Beyond the Inflationary Big Bang

The answer most people would likely give to the question of how the universe began is, the “Big Bang.”  But it’s a fair guess that this same group of people do not know what the Big Bang is, or that it has in fact been replaced by another model known as the inflationary Big Bang.

The interesting part of this story is why cosmologists decided to revise the standard Big Bang model in the first place.

It turns out that the original Big Bang possessed a number of features that deeply perplexed scientific theorists.   Two of these features are the smoothness problem and the flatness problem.   Without getting into unnecessary details, the smoothness problem arises as a result of the near uniformity of the so-called cosmic background radiation — the supposed “afterglow” from the Big Bang.   This background radiation happens to be uniform across the celestial sphere to 1 part in 100,000.  How is it possible for a near-infinite, random explosion to have produced such a uniform distribution of energy across the heavens?

The “flatness” problems presents a similar dilemma.  The term “flatness” describes the geometry of the universe, or the ratio of mass to gravitional strength.  Of all the possible geometries, or lay-outs, of the universe, a flat universe is the most unlikely because it requires a precise equilibrium between the total mass and gravitional power in the universe. If either mass or gravity predominated, the universe would have long ago either collapsed upon itself or rocketed off to nothingness.

Both the smoothness and flatness problems require the Big Bang to have begun with unique conditions; specially tuned setttings that launched the Big Bang with precisely the right strength and mass to have evolved into the balanced universe we see overhead.

But modern science does not take well to special conditions because first, they are highly improbable, and second, they are suggestive of a guiding intelligence.

Enter the inflationary Big Bang.

This model, which is now the textbook account of the early universe, holds that at its inception, the Big Bang expanded in size at an unimaginably rapid rate in a flashing moment.  After this instantaneous period of inflation, the growth spurt ended, and the universe began tracking the original Big Bang model.  How fast was this inflation?  Roughly 50 orders of magnitude in less than one-trillionth of a second. 

The inflationary Big Bang solved the smoothness problem because, theoretically, the thermal equilibrium of the cosmos was locked into a small area that later grew into the universe.  The inflationary model solves the flatness problem by supposing that the universe we experience appears flat because it is actually a small part of a gigantic ballooning mega-universe.

But now the inflationary Big Bang is under fire.  And the critic is one of the original theorists who developed and refined the inflationary Big Bang, Professor Paul Steinhardt of Princeton University.  In an April 2011 article in Scientific American, entitled, “The Inflation Debate: Is the Theory at the Heart of Modern Cosmology Deeply Flawed?” Professor Steinhardt concludes that if inflation occurred it is much more likely to have been “bad inflation;”  in other words, a period of accelerated growth that would have produced a universe other than what we observe.   When all is said and done, Professor Steinhardt says, the original Big Bang without inflation is more likely to have produced our universe than one with inflation.  So where does this leave modern cosmology?

I address these questions and others with Professor Steinhardt in a radio show entitled, Beyond the Inflationary Big Bang,  on Conversations Beyond Science and Religion available for downloading at




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