The speed of light is a fundamental physical constant representing how fast light and electromagnetic waves propagate in a vacuum.
Since 1983, the meter itself has been defined based on the speed of light, making its value exact by definition rather than measured.
Measurement system: Fundamental SI physical constant. SI equivalent: c = 299,792,458 m/s (exact, by definition).
Speed of Light facts
- Unit name
- Speed of Light
- Symbol
- c
- Category
- Speed
- Measurement system
- Fundamental SI physical constant
- SI equivalent
- c = 299,792,458 m/s (exact, by definition)
- Common uses
- Physics, astronomy, relativity theory and GPS systems
Definition of the speed of light
The speed of light is a fundamental physical constant representing how fast light and electromagnetic waves propagate in a vacuum.
Measurement system and SI relationship
Fundamental SI physical constant
SI equivalent: c = 299,792,458 m/s (exact, by definition)
History of the speed of light
Since 1983, the meter itself has been defined based on the speed of light, making its value exact by definition rather than measured.
Where is the speed of light used?
Physics, astronomy, relativity theory and GPS systems