomical unit (AU) |  |  |