Dark Energy Found?

Simulated dark energy. Courtesy of Andrey Kravtsov

Physics has a big problem: 75 percent of the universe is in the form of what is called “dark energy.” As the name implies, scientists have no idea what dark energy is. They do know, however, that it’s working as a giant cosmic antigravitational force, pushing the universe apart at the seams. Since its discovery in 1998 by two competing research teams, cosmologists and particle physicists have struggled to come up with an explanation of what could possibly be creating this force, to little avail (the most common estimate, which involves the existence of as-yet-undetected exotic particles, is off by a factor of 10^120).

A new paper by three Italian physicists proclaims, rather boldly, to have solved the dark-energy problem, perhaps the most perplexing question in modern physics. Their solution? Neutrinos, ephemeral but numerous particles left over from the big bang. There are three types, or “flavors,” of neutrinos, and the flavor of a neutrino can change through a process called mixing. According to the researchers, this mixing of neutrinos throughout the universe creates just enough energy to explain away dark energy. As they put it:

^{. . . the neutrino mixing phenomenon appears to provide an explanation, till now unsuspected, of the vacuum dark energy component. Our discussion leads to the conclusion that there is no further need to search for exotic candidates (e.g. scalar particles) for the dark energy component . . . [emphasis mine]}

In other words: Don’t worry, everyone, we’ve solved the biggest problem in physics; no need to continue looking for alternative explanations. Clearly, whether or not they have solved the dark-energy problem—and the jury on this one has barely started to convene—telling everyone that they can quit looking for other explanations seems wildly brazen and premature. Perhaps we should wait for some experimental confirmation of your calculations first, eh, gentlemen? —Michael Moyer