THE NATURE OF SPACE AND TIME

By Stephen Hawking and Roger Penrose

OUP

Price: Rs 175

French mathematician Laplace assured Napoleon Bonaparte in early 19th century that if you knew the state of the universe at a certain point of time, it is possible to determine the state of the universe at any other point of time, in the past as well as in the future. Towards the end of the same century, Lord Kelvin, the British physicist, declared that there were no more great questions left to be answered in physics. Soon after, Einstein's Theory of Relativity knocked the bottom out of Newtonian physics, and quantum mechanics introduced fatal indeterminacy into the nature of things.

As we hurtle towards the 21st century, two of the best minds in contemporary physics in the English-speaking world, Stephen Hawking from the University of Cambridge and Roger Penrose from the University of Oxford, have tried to offer possible answers which would give a final picture of the universe. Hawking and Penrose had delivered three lectures each at the Isaac Newton Institute for Mathematical Sciences, University of Cambridge, in 1994, and these have been published for the first time in India this year.

The lectures do not really point to any exciting new things, but reveal that two scientists, like any two ordinary human beings, disagree with each other, if not violently, at least strongly.

Unlike Hawking's runaway best-seller, A Brief History of Time, and Penrose's popular work, The Emperor's New Mind, this book is a mine-field of mathematics, which would certainly scare the general reader away. But the reader who knows no mathematics will discover that the reading of the book is tough and rewarding. By the time, he reaches the end of the six lectures and the seventh featuring a debate between Hawking and Penrose, the reader will realise that the most complicated mathematics at our command is incapable of giving an accurate picture of the universe.

Both Hawking and Penrose seem to be juggling with geometries to describe space-time at the very beginning and at the very end. Hawking offers a combination of Euclidean and Lorentzian spaces, which takes care of the inherent curvature of space-time due to gravity. Penrose rests on `twistor space', which is his contribution to explain a space with particles -- in the calculations they are the positive and negative numbers -- flying backwards and forwards, into the past as well as into the future. But these are mere details.

The real questions are something else altogether. And they are quite old ones. Hawking returns to the question of entropy, to the second law of thermodynamics, which states that the arrow of time moves inexorably in a single direction, from the past into the future, and a system moves from orderliness to ever-greater disorderliness. He states in characteristically picturesque language:

``The universe would start smooth and ordered and would get more disordered and irregular as it expanded. However, I thought it would have to return to a smooth and ordered state as it got smaller. This would have implied that the thermodynamic arrow of time would have to reverse in the contracting phase. Cups would mend themselves and jump back on the table. People would get younger, not older, as the universe got smaller again. ... I wrote a paper claiming that the arrow of time would reverse when the universe contracted again. But after that, discussions with Don Page and Raymond Laflamme convinced me that I had made my greatest mistake, or at least my greatest mistake in physics: the universe would not return to a smooth state in the collapse.''

Penrose admits the need for philosophy to face up to some of the questions, especially relating to the teaser of the Schrodinger's cat -- whether it is dead or alive at any point of time: ``... we have to solve the problem of why we do perceive either a live cat or a dead cat, but never a superimposition. I think philosophy is important in these matters, but it doesn't answer the question.''

Scientists may have to think of other routes than mere mathematical ways. Hawking and Penrose, and the other brave physicists, may find it useful to read a book written in 1926 by a British philosopher, Samuel Alexander, called Space, Time and Deity, which has the interesting aphorism: ``Space is the body of God, and Time is the mind of God."

Copyright © 1997 Indian Express Newspapers (Bombay) Ltd.