What is the speed of light?
Beyond the theories that are difficult to prove, the speed of light is one of the indispensable tools for astronomy and physics. Thanks to them, we can know how far we are from other places in the universe. But, how fast does light travel?
The first person to measure it was the English astronomer James Bradley, who determined in 1728 that light moves at 301.000 kilometres per second. The calculation was made by observing the Earth’s travel around the Sun. In 1983, the General Conference on Weights and Measures redefined the metre. Since then, electricity has an exact speed of 299.792,458 kilometres per second.
However, its speed varies as a function of its average. For example, in space, light travels at its maximum speed. However, in air, its speed drops to 299.708 kilometres per second. If it comes into contact with a diamond, it reaches its lowest speed: 123.957 kilometres per second.