While searching for some of the works of Rabindranath Tagore, a librarian drew my attention to his book Visva-Parichay (meaning, getting to know the universe). What delightfully surprised me was that the account of contemporary knowledge of the universe carried in the book would have done any professional scientist proud. Written in the 1930s, the book carried the information and implication of the 1929 work of Edwin Hubble on the expanding universe. Cosmology, the subject of the study of the universe, took off from that stage. Today most professional cosmologists would claim to have reached the end of the quest — that barring a few details most important features of the universe are known.
Human perception of visva has changed over the years. Thus, starting with concepts like the Indian Brahmanda or the Norse World Tree, we have had imaginative and picturesque ideas of how the cosmos may be shaped and how it works. These are interesting concepts and tell us about the imaginative minds of our ancient forefathers. One also gets the impression that intellectuals from all old cultures were anxious to have visva-parichay comple-ted during their lifetimes.
However, as science began to take shape, the enquiry passed on to scientists with the difference that claims about the universe had to be substantiated by facts. Take, for example, the claim of the followers of Pythagoras that the Earth goes round a central fire and not round the Sun. When the Pythagoreans were asked as to why we do not see the fire, they argued that there exists a “counter-Earth” which also moves round the fire but always manages to stay between the Earth and the fire!
When sceptics further asked why we do not see the counter-Earth, Pythagoreans took shelter behind the spherical Earth, stating that Greece happens to be on the other side facing, away from the counter-Earth. As people went round the other side and could not see the counter-Earth, the idea gradually died a painless death.
The scientific spirit had won. The episode also showed the important role sceptics play in testing a theory that claims to be scientific.
So what moves round what in our celestial environment? Except for Aristarchus of Samos, a thinker from some three centuries Before Common Era, most Greek intellectuals believed that the Sun moves round a fixed Earth.
Aristarchus had proposed tests, which, if carried out successfully, would have shown that the Earth does indeed move. But observing techniques of his times were too crude to support his prediction. The human ego dictated that man’s habitat, the Earth, should be at rest in the centre of the universe.
Thanks to Copernicus, Galileo, Kepler and Newton, the 17th Century ended with our understanding of the local world of Sun and planets firmly controlled by scientific laws of motion and gravity. The human ego suffered somewhat that the Earth is not at rest in the centre of the universe. But man consoled himself that at least his Sun is at the centre of the vast galaxy of stars, the Milky Way. Indeed, the 18th Century English astronomer William Herschel, after extensive observations of the starry sky, had compiled a map of the Milky Way showing the Sun at the centre.
Man’s pre-eminence was thus preserved, but only for a century or so! Better telescopes in the first two decades of the last century showed that the Sun is not at the centre of the Milky Way, but is orbiting the centre from a distance of around 25,000 light years. A light year is the distance traversed by light in one year, which is approxi-mately 10,000 billion kilo-meters.
Although this makes the Sun an ordinary suburbanite rather than a VIP at the Galactic Centre (GC), this mediocrity is much to be preferred because the GC is a location of violent activity not hospitable to life. Although successive findings had thus deprived man of a special status, there was one belief he could still cling to — which is what most astronomers did till a hundred years ago. The majority of them firmly believed that the Milky Way was the only galaxy of stars they could see in the universe. A small minority had suggested that some nebulae, that is diffuse cloudlike structures seen across the Milky Way, were galaxies in their own right lying far beyond our galaxy. They were heavily criticised, perhaps not as severely as Copernicus and Galileo were in their times.
This majority belief in the uniqueness of our galaxy fell apart as many of the nebulae with clearer images turned out to be galaxies of stars. For example, the Milky Way has a near neighbour in the galaxy Andromeda which is bigger in size. Do galaxies appear in isolation or are they found in large collections?
The discovery of clusters of galaxies put paid to that query. As a research student at Cambridge in the early 1960s, I had used a model of the universe that admitted superclusters, that is clusters of clusters. These large collections of matter extending over hundred million light years were supposed to be alternating with equally vast empty regions. Senior astronomers felt that this was an unnecessary complication and the universe was more homogeneous. Two decades later observations revealed the existence of superclusters and voids.
All this is history of claims arising more from prejudices than facts: But we rarely learn from it. Ask a cosmologist today about visva parichay and he will take you for a ride in the universe after its origin in a “big bang”. On closer examination, a lot of it will turn out to be highly speculative, but the narrator will express full confidence in its factuality. This is where one may quote Fred Hoyle who was well-known for his highly original mind and scepticism of the big bang universe.
In a meeting in 1970, where scientists were claiming to have solved the universe, Hoyle said: “I think it is very unlikely that a creature evolving on this planet, the human being, is likely to possess a brain that is fully capable of understanding physics in its totality… even if it should be so, it is surely wildly improbable that this situation should just have been reached in the year 1970…”
