From Natalie Wolchover at Quanta:
Different “grand unified theories” or “GUTs” tying together the strong, weak and electromagnetic forces make a range of predictions about how long protons take to decay. Super-K’s latest analysis finds that the subatomic particles must live, on average, at least 16 billion trillion trillion years, an increase from the minimum proton lifetime of 13 billion trillion trillion years that the team calculated in 2012. The findings, released in October and under review for publication in Physical Review D, rule out a greater range of the predicted proton lifetimes and leave the beloved, 1970s-era grand unification hypothesis as an unproven dream. “By far the most likely way we would ever verify this idea is proton decay,” said Stephen Barr, a physicist at the University of Delaware.
Without proton decay, the evidence that the forces that govern elementary particles today are actually splinters of a single “grand unified” force is purely circumstantial: The three forces seem to converge to the same strengths when extrapolated to high energies, and their mathematical structures suggest inclusion in a larger whole, much as the shape of Earth’s continents hint at the ancient supercontinent Pangea.
“You have these fragments and they fit together so perfectly,” Barr said. “Most people think it can’t be an accident.”
Grand unification hasn’t died, exactly. The circumstantial evidence is as compelling as ever. But the idea could remain in perpetual limbo, rather like the proton. More.
What if, instead of a grand unified theory, the laws that hold the universe together are a creative tension, like a triangle? If so, a search for the single corner or side that did everything would not be useful. That is, what if the critical factor is relationships as such?
Note: Yes, by the way, that Stephen Barr.
See also: Why physicists crave a grand unified theory
Follow UD News at Twitter!