Light speed



The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Its value is exactly 299,792,458  meters per second. Or 1,080 million (1.08×109) km/hr. From Sol to Terra (1 AU) takes 8.3 minutes.

The speed at which light propagates through transparent materials, such as glass or air, is less than c.