The following question was posed to Brian Greene, author of The Fabric of the Cosmos, and host of TV show, NOVA: The Elegant Universe, and professor Physics and Math at Columbia University:
It’s become my understanding that among physicists and cosmologists there is something of an issue that the fundamental constants of the universe just happen to be exactly right to be hospitable to life and that the vast majority of them if they were changed by just a small amount, would make life impossible. There seems to be some consternation as to what the possible reason for this is. Do you have any thoughts about that?
Brian Greene's response:
Well, yeah, I think that is one of the main “alternative” driving forces for a theory like string theory. So you’re absoloutely right. It turns out that there are roughly 20 – a little bit more – numbers that experimental physicists have measiured with great accuracy. Numbers like the mass of the electron, the mass of the quark, the strength of gravity, the strength of the electro-magnetic force, and so on. They’ve measured those numbers, so we know their numerical values with great accuracy, but nobody has any explanation for WHY they have those particular numerical values. And the reason why that’s a compelling issue is, what you mentioned, if you fiddle with those numbers, you know, if I have twenty dials up here and I let you come up and start to fiddle with the mass of the electron, the strength of gravity, and you see, for almost any fiddling that you do – you destroy the universe. For any fiddling that you do, you destroy the nuclear processes that power stars. Without stars, there isn’t a universe as we know it. So the question is: Why do those 20 numbers have just the right values to allow the universe to be the way it is and, certainly, to allow life to form on one planet?
No theory has given any answers to that question. String theory hasn’t given an answer either. But, for the first time, it has set up a framework, with a capacity to provide an answer. And basically, in string theory, those 20 numbers reflect the vibrational patterns of strings. Now the vibrational patterns depend on a lot of things, including the exact shape and form of the extra dimensions that the theory requires. So the basic message is, if we understood string theory completely -- we don’t yet – but if we did, we might be able to calculate the allowed vibrational patterns, and in that way, hopefully, calculate those numbers. And truly, if the calculations agreed with what the experimenters have found … I think it’s hard to deny that that would be the first fundamental explanation of why the universe is the way it is.