I just came across Stephen Wolfram’s latest post. I suppose that everybody knows who this guy is. In my opinion, he definitely qualifies as a genius. I do not say that lightly: on the contrary, you might actually think from reading this blog that I tend to be worried, skeptical or even angry at physics, physicists or science in general. But Wolfram embodies this wild spirit of folks who boldly go where no man has gone before.
A new kind of science?
I certainly was aware of his New Kind of Science (who wouldn’t?). But I didn’t really feel a need to read it, being under the impression that it was just a book about cellular automata. Having read the blog, which contains a number of links to the on-line version, I discovered that it was much richer than this. As a matter of fact, after reading just a few pages on line, I ordered the book right away.
I think, for instance, that there is something really deep in the following:
I’ve built a whole science out of studying the universe of possible programs–and have discovered that even very simple ones can generate all sorts of rich and complex behavior.
Why is studying the universe of possible programs interesting? Because mathematics is the manipulation of symbols using specific rules, so in that sense, mathematics as a whole are a subset of what Wolfram just described, the universe of possible programs. Even if for him it is only a “hobby”, I find the approach much less amateurish than more “professional” work on the same topic.
This does not mean that I immediately agree with the notion that everything can be described using an ultimate reductionist representation like network graphs or cellular automata. Instead, it means that like fractals, these tools look like an original way to explore physics. Not the way, mind you, one more way. And I like a rich vocabulary to express ideas. I see Wolfram’s “new science” as a useful tool in exploring the relationships we observe between our measurements.
On the other hand, I do not entirely subscribe (yet) to the idea that you can recover quantum mechanics from a deterministic set of causal relations. I am not even convinced at this point that there would be a single such network, in the sense that the network we detect might depend on what physics process we use to probe it. This dependency on the measurement is one of the core ideas in my own theory of incomplete measurements, and I gave enough examples in the article to explain why I lost my belief in “the ultimate spacetime metric”, which Wolfram is looking for as far as I understand. Time will tell.
Finally, the approach is fraught with difficulties, something that Wolfram is very aware of:
OK, but what is the rule for our universe? I don’t know yet. Searching for it isn’t easy. One tries a sequence of different possibilities. Then one runs each one. Then the question is: has one found our universe?
Clearly, the problem of exploring all possible programs is not really different from exploring the landscape in string theory. Where do you start? The difference I see with string theory is that the search could be largely automated. This is why I see this as a brilliant approach: if the rule is simple enough that it can be generated by enumeration, instead of probing slowly using the human mind, let’s probe quickly using computers. It will not necessarily work, but it will tell us something.
Anyhow: Recommended reading.