A tribute to our Professor J. N. Islam

Professor A. M. Harunar RashidFellow, Bangladesh Academy of Sciences

Professor J. N. Islam (birth: February 24, 1934; death: March 16, 2013) is one of the most famous scientists of Bangladesh who was internationally well-known as a mathematical physicist, astrophysicist, cosmologist and occasional economist. He became a legend during his rather short life-time, and he was very famous due to his very well written book “ The Ultimate Fate of the Universe” (1983) which quickly became popular in his own country as well as in many other countries of the world, particularly in that section of the scientifically oriented readers who enjoy reading what theoretical physicists have to say about the eventual fate of the Universe. Now-a-days, we the student of science believe in the theory of the Big Bang which created the present Universe of stars and galaxies and we know that this Big Bang is the follow-up of the Albert Einstein’s incomparable General Theory of Relativity and its extension, Cosmology, which has given us the present theory of the creation of the Universe. But of course we cannot forget that

the scientist who spoke first about the Big Bang was the famous American Cosmologist, Edwin Hubble, who was the first person to identify from the results of his cosmological investigations that the Universe of ours is forever expanding from the very first moment of its creation.

Edwin Hubble obtained his result in 1929 in his study of the spectral lines of the light emitted from the stars and the galaxies, although as early as 1917, the Cosmologist Vento Slipher noted this evidence of expansion of the Universe. Edwin Hubble clearly stated that the result of his spectral investigations leave no doubt that the far away galaxies are continuously receding from us till the time so that no body can say,

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A brief introduction “The Ultimate Fate of the Universe”:

Curiously enough J. N. Islam wrote the first version of The Ultimate Fate of the Universe almost at the same time as when Steven Wenberg wrote his highly publicized The First Three Minutes which became for us an indispensable book when we were students. These books brilliantly describe a range of apparent miracle, i.e. events which ultimately combine to make it possible for our Universe to evolve from its moment of birth to its present familiar structure involving atoms, molecules, stars, galaxies and combination of galaxies on the one hand and on the other, atoms, molecules, carbon bonds and ultimately life itself. This is a tantalizingly fascinating story which

has no parallel in anything that man has created and it cannot but instill in deep sense of awe and respect for the wonderful science of Cosmology which tells us all about creation of the Universe. Even more intriguing is the question, “what will happen to this Universe in the long run? This is the kind of question that J. N. Islam has raised at the end of his splendid book and he has tried to offer an answer in the context of our present state of knowledge about the structure of the Universe and the presently known laws of physics which rigorously determine the birth and death of the stars and galaxies constituting the infinitely spread out the panorama called the Universe.

As we have already stated, our present knowledge tells us that the Universe is expanding. But the most crucial question is, “Will this expansion continue for ever or will it come to a halt at some point of time in the future and then a kind of universal contraction will set in”? Or will there be a big crunch or an enormous Ripoff leading to the vanishing of this Universe of ours? The model of the Universe which we can discuss scientifically in our cosmological studies and which expands for ever is called an “ open Universe“ and the Universe which stops expanding some time in the future and starts contracting is called the “Closed” universe.

As J. N Islam has rightly emphasized the ultimate fate of the universe critically depends on the unambiguous answer to this question which depends for its answer on the density of the matter and radiation present in the universe. All the stars and galaxies evolve in time and eventually they will expire in the sense that they will reach a stage where no further evolution can take place any more in the time scale of billions of years. In fact our present knowledge tells us that there are just three definite final states or stages for a star namely the stage of white dwarf, the stage of neutron star and the stage of Black Hole.

We believe now-a-days that these are the states in which matter is in a highly condensed form and the most condensed form being the state of the black hole. Eventually, therefore, all the stars in all the galaxies will die to reach one of these final state of white dwarf, neutron star or black hole because these are the final states of the stars when they are “dead and gone”. This will happen in a thousand billion years and then a large number of these dead stars will be ejected from the galaxies by collision with other dead stars.

In a billion, billion (1018 years or 1027 years), 99% of these dead stars will be ejected from the galaxies and the remaining 1% will form a dense core coalescing into a single black hole of mass several billion solar masses. This is the ultimate black hole – the final state of the dynamical evolution of the universe.

J. N. Islam has drawn the curtain on this rather fairy-like story by saying that super-galactic black hole will eventually evaporate completely in about 10100 years (a gogool!). I find this story absolutely incredible mainly because J. N. Islam has not mentioned any shred of evidence in support of this story and there is not even a reference where the interested readers may look up for further reading. It is a pity that J. N. Islam did not live long to add such references to his most readable account of the Ultimate Fate of the Universe. According to him this Universe will completely evaporate in 10100 years and clearly we have plenty of time to think about this Universe of ours and contribute to its safe keeping so that we do not destroy it by exploding a few atomic bombs.