Abubakar Farooqui is a a student of International Relations at the Quaid-i-Azam University, Islamabad, Pakistan who describes cosmology as his childhood passion. He is interested in Relativity, Quantum and String Theory.
The universe we live in, is an elegant and mysterious place. These two characteristics have only intensified in the past century as a result of two major theories that marked the beginning of a new era in Physics. These theories, i.e. Albert Einstein’s relativity and Max Plank’s Quantum theory, independently started to magnify our view of the universe, the former at macroscopic while the later at the microscopic levels. The increased elegance and mystery of the universe, as we perceive them today, owe a great deal to the likes of Albert Einstein, Neils Bohr, Stephen Hawking and many more.
Modern Physics, the era of Physics that starts with the advent of the twentieth century, has been an era of transformation in the Scientific world in general and the world of Physics in particular. The way we look at the universe today, is way different than how great physicists like Isaac Newton would have looked in their entire lifetimes, notwithstanding the fact that we still apply Newton’s laws of motion and gravity in describing the universe around us with precision. This transformation has taken place at such a brisk pace that the Classical Physics, which deals with matter and energy independently, now appears to us as a matter of past that would only fuel Modern Physics. Maxwell, Plank and Neils Bohr made us take a quantum leap and Einstein ensured that it was at a relativistic speed. This transformation is vital to our understanding of the cosmos and the journey ahead.
In the world of Classical Physics, no name is greater than that of Isaac Newton’s, the great genius of the 17th century who discovered gravity and came up with a law of gravitation which would allow us to measure the force of gravity between two objects with precision. However, despite being able to predict how much the force of gravity would act between two celestial objects or heavenly bodies, the question of how the gravitational pull would occur remained unanswered by Newton. In other words Newton would help you measure Gravity but what caused it, was a challenge that he left to his successors. Regarding what caused gravity, Newton himself wrote that he would leave that matter to ”the consideration of (his) readers”. This is much analogous to Cristopher Nolan’s direction who leaves the mind-bending endings of his movies open to viewers’ perception, except in this case, Nolan knows the endings himself.
The challenge of digging up gravity, which was Newtons’ legacy, was taken up by Albert Einstein who was fascinated about chasing a light beam at a speed of light since his childhood but was also willing to explore the challenging horizons of gravity now. In 1905, Einstein came up with his special theory of relativity that transformed our understanding of the universe. He established that the speed of light would remain constant in all inertial frames of reference. This meant that no matter how fast you travelled and wherever in the universe you were, you would always measure the speed of light to be exactly 186 million miles per second.
Einstein’s special relativity gave Physics a new power to look at the universe. This development in terms of theories, was as significant as the invention of telescope by Galileo Galilei before which, the Earth was perceived to be the centre of the universe. The old established notion of time being absolute, as erected by Newton, was shaken by its edifice, thanks to Einstein’s relativity. The idea that time was neither absolute nor an independent entity and how much it elapsed for someone, depended on the motion of the observer was a breakthrough in Physics. In Physicist Brian Greene’s analogy, as opposed to Newton’s visualisation of time as a flowing river whose water would pass over objects in it almost in equal quantity, Einstein’s showed time was more like a frozen river and the observers were travelling in it at their own speeds.
Relativity established that when an object moved in any of the three known spatial dimensions, i.e. up and below, back and forth, left and right, then during the motion, lesser time would elapse for that moving object compared with the object at rest. This phenomenon is known as ‘Time Dilation’. It showed that time was another dimension, the fourth one, along with the three spatial dimensions mentioned above and was not independent of space. As opposed to Newton’s view of space and time being independent and absolute, Einstein’s relativity established that they were interwoven in a single fabric referred to as Space-Time fabric or Space-time continuum.
Newton’s theory of gravity was important as it allowed us to make precise calculation about the motion of planets and other celestial objects but Einstein would look forward to come up with his own theory of gravity that would be compatible with his special theory of relativity. This was primarily because the idea of space and time being independent had become null and void and Einstein needed a theory of gravity compatible with his special theory which would describe the cause of gravity, the challenge Newton left to his readers’ consideration. Remember, despite the fact that Relativity was a ground-breaking theory in Physics, it was not a theory of gravity.
After almost a decade of immense hard work, Einstein came up with his general theory of relativity, which would leave the Physicists across the globe in awe. The General theory of Relativity published in 1915, shattered the Newtonian view of the universe. It was regarded as a revolutionary theory for it described the cause of gravity. The theory defined gravity as ‘curvature of space-time’ and hence the challenge left by Newton was resolved.
Einstein showed via his general theory of relativity, how mass impacted space-time. This was a major achievement as it unlocked the geometry of the universe for the first time. Any massive object would curve the space-time around it and the curvature depended upon mass. This meant that you and me would also curve space-time around us, just like any other object which has mass, but the curvature is not felt by us for being negligibly small in our everyday life, much like we do not experience time dilation despite the fact that it continuously happens every day when we move across spatial dimensions, which fortunately most of us can do of course.
Einstein’s general theory, applying to the celestial objects made sense of how different planets would revolve around stars and how they would remain in their orbits. It cleared that the sun does not attract the earth, rather the earth has to follow a curved space-time as it moves. This curved space-time is the impact of the sun’s massiveness on the space-time. Similarly, the moon follows the curved space-time which is the impact of the earth’s massiveness on the space-time. In other words, the more massive an object would be, the more curved the space-time around it would be and the same goes for gravity because ‘gravity is in fact the curvature of the space-time’.
The curved space-time is easy to visualise at the two-dimensional level and hence most of the depictions of space-time fabric we see in our everyday life are two-dimensional graphics. However, physicists are sure of at least four dimensions as argued by Einstein’s General Theory and the space-time is curved in fact in four dimensions, i.e. three spatial dimensions and one dimension of time, but is very hard to visualise. It is a theoretical concept whose mathematical basis are firm but its visualisation is next to impossible because the fourth dimension is invisible as compared with the three spatial dimensions all of us can experience in our everyday life.
Einstein’s General Theory was a revolution in Physics whose impacts are being felt even today. In 2016, After completion of 100 years of the theory, The Laser Interferometer Gravitational-Wave Observatory (LIGO) in USA succeeded in detecting cosmic gravitation waves and proved Einstein right on a whole new experimental level. The LIGO detection of gravitation waves confirmed the ripples in space-time just as Einstein’s General Theory of Relativity predicted.
Einstein’s theory of gravity also brings us towards shedding light on black holes where because of mass being packed into an infinitesimally small volume of space, a two dimensional point called space-time singularity, the space-time gets distorted to an extent that even light cannot escape out of the intense gravitational pull generated. Black holes require a great deal of emphasis and require special attention therefore, in the light of Stephen Hawking’s work, but the idea owes a great deal to Einstein’s conceptualisation of space-time continuum and is therefore worth mentioning.
Einstein’s general theory is incredibly accurate at predicting curvature of space-time but it is incompatible with Quantum Theory which is also incredibly accurate in its own domain of subatomic world. The challenge is, both the theories are accurate in their own domains but are incompatible. The Physicists till date are trying to combine Einstein’s relativity with quantum theory to formulate a unified theory of everything that would unify four known forces of nature but the challenge has been too hard. The physicists have not been able to succeed in this objective so far but have made significant developments in the direction and we never know when a new revolution will create ripples in the space-time of Modern Physics.
Project Cosmos 