space time continuum

Albert Einstein was one of the most influential thinkers of the 20th century who achieved global acclaim that has truly passed the test of time. Einstein has stood as a natural synonym to the term ‘genius’ and is famous for his ‘Theory of Relativity’ to a very large population from a young age (including myself) who probably don’t really understand what exactly it is that he contributed to the world of science. I have had a raging curiosity to learn about his life and understand the work he did that catapulted him to his status of fame. A detailed account penned down by renowned biographer Walter Isaacson on Einstein gave me a really good insight into what I was seeking. Einstein was a perpetual non-conformist who challenged conventional wisdom and a spiritual being at heart who admired the harmonious design of the universe. Einstein redefined how we fundamentally view the universe by boldly adopting very contrarian ways of thinking. Einstein was famous for his ability to vividly visualize concepts, conduct thought experiments and generate powerful theoretical deductions by interconnecting pre-existing ideas. Einstein believed in the existence of a single universal theory that could coherently explain all the different phenomenon of the universe and uncovering this theory was the supreme goal of his scientific career.

Now coming to his work : While Einstein won the Nobel Prize in Physics for his work on ‘Photoelectric Effect’, he is renowned for his ‘Theory of General Relativity’ which is built upon his initial work viz ‘Theory of Special Relativity’. The theory of relativity plays with the concept of time which we intuitively consider to be an absolute quantity but time just like speed is relative according to Einstein i.e. the perception of time for the same event can vary for an observer depending on their frame of reference. The idea behind the relativity of time came initially from the ‘Light Postulate’ which states that light travels at a definite speed (3 x 10^8 m/s) as measured in any frame of reference which is independent of the speed of the light emitting source i.e. even if the light emitting source is moving at a certain speed towards an observer, the light emitted from the source will not travel faster than it would if the source was stationary. This sounds counter-intuitive as soundwaves in contrast would appear faster if the sound emitting source was moving in the direction of the wave but the ‘Light Postulate’ has been verified through experiments and the speed of light remains constant irrespective of the relative motion of its source. In his paper on the ‘Theory of Special Relativity’, Einstein conducted a thought experiment where we have a moving train and an observer inside the train and another stationary observer outside the train. The observer inside the moving train shines a light beam at a reflective surface inside the train. For the observer outside the train, the light beam travels a larger distance to and from the mirror in comparison to the observer inside the train but owing to the ‘Light Postulate’, the speed of light for both observers will be the same. Since speed is equal to distance by time, a larger amount of time would have lapsed for the observer outside the train in comparison to the observer inside the train for the same event of light hitting the reflective surface and coming back, so as to maintain the same speed of light in both frames of reference. This theory changed the perception of time as an absolute quantity and redefined the equation of conventional mechanics to include time as a covariant fourth dimension in addition to the traditional three-dimensional space coordinates which basically means that the perception of time can vary with respect to change in spacial coordinates of an object. This new interpretation of time born as result of observed properties of light sounds very hard to intuitively digest but there are few important points we need to take into consideration : firstly light waves do not propagate with respect to a medium unlike sound waves hence the counter-intuitiveness of the ‘Light Postulate’ can be accounted for due to this unique property of light and additionally our illusion of time as constant dimension rather than a covariant fourth dimension occurs as dilation in time as a result of change in space coordinates is more apparent at extremely high speeds (like the speed of light) and negligible for the typical motions we observe in our day to day life. The ‘Theory of General Relativity’ was postulated with the goal of explaining gravitational phenomenon through a broader lens which took into consideration the dimensions of both space and time. This theory came into inception after a thought experiment by Einstein that a person inside a closed window-less chamber who feels his feet pressed to the ground will not be able to tell whether he is at rest in a gravitational field or being accelerated upwards in vacuum. This thought experiment made him theorize the equivalence of gravitational field and accelerated motion which appear to be manifestations of the same structure. In the absence of gravity, objects in motion pass through dimensions of space and time in their natural trajectory of motion which is a straight line even when observed from afar. The theory of general relativity postulates discarding the conventional understanding of gravity as a force between two objects of mass but rather a curvature in the dimensions of space and time caused by an entity of heavy mass which curves the line of motion of a nearby object rather than moving in a straight line. The curvature of space time depends on the mass of the body causing the curvature i.e. higher the mass, larger the curvature which means that the space coordinates of a moving object face larger deviation from the straight-line path it would have taken in the absence of a curvature and time also gets dilated which means time will be slower as the observer moves towards the body of mass causing the curvature.