This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Neutrinos are pervasive yet intangible particles that permeate the universe, streaming through whole planets, stars and our bodies by the trillions each second. The elementary particles are often described as "ghostly" for their near-zero mass and elusive nature, as they have very little interaction with normal matter.
Since their discovery in 1956, neutrinos have continued to surprise physicists with their unexpected properties and behaviors. For instance, the particles come in multiple "flavors" and can morph from one to another like subatomic shape-shifters. Neutrinos may also be their own antiparticles, in a Jekyll-and-Hyde-like quantum duality.
And their extremely weak interactions make them nearly impossible to detect. Last year, scientists seemed to add to the particles' mystique with a concept for a neutrino laser. They proposed that a concentrated beam of neutrinos could be produced by cooling a cloud of radioactive atoms to nanokelvin temperatures, one-billionth that of interstellar space.
Slowed to a near-frozen crawl, the atoms would form a Bose-Einstein condensate and should act as one quantum, coherent whole, speeding up and amplifying their radioactive decay. The physicists assumed that neutrinos, being a natural byproduct of radioactive decay, should also be amplified and that such a process should emit a laser-like beam of the ghostly particles. But newer work by MIT physicists has now shown that the neutrino laser concept, and a similar proposal for gamma rays, are impossible.
In two companion papers appearing today in Physical Review Letters, Wolfgang Ketterle, the John D. MacArthur Professor of Physics at MIT, together with postdocs Hanzhen Lin and Yu-Kun Lu, presents a two-part analysis demonstrating that both concepts are physically and fundamentally impossible. More specifically, they have shown that the neutrino laser concept is flawed because of "recoil" (that is, the kinetic energy created by the reaction) and a neutrino's fundamental "fermionic" nature.
"These two papers are sort of punch one and punch two," Ketterle says. "Each paper would have killed the proposal." MIT professor of physics Joe Formaggio, who put forth the neutrino laser proposal with Ben Jones, then an associate professor of physics at the University of Texas at Arlington, sees the new results as a convincing and constructive challenge. "When a new idea—such as the one we proposed—is shared, it is the duty of the community to scrutinize it.
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