The First Lightbender

Einstein’s conviction that nature abided by the poetry in mathematical equations, revealed to human intelligence a whole host of exotic possibilities which lay embedded in reality. 

On May 29, 1919 a total solar eclipse occurred. During that eclipse, the Sun crossed the Hyades star cluster, the nearest galactic cluster to the solar system. Two groups of scientists positioned in different parts of the world were eagerly waiting for the event: one group led by famous British astrophysicist Sir Arthur Eddington at Principe island in the in the Gulf of Guinea, west equatorial Africa, and the other group at Sobral, Brazil. The total eclipse duration was six minutes and the groups took several pictures.

They were testing the theory of a ‘relatively’ new comer in physics, Albert Einstein, which was published by 100 years ago on 25th November 1915—the General Theory of Relativity.

Sir Isaac Newton in his famous ‘Philosophiae naturalis principia mathematica‘ (1687)  had formulated the law of universal gravitation. Though troubled with certain problems like the small deviation in the way the path of Mercury shifts with each elliptical rotation around the sun, over all the law of universal gravitation worked well.

When Einstein proposed his General Theory of Relativity he proposed a four-dimensional space-time continuum in which the mass of the objects create geometric distortions and depending upon the mass of the object the space-time distortion would vary. This field created by gravity will act upon light as it acts upon matter, stated Einstein.

The idea that light would be affected by gravity is in itself not very new. As early as 1784 British scientist Henry Cavendish had pointed out that light from a star would bend along a massive celestial object due to gravitational force. Einstein’s paper on General Theory of Relativity views gravity as a geometrical distortion of space and time. Calculations based on Einstein’s relativity and those based on Newton’s theory of gravitation differed in their values. The values calculated by Newton was half as that of Einsteinian calculations.

It was the solar eclipse of 1919 which provided the dramatic confirmation of Einstein’s theory of general relativity and hence gravity as the geometrical distortion in the fabric of space-time continuum. On November 6, 1919 Eddington announced the findings of his team and the verdict clearly showed that Einstein was right.

Einstein famously quipped ‘Then I would have been sorry for the dear Lord’ when queried how he would have felt if the observations went against his theory. What Einstein stated through those words was his conviction in an underlying order, an order that is expressed through mathematical equations, – a sort of expression of a cosmic impersonal mind. In his ‘Herbert Spencer memorial lecture’ (1933) Einstein declared that his experience hitherto justified his belief that “nature is the realization of the simplest conceivable mathematical ideas”.  In that he was a deeply Spinoza-inspired mathematical mystic. This conviction in nature abiding by the poetry in mathematical equations, has revealed to human intelligence a whole host of exotic possibilities which may lay embedded in reality: black holes, big bang, dark matter and perhaps even the possibility of time travel – after all, along with space, time also can bend around a massive gravitational field.

However, the smooth continuum of four dimensional space-time in which gravity is geometric distortion, cannot be that smooth from the view of another great pillar of new physics: Quantum Mechanics. When we reduce all physical interactions at the very fundamental level into four, gravitation is just one among these four interactions. The others being electro-magnetic, strong and weak interactions. Each of these interactions has its force carrier particle (except Gravity). Well known examples are of course the photon of the electro-magnetic field and lesser known are the gluons mediating strong force and W & Z bosons mediating the weak forces.(Incidentally Pakistani physicist Abdus Salam unified weak and electromagnetic interactions.)

But for gravity, the explanation is through the general theory of relativity.

Let us consider those exotic objects called black holes for example. Today we know that, as astrophysicist Chandrashekar predicted, stars exceeding certain critical mass would ultimately become black holes. Newtonian physics has also anticipated black holes in its own view. We know that more massive and dense a body, more will be its escape velocity. Black holes are then bodies whose mass is so great and compressed so densely that even light cannot escape from them. At the heart of the black hole, the general theory of relativity sees an infinite curvature of space and time – what is called the singularity condition. And at the heart of the black hole, the general theory collides with the quantum mechanics. The core of black hole according, to general theory of relativity, has zero radius. But quantum mechanics considers that there will be a small very very small radius.

The debates continue and mind-baffling scenarios bubble out from the equations.

General Theory of Relativity was not without its detractors. Many Nazi sympathizers denounced it as ‘Jewish science’.  In 1922, German physicist Philipp Lenard warned fellow German physicists against betraying their ‘racial allegiance’.  Marxist regimes also were equally anti-relativity. As late as 1968 Chinese Academy of Science (CAS) had created a special group called ‘Mao Zedong Thought Study Class for Criticizing Reactionary Bourgeois Standpoints in Theories of Natural Sciences’ which conducted ‘Criticizing Relativity Study Class’ (CRSC). It is interesting that teaching a scientific theory which has nothing to do with terrestrial politics and much to do with celestial objects, became a sort of symbol of freedom and democracy in any society.    

Today physicists are on the search for the Holy Grail that will unite general theory of relativity and quantum mechanics. Though the stubborn opposition of Einstein in regarding quantum mechanics as a complete theory made many physicists of his time feel if the grand old man of physics had really become old, the legacy of Albert Einstein still lives in the spirit. When he said he would feel sorry for the dear Lord if the theory went wrong, he essentially celebrated the mathematical aesthetics and elegance of his equations.  God may or may not play dice and may even throw the dice where one cannot see as Stephen Hawking stated once.

Yet the Einsteinian spirit lives in the search for elegance and beauty, which have become an integral part in the mathematical theories of the universe. Consider the following quote by Roger Penrose on the attempts to harmonize General Theory of Relativity with Quantum Mechanics:

I would not dispute that some changes in classical general relativity must necessarily result if a successful unison with quantum physics is to be achieved, but I would argue strongly that these much be accomplished by equally profound changes in the structure of quantum mechanics itself. The elegance and profundity of general relativity is no less than that of quantum theory. The successful bringing of the two together will never be achieved, in my view, if one insists on sacrificing the elegance and profundity of either one in order to preserve intact that of the other. What must be sought instead is a grand union of the two – some theory with a depth, beauty and character of its own (and which will be no doubt recognized by the strength of these qualities when it is found) and which includes both general relativity and standard quantum theory as two particular limiting cases.         

Even when gravitons are found and quantum gravity becomes part of the standard text books Einstein will live in those equations for eternity.