The Landscape lectures at Erice are over. I'm not very optimistic about the anthropic principle --- for example, see my
paper with Graesser, Jenkins and Wise on how even Weinberg's original anthropic prediction of the cosmological constant is critically sensitive to the assumed level of initial density perturbations. Nevertheless I learned something interesting from Lenny's lectures. Since the Landscape involves many metastable vacua, it is very likely that our universe, with its small vacuum energy, was produced via bubble nucleation from a parent universe with much larger vacuum energy. In this case it is unavoidable that the spatial geometry of our universe has negative curvature. A subsequent era of inflation can reduce this negative curvature to almost zero, but there is a definite prediction that k is negative. If an observation by Planck (next generation CMB probe after WMAP) yields a small positive k, the Landscape will be strongly disfavored. By the usual Popperian definition, the Landscape is then science: it makes a falsifiable prediction! (Lenny, being quite honest, confided that Andre Linde would almost certainly find a way out, but it would have to be quite contrived :-)
[See more recent post
here. The prediction of negative curvature isn't as robust as I had originally thought. 10.24.2006]
Having argued that the Landscape is sort of falsifiable, let me now turn to a reductio ad absurdum of anthropic arguments.
Let R = the ratio of number of artificially intelligent virtual beings to the number of "biological" beings (humans). The virtual beings are likely to occupy the increasingly complex virtual worlds created in computer games, like Grand Theft Auto or
World of Warcraft (WOW will earn revenues of a billion dollars this year and has millions of players). In the figure below I have plotted the likely behavior of R with time. Currently R is zero, but it seems plausible that it will eventually soar to infinity. (See previous posts on the
Singularity.)
If the integral of R diverges, then anthropic reasoning suggests that we are overwhelmingly likely to be virtual beings living in a virtual world. The electron mass and string flux compactification parameters were set by a programmer (himself virtual) working for a game company within yet another simulated world :-)
