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WHAT IS THE FUTURE OF COSMOLOGY? - cont.

This is possible because, since Darwin, we know that structure and complexity can be self-organized. We understand that there are natural processes, easily comprehensible, by which organization can arise naturally and spontaneously, without any need for a maker outside of the system. This requires, however, that we take a more historical view of fundamental physics and cosmology. We must be open to the possibility that the answers to many of the questions we have about why the elementary particles or the fundamental forces are as they are—and not otherwise—may have answers that are, at least in part, historical.

       This goes against the expectation that the more fundamental an explanation, the less historical it is. It also goes against the expectation that the ultimate answers to all questions about the elementary particles will be found with the discovery of a final, unified theory. This theory is presumed to be based on some mathematical principles that are both powerful and beautiful, in a way that will single it out for consideration as the unique possible fundamental theory. Our job, as physicists, is to discover this fundamental theory. We have implicitly believed that if we found it, it would be unique, so that there would be no room left to ask: Which fundamental theory holds true in our universe?

       It hasn’t turned out this way. The best candidate we have for a fundamental theory, string theory, comes in a great many versions, which each describe different possible universes with different elementary particles governed by different laws. As far as we know, all are equally consistent unified theories. So it seems like we do have to ask why one theory rather than another describes our universe.

       It is possible that all these theories are aspects of a single theory. Recent work tends to suggest that they all describe something like different phases: Just as water molecules may be organized into a liquid, solid or gas, the fundamental “stuff” seems to come in a large number of different phases, which look to observers on large scales like different fundamental theories.

       We are recently making some progress towards this unified string theory. Although its shape is not yet completely clear to us, it already has a name: “M” theory. Indeed, part of the search for this theory involves reformulating string theory in a way that is more relational, and less based on notions that space and time are absolute and independent of what exists. But it looks more and more like this theory will not allow the world to exist in a great many phases, and it will even be possible for the world to make a transition from one phase to another. Just as ice can be melted, it seems likely that in sufficiently energetic and violent events, the world may change from one phase to another, resulting in a change in the apparent laws of nature. Such violent events certainly include the approach to black hole singularities and the Big Bang of our universe.
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Michio Kaku: Is There a Theory of Everything?
 

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