Six months ago, scientists were excited to find gravitational waves in the cosmic microwave background that seemed to prove the universe itself inflated during the Big Bang. For me, the most beautiful video detailing the discovery wasn’t cosmic in scope; it involved a veteran physicist named Andrei Linde, a firm advocate of inflationary theory who did not seem to expect to see direct evidence of cosmic inflation during his lifetime:
As it turns out, that may have been a realistic expectation. More recent analysis of the BICEP2 evidence has found that what physicists took to be gravitational waves were more likely indicative of cosmic dust, and that this discovery may actually disprove many models of cosmic inflation. Putting aside the question of what this could mean (a question that may change our understanding of the Big Bang itself), I have one question:
Lets put aside the details of theoretical physics for a moment and consider this on the level of basic logic: advocates of cosmic inflation did not expect the BICEP2 data to confirm their theory. It nevertheless appeared to do so. Now that it appears not to have done so after all, wouldn’t it be reasonable for advocates of the cosmic inflation theory to shrug their shoulders, go “oh, well; guess I was right the first time,” and carry on?
That’s certainly the position taken by Linde’s colleague Alan Guth:
Guth thinks there could still be a signal that supports simple inflationary models. And he emphasises that if the signal does end up being dust, that is not evidence against inflation, since most inflationary models predict a much smaller signal that would require more work to find. ‘If BICEP2 has not seen [evidence of] gravitational waves, then only certain inflationary models are ruled out, while the concept of inflation remains completely healthy.’
We’ve seen a similar dynamic over the past couple of years with string theory: whenever advocates of a theory fail to find low-hanging fruit that they never really expected to find in the first place, the mainstream press tends to take this as proof against whatever theory the phantom evidence might have supported. Potent criticism of the BICEP2 evidence is a major blow against proving cosmic inflation within the near future, but it doesn’t have much to do—pro or con—with the validity of cosmic inflation itself. The fact that you didn’t find something in the first place you looked doesn’t necessarily mean that it doesn’t exist at all. Or to put this in more simple human terms: disappointment is not necessarily the same thing as defeat.