A challenge to the accepted theory of the universe’s origin has started a beef in the science community that’s so contentious, it’s got scientists writing public letters like rappers releasing diss tracks.

On Friday, Stephen Hawking and 32 of the world’s leading physicists published an angry letter defending the origin hypothesis known as the inflation theory, and denouncing the efforts of a group of scientists determined to undermine its credibility.

It all started in February when an article penned by Anna Ijjas, Paul J. Steinhardt, Abraham Loeb in Scientific American criticized the inflation theory, a long-held belief that the cosmos expanded rapidly like a balloon following the Big Bang.

Based on recent research, “Pop Goes the Universe” posits that if the theory was legitimate, the universe’s inflation would have generated primordial gravitational waves — which have never been found. In the article’s brief the scientists note that “the data suggest cosmologists should reassess this favored paradigm and consider new ideas about how the universe began.” Within the article, they claim that the inflation theory “cannot be evaluated using the scientific method” and that it lacks empirical evidence.

“Some scientists accept that inflation is untestable but refuse to abandon it. They have proposed that, instead, science must change by discarding one of its defining properties: empirical testability. This notion has triggered a roller coaster of discussions about the nature of science and its possible redefinition, promoting the idea of some kind of nonempirical science.”

In other words, the inflation theory is not real science — a pretty controversial statement considering it’s been the status-quo explanation for the birth of the universe since the ‘80s.

The article that's making scientists really angry.
The article that's making scientists really angry.

In their response — also published in Scientific American — Hawking and the group of scientists attacked Ijjas, Steinhardt, and Loeb’s argument that the inflation theory couldn’t be properly tested with science. “We disagree with a number of statements in their article,” they said. “But in this letter, we will focus on our categorical disagreement with these statements about the testability of inflation.”

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The letter goes on to assert that it is standard practice to modify theories as new data come to light and while not every model of the inflation theory has been proven over time, numerous tests continue to prove its validity.

“By claiming that inflationary cosmology lies outside the scientific method, IS&L are dismissing the research of not only all the authors of this letter but also that of a substantial contingent of the scientific community. Moreover, as the work of several major, international collaborations has made clear, inflation is not only testable, but it has been subjected to a significant number of tests and so far has passed every one.”

The letter has prompted a response and a FAQ from Ijjas, Steinhardt, and Loeb, who still claim that the idea of inflation as we know it is an outdated theory that ignores the more recent data pointing to its fundamental problems.

“Our point is that we should be talking about the contemporary version of inflation, warts and all, not some defunct relic. Logically, if the outcome of inflation is highly sensitive to initial conditions that are not yet understood, as the respondents concede, the outcome cannot be determined.”

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Warts or not, it appears a large contingent of the scientific community won’t be changing their minds on the inflationary universe anytime soon.

Photos via Scientific American, February 2017, Flickr / Tycho's Nose