# Difference between revisions of "Manuals/calci/SPEEDOFLIGHT"

SPEEDOFLIGHT (Units)

• Units to be display.
• SPEEDOFLIGHT(), returns the speed of light per year.

## Description

• This function shows the value of speed of light.
• The speed of light value is .
• The approximate value is approximately .
• It is exact because the unit of length, the meter, is defined from this constant and the international standard for time.
• Speed of light is the distance of light which can travel in a unit of time through a given substance.
• Speed of light in vacuum is denoted by c.
• The speed at which light propagates through transparent materials, such as glass or air, is less than c.
• Similarly, the speed of radio waves in wire cables is slower than c.
• A light year, or the distance light can travel in a year, is over five trillion miles.
• Light from the sun takes about eight minutes to reach the Earth.
• Speed of light is mainly used in Einstein's formula .

## Examples

1. SPEEDOFLIGHT("cm") = 29979245800 cm s-1.
2. SPEEDOFLIGHT("mm") = 299792458000 mm s-1.
3. SPEEDOFLIGHT("km") = 299792.458 km s-1.

Speed of Light