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 :-)
So the Anthropic Principle predicts "There is no spoon."
ReplyDeletePardon my amateurism for butting in :)
ReplyDelete1) It seems to me that the anthropic principle (for example the WAP on the Wikipedia page) doesn't necessarily solely rely on the composition of our universe in a multiverse situation, but it can be interpreted as anthropic "all the way down".
2) I don't understand what you mean by "If the integral of R diverges". The integral is the area under the curve; diverges from what?
This is the "other" M(atrix) Theory, as in Keanu Reeves. I've seen some other half-serious speculation along these lines. Then you have people arguing that the universe is just a giant quantum computer. It seems we have the makings of the perfect fusion of physics, philosophy, computer science and religion.
ReplyDeleteBarry: I don't understand (1). Re: (2), diverge means the area goes to infinity, which means most intelligent beings that have ever lived are virtual (inside a simulation).
ReplyDeleteAll: the Matrix/Singularity scenario is tongue in cheek (although not impossible, of course). It shows some of the difficulties of anthropic arguments...
steve: re 1) taking the anthropic principle to imply that there is nothing particularly "special" about our universe esp. with respect to humans per se (as opposed to life at all), because we just happen to be living in the universe with the right parameters out of all possible universes, then if some universes such as our own are more likely due to some theory of emerging from another parent universe, that still doesn't preclude the anthropic principle, since it can apply to the whole chain of parent universes etc.
ReplyDeleteBarry, nothing really precludes the anthropic principle.
ReplyDeleteThat's not a virtue.
Steve, I heard Lenny give an anthropic talk earlier this year and there were questions about falsafiablilty (is that a word?), which he wasn't sure about. Is this negative k prediction a recent development? And how non-zero would the curvature have to be for PLANCK to measure it?
ReplyDeleteInteresting discussion!
ReplyDeleteI find anthropic discussion unconvincing. On the other hand, I find "naturalness/fine-tuning" arguments for the necessity for physics beyond the standard model not convincing either. Not to mention the tight bounds from the values of the electroweak precision observables...
What do you make of Connes work? Fancy way of writing the SM Lagrangian? Of course, different ways of saying the same thing can be illuminating(Newtonian vs Lagrangian or Hamiltonian, for example)...
BTW, is that you in the red T-shirt in this picture?
MFA
Eric: their paper came out in 2005, so the result is only new to me. He wasn't pushing the falsifiability very hard, but it seems convincing to me.
ReplyDeleteMFA: I haven't followed Conne's work at all. I'd be surprised if something that purely mathematical works out. Yes, that's me in an orange shirt at the front. We had a final dinner for the school last night, which was also a 60th bday party for 'tHooft.
Trackback from "Science-in-Crisis"... "Happy Birthday, t'Hooft"
ReplyDelete