Back in February, a group of rebellious scientists penned a piece for Scientific American in which they criticized inflation theory, one of the key concepts related to the formation of the universe. In short, inflation explains that the early cosmos expanded exponentially fast for a fraction of a second post-Big Bang.
To say the letter was controversial would be an understatement.
Every theory gets updated over time with more accurate information, but inflation has become something of a central tenet of cosmology. Although skepticism is always welcome in science, questioning it – particularly in the manner of the original letter, which claimed that it could not be tested – is tantamount to an insurrection, as the data associated with it fits so well with the theory.
So when this letter popped up, it caused physicists up and down the land to frown profusely. A band of scientific Avengers – including Stephen Hawking, Andrei Linde, Sean Carroll, and ringleader Alan Guth, along with dozens of other high-profile physicists – are having none of it.
They’ve penned a letter themselves in response, and it’s as strongly worded as scientific discourse would possibly allow. In fact, they attest that the original letter has left them “bewildered.”
“During the more than 35 years of its existence, inflationary theory has gradually become the main cosmological paradigm describing the early stages of the evolution of the universe and the formation of its large-scale structure,” it reads.
“Scientific theories don’t get proved the way mathematical theorems do, but as time passes, the successful ones become better and better established by improved experimental tests and theoretical advances,” it adds.
“This has happened with inflation.”
The original letter claimed that inflation could not be evaluated using the scientific method. Not so, say Guth et al., who point out that many inflation models – all of which have been studied extensively – have been ruled out thanks to empirical evidence, while the ones that fit the data are still being thoroughly tested.
“Inflationary models, like all scientific theories, rest on a set of assumptions,” they note. “This, however, does not undermine the success of inflationary models.”
They compared the situation to that of the Big Bang theory itself, pointing out that the fact that it hasn’t answered every single question about the origin of the universe doesn’t mean that its multitude of correct predictions and descriptions should be undermined or disregarded.
The letter ends with “Empirical science is alive and well!” after which we presume they drop the mic and walk out of the room.
For their own part, Ijjas, Loeb, and Steinhardt, the authors of the original letter, have given a Q&A counter-response to Guth et al., which you can read here. Something tells us the fiery debate won’t cool down anytime soon.