The speed of light, commonly symbolized by the letter c , is a fundamental constant in the realm of physics. It refers to the speed at which light photons travel in a vacuum and is measured in the SI unit of m/s . The value of c is a constant throughout the universe and plays a significant role in various physics disciplines. Learn the definition, value and units of speed of light in vacuum and air. Explore the applications of this physical constant in various fields of physics. When comparing the speed of light in vacuum with the speed of light in air, the speed of light in air is 1.0003 times slower than the speed of light in a vacuum. The speed of light in vacuum, c, forms the basis for the definition of the unit of speed, the metre per second. The fixed numerical value of the speed of light in vacuum, c, is defined exactly:
