# Vacuum (classical)/Related Articles

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## Parent topics

- International System of Units [r]: Metric unit system based on the metre, kilogram, second, ampere, kelvin, mole and candela.
^{[e]}

## Subtopics

- Speed of light [r]: A physical constant
*c*describing the speed of electromagnetic radiation in vacuum. In the International System of Units the metre is the distance light travels in classical vacuum in 1/*c*seconds, using the defined value*c = c*≡ 299 792 458 m/s (exact)._{0}^{[e]} - Metre (unit) [r]: Unit of length; one of the seven SI base units.
^{[e]} - Second (physics) [r]: Unit of time; one of the seven SI base units.
^{[e]}} - Electric constant [r]: A physical constant in the International System of Units (SI) relating capacitance to area in classical vacuum with an exact value
*ε*= 10_{0}^{7}/(4πc_{0}^{2}) F/m,*c*being the defined value for the speed of light in classical vacuum in the SI units._{0}^{[e]} - Magnetic constant [r]: A physical constant in the International System of Units (SI) relating mechanical force and electric current in classical vacuum with a defined value
*μ*= 4_{0}*π*× 10^{−7}N/A^{2}.^{[e]}

- Vacuum (partial) [r]: A realizable vacuum with a gaseous pressure that is much less than atmospheric.
^{[e]} - Vacuum (quantum electrodynamic) [r]: The term
*quantum electrodynamic vacuum*, or QED vacuum, refers to the ground state of the electromagnetic field, which is subject to fluctuations about a dormant zero average-field condition.^{[e]}