Saturday, March 17, 2012

19. Why Are the Laws of Nature What They Are?

This used to be a very profound question till recently. Developments in physics during the last few decades have now made it rather trivial and trite.

Such questions used to be in the domain of philosophy, and human history can boast of a truly dazzling succession of great philosophers. But the question now is: What is the true worth of an otherwise great philosopher who was/is innocent about the finer points of quantum mechanics?

Modern physics has come up with plausible answers to fundamental questions over which philosophers fretted for centuries. No wonder, Hawking & Mlodinow wrote this in 2010, somewhat facetiously perhaps:
Traditionally these are questions for philosophy, but philosophy is dead. Philosophy has not kept up with developments in science, particularly physics. Scientists have become the bearers of the torch of discovery in our quest for knowledge.
An answer to the question 'Why are the laws of Nature what they are?' comes from M-theory (cf. Part 14). According to it, there are actually 11 dimensions. We see only four because the rest of them have got 'curled up' so much that they are not visible to us. There are ~10500 different modes of curling up, meaning that that many different universes are possible. One of them is the universe we inhabit. The apparent laws of a universe depend on how the extra dimensions in that universe got curled up. We say ‘apparent laws’, because the more fundamental laws are those of the M-theory.

Thus, there are multiple universes, or MULTIVERSES, each with its own set of apparent laws. We just happen to be living in a universe with a certain set of laws and a certain set of values for the fundamental constants. If the laws of a universe are not conducive to emergence and evolution of life, living beings cannot possibly exist in that universe, discussing such questions.

In Newtonian physics, the past was visualized as a definite series of events. Not so in quantum physics. No matter how thoroughly and accurately we observe the present, the unobserved past, as also the future, is indeterminate, and exists only as a ‘spectrum of possibilities’. This means that our universe does not have just a single past or history. Since the origin of the universe was a quantum event, Feynman’s sum-over-histories formulation for going from spacetime point A to spacetime point B occupies centre-stage (cf. Part 4). But we have knowledge only about the present state of the universe (point B), and we know nothing about the initial state A. Therefore, as emphasized by Hawking, we can only adopt a ‘top down’ approach to cosmology, wherein every alternative history of the universe exists simultaneously, and the histories relevant to us are those which, when summed up, have a high probability of giving us our present universe (point B).

The picture that emerges is that many universes emerged spontaneously (simultaneously or otherwise). Most of these universes are not relevant to us because their apparent laws are not conducive to our emergence and survival. The M-theory offers ~10500 possibilities of start-up universes. We have to single out those which correspond to the curling up of exactly those dimensions which we find to be the case for the universe we inhabit. Further, we have to select those histories which reproduce, for example, the observed mass and charge of the electron, and other such observed fundamental parameters.

WHAT IF THE M-THEORY DOES NOT GET DUE VALIDATION? The multiverse idea would be still intact; via the cosmic-inflation theory (cf. Part 17). The inflation episode is an integral part of modern cosmology.

It is now time to recapitulate some points I have made in these 19 posts. First I gave purely classical arguments to explain how our universe could emerge out of 'nothing', without a violation of the principle which says that the total mass/energy is always conserved, and that nothing extra can get created. This classical argument is simple to understand, but is, at best, only a crude statement. The real explanation has to come from the laws of quantum mechanics, because these laws govern all natural phenomena. The vacuum state in quantum field theory is not at all a state of 'nothingness'. It has an energy of its own. Our universe emerged out of vacuum as a quantum fluctuation, without violating the principle of conservation of energy/mass. And the M-theory and the cosmic-inflation theory are powerful explanations for why our universe has the laws it has. Our universe got created in accordance with the laws of physics (or rather because of them), without the help of a Creator.

Euclidean geometry holds true in our universe; i.e., ours is a flat-geometry universe. Which is just as well. As explained in an accessible language in a recent book 'A Universe from Nothing', only a flat-geometry universe can satisfy the requirement that the sum total of positive and negative contributions to the overall energy of the universe add up to zero. The energy-conservation law was not violated when our universe emerged out of 'nothing'. The total energy is still zero.

Watch this video for more:

The next set of posts in this series will explain how life emerged out of non-life, without any help from a Creator or Designer. It was all a matter of evolution of 'complexity' in an expanding and cooling (and therefore gradient-creating) universe. At our terrestrial level, the steady ingress of solar energy into our ecosphere has been the local factor creating gradients or non-equilibrium situations. The natural tendency to seek equilibrium configurations often leads to new patterns and structures. This is how 'complexity' evolves. The emergence of life in one such example of what thermodynamically open systems can achieve. There is nothing divine or mystical about that.

From now on the narrative will become more and more life-centric and anthropocentric. In the next post I shall discuss the Anthropic Principle.