From the cosmos to the neutrons

COMPANION TO THE COSMOS: Rs. 395;

Q IS FOR QUANTUM - Particle Physics from A to Z: Rs. 450. Both by John Gribbin; Published by Universities Press (India) Ltd., Hyderabad- 500029; Distributed by Orient Longman Ltd., 160, Anna Salai, Chennai- 600002.

THE EARLIER part of the 20th century witnessed the emergence of two great theories: the General Theory of Relativity that deals with the unbelievably large, namely the cosmos, and, the Quantum Theory that deals with the incredibly small, the world of sub- atomic particles. In the two books under review, the author, who is without doubt among some of the well-known science writers of today, has presented the reader with an overview of the cosmos on the one hand and the sub-atomic particle world on the other.

These books are essentially encyclopaedic in their treatment and offer a brief introduction to the respective subject followed by 400-odd pages of A-Z dictionary which deals with events, discoveries and theories in these fields apart from giving the biographical sketches of various scientists who have contributed towards the advancements that both these fields have witnessed. The A-Z dictionary is followed by a section titled ``Timelines'' which gives the key dates in the development of physical sciences and events important in the scientific context as well as the birth dates of many scientists who contributed significantly in these areas. The time slot covered, stretches from as far back as 15,000 B.C. to the present day.

In the introduction to the first book, the author begins with that eternal riddle ``where do we come from'', the story of our origin that intrigues everyone, and proceeds in steps to discuss the universe at large. All our information relating to this comes to us in the form of electromagnetic radiation that travels at the enormous speed of 300 million metres per second. But the sheer size of the cosmos reduces even this figure to insignificance, as light from the distant galaxies takes several years to reach us. And this unbelievably large universe continues to expand. That the universe is expanding was discovered only in the late 1920s when Edwin Hubble and his co-workers established that the galaxies were moving apart from one another. This realisation is only as old as the average lifespan of the human, in Biblical terms, three score and ten. Before that the universe was considered to be eternal and unchanging, so much so, that even Einstein was fooled into committing his ``biggest blunder'' of adding that extra term, the cosmological constant, in his equations of the General Theory of Relativity which clearly pointed to an expanding universe. The cosmological constant was added to annul this expansion.

The author then discusses the moment when the universe was born in a Big Bang, a moment in time known as the singularity where all physical laws break down. Just a minute fraction of a second after the Big Bang, the conditions became amenable to be explained by the physics of the incredibly small, the quantum mechanics. That was a moment dominated by radiation, a moment in space-time giving the kick start for the evolution of the universe with the creation of matter and anti-matter, with a slight edge in favour of matter. The author discusses the ``Horizon problem'' leading to Alan Guth's inflationary theory and the findings of the COBE satellite that established the wrinkles in space-time when the universe was just 300,000 years old. These are sometimes referred to as the Holy Grail of cosmos, the seeds around which galaxies were formed. According to the author, this is the point in space-time where we can pick up the story as to how we got to be here. Does the term ``universe'' refer to the observable universe or to all of space-time? He suggests that we may use the term ``cosmos'' to refer to the entirety of space-time, within which there may be a large number of other expanding bubbles of space and time, other universes with which we can never communicate.

In the introduction to the other book, the author talks about quantum mechanics, the theory of the micro-world of particles which is the real quantum domain. We have come a long way since J. J. Thomson discovered the electron in 1897. Now we have a standard model of particle physics based on the rules of quantum mechanics that tell us how our world is built from the fundamental building blocks of quarks and leptons held in place by the exchange of particles called gluons and vector bosons.

However, this standard excludes gravity which belongs to the realm of the General Theory of Relativity. Unifying these two great theories into one package is the ``Holy Grail'' that physicists are striving for. With its wave-particle duality and its principle of uncertainty the quantum world does look like a weirdo by the standards of everyday world. But it is not an exotic theory that bears no relevance to the world we are familiar and comfortable with.

It governs many areas: making of the bomb, designing nuclear reactors, building equipment that have semiconductors and microchips, in coming to terms with the way superconductors conduct electricity, in understanding the chemistry of life itself - in short, everything that relates to life in some way or the other can be explained in terms of the way in which the particles of the subatomic world react with one another. Gravity, of course, is excluded from all this.

During the late 1940s Richard Feynman developed new techniques for considering electromagnetic interaction within the Quantum Theory and his work contributed greatly to a new Theory of Quantum Electrodynamics, QED, which tells us of the interaction between light (quanta) and matter. QED was followed by quantum chromodynamics, QCD, that describes what goes on inside protons and neutrons, the building blocks of the nucleus. The idea of light quanta assumed importance when Einstein took up its study and established the reality of the photons. Then in the early 1920s the French physicist, De Broglie went beyond the idea of waves acting as particles and suggested that particles could behave as waves.

The wave-particle duality was used by Schrodinger in his formulation of quantum mechanics. By the end of the 1920s physicists had a choice; they could choose from different mathematical descriptions of the particle world. Finally, in the early 1940s Richard Feynman was to provide yet another mathematical description of the quantum world using his ``path integrals''. This turned out to be the most elegant of all mathematical treatments of the particle world.

The icing on the cake, if one may call it so, to this whole quantum saga was to come from Feynman himself. In one of the lectures he delivered at the Cornell University on the theme ``The character of physical laws'', he said: ``I think I can safely say that nobody understands quantum mechanics... nobody knows how it can be like this.'' That, says the author, is the spirit in which this guide to the quantum world is offered. Just relax and enjoy it.

C. V. SUBRAMANIAM

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