Thoughts about cosmic expansion (or the lack thereof)


I grew up with the notion that our universe was either going to slow its expansion enough to re-collapse, or was going to slow but never quite stop expanding—asymptotically approaching zero growth—or that it would continue to expand, slowing down over time but never quite reaching zero growth.  Though it was perfectly clear to me that, barring some extremely improbable events, there was no way I was going to be alive to know for certain which was right, it was nevertheless a question that I found deeply gripping…much more so than any politics short of the fear of World War III, and probably more important to me even than that.

Of course, the fall of the Soviet Union in 1991 came as a terrific surprise, something that I never would have even considered possible in my younger days (I was 21 when it happened…still pretty darn young, come to think of it).  Nevertheless, though this stopped me from being quite so convinced about the inevitability of nuclear Armageddon, it didn’t really hit me emotionally.  It was just a big surprise.

In 1998, though, when I heard about the supernova evidence of the increasing rate of cosmic expansion—now called dark energy, consistent with some version of Einstein’s previously discarded idea of the cosmological constant—I was excited beyond anything I can recall feeling before or since that wasn’t a literal milestone in my own life.  Seriously.  And when you get right down to it, the only personal milestones that beat it were my marriage and the birth of each of my two children.  Graduating med school didn’t even come close.  This was the most exciting and unexpected thing I’d yet learned, as a discovery in science…new, deep information about the nature and fate of the very universe itself.

Part of my excitement was surely due to the fact that I was learning it literally at the same time as everyone else.  But I’ve always loved cosmology, all the way at least back to when I got Cosmos (the book) as a birthday present when I was ten or eleven and was as happy with it as any other present I can recall having received.  To understand the structure and workings of the universe is just remarkable.  It makes me feel, in just a small way (if that’s not contradictory) that the whole universe is within me.

And of course, as I said, learning about accelerating universal expansion and all the subsequent, related cosmological information, including details of the CMB and its mapping, all that wonderful stuff, was just an incredible adventure.

Now, recently, a paper has come out positing that the conclusions about increasing cosmic expansion might have been premature.  Of course, there’s a lot of push-back against that, which makes sense, but the points made are apparently not unreasonable or outrageous.

On hearing this, I had to ask myself what I would think if it turned out that dark energy were incorrect.  It doesn’t seem terribly likely that dark energy will fall completely, since it jibes with a great many other things as a general part of our picture of the universe, but I could be wrong.  As I thought about it, though, I realized that, if dark energy turns out to need revising, I think I’d be nearly as excited as I was when I heard about it in the first place.  Because whatever the truth is, it is, no matter what we want it to be.  Learning where you’re wrong is the surest step in figuring out the truth…and learning what the actual rules are to the game in which we live is surely just about the coolest thing we can do.

Compared to that, even playing the game—by which I mean, living one’s life from day to day, and from birth to death—seems only a distant second.