2014 : WHAT SCIENTIFIC IDEA IS READY FOR RETIREMENT?

Einstein once said: "The question that most interests me is whether God had any choice in the creation of the universe." By 'God', of course, he didn't mean God. What he was referring to was the question that has driven most scientists who, like me, are attempting to unravel the fundamental laws governing the cosmos at its most basic scale. Namely: Is there only one consistent set of physical laws? If we change one fundamental constant, one force law, would the whole edifice tumble?

Most scientists of my generation, like Einstein before us, implicitly assumed that the answer to these questions was, yes. We wanted to uncover the 'One True Theory', the mathematical formulation that explained why there had to be four forces in nature, why the proton is 2000 times heavier than the electron, etc. Historically in recent memory this effort reached its most audacious level in the 1980's, when string theorists argued that they had found the Theory of Everything—that using the postulates of string theory one would be driven to a unique physical theory, with no wiggle room, that would ultimately explain everything we see at a fundamental level.

Needless to say, that grand notion has had to be put aside for now, as string theory has failed, thus far at least, to live up to such lofty promises. In the process, however, in part driven by string theory's lack of success, we have been driven to the opposite alternative: the laws of nature we measure may be totally accidental, local to our environment (namely our Universe), not prescribed with robustness by any universal principle, and by no means generic or required.

String theory, for example, suggests a host of new possible dimensions and to make contact with our observed four-dimensional universe, it requires the other dimensions to be invisible, either by curling up on such small scales they cannot be probed, or by requiring the known forces and particles to be restricted to live on our 4 dimensional 'brane'. But, it appears that there are many, many different ways to hide the extra dimensions, and each one produces a different four-dimensional universe with different laws. It also suggests that four dimensions themselves need not be universal. Perhaps there are 2 dimensional universes, or six dimensional ones.

One does not have to go to such speculative heights to be driven to the possibility that the laws of our universe may have come into existence when our universe did. The theory of Inflation, which is currently the best theory for how our current universe obtained the characteristics it is measured to have on large scales, suggests that at very early times there was a runaway period of expansion. In different places, and perhaps different times, small regions will stop 'inflating', as a cosmic phase transition occurs in those regions, changing the stable configuration of particles and fields. But in this picture, most of the 'metaverse', if you will, is still inflating, and each region that departs from inflation, each universe, can settle into a different state, with different laws, just as ice crystals on a window can form in different directions.

All of this suggests very strongly that there may be nothing fundamental whatsoever about the 'fundamental' laws we measure in our universe. They could simply be accidental. Physics becomes, in this sense, an environmental science.

Now, many people have picked up on this notion to suggest that somehow we can understand our laws because they are selected anthropically—that is, if they were any different, life wouldn't have developed in our universe. However, this idea is full of problems. Not least because we have no idea what possibilities exist, and whether changing a few, or a huge number of fundamental parameters could result in viable habitable universes. We also have no idea if we are 'typical' lifeforms. Most life that evolves or will in our universe in the future might be quite different.

Focusing on anthropics misses the point in any case. The important fact is that we must be willing to give up the idea that the laws of physics in our universe reflect some underlying fundamental order… that the laws are somehow pre-ordained by principles of beauty or symmetry. There is nothing new about this. It was myopic to assume that life on our planet was pre-ordained. We now understand that accidents of natural selection and environmental traumas governed the history of life that led to our existence. It is equally myopic to assume that we are somehow the pinnacles of evolution—that all roads lead to us, or that we will not lead to something completely different in the future.

It is myopic to assume that the universe we now live in will always be this way. It won't be. As several of us have argued, it seems that in the far future all the galaxies we now see will disappear. But it may be much worse. It is myopic to assume our laws are universal in time and space even in our Universe. Current data on the Higgs particle suggests that the Universe could yet again undergo a cosmic phase transition that would change the stable forces and particles, and we and everything we see might disappear.

We have come to accept the notion that life is not preordained. We need to equally give up the quaint notion that the laws of physics are. Cosmic accidents are everywhere. It is quite possible that our entire universe is just another one.