Over the last few days the World Science Festival has been running in New York and has featured some very interesting discussions amongst scientists on a variety of popular science subjects such as the mutiverse and the search for life in space. I have been following it because it had been said that the results of the FQXi essay contest (Is Reality Digital or Analog) would be announced at the festival and I am interested to see which authors are going to beat me to all the juicy prizes. So far nothing seems to have been mentioned about that but last night there was an interesting discussion broadcast live with the title “Rebooting the Cosmos: Is the Universe the Ultimate Computer?” It could have been inspired by the essay contest. Two of the four scientists (Ed Fredkin and Seth Lloyd) were cited in my essay for the contest and another (Fotini Markopoulou) was cited in my earlier FQXi essay on the nature if time. The final member of the panel was computer scientist Jürgen Schmidhuber. So this was a discussion of great interest to me and I was not disappointed by it.
The main question up for discussion was, “Is the universe a giant computer?” There is an argument that says that in the future we will build computers so powerful that we will be able to simulate universes in great detail. Assuming that life continues for a long time and that a few people are interested in playing such games, there will be vast numbers of such simulations. In fact, within the multiverse there will be so many simulations going on inside computers that they will vastly outnumber all the “real” universes. The conclusion is that we are infinitely more likely to be in a simulation ourselves than in a “real” universe. Actually we really have to conclude that there are no real universes, just simulations within other simulations.
I don’t take this argument too seriously, but a growing number of physicists are taken by such ideas and it is at least worth thinking about on a philosophical level. Does this mean that we are vulnerable to the possibility that the being running our particular simulation might decide to pull the plug at any time and we would just cease to exist? Some people seem to think so! I take the view that if there is one simulation running that matches our universe then there must also be infinitely many of them, by the same argument. We have no way to distinguish which one we are in because we have no access to the outside “other” world as Ed Fredkin calls it. So what we should experience is the combined effect of all the simulations that matches ours at any given place and time. In that case it is safe to assume that the simulation will go on in most cases so we are in no real danger of being stopped, phew.
Although these ideas seem wacky and untestable, I think they are worth thinking about because they can give us some clues about how the universe could work is we accept that such possibilities can make sense. This is how the role of philosophy in physics should work. The broad concepts may not be scientifically falsifiable themselves but they can lead eventually to other ideas that are. Everyone understands this, right? I think it is not unreasonable to say that the universe runs like a quantum computer, rather than it is a quantum computer. This may become more apparent in the fundamental laws of physics when we come to understand them better.
As an independent physicist who sits at home linked into the internet I don’t get to meet real physicists very often. However, it happens that I have had the good fortune to meet Ed Fredkin and exchange some ideas with him. I even have a little anecdote so I am going to finish of with that. Fredkin is remarkably accomplished in a number of fields. He was an airforce pilot who became a professor of computer science at MIT despite a lack of academic background. As an architect of some of the early PDP computer systems he quietly invented a number of concept in operator systems that form the basis of all computers today. he also invented several technologies such as a desalination process that earned him considerable wealth. His interest in applying digital ideas to physics have also been very influential especially through his contact with Feynman, ‘t Hooft and others. You can hear about some of that in the program.
A few years ago I got to know Fredkin because of his interest in some things I wrote in my online book about “Event-Symmetric Space-Time” the last time I met him was in Antibes where he keeps his yacht and we discussed his work on cellular automata. It is in a picturesque bay where they are used to celebrities passing through. One evening we were is a restaurant and he was telling me about his role in the Sakharov affair, another unrecorded episode of his amazing life story. As we talked I noticed over his shoulder that the waiter who had served us was looking towards us curiously. Fredkin turned round and caught his eye, then he turned back to me and said “oh dear, I know what is going to happen next” Sure enough the waiter came back over to our table and spoke nervously. “Excuse me, but could I have your autograph?” he asked. “Of course” said Fredkin, “but who do you think I am?”, The waiter paused looking a little confused, then burst out, “Sir. I recognized you immediately. You are Steven Spielberg!”