Three Roads to Quantum Gravity - Lee Smolin - Review

One of the boldest books read in recent times Lee Smolin takes the courage to disagree with Heisenberg's Uncertainty principle, for a brief though, and takes a surge up to breathe back suggesting that there are more reasons to agree with this principle than not to - albeit with a suggestion that determination of a position would require at least one dimension out of three and the calculations thus.  It made quite a thrilling reading because we matured unto the post graduate status gulping this principle along with relativity and Quantum doses.

Smolin gathers these theoretical activities into three categories: studies of black holes, string theories and his own specialty, loop quantum gravity. In black holes, as espoused by John Wheeler of Princeton and Stephen Hawking at Cambridge, he finds ''microscopes of infinite power which make it possible for us to see the physics that operates on the Planck scale.'' String theories, recently popularized by Brian Greene of Columbia, reduce matter not to elementary point-like particles but to one-dimensional threadlike entities that flutter and vibrate with differing beats corresponding to the observed spectrum of particles.

Loop quantum gravity will prove difficult to grasp unless readers have followed the recent history of particle physics, the LHC and LIGO. According to this approach, ''space is made of discrete atoms each of which carries a very tiny unit of volume.'' This may sound like a simple idea, but Smolin manages to make it exceedingly complex - perhaps because he does his own theoretical research in this arena. What appears obvious to him is nearly opaque for the rest of us.

All three approaches seem to require that space and time be fragmentary at the Planck scale. But they have extremely fine-grained structures, which helps explain why they appear so smooth to us: ''A blink of an eye has more fundamental moments than there are atoms in Mount Everest.''

There are some unusual frank expressions by the author too.  That he would count on 'tales' to prove his points beginning with superimposibility of the quantum states of a dead or alive mouse proves funny. He gives room for all other tales connected with more such proposals. It is a generous thing on his part that he would find at least one reason to agree with other's theories. Like, for instance, he imagines Galileo and Kepler working in the same building (different floors though) over different theories and claiming each one is true, because Galileo talked about motion of the planets while Kepler stuck to the shape of the orbits.

These kind of lucid narration asks us to rethink the epistemological roots of the mental pictures we make about nature and space. It is one of the most difficult intellectual challenges humanity has ever faced. Quantum mechanics accurately describes realms of the very small, while Einstein's general theory of relativity applies to vast, cosmological distances spanning galaxies or groups of galaxies and to enormously massive objects, such as the billions of stars in them. The goal of combining these two disparate theories into one eluded physicists for most of the 20th century, but progress has occurred during the last few decades.

Faster than light concept of wave, quantum fluctuations of vacuum, zero point motion and energy, zeroth law of thermodynamics, large number of event and information flow, black holes and their horizons (along with Hawking Radiation), the illusion of continuous space, Feynman's diagrams, vibration and heat association of system with lower temperatures, empty space with non-zero density, 'cosmological constant' dilemma and 'information becoming geometry' are brilliantly discussed to the pleasure of the intelligent layman.

That Mathematical consistency in itself follows one theory of nature is a stark reality and the author merges all his open discussions with this solid liner. Some questions on M Theory and the beautiful point that science will become religion if it is proved makes interesting reading.