If we look deep into the universe, we see stars and galaxies of all shapes and sizes. What we do not see, however, is that the universe is filled with particles called neutrinos. These particles - which have no charge and have little or no mass - were created less than one second after the Big Bang, and large numbers of these primordial low-energy neutrinos remain in the universe today because they interact very weakly with matter. Indeed, every cubic centimetre of space contains about 300 of these uncharged relics.
Trillions of neutrinos pass through our bodies every second - almost all of these are produced in fusion reactions in the Sun's core. However, neutrino production is not just confined to our galaxy. When massive stars die, most of their energy is released as neutrinos in violent supernova explosions. Even though supernovas can appear as bright as galaxies when viewed with optical telescopes, this light represents only a small fraction of the energy released.
In the May issue of Physics World, Hitoshi Murayama of the University of California, Berkeley, explains how the current research into neutrinos may reveal the very origins of our existence.