Lee Smolin has a new preprint discussing the “anthropic principle”. He argues that one standard form of the anthropic principle that has been invoked by proponents of the “Landscape” is not falsifiable and he gives an eloquent explanation of the importance of falsifiability for a shared scientific enterprise. He also discusses the “prediction” of the rough magnitude of the cosmological constant that supposedly uses the anthropic principle and is due to Weinberg. He points out that this argument really isn’t an anthropic one, since it is independent of the existence of intelligent life. It just relies on showing that there is a relation between the cosmological constant and the existence of gravitationally bound structures. Then, since we see galaxies, we know something about the cosmological constant.
One of Smolin’s concerns is to show that his theory of “cosmological natural selection” (discussed in his book “The Life of the Cosmos”), while being a theory of a “multiverse” just like the string theory Landscape, is different in that it is potentially falsifiable, unlike some recent anthropic arguments.
He states well the predicament that theoretical physics finds itself in, with the tactic that worked so well throughout the 20th century, that of searching for unification by exploiting symmetry, no longer having much success. While I agree with most of what he has to say in this preprint, I’m more optimistic than him that future progress through new ideas about unification and the exploitation of symmetry is still possible. My point of view is more that the reason the last twenty years have seen no progress of this kind is that virtually all the field’s effort has gone into pursuing one very speculative and not very promising idea about unification, ignoring other possible lines of research.