By Kirthi Tennakone –
Black holes are no longer curious imaginations fitting into realm of science fiction. This year Physics Nobel Prize was awarded to the mathematical physicist Roger Penrose and two astronomers Reinhard Genzel and Andrea Ghez for demonstrating the reality of black holes as objects existing in the universe. Fascinating black holes needed convincing evidence to prove their existence
Nobel prizes are awarded for extraordinary breakthroughs in science – after strict scrutiny of the validity of the finding to satisfaction of the peers and the Nobel Committee.
Science require irrefutable evidence. Even if one is a genius, his or her finding will not be accepted as truth, unless proven right – very different from other human affairs where people endorse hearsay, traditions and ideologies without questioning.
Verification of Einstein’s Theory
In 1915 Albert Einstein formulated his famous theory of general relativity. It is an elegantly consistent theory successful in removing a major discrepancy in our understanding of gravitation – the force determining the large scale structure of the universe and its origin. Theory challenged the conceptual basis of Sir Isaac Newton’s mechanics, predicting new phenomena.
According to Einstein’s new theory, light, just like materials objects has to be attracted by the sun and other massive bodies. Einstein suggested, the predicted effect could be tested during a total eclipse of the sun as an apparent change in the position of a star shining close proximity to the solar disc.
To test Einstein’s assertion, the renowned English astronomer Arthur Eddington conducted observations in the island of Principe near west coast of Africa at the time of the total solar eclipse 29th May 1919. After a quick analysis of results obtained, he immediately declared the theory of Einstein has been confirmed – agitating scientific community as well as general public.
Nobel Prize awarded to Einstein was not for his Theory of Relativity
After Eddington’s announcement, Albert Einstein, not so well known to the world was elevated to a scientific celebrity overnight. Newspaper headlines all over the world covered the event sensationally – implicating the intellectual giant Sir Isaac Newton has been dethroned. Nevertheless, the scientific elite hesitated to acknowledge the result without further confirmation. Despite nominations and much lobbying, the physics Nobel Prize 1919 or the following year was not awarded to Einstein.
The Nobel committee was concerned of the of the accuracy of 1919 eclipse measurement and probably influenced by the thinking at the time, the theory of relativity amount to a faith rather than a subject of physical reality testable by experiment. World astronomers decided to repeat the experiment during the next total solar eclipse forecasted to happen 21st September 1922, visible to Christmas Island and Southern Australia. Observatories in Europe and United States arranged expeditions to conduct measurements at the time of the eclipse.
Unlike prompt disclosure of the results of 1919 eclipse experiment at the Island of Principe, the astronomers who observed the 1922 eclipse in Australia were cautious to announce a premature result – no news of the measurement as late as October 1922, worrying Einstein. As physics Nobel Prizes are normally announced in October each year. The prize meant more than prestige to Einstein. The divorce settlement with his first wife Mileva Meric has been, the money he gets from a future Nobel Prizes goes to her and two sons under her custody. Prevailing uncertainties for persons of Jewish origin in Germany also bothered Einstein – the warning that his name is in a Nazi hit list.
Considering the predicament, Einstein decided to be away from Germany for a while and accepted an invitation to tour Japan. Enroute Japan, Einstein and his second wife Elsa arrived in Colombo 28th October 1922. A reporter from Times of Ceylon interviewed him questioning results of the eclipse experiments. Einstein had responded saying the Christmas Island experiment failed owing to cloudy weather but he expects a good result from the Australian experiment.
The ship departed Colombo next day, about a week later the captain of the ship met Einstein and handed over a telegram from Stockholm.
Unexpectedly, the Nobel Prize was not for his theory of relativity. The award citation said he has been honored for explaining photoelectric effect (how metals shined with light emit electrons) and contributions to theoretical physics. Why was Einstein’s major contribution, the theory of relativity omitted from the citation? To the scientific establishment, theory seemed to be radically away from the mainstream thinking and barely supported by experiment.
Relativity succeeded in understanding expansion of the universe concluded by observation of Edwin Hubble. However mathematically awesome theory faced a major difficulty.
Endless contraction of massive objects by their own gravitation creates black holes
Einstein’s theory tells that stars and other astronomical objects much heavier than sun, should contract endlessly under their own gravitation. Upon reaching a critical radius, the gravitational pull turns so strong counteracting even emission of light. Resulting formation of a boundary of no return termed the event horizon. Such elusive objects known as black holes aroused curiosity motivating best minds to ponder. A problem that remained difficult to resolve was, the theory required the contraction to continue even after crossing the event horizon – crushing matter virtually to a point – mathematically referred to as a singularity. Physically such a consequence would be an impossibility – casting much doubt on reality of black holes or even the validity of the general theory of relativity.
The idea of cosmic censorship – You needn’t worry about hypothesized happenings that are unobservable
English mathematical physicist Roger Penrose provided a lasting solution to the puzzle of the reality of black holes in 1965. Penrose proved that irrespective of shape and extent of the event horizon, continuation of collapse leading to a point like crushing or a singularity is inevitable. However, any information related to happenings inside the region bounded by the event horizon remain inaccessible observers outside. As you cannot pass the event horizon and return, observing existence of singularity is forbidden. Penrose referred to this phenomenon as ‘cosmic censorship’. The idea has profound philosophical implications. You needn’t worry about hypothesized happenings that forbid observation. A good lesson for many of us who believe in happenings that can never be seen to happen.
The work of Penrose dispelled the doubt that black holes are unreal and encouraged astronomers to search them and their effects.
Until 2015 Einstein’s relativity theory continued to face another problem. As shown by Einstein in 1916, his theory demanded existence of gravitational waves – to and fro undulations of space – time itself. Close motion of very massive astronomical objects and their collisions create these waves, shaking stars and planets far away. In 2015 an intricate detector set-up in United States, after years of research, recorded gravitational waves emanated from a catacalmic event happened in the universe eons ago – a signal consistent with impinging of two black holes rotating around each other. Three American physicists received 2017 Nobel Prize for this work.
After the monumental contribution of Roger Penrose, physicists realized black holes are not mere mathematical artifacts of the general theory of relativity, but an inescapable consequence of endless contraction of gigantic agglomerations of matter under their own gravitational attraction – persuading astronomers to look for them among diverse variety of mysterious structures in the universe.
Since 1990 astronomers Reinhard Genzel and Andrea Ghez, working in Germany and United States studied motion stars at the center of galaxy. Their analysis concluded an invisible supermassive object, heavier than 4 million times the mass of the sun, sitting at the center of the galaxy – a black hole, pulling and orbiting stars in the vicinity. The black hole will continue to grow eating nearby stars!
Proving the existence of black holes and finding them revealing an enormously massive black hole at the center of our galaxy is a remarkable milestone of human advancement. Physics Nobel Prize 2020 recognized this accomplishment. Einstein’s general theory of relativity, not honored by a Nobel Prize had passed all tests, including existence of black holes, stubbornly resisting refutation.