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Neutrinos have a weight problem

cmb neutrinos

Photo credit goes to: ESA and the Planck Collaboration

There have been some unfortunate problems with the Standard Model of Cosmology. These problems came from the fact that the neutrinos mass was never accurately measured. Thanks to some new observations, we now have managed to [hopefully] find the mass of a neutrino for the first time.

The study I am referring to was completed by Richard Battye and Adam Moss. It was recently published in Physical Review Letters. Using the Planck satellite, which was launched in 2009, scientists have been able to observe directional dependent aspects of the Cosmic Microwave Background [CMB].

The CMB radiation was formed shortly after the big bang and gives us the best snapshot to measure the age of the universe and the matter in it. As you can see by the colors in the photo, it isn’t homogeneous however, it is the oldest ‘light’ in the universe.

So what does this have to do with neutrinos? Neutrinos come in three different ‘flavors’. Named for the associated lepton [another elementary particle] at the formation.  Neutrinos are unique, because they only very weakly interact with matter, carry no charge and move at roughly the speed of light.

This had proven to be a formidable problem for scientists, who like to  be able to measure and study particles. With no charge and no way to slow them down, scientists originally thought they were massless. Thanks to particle physics experiments though, they were found to have some mass, but finding it accurately has proven allusive.

Battye [who co-authored the paper] was using gravitational lensing [sort of a cosmic telescope effect] to study distant galaxies. The ‘signal’ that he got was far weaker than calculated. Battye then suggested that a way to resolve this was for neutrinos to have mass.

From previous experiments the total mass for the three types of neutrinos was thought to be above 0.06 eV [Electron volts]. Thanks to these new observations the mass has been 0.320 +/- 0.081 eV which may not seem like a huge number, but for particles it is quite a big difference.

If this result holds under further analysis of the data and future observations this will significantly add to the understanding of particle physics, as well as helping fine tune the standard model.


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