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Massive Neutrinos Help Correct the Standard Model of Cosmology

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Lisa Winter

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307 Massive Neutrinos Help Correct the Standard Model of Cosmology
ESA and the Planck Collaboration

The standard model of physics has problems. Until recently, one of these problems was the lack of correct accounting of the mass of neutrinos. Previous studies have estimated the mass, but there has not before been a precise measurement. New observations have helped solve that dilemma by calculating the mass of neutrinos for the first time.  The study was completed by Richard Battye and Adam Moss and was published in Physical Review Letters.

The Planck spacecraft observes the directional-dependent aspects of Cosmic Microwave Background (CMB). The CMB is the radiation that was formed shortly after the Big Bang and is used to help measure age and matter in the Universe. The CMB is not homogenous and sometimes large galaxies can interfere with the signal. 


Neutrinos are weakly-interacting sub-atomic particles that do not carry an electric charge, which makes them incredibly difficult to study. Because their special properties they do not readily react with normal matter and travel at near-light speed. In fact, neutrinos would be able to travel through a block of lead over a light year long and half of them still wouldn't slow down to a stop. Neutrinos come in three types, named for their associated lepton at formation: electron neutrinos, muon neutrinos, and tau neutrinos. Neutrinos have been suspected of playing a role in the inconsistencies of the CMB.

Recently, Battye was using gravitational lensing to observe distant galaxies and noticed that the resulting signal was weaker than anticipated. In order to reconcile the predicted model with the observations, neutrinos would have to be massive. If neutrinos has enough mass, they would be able to influence the formation of large structures like galaxies and could be further implicated in manipulating the CMB. Previous estimates had put the sum of the masses of the neutrino at about 0.06 eV, though these new calculations show that the sum is much higher, at 0.320 +/- 0.081 eV. For a comparison, a single proton is right about 938000000 eV.

These new calculations for the mass of a neutrino will extend our knowledge into the world of particle physics as well as expand upon the standard model of cosmology. With a better model, physicists will be able to make better predictions when carrying out experiments to further explore our Universe.


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