I’ve seen a number of news reports over the last day talking about the newly announced detection of primordial gravity waves by the BICEP program at the South Pole. Most of them trumpet these results as proving the Big Bang. That’s not what’s going on here.
What’s been found is the first experimental evidence of a theory that’s been widely accepted but never “proved” by primary data, that very early on in the existence of our Universe, space-time expanded at rate far exceeding the speed of light. We don’t really know why that happened, and we don’t really know for sure that it stopped happening, but the fact that it happened was used to explain the relative homogeneity of matter and energy in the early Universe, and the fact that the space-time manifold is nearly flat.
The “nearly flat” part was the motivation for the original idea behind what’s called the “Inflationary epoch” of the Universe. When I was a physics student back in the mid seventies and mid eighties the big push in observational cosmology was to try to determine whether we lived in an open or closed Universe. A closed Universe would have had a overall curvature of space-time that would be “spherical” in a four-dimensional sort of way – like the two-dimensional surface of the earth is curved in a spherical way in three dimensions. An open Universe would have been curved like a saddle shape. A good chunk of my graduate studies were involved in working out some of the basic mathematics of a curved Universe (specifically: finding coordinates under which the Klein Gordon Equation was separable into individual spatial unit vector terms). We talked about the funny but completely unexpected possibility that the Universe was “flat” – and had exactly zero curvature. That was the Euclidean ideal, but no one executed to find it.
Except we did. The data kept coming in and as it got better and more precise, the observed curvature was shown to be about as perfectly flat as anyone could measure.
That was a big surprise. Of all the infinite values that the Universal curvature could be, the odds of it being exactly flat were vanishingly small. Something must have made it that way.
So cosmologists guessed that for some unknown reason the Universe had gotten very very big at some early moment in its history. And that while it was curved in some fashion at the largest scale, we could only observe a very very small portion, and that small portion was so stretched out that it looked flat to us. (That link is from 2011 btw.)
What the BICEP data is showing is something that was expected if Inflation was real, but hadn’t yet been observed, that the would be gravitational perturbations from that early epoch that would still be visible. The discovery of these waves is experimental proof that Inflation happened. So the idea that was invented to solve a puzzle about the flatness of space is now seen to have really happened.
Here’s an excellent sort of technical explanation of what is going on in these observations. (It was posted the evening before the announcement was formally made.)
And here’s a superb(!) explanation of why this might be a very very big deal – we finally have data that takes us back to the very beginning. From this we might be able to say something about what was going on before our Universe was born. Note that I said “our” Universe. Because this almost directly implies (and maybe not almost) that there was something before we were. That’s a big deal.
(I have a book in front of me that argues from these principles and others that the possibility that there is something existence before we were might just give a full physics based reasoning for something we in theology call “eternity” – and maybe even more. I’m reading the book for my Lenten journey. Hope to be able to post on it later.)