The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos
384 pp., $29.95
Karl W. Giberson
George Bailey's Wonderful Universes
Too Much of a Good Thing
There was a young man from Trinity,
Who solved the square root of infinity.
While counting the digits,
He was seized by the fidgets,
Dropped science, and took up divinity.
Greene is convinced, although far from dogmatic, about the reality of the multiverse. He is impressed that so many "parallel-universe proposals … emerge unbidden from the mathematics of theories developed to explain conventional data and observations."
The unbidden character of the multiverse is a most interesting development. Quantum mechanics, for example, was developed in the early part of the 20th century to explain the structure and behavior of matter and its interactions with light. A half-century later, some physicists became convinced that the theory predicted the multiverse. Inflation theory was developed to explain some odd features in the expansion of this universe after the Big Bang. A decade later it seemed to suggest that universes were constantly inflating. With so many different ways to make a multiverse, how can we not get onboard?
I am not so sure I agree with Greene on this point. In fact, it seems to me that the "unbidden emergence" of the multiverse from so many different theories might more reasonably be viewed as an artifact of complex mathematics. Perhaps any mathematical system capable of describing a universe will somehow imply the existence of other universes. If inflation and quantum mechanics, for example, separately suggest, via two unrelated mechanisms, that there are many universes, one of them is probably wrong. And if there are nine unrelated ways to produce a multiverse, then eight of them are probably wrong. And if eight separate mathematical systems can all spuriously imply the reality of a multiverse, what real confidence can we place in number nine? We might compare this to a prosecutor who has a really solid embezzlement case against nine unrelated people, all of whom would have committed the crime in very different ways. Far from seeming like a compelling argument that the case is solved, this might suggest that our prosecutor is a bit too creative.
So Why Believe?
Maybe there is only one universe, and it is the way it is because it is not any old world; it is a creation that is endowed by its Creator with precisely the finely tuned laws and circumstances which have enabled it to have a fruitful history.
—John Polkinghorne, biologos.org/blog/john-polkinghorne-on-natural-theology-part-iv/CP3/
I mentioned above that there is one possible exception to the non-empirical character of the multiverse: that is the anthropic principle. Our universe is provocatively fine-tuned for life. The agnostic Fred Hoyle famously wrote, in 1981:
A common sense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question.
Hoyle's "common sense interpretation" is widely, although not universally, accepted. Our universe does seem unusually fine-tuned for life. This is an empirical claim, based on observations, not a faith claim based on theology. Cosmic fine-tuning implies the multiverse in the same way that the motion of galaxies implies the existence of dark matter. An infinity of different universes solves the mystery about why one universe is finely tuned for life. In this sense the multiverse is simply a good theory—hypothesis would be a better term—explaining some puzzling observations.
Such a claim, however, makes sense only with the assumption of naturalism. If everything must be explained in an exclusively scientific way, then this may be the best option. But what if naturalism is not an all-encompassing explanatory constraint? Is it possible that our universe might be a creation with its properties determined by a creator? In that case, there is no mystery as to why the universe is finely tuned: A super-intellect has monkeyed with the physics.