The Discovery of the Neutrino

The answer to missing energy from radioactive decay and ninety percent of the universe’s mass may be found in a tiny particle called the neutrino.  The neutrino is a tiny, elementary particle.  It could explain the structure of the universe.  The following defines the neutrino and explains its discovery.

Neutrinos are reported to be very common.  They are believed to be produced during radioactive decay in the “Big Bang”.  There are three different types of neutrinos:  electron neutrinos, muon neutrinos and tau neutrinos.  There is also an antimatter form called antineutrinos. 

A neutrino is so small that it cannot be seen by almost all instruments.  One could go through the Earth as if it was no more than a cloud.  An estimated sixty million neutrinos pass through each square centimeter of the Earth’s surface.  There are approximately one billion neutrinos for every proton in space. 

The neutrino was first proposed in 1930 by Wolfgang Pauli.  He said that this new particle could explain an energy discrepancy in some experiments.  According to Pauli, every time nucleuses under goes beta decay, the neutrino is emitted.  It then leaves carrying off a piece of the energy. 

Pauli thought of his idea as a “desperate remedy.”  The charge-less neutron was discovered in 1932.  This encouraged Pauli to publish his idea.  A physicist named Enrico Fermi was the one to name it neutrino which is Italian for “little neutral one.”  Many physicists found the neutrino hard to believe.  It had almost no mass and no charge.  It was merely a speck of energy from a radioactive atom.  Proving Pauli’s idea would be very difficult. 

In 1956, Clyde Cowan and Fredrick Reines proved the existence of the neutrino.  They called their experiment Project Poltergeist.  They performed it at a South Carolina nuclear power plant.  They produced trillions of neutrinos in a reactor’s core.  The neutrinos they went through a ten ton detector.  The neutrinos were detected by the flecks of radiation left behind.  This entire process took more than three years but it still did not prove neutrinos had mass. 

Scientists at Los Alamos National Laboratory believe they can show the neutrino has mass.  They believe that neutrinos change into other types of neutrinos while on rout from the sun to the Earth.  This process is called oscillation and for it to occur the particles must have mass. 

The scientists’ experiment which took place at Los Alamos took place in 1993, involved catching the neutrinos while oscillating.  The produced a beam of protons with a particle accelerator.  The beam produced all three types of neutrinos.  It was aimed at a container of water surrounded by a copper and steel shield.  A Liquid Scintillator Neutrino Detector (LSND) was set up thirty meters away.  The LSND is a tank filled with mineral oil and chemicals and lined with 1,220 phototubes.  This detected the produced signal when the neutrinos oscillated into antineutrinos. 

The experiment detected signals from eight antineutrinos.  This proves that the neutrinos did oscillate and thus did have mass.  The mass is estimated at 0.5 to 5 electron volts (eV).

There may be a substantial amount of neutrinos in the universe.  About ninety percent of the universes’ mass is immeasurable. Perhaps the findings of Pauli and the scientists at Los Alamos National Laboratory have found the particles that make up the missing mass. 


Bartrisiak, M.  Through a Universe Darkly.  New York:  Harper Collins Publishers, Inc., 1993.

Morris, R.  The edges of Science.  New York:  Prentice Hall Press, 1990.

 Weaver, J.  The World of Physics.  New York:  Simon and Schuster, 1987.  

Disclaimer:  This is a short paper that they young Susie Science wrote in 1996 therefore data in the proceeding text may not be entirely accurate.  I actually found a hand written copy of this in my basement.  This was written back in the dark ages when young scholars had the option of hand writing a paper or typing it on a computer because (gasp!) at one point not everyone had a computer!  Looking back now, I think my little paper was not too shabby.  🙂