Special Theory of Relativity Part 1 - The Mysteries of Light

To understand the universe and the fundamentals of physics with greater depth, we'll have to discuss the ideologies that shaped the structure of modern physics.

The Special Theory of Relativity, formulated by Albert Einstein, had a lasting impact on the subject of physics that influenced man's perception of the universe. I'll discuss this theory over the span of 4 blogs. To start off, let's understand the science behind light.

Light

There are mysteries about the nature of light that have eluded all explanations of science. How does light originate? Is light a particle, vibration or pure energy? Scientists have only been able to find partial answers to these challenging questions but at the deepest level, they still remain unanswered and may not even be answerable. This quest to understand the nature of light has resulted in two great scientific revolutions of the twentieth century: quantum theory and relativity.

In the seventeenth century, a youthful Isaac Newton directed a beam of sunlight onto a glass prism. The white light deflected and transformed into a spectrum of rainbow colors on the distant wall. Newton investigated and pondered on this dispersion of light into its many hues. He concluded that white light wasn't simple and indivisible. It consisted of color elements or rays that were separated by the prism. This didn't however explain the nature of light. Was light a wave that passed through mediums or did light consist of particles?

This controversy continued long after Newton's death, but during the nineteenth century, evidence supported the theory of light being a wave. The final blow to the "particle of light" theory was delivered by James Clerk Maxwell through his brilliant theory of electromagnetism. He described that electric and magnetic phenomena moved through space in the form of waves. He went on to show that light was one of the many types of electromagnetic waves which today include radio, gamma rays etc. Scientists believed that the mystery of light was finally solved, but this was not the first nor the last time that scientists would mistakenly anticipate the completeness of science.

Light and relative motion 

Among the details that required attention was one nagging feature of Maxwell's theory. It stated that the speed of light was a constant, whether measured by someone at rest or in motion. This brought controversy as people knew to calculate relative motion from the time of Galileo. Maxwell however said that Galileo's method for calculating relative motion wouldn't work for light. This bought in a conflict between the two methods. So, scientists started looking at the data and evidence. Many experiments were performed, and the result was the same proving the incorrectness of Galileo. The first experiment to verify Maxwell's prediction was done by Edward Morley and Albert Michelson, who did a series of experiments calculating the speed of light at very small distances. All their experiments displayed that the speed of light remained the same. Michelson and other scientists were confused at why light doesn't have relative speed. 

Catching up to light

There was one physicist who needed no convincing from Michelson or anyone else. That scientist was Albert Einstein who convinced himself that you could never catch up to a light beam. At the age of sixteen, he contemplated a hypothetical experiment, in which he assumed for argument's sake that Galileo was right. He argued that if he could attain the speed of light, he could ride alongside a light beam. According to Maxwell's theory, light is a vibrating wave. hence, if he could move alongside a light beam, it would appear as a wave that is stationary in space. This is impossible according to Maxwell's theory as "stationary light" is impossible and hasn't ever been observed. What Einstein meant was that a vibrating electromagnetic wave can never be at rest. The vibrations of the wave are a result of both its motion and its spatial variation (when a quantity differs across different locations in space). When a spatially varying pattern moves past you, it appears to be changing in time.  This can be compared to seeing a film. Each frame is slightly varied from the previous one and when its flashed successively in front of your eyes, you perceive motion. If you stop the film, the perception of motion too stops. You can see the motion (light), only when the film (light wave), moves in respect to you. 

Frames of reference

Einstein's Special Theory of Relativity is based on the idea of reference frames. A reference frame is simply "where a person (or other observer) happens to be standing". You, at this moment, are probably sitting on your sofa. That is your current reference frame. You feel like you are stationary, even though you know the earth is revolving on its axis and orbiting around the sun. Here is an important fact about reference frames: There is no such thing as an absolute frame of reference in our universe. In other words, there is no place in the universe that is completely stationary. Since everything is moving, all motion is relative. Think about it - the earth itself is moving, so even though you are standing still, you are in motion. You are moving through both space and time at all times. Because there is no place or object in the universe that is stationary, there is no single place or object on which to base all other motion. Therefore, if A runs toward B, it could be correctly viewed two ways. From B's perspective, A is moving towards B. From A's perspective, B is moving towards A. Both A and B have the right to observe the action from their respective frames of reference. All motion is relative to your frame of reference.

Part 2 will release shortly.

References:
1. Physics for the rest of us - Roger S. Jones
2. howstuffworks.com