Читать книгу String Theory For Dummies - Andrew Zimmerman Jones - Страница 28

One of the most unexpected and disturbing discoveries of string theory is that instead of one single model of the universe, it turns out that there may be a huge number of possible models (or, more precisely, possible solutions to the theory) — maybe as many as 10⁵⁰⁰ different solutions! (That’s a 1 followed by 500 zeroes!) While this huge number has prompted a crisis among some string theorists, others have embraced it as a virtue, claiming it means that string theory is very rich.

In order to wrap their minds around so many possible models, some string theorists have turned toward the anthropic principle, which tries to explain properties of our universe as a result of our presence in it. Others instead argue that the vast number of possible string models is to be expected — or even that it’s a feature, not a bug, so to say. For them, it’s just a matter of nailing down the particular string solution that does describe our universe.

With such a large number of theories available, the anthropic principle allows a physicist to use the fact that we’re here to choose among only those theories that have physical parameters that allow us to be here. In other words, our very presence dictates the choice of physical law — or is it merely that our presence is an observable piece of data, like the speed of light?

The use of the anthropic principle is one of the most controversial aspects of modern string theory. Even some of the strongest string theory supporters have expressed concern over its application because of the sordid (and somewhat unscientific) applications it has been used for in the past and their feeling that all that’s needed is an observation of our universe, without anything anthropic applied at all.

As anthropic-principle skeptics are quick to point out, physicists adopt the anthropic principle only when they have no other options, and they abandon it if something better comes along. It remains to be seen if string theorists will find another way to maneuver through the string theory landscape. (Chapter 12 has more details about the anthropic principle.)