SCIENTIST: INDIA'S PRIDE
Indian Scientist Who Challenged Hawking's Blackholes Theory Proved Right
BY: Mrutyunjoy Bose
Mumbai, Aug 8(2k4): A Bhabha Atomic Research Centre (BARC) scientist, who four years ago virtually questioned the existence of blackholes as propagated by none other than Stephen Hawking, proved to be right after the world renowned astro-physicist himself said there are no blackholes ''in the absolute sense''.
Forty-nine-year-old Abhas Mitra, who works with the Nuclear Research Laboratory of the BARC at Trombay here, is a happy man today. In December 2000, Dr Mitra, then working with BARC's Theoretical Physics Division, in a research paper published in the 'United States Foundations of Physics Letters', had claimed that Albert Einstein's General Theory of Relativity (GTR) did not allow the formation or existence of blackholes, regions in space from where no matter or radiation can escape.
The research paper was titled 'Non-Occurrence of Trapped Surfaces and Black
Holes in Spherical Gravitational Collapse'.
Dr Mitra, working since 1980 with BARC, India's premier scientific research establishment, says that no truly realistic
calculations ever showed the creation of blackholes in the real sense. When Dr Mitra's paper was published in the US journal, UNI had broken the story on December 25, 2000.
Mr Hawking, a living legend in the field of science, around a fortnight ago,
in Dublin, Ireland, admitted that there is no black
hole ''in the absolute sense''. Dr Mitra points out that Einstein, the Father of GTR, unsuccessfully struggled to convince his followers and peers that his theory actually does not allow the existence of blackholes. Interestingly, this is also the 90th year of discovery of GTR.
Despite Einsteins objections, the concept of blackholes grew like a sphinx
in the Sixties and continues to fascinate not only
modern astrophysics but theoretical physics in general. In fact, Dr Mitra in his paper had pointed out that all ''idealised'' calculations (by J Oppenheimer and H Snyder) or some of the crucial assumptions by Mr Hawking, Roger Penrose and other
scientists which consolidated the notion of blackholes are either ''faulty or invalid''.
Dr Mitra based his findings on the principle that the (local) speed of collapsing matter cannot exceed the speed of light.
According to GTR, the actual physical space (time) is something like a rubber membrane which curves or sags by the presence of mass or energy. And this curvature of space (time) is the manifestation of gravity. As the collapsing object becomes more and more compact, he said, the gravity associated with it sags the space (time) membrane without any limit. As a result, the star continues to collapse indefinitely in its infinitely deep pit, the BARC scientist added.
Technically, this means that for isolated bodies like stars, the GTR may be
the lone truly ''singularly free'' theory, a theory which
does not allow occurrence of infinite density or pressure. As the massive star collapses indefinitely and no (finite mass)
blackhole is formed, the star tends to radiate away its entire mass energy, said Dr Mitra, who had no international tag behind him.
Adds Dr Mitra, while talking to UNI, ''The monolithic and stubborn features
of a classical blackhole itself may be construed
as loss of information from the observable universe and against one of the basic tenets of General Relativity, namely, the ability to unwind events in reverse direction (time reversal).''
But in the 70s, Mr Hawking introduced quantum mechanics (QM) in the problem
and claimed that blackholes do radiate albeit at an extremely slow rate. As
a blackhole radiates, it loses mass energy and in a certain finite time vanishes
However, the emitted radiation from the blackhole is of random nature (thermalised) and does not carry any information about the properties of the elementary particles trapped within the EH (event horizon), that is, the blackhole keeps on trapping information and matter.
And worse, when the blackhole vanishes into nothingness, all the trapped information
gets permanently erased from the physical
universe. This consequence is in direct conflict with established physical laws and in particular with QM. This is the Information
Loss Paradox associated with blackholes. Dr Mitra claimed to show that no realistic gravitational collapse can actually produce any Trapped Surface (the progenitor of an EH) or blackhole. On the other hand, collapse of massive stars can at best asymptotically approach the state of a blackhole. He called such an object an ''Eternally Collapsing Object (ECO)''.
The essential reason for non-occurrence of Trapped Surface or a blackhole (BH) is very simple. Dr Mitra showed that if there would be a Trapped Surface, the speed of the collapsing fluid would become equal to the speed of light (c) and then it would even exceed c. Similarly, if there would be any EH, a test particle dropped above it would acquire the speed of light at the EH and then its speed would exceed c. But since Relativity forbids occurrence of the speed of light in a material particle, let alone exceeding it, Dr Mitra said there cannot be any EH or blackhole of finite extent and mass.
In a subsequent paper, Dr Mitra showed that, as a test particle is dropped above the EH, its acceleration, an important measurable physical quantity, becomes infinite and as the particle would go within the supposed EH (if it is of finite size), its acceleration would become an imaginary quantity. Thus, in no way, can any EH or any BH of finite extent be allowed. In this latter paper, Dr Mitra mentioned that since there is no BH or EH in the strict sense and gravitational collapse only asymptotically tries to attain such states, there is no Information Loss Paradox at all.
He added that ''We can predict with absolute certainty that no such event (BH evaporation) would ever be detected because General Relativity does not allow formation/existence of finite mass BHs.'' At the same time two American astrophysicists confirmed Dr Mitra's contention that at the EH or a Trapped Surface, matter would behave like light, which is not allowed by Relativity. Although Mr Hawking presented his new version of BH theory in an international conference in Dublin, and no preprint of his work is available at this moment, the abstract of his paper does mention that ''The way the information gets out seems to be that a true Event Horizon never forms, just an apparent horizon''.
Although Mr Hawking might show this result by using Quantum Mechanics, the eventual conclusion agrees with what Dr Mitra has shown by using the fundamental constraint that ''no speed can exceed the speed of light''. According to Mr Hawking's close co-worker Garry Gibbons, whom Dr Mitra quotes from material available on the subject, ''The view seems to be forming in his mind that there isn't a blackhole in the absolute sense..'' and ''Hawking's black holes, unlike classic black holes, do not have a well-defined Event Horizon that hides everything within them from the outside world''. //EOM//