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The Twilight Of The Big Bang

An artist's impression of a quasar located in a primeval galaxy (or protogalaxy) a few hundred million years after the big bang. European Space Agency and Wolfram Freudling/ESO hide caption

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European Space Agency and Wolfram Freudling/ESO

An artist's impression of a quasar located in a primeval galaxy (or protogalaxy) a few hundred million years after the big bang.

European Space Agency and Wolfram Freudling/ESO

We live at the end of an era. We live in one of those singular moments in history when one scientific and culturally accepted concept of cosmic origins is fading and others, yet unproven, vie for ascendency.

We live at the twilight of the big bang.

The consequences of this coming reorientation in perspective will reach far beyond observatories and physics classrooms. Every culture needs a cosmology to justify itself and place its activity into the broadest of perspectives. This is a theme I explore in my new book and, as promised, will be a topic I will blog on periodically.

It was in the process of researching a book on just new cosmological ideas that I recognized the intricate braiding of cosmology and culture. A cosmology, I found, can not be switched out easily, like some carburetor on the engine of a culture's imagination. Far more than textbooks are going to have to change. But to understand those deep entanglements we must first start at the beginning. In our case that beginning is the end: the end of the big bang.

First, let us be clear: The Big Bang as a theory of what happened after the moment "creation" is doing just fine.

What made the big bang so radical when it was first introduced some 80 years ago (first by George Lemaitre and later by George Gamow and Ralph Alpher) was the assumption that the universe looked radically different in the past then it does now. The big bang was first and foremost a theory of the universe's evolution. It told a story of a Universe that was once in a state of extreme compression and extreme temperature, a universe that expanded like the skin of an inflating balloon into the relatively empty and relatively cold state we see today.

This story of "after," built on a mix of particle physics and Einstein's classical theory of relativity, has been an astonishing triumph. A hundred years ago the evolution of the universe used to be a foggy territory, half physics and half philosophy. Now we can run the clock on cosmic history back to fractions of a second after its expansion began and be confident the story we tell is correct.

But as a theory of the beginning itself — as a theory of some kind of genesis — the big bang was never very helpful. If you run the idea backward far enough, space and, most importantly, time just disappear into an explosion of infinities that essentially tell you that you have gone too far. The theory, in particular Einstein's theory of relativity, rolls over and wiggles its legs in the air like a bug dosed on Raid.

The infinities that appear in the big bang, if you wind things back all the way to t=0 are, taken together, called the singularity. Physicists knew the problem was that Einstein's theory for gravity was a classical one. For all its awesome power and insight, it treated the flexible fabric of space and time (space-time) as a continuum — a smooth, ever-divisible whole. But physicists know that on microscopic scales nature is not built that way. Zoom in to a small enough level and the quantum is king; nature is chopped up, discrete and "sandy."

Many physicists suspected that once a theory of quantum gravity was in hand, the difficulties with the singularity would be resolved. We might, for instance, learn how to get through the singularity to see a "before" the big bang. While we still do not have anything close to a complete theory of quantum gravity, enough has been learned that many scientists believe the outlines are resolved. They are ready to begin moving beyond the idea of the big bang as the single and singular moment of creation.

But the end of the big bang was not simply a matter of theory. In many ways we have reached the twilight of the big bang, as a story of the beginning, through better examinations of the very data that convinced us it was a good story of after in the first place.

In 1964 two Bell Labs scientists discovered fossil microwave light imprinted with signals from the baby universe. This cosmic microwave background (CMB) was the nail in the coffin for all competing theories of cosmic history. But within the big bang's triumph were the seeds of its own difficulties. As years passed and scientists took ever higher resolution images of the CMB, they found it held paradoxes that challenged the orthodox version of a Universe smoothly expanding from t=0. From this and other paradoxes was born inflationary cosmology.

Inflation grafts a brief moment of hyper-expansion on steroids onto the classic big-bang theory to resolve the paradoxes. But by adding this new feature at 10-33 of a second after the big bang, it shook the foundation of what we mean by cosmology. The much-needed inflation — the big bang no longer makes sense without it — opened the door to the idea that the universe we see is not the entire universe.

Physicists always knew we could not look beyond 13.7 billion light years (since that was the age of the cosmos). Inflation, however added its own twist to the idea of cosmic "horizons." Inflation theory implies that there might be other parts of the universe that look nothing like our own and might be in entirely different states. Most importantly, it hinted that there might, effectively, be more than one universe out there. Thus it became possible that the big bang was simply our big bang. It was demoted from "The Creation" down to "a creation."

And so we find ourselves at the precipice. Each one of the ideas outlined above is, of course, worth far more explanation and I will try to cover them in future posts. The critical point for today is that we are at the edge of a new cosmos and we do not know what the next step will look like.

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