Science writer John Horgan (who is not a physicist) is intrigued by the recent evidence for the theory of cosmic inflation, but is also holding out for some additional confirmation, support, and explanation before he buys what some prominent physicists, such as Alan Guth and Andrei Linde, are now saying about it:
I’m intrigued by today’s news that observations of gravitational waves provide “direct proof of the theory of inflation,” as my colleague Clara Moskowitz puts it in a terrific, information-packed post. “The Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) experiment in the South Pole,” she continues, “found a pattern called primordial B-mode polarization in the light left over from just after the Big Bang, known as the cosmic microwave background (CMB). This pattern, basically a curling in the polarization, or orientation, of the light, can be created only by gravitational waves produced by inflation.”
“If corroborated,” Dennis Overbye writes in The New York Times, the BICEP2 study “will stand as a landmark in science comparable to the recent discovery of dark energy pushing the universe apart, or of the Big Bang itself. It would open vast realms of time and space and energy to science and speculation.”
I hope that turns out to be the case, because cosmology and physics desperately need a jolt of energy (which the anti-climactic discovery of the Higgs boson did not provide). But here is what I’d like to see: First, corroboration of the BICEP2 findings by other groups and observatories. Second, experiments from high-energy physics that provide some sort of corroborating evidence of the driving mechanism of inflation. Third, an explanation of why the Alice’s Restaurant Problem [theories that can accommodate all evidence] isn’t still a problem. Fourth, an explanation of why only inflation, and not other more conventional physical phenomena, can account for the gravity-wave findings.
Direct evidence of cosmic inflation is such a great story. I want it to be true, and there are plenty of physicists who are treating this like a done deal; a discovery. But Horgan’s caution also sounds reasonable.
On the other hand, Horgan, not being a physicist, seems to be raising the bar higher than the consensus of physicists would in terms of proof. For the physics community, the fact of inflation may be reasonably established if the recent observational results are robustly confirmed and there are no other seriously competing hypotheses to account for the curling of gravity waves. Horgan, by contrast, wants two additional things:
- a mechanism established for inflation’s occurrence via, say, Large Hadron Collider research; and
- a philosophical dispute settled. (If inflationary scenarios can ultimately accommodate all data, regardless of what it is, and many of them imply multiverses, and multiverses also imply nonfalsifiability, might accepting inflation as true ultimately seduce physicists down a rabbit hole of undecidable metaphysics?)
Neither of these bars is entirely reasonable to require of scientists before they treat inflation as true. At this point, in other words, Horgan is starting to reason like an intelligent design creationist about evolution: I want mechanism and metaphysical issues addressed before I’ll follow the consensus of experts that plant and animal species have changed over time!
So Horgan’s concerns about the discovery can largely be dismissed. Yes, of course, we need confirmation; and, of course, physicists need to reason to the best hypothesis; and, of course, the implication of inflation for such things as multiverse speculation and the nature of science will require ongoing debate. It’s not like these things aren’t already going on.
But once the consensus of physicists is reached that inflation is true–as is likely to happen within the next year–it will no longer belong to the realm of speculation, but of fact, and that means that those of us outside the physics community would do well to incorporate inflation into our own background knowledge as something that scientists have, like the big bang itself, reasonably established. We may not wholly understand the science of inflation, or how physicists got from uncertainty to certainty about it, but our confidence should be their confidence.
The analogy is to chess: if an expert chess player looks at the board and, making a particular move, says, “I’m sorry, but this move decides the game,” and you don’t play chess much–and the other chess experts at the table nod with agreement–then you know you’re within a few moves of being checkmated; that it’s inescapable.
If you then get a non-expert like John Horgan putting his nose in and saying, “No, keep playing, the issue is not decided,” you can pretty much ignore him.
Below is one physicist telling another physicist that his competitors are heading unmistakably for checkmate (John Horgan notwithstanding). Being experts at the physics game, they both know which moves make for checkmate with regard to the question of inflation–and which ones do not. If you’re an expert in a subject, you aren’t likely to pop corks in so public a fashion without detecting unmistakable signals in the noise–and thus knowing when the game is essentially over.
And Horgan is simply not qualified to make this call.
Also note that the intelligent design website of The Discovery Institute–Uncommon Descent–has already latched onto Horgan’s skepticism with the following announcement: “Scientific American Science writer John Horgan still doubts cosmic inflation…despite gravitational wave findings.” This is blue pipe smoke and mirrors. Better to attend to what actual physicists are saying.