Last night a new paper by Lenny Susskind appeared on the arXiv, carrying the title The Census Taker’s Hat. It seems that Lubos Motl stayed up much of the night reading it, with a long posting on the subject appearing before 8 am in the Czech Republic.
Now that he’s no longer employed within the string theory academic community, Lubos feels free to treat Susskind in much the same way he did Lee Smolin, characterizing Susskind and collaborators as a “gang” of “leftists”, and making fun of the central notion in Susskind’s paper (that of a preferred observer called the “Census Taker”) by referring to it as “Stalin the daddie”. He gives a detailed section-by-section critique of Susskind’s paper, here’s some of the flavor:
Well, this is about 7th assumption that seems obviously wrong to me – this one is really bad – but let’s go on reading. I still haven’t understood what question he exactly wants to be answered. Equally seriously, I don’t understand whether he thinks that his speculation about the location of the central committee is a hypothesis with some evidence, a nice hypothesis without evidence, God’s ad hoc decision, or why does he exactly believe it.
Unlike Lubos, I haven’t tried to follow the details of Susskind’s 65 page argument, but did try to figure out how he addresses the central problem of any multiverse scenario: how do you test it? If you can’t test it, it’s not science. Susskind describes exactly two possible ways that information about the “Ancestor” universe to ours may be accessible.
Susskind begins by claiming that “To many of us, eternal inflation, bubble nucleation, and a multiverse, seem all but inevitable”, but goes on to note that the fact that one has an infinity of universes that one doesn’t know how to count means that “the inevitable has led to the preposterous”. A reasonable person might decide that this means that things weren’t so inevitable, but Susskind feels that one must soldier on, although “In my opinion, this situation reflects serious confusion, and perhaps even a crisis.” This paper is his attempt to address the crisis.
Susskind quotes Bjorken as having told him that the Multiverse is “the most extravagant extrapolation in the history of physics”. He seems rather proud of this, but somehow I suspect that Bjorken didn’t mean this as a compliment…