Light is a form of energy which travels in the form of crusts and troughs. And and another definition is that light is an electromagnetic wave which consist of seven colours and due to this it is also called WHITE LIGHT . And this is proved by SIR ISSAC NEWTON in 1666 , when he is working on light with the prism. So here is knowledge which will tell us about the actual speed of light. Firstly we need to know is that why r we not using its exact speed of light, the reason is its original value is. tough n the original value is 299792458m/s. It is also written in the holy Quran about the fact that the speed of light is Now we will discuss that how much time does light take in traveling from one place to another place in this universe Now we will come to our main point that this speed of light can be calculated from a book which is written 14 centuries ago from now Now we will see some pictures