For several years, increasing data are pointing to the universe being infinite in size and inventory: space that never ends, and limitless galaxies, stars, planets and energy. This would be a huge change from our longstanding model of a finite-but-unbounded Cosmos – meaning that there’s no physical boundary anywhere, and yet the Cosmos contains a finite amount of material and energy.
I just spoke with Shirley Ho last Tuesday. She’s part of the Berkeley team that on January 10 released the results of a major study of 900,000 galaxies using baryon acoustic oscillations and a few other complementary methods, to give us the best-ever view of the large-scale structure of the Cosmos. I asked her if their data supported the claim that the universe is infinite. Her answer: “Yes, our results support that claim.”
She went on to elaborate: “The argument is relatively simple, since we conclude (when including other data sets such as WMAP and Hubble parameter prior) that we place a very strong constraint on the geometry of the universe to be flat. This implies the universe is infinite.” She added, “We only can sample a very, very small fraction of the universe. We, however, observe a significant fraction of the observable universe.”
Her one mistake was saying that we sample “a very, very small fraction” of the universe. In truth, if infinite, then the fraction that we can see is not very small. Rather, it is exactly zero. And if we indeed have a sampling size of zero, then our conclusions about the nature of the Cosmos at large are so untrustworthy as to be worthless. It is this sobering reality that cosmologists are loath to face right now, I think.
No one can picture an infinite universe. Nor, now, can anyone utter a syllable of confident knowledge about the universe as a whole. Does it have vast neighborhoods where separate “constants” rule? Do we really have to tell kids who ask that, yes, the universe indeed goes on and on with literally no end to the galaxies and stars? Who can grasp that?
I’m reminded of the early Greeks, when some of them like Aristarchus figured out the heliocentric business and relative distances to the Moon and Sun; but as for the really deep issues, they’d just laugh and drink their wine. Maybe they had it right.
Astronomy has become an extreme dichotomy. On the one hand, we have facts like the Martian rotation period of 24 hours, 37 minutes, 23 seconds that are rock solid and will not change. It’s part of a large body of knowledge that we’re forever learning and refining. But the biggest, most bedrock issues involve: What is this universe? Was it born? What’s it made of? What are its rules, its parameters? In short, the field of cosmology. A Cosmos infinite in spatial extent and also in inventory means that these biggest-of-all inquiries become unknowable.
The universe as unknowable: unknowable forever. My science-brain hates this. The part of me that experienced “cosmic consciousness” at age 20 has no problem with it, realizing on that non-intellectual but vastly more-real level that there are no birth and death, that all is one, that all is perfect. But that’s not science. This infinity business places the universe-at-large totally off-limits to our math, physics and reason. We’ve been given zero percent to probe, and this playground that once seemed satisfactorily vast now seems chokingly confining.
An unknowable universe! Doesn’t this change the underlying mindset of cosmology? Well, it should. But so far, the mass media have ignored it, in favor of TV documentaries where cosmologists just spout on and on as if they know what they’re talking about. Maybe it’s just too ego-upsetting, too disconcerting. Probably the official stance will be simply to ignore the fact of infinity and instead concentrate on the observable universe: the zero percent that is ours to explore.
So I’ll wipe these little flecks of foam from my mouth and calm down, and pretend like everyone else that we have some sort of handle on the big picture. Don’t worry: I won’t keep bringing this up. I’m just going through some sort of celestial Kübler-Ross stage, and I’m on my way to “acceptance.”
Join the family! 
