The Natural Constants

A scientific fact: The constants and laws of nature fall perfectly within narrow ranges that allow life to exist.

I have recently been watching a few lectures on Academic Earth, specifically an introductory astrophysics course by Yale lecturer Charles Bailyn. In the final lecture of this series he raises the self-evident but often forgotten fact, that we exist. He goes on to explain how our existence is entirely dependent on a whole host of natural constants each falling within very small ranges, which of course they do, because we exist. These are numbers that physicists have worked out that fundamentally describe certain functions and aspects of the universe, and each of them is quite perfect. Perhaps a couple of examples.

The universe is expanding, as it has done since the moment of initial singularity (Big Bang theory). The density of the stuff in the universe slows it down through gravitational forces between itself. The cosmological constant (Λ) is proposed as a fundamental property of the universe; if it were much larger than it is (a mere ten times larger) the universe would not be dense enough, it would not be able to stop expanding, and we would have catastrophic inflation. This would not allow matter to congregate enough for stars to form, let alone planets with enough complexity to allow life.

The gravitational constant and the speed of light are other examples, especially as they relate to the Schwarzchild radius (r_s). This is a given radius for every quantity of mass. If an object is smaller than it's Schwarzchild radius, neither light nor particles can escape the region from the inside, and you get a black hole. Its value is given by:

where G is the gravitational constant, m is the mass of the object, and c is the speed of light. If G were slightly larger, or if light travelled slightly slower, then the Schwarzchild radius of any object would be larger. If this radius was larger than a white dwarf star (the usual graveyard-type form of a star at the end of its life) then every star would end as a black hole. This means the material in stars would never be expelled in supernovae, so no heavy metals would become available for the construction of planets, or of life.

We are carbon-based life forms. Carbon is really good at working itself into a myriad and endless array of complex structures (carbon chemistry is, as a result, the most complicated kind of chemistry). The properties of carbon that allow it to develop this complexity- and complexity is a necessity for the emergence of life- would dissapear or would never have developed if a whole host of other constants and forces did not sit at their existing values; the fine structure constant (α), which dictates the strength of the electromagnetic interaction, is an example. If the strengths of the fundamental forces (the strong and weak nuclear forces, the electromagnetic force, and the  gravitational force) were tweaked ever so slightly, they could cause seemingly minor things to play out differently and, over the long course of the development of the universe, could make hundreds of catastrophic differences that would all result in the non-emergence of life.

So almost all of the natural constants are fine-tuned in such a massive, perfect system that has allowed, in this universe, life to develop; and further, intelligent life capable of observing those very same constants. Now for the big question: why? Possible answers:

1) It's an accident. A totally freakish coincidence.

2) It was done that way on purpose.

3) There's actually a multiverse and we are the lucky one that got it right.

Number one is entirely unsatisfactory and frankly no fun at all. Number two is the very obvious answer. It does not necessitate a religious belief; see the Strong Anthropic Principle, the idea that the universe for some reason must be such that observers are created in it at some stage, for example. But atheists are pesky buggers, and number three demonstrates some pretty impressive imagination to get around the need for a God. It draws on the ideas of probability theory; basically, everything will happen at some point somewhere if we try enough. If we do an experiment in which we roll a dice fifty times, it will be very unlikely that we will get fifty sixes. But if we run that experiment enough times, we will eventually get that result. So if there are millions of other universes out there, each with slightly different natural constants, surely one of them will get them within the ranges necessary for the emergence of life. And, indeed, one did. This can be dismissed as cold and impersonal (both true) or just too absurd. I don't want to go into details, but there are plausible theories as to where these other universes are: they are beyond the 'cosmic horizon', very very far from us; they lie in other dimensions (proposed by string theory) that we can't access; or new universes are born through black holes. Science fiction much?

So we still do not know why the physical constants have turned out so perfectly. It is natural to postulate the existence and role of an omniscient creator, but this is not the only explanation. The question will probably be solved in the future by the arrival of better intruments of measurement (or God himself). Until then, let's continue to live with the same assumptions we had before. And read sci-fi.