Happy New Year!
On Christmas Eve Day, I mentioned a recent book, Why String Theory? by Joseph Conlon. I said I'd discuss its philosophical significance this week. Here we are, at the start of a new year, and we can start 2017 off with something weighty.
String theory is often presented as a "theory of everything" or ToE. This is both its charm and (in many minds) its downfall. These fundamental strings winding through X dimensions might allow for a geometrical description of all the particles, and the forces, enumerated in modern physics courses. The bestiary of different subatomic particles has become confusing and crowded -- the strong demand of human minds for conceptual order requires some clean-up work there.
As to forces, the "force left out" is always gravity. The other forces -- strong nuclear, weak nuclear, electromagnetic, have all made their peace with one another through the magic of quantum mechanics. Gravity remains aloof. One big goal of string theory is to bring gravity in line. This is the answer to the "why" question that serves as Conlon's title.
And yet string theory has become a brick wall against which some of the brightest minds in the world keep hitting their heads, making no dent. The problem is that the "theory" remains frustratingly vague, capable of explaining 'everything' only because it could explain ANYTHING. Thus without falsification, without verification. As one critic says, it is "not even false."
Conlon responds to all this, it seems to me, by abandoning the grand claims for string theory and looking at it NOT as a theory of everything, not even really as a theory at all, but as a source of inspiration -- as a fireworks display, which is aesthetically appealing itself and which can throw unexpected illumination over a lot of different areas.
Thus, he says, what string theory meant in 1970 when it got its start was not what it meant in 1985, and that again not what it meant in 2000 or 2015.
That's good. Lets hope it keeps changing, like the Martians in a Ray Bradbury story, who changed until then couldn't change any longer, and then died.
For in the philosophy of science, I have to stick with the construction Susan Haack calls the "shadow Popper." It is an understanding that can't accurately be traced to Popper himself -- that is in important respects contrary to what the historical Popper argued, but that is often attributed to him in order to have a Big Name behind it., Furthermore, it is an understanding of the world and of scientists' interaction with (the rest of) the world that works fairly well.
The fireworks show is not a sustainable substitute for reliable illumination, and when the right ideas HAVE been inspired (from whatever source) string theory will have become obsolete from the perspective of this defense thereof.