"Although string theory resists translation into ordinary language, its central conceit boils down to this: All the different particles and forces in the universe are composed of wriggling strands of energy whose properties depend solely on the mode of their vibration. Understand the properties of those strands, the thinking once went, and you will understand why the universe is the way it is. Recent work, most notably by Joseph Polchinski of the University of California, Santa Barbara, has dashed that hope. The latest version of string theory (now rechristened M-theory for reasons that even the founder of M-theory cannot explain) does not yield a single model of physics. Rather, it yields a gargantuan number of models: about 10500, give or take a few trillion.
Not one to despair over lemons, Susskind finds lemonade in that insane-sounding result. He proposes that those 10500 possibilities represent not a flaw in string theory but a profound insight into the nature of reality. Each potential model, he suggests, corresponds to an actual place - another universe as real as our own. In the spirit of kooky science and good science fiction, he coins new names to go with these new possibilities. He calls the enormous range of environments governed by all the possible laws of physics the "Landscape." The near-infinite collection of pocket universes described by those various laws becomes the "megaverse."
Susskind eagerly embraces the megaverse interpretation because it offers a way to blow right through the intelligent design challenge. If every type of universe exists, there is no need to invoke God (or an unknown master theory of physics) to explain why one of them ended up like ours. Furthermore, it is inevitable that we would find ourselves in a universe well suited to life, since life can arise only in those types of universes. This circular-sounding argument - that the universe we inhabit is fine-tuned for human biology because otherwise we would not be here to see it - is known as the Anthropic Principle and is reviled by many cosmologists as a piece of vacuous sophistry. But if ours is just one of a near-infinite variety of universes, the Anthropic Principle starts to sound more reasonable, akin to saying that we find ourselves on Earth rather than on Jupiter because Earth has the mild temperatures and liquid water needed for our kind of life."
To read the entire fascinating review, click here.