Alan Guth

Alan Guth is one of the founders (perhaps, even the father) of the inflationary theory of the creation of the universe. It’s not exactly correct to think of this theory as contradicting the famous “big-bang” theory: It does nothing of the sort. Think of it as a very large refinement and adjunct to the “big-bang” theory. Inflation goes far towards explaining several observable facets of our universe that are not explicable (“Why do we not see magnetic monopoles?” and “Why is the micro-wave background energy the same level at opposite ends of the observable universe, when they haven’t had enough time to equalize the temperature?”)

For almost twenty years now, a new approach has promised to lead to even more fundamental understanding – String Theory. But for most of those twenty years, all efforts to torture the fiendishly difficult mathematics involved to reveal a testable result have failed. Not one prediction has been made that comes from String Theory, that can be tested against reality.

But “it feels right.”

Of late, Alan Guth has debated the finer points for us. From his debating partner Neil Turok:

This picture emerged out of a new understanding of the laws of physics which is called M Theory. … [a]ccording to this picture, the world may be comprised of two objects called branes, short for membranes. … And so the picture is that we live in a three-dimensional world, just the height, width and length of ordinary space but separated from our dimensions by a very tiny distance are another three-dimensions and so the whole world is four-dimensional in this picture and these two sets of dimensions can actually collide with each-other. What we discovered is, if they do collide, then something like a Big Bang happens but the density of matter and the size of the universe is not zero at that point. It’s as if two objects clash together and this clash is what releases radiation which fills space.

To which Guth responds:

What we call the Big Bang was almost certainly not the actual origin of time in either of the theories that we’re talking about. … The main difference I think [between the inflationary theory and Neil and Paul’s theory] is the answer to the question of what is it that made the universe large and smooth everything out. … The inflationary version of cosmology is not cyclic. … It goes on literally forever with new universes being created in other places. The inflationary prediction is that our region of the universe would become ultimately empty and void but meanwhile other universes would srput out in other places in this multiverse.

Jenna Levin follow up:

There’s a little more resistance to the cyclic model but maybe that’s because of the successes so far of inflation. Yet, we do know that there are fundamental things about the early universe and the Big Bang that we don’t understand. … String theory or M theory or these other models of fundamental physics are going to be important in terms of formulating that early universe picture but they’re not complete yet.

Yet Guth is not satisfied. From saudijack’s blog (from Northwestern, I presume) an interesting observation:

He seemed to have been converted over to thinking that anthropic arguments might have some merit. Particularly with the value of the cosmological constant. Why is it so remarkably small? It’s only very specific values that can support life as we know it. (Edit: Don’t think Alan Guth is going around promoting the anthropic principle as “the answer”; just that it may have merit.)

The idea that Guth may be thinking the “Anthropic Principle may have some merit” is depressing to some at Not Even Wrong, a blog devoted to discussions of String Theory.

Why is this important? The weak version of the Anthropic Principle says that the universe seems finely tuned to permit our existence, but that’s because anything not so compatible would not find us here to observe the fine tuning (it’s almost a tautology – we find ourselves existing in this universe because we exist in it. If we didn’t, we wouldn’t discover that fact). The strong version, however, says that this is the entire point of the universe – to permit our existence. That comes uncomfortably close to Intelligent Design (and therefore, Creationism) for some.

Update:There’s a very good discussion the book Endless Universe by Neil Turok and Paul Steinhardt at the blog Not Even Wrong.

Explore posts in the same categories: Science, Space

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