In the middle of the nineteenth century, it has been known for quite some time that electricity can be used make a magnet and that magnet can be used to make electricity. The man who made the first color photograph, James Clark Maxwell unified everything known about magnetism and electricity in four brilliant equations. These equations described that an electromagnetic wave would travel through empty space with exactly the same speed of light. In fact, this wave was light. According to Maxwell light was an electromagnetic wave that move through empty space with the speed of one hundred and eighty six thousand miles per second, but from the viewpoint of classical relativity the question logically arises, Relative to what?
The equations seemed to say that the light moves at one hundred and eighty six thousand miles per second relative to everything. This was the first conflict (Read the Three Conflicts here) of physics at that time when classical physics and Maxwell’s equations were moving apart. According to Maxwell’s equations, light always travels with the speed of “c” and that is one hundred and eighty six thousand miles per second. According to classical physics there were no absolute velocities. Both these theories and equations have revolutionized the physics of that time and everyone was well aware of that, but this conflict made physicists to come up with new ideas. The very groundwork of physics was in crisis and a new theory was require for better understanding.
Albert Einstein was the one who gave the clear idea about the speed of light. He presented his theory of Special relativity and it helped physicists in understanding the true nature of the speed of light. Einstein accepted that these two theories had changed the course of science in the past. He also accepted the idea of relative motion. He said both moving and stationary observers will go through the same laws of physics always. As the speed of light is also the law of physics so Einstein postulated that all observers will observe the same speed of light regardless of the state of their motion. Speed can be described as a measurement of distance in a given time and to agree on the speed of light different observers might have to disagree about time and distance. In special relativity the term time was defined in a wonderful way and that is, time is not same everywhere and the factor of time was one which balanced understanding of the speed of light for different observers. Over the last 100 hundred years, countless experiments show without any doubt that it is the time that slows down when an observer or any object is in motion and speed of light always remains the same. Time and length will be measured differently in different inertial frames, time will dilated and length will be contracted.
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