Friday, January 8, 2010

279. Babel

I happen to be a big "fan" of modern physics and cosmology, reading as much of the popular literature as I can find time (and money) for and trying to keep up with new developments, largely by ignoring the "do not read the magazines" signs and thumbing through the latest issue of Scientific American every month. Sometimes I buy a copy. Though strictly an amateur, I do believe that exposure to the imaginative and sophisticated ideas of some of the most interesting people in these fields has helped me think through some of the toughest challenges in my own field (don't ask what that is, because I've got my fingers in so many different pies at this point I'm not sure what to call myself).

I've been going on a lot lately about this "bottleneck" idea and how it could explain the huge cultural gap I see between Africa and Southeast Asia. And, aside from Stephen Oppenheimer, who sees a genetic and archaeological gap in exactly the same place, no one else seems to have noticed it, or feels much of a sense of urgency in explaining it. And it's occurred to me that one way to help others understand the problem I see is by drawing an analogy with what appears to be a very similar problem in the field of cosmology. Realistically, of course, I'm aware that for most people reading here cosmology is an even more esoteric topic than what I've already been discussing -- but I'll give it a shot anyhow.

I’ll start where it all started: the Big Bang. The Big Bang is actually a very interesting event for us to contemplate, because it is in some ways analogous to what could be called the genetic Big Bang, the conception of the very first Anatomically Modern Human (AMH), somewhere in Africa, some time around 200,000 years ago. For our purposes, the analogy I’d like to draw is with another, more modest, “bang”: the exodus of a small band of AMH from Africa to Asia, some time between 85,000 and 60,000 years ago.

As we know, the cosmological Bang began with what is called a “singularity,” i.e., a one-time only event that took place when all the mass of the entire universe was compacted into an incredibly dense, tiny ball. Following my analogy, we could say that the migration out of Africa was also a kind of singularity, a one-time only event, when all peoples native to Asia, Europe, Australia, Oceania and the Americas, from all periods of history down to the present day, were “compacted” into the sexual desire of a small, dense, ancestral group of maybe a hundred or so individuals. And just as the Universe expanded in all directions in space, the descendants of this founding group also expanded, ultimately, in all possible directions on Earth. It gets even better, because both the Universe and the human population expanded, and continue to expand, at an ever accelerating rate.

Despite their considerable ingenuity in recreating the earliest stages of the Big Bang, there is a problem for cosmologists seeking to understand what happened next, because there is a puzzling gap between their theoretical reconstruction of events shortly after the Big Bang and the evidence we now see as our telescopes take us into the deepest depths of space and time. To greatly oversimplify, the density of the present universe is homogeneous, or “flat,” a state that is inconsistent with the initial conditions that would have to have existed just after the Big Bang in order to explain other properties of today’s Universe:

Our universe is apparently flat. That is, it appears to have just the "right" density--or nearly so--to continue its slow expansion forever. Too much matter, and the universe eventually collapses in on itself under the influence of its own gravitational pull. . . Too little matter, and gravity will never be able to halt the expansion of the universe . . .

To make the Standard Big Bang theory correspond to reality, cosmologists had to make the assumption that the average density of the universe was equal to the density immediately following the Big Bang. But how? This assumption, like the isotropy assumption, isn't explained. . . . Inflation comes to the rescue again. Inflation's rapid expansion caused space to become flatter . . . Even if the pre-inflation universe were curved like a sphere . . . or hyperbolic . . . , that tremendous burst of expansion forced the scale of any curvature to flatness, just as our Illinois soybean fields appear flat on a curved earth. (The Flatness Problem).

Never mind if you can’t understand all the details. What’s important for the analogy I’m drawing is that there was an inexplicable discrepancy between what was deemed necessary for the initial conditions of the Big Bang and the present condition of the Universe. Flatness is only one part of this discrepancy, there are others as well. Cosmic Inflation, as devised by physicist Alan Guth, “comes to the rescue” by arbitrarily inserting a dramatic event into the works only a few seconds after the “Bang” begins, a brief period of very intense expansion, well beyond what the initial conditions would have predicted. The resulting “inflation” is perfectly calibrated mathematically to produce exactly the equations needed to match the universe we see today.

This looks very much like a “fudge factor,” i.e., an ad hoc “solution” devised simply to account for a discrepancy rather than a theory that follows naturally or inevitably from everything that came before. Nevertheless, the explanatory power of Inflation is so great that it has become part of the mainstream of modern physics and cosmology. It accounts for so much that would otherwise be inexplicable and fits too much of the evidence too well to be dismissed. While a less contrived solution, based on standard evolutionary principles of gradual continuity through time and space, might seem preferable, the radical discontinuity introduced by Guth enabled scientists to produce a coherent picture of the Universe at all stages of its development.

(to be continued . . . )

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