This is PART III of the four part series about the Edge discussion between Lee Smolin and Leonard Susskind. After criticizing Smolin the last time in PART II, it is now time to turn on Susskind.

Leonard Susskind is well read, certainly enough to know about the measure (not “measurement”) problem in modern quantum physics (introduced in PART I). Nevertheless, he argues against Lee Smolin by telling him that eternal inflation makes “more” universes, which without a good measure, like some density, a number per volume or suchlike, is perfectly senseless. Moreover, and as discussed before, what if you make another billion dead universes for every one like ours? It doesn’t change anything except eliciting the feeling that we are uncommon, which Susskind wants to elicit in order to have a case for applying anthropic principles.

Yeah, sure we are uncommon if you count enough dead stuff. However, it certainly does not address the fact that Smolin is already on the next level by demanding more careful consideration of how your statistical ensemble is constructed and what you want to do with it. It only tricks the reader into a side issue.

Leonard Susskind provides bad analogies: When Lee Smolin talks about that some knowledge cannot be had on principle, Susskind replies that if we had thick clouds and could not see the stars, then we would have likely argued similarly about not being able to see the stars. All his analogies, for instance the one mentioning Darwin and not being able to investigate the fossil record yet, and the many other, gratuitous examples, fail badly, because cloud covers and suchlike you can always hope to pierce through eventually.

However, a black hole event horizon, once you fall through, is something you cannot look back through on principle. On what principle? On the very principle that Susskind defends so vigorously when it comes to black holes conserving their information: You can on principle not copy quantum information. This is not a little hurdle you can hope to overcome with further advancements in technology; it is a hurdle that underlies the whole darn fundament of physics and thus reaches epistemological relevance.

We are dealing with the Kantian a priori, the absolute no go, not just with silly Mach opining that atoms will be forever unobservable. Does Leonard Susskind know about this difference between not-yet-observable and on-principle-unobservable? Of course he does! He himself partially discovered black hole complementarity and the holographic universe. This leaves two possibilities: He either argues disingenuously or he is effectively (Without realizing, like too many physicists) a direct, naïve realist, as somewhat discussed in PART I.

Without realizing” means here that although he partially was personally involved in dismantling realism, he just cannot shake it [Such happens often at the cutting edge of research – Einstein helped discover quantum mechanics but also never believed (grasped?) its core.].

There are many other little remarks that could be made, like that he disregards (in attacking Smolin at some point) the fact that information in a black hole is only shown to be conserved in theories that have some sort of absolute quantum time, and so on. However, listing those would distract from the important points above, which are so important since they reveal either a dishonest or naïve Susskind, and this is something that I write not without difficulty about somebody who was my absolute hero just ten years ago.

After I ripped on both contenders, next time the judge’s decision as if anybody cares. ;)