The "Multiverse" & Occam's Razor (12/27/2009)

This was originally posted on a horrible site called Myspace. When Myspace underwent a redesign in Fall 2010, hundreds of insightful reader comments that had been left over the years were lost. I have since deleted my account there.

Everyone is talking about the "multiverse" these days — the idea that our Universe is just one of many, that there may be billions of "pocket universes" as real as our own Universe but extremely far away, or in the form of isolated "bubbles," such that we may never be able to contact them. The cover story of the January 2010 issue of Scientific American is "Life in the Multiverse," and the illustrations depict universes connected to each other like grapes on a vine. Once pure speculation and a science-fiction device, this concept of multiple alternate universes is now front-and-center in mainstream physics as well as pop culture.

In part, the motivation has been to explain the "fine tuning" of our Universe: the handful of physical constants which, if any were different by a tiny amount, would disallow the existence of matter and therefore us. Some of these amounts are so minuscule, our Universe seems to balance on a knife-edge between various prohibitions to our existence. While theists consider this proof of an intelligent designer, the prevailing approach among physicists is to invoke the anthropic principle: We must find ourselves in a universe with conditions suitable for life, because if we weren't in such a universe, we wouldn't be around to notice.

This raises a couple of questions. Do we find ourselves in a life-allowing universe because ours ended up this way by accident? Or, is it because there must be many different universes, and we are here because, by sheer numbers, at least one of them must support life? The second has become the conventional explanation.

I wish to challenge this conclusion. It reminds me of a moment in Carl Sagan's Cosmos, during a discussion of past theories about life on Venus. "Observation: Can't see a thing. Conclusion: Dinosaurs!" In this case, it's, "Observation: One universe and one universe only. Conclusion: Billions of universes!"

Imagine you are watching TV through a cable box that's broken (unbeknownst to you) and gets only one channel. You then learn that the cable company is providing hundreds of other channels, and that the signals are getting into your home, even though you've never seen any of them. So, you go searching for the hundreds of other cable wires passing through the wall, and finding none, you conclude that the cables must be there, and must be perfectly real, but they are coming in where you can't find them. Now, is that the only conclusion, or the best conclusion, that could be drawn from what you know? A more elegant solution is that the other channels are coming through the same one cable — the one that you know exists — but for whatever reason, you can see only the one channel.

Similarly, I believe a more elegant solution to the "multiverse" question is that all potential universes are interlaced with the one that we observe, but for whatever reason, we observe only our familiar Universe. In other words, the alternate universes are not real to us in the way that our own Universe is real, but rather, they coexist with ours in a state of potential.

This issue seems to be a good candidate for the conceptual tool known as Occam's Razor. It says that if one solution to a problem requires multiple things with special conditions and assumptions, and another solution has fewer of these requirements, then the simpler solution is preferred. If there is another explanation, why must billions of perfectly real universes "out there somewhere" be required to exist just for ours to be able to exist?

Physicists have no problem describing a light wave as a probability function, a summation of all potential locations for a photon. I don't see why our Universe cannot be viewed the same way as the photon in this example: one possible universe "filtered out" or "made real" among all potential universes, all of which make up one giant probability function. This just seems to be a far more elegant solution than an insane web of billions of individual, discrete "pocket universes." Stop the madness!