There is a lot of hub-bub about a neutrino that was witnessed moving faster than the speed of light, a feat which was deemed impossible by Albert Einstein’s theory of relativity. The science community is working overtime to figure out if the experiment can be repeated and confirmed, as it would have a major impact on our understanding of physics.
I’ve been doing some reading to get a better grasp of what, exactly, a neutrino really is. It is a rather elusive particle, which adds an air of mystery (not to mention difficulty) to any observation experiments.
One thing I do know is that, at this very second, billions of neutrinos are passing straight through your body without even slowing down.
The existence of the tiny neutrino particle was proposed as a solution to some “missing energy” observed in radioactive decay. It was theorized that some sort of particle was carrying this energy away. Shortly thereafter Enrico Fermi worked out the specific role that the mystery particle needed to fill, dubbing it the neutrino due to it having no electromagnetic charge… the particle was neutral.
The fact that it is neither negatively or positively charged is what makes it so hard to detect. It has so little interaction with other particles that it can zip right through objects without stopping, slowing, or changing direction. All the neutrinos that are generated from our sun not only pass through your body, but right through the core of the earth and out the other side on their journey across the universe.
That’s the trouble. If they pass through the solid granite of the earth without a second thought, how can our scientists “capture” neutrinos in any sort of observation equipment? Studying neutrinos is a bit like trying to spot bigfoot… if bigfoot was also invisible and moving about the speed of light. All they have to go on is the footprints and broken branches left behind.
The original experiment that caught a glimpse of neutrinos occured in 1956. There was a big water tank. While the vast majority of neutrinos pass through silently, due to sheer volume they would sometimes collide and interact with protons in the water. This would create positrons, which would in turn create a pair of gamma rays if it collided with an electron. The gamma rays excited a scintillator, which is a material that absorbs gamma rays and emits light. Finally, the tiny flashes of light were recorded by sensors inside the tank.
It was a Rube Goldberg machine on the atomic scale, but it worked. The experiments recorded about three light flashes per hour. More intricate, modern experiments can not only catch the existence of neutrinos, but capture information about the direction and speed of travel. The largest neutrino-catcher actually uses the solid ice of Antarctica as its water tank. Through this we are able to see evidence of cosmic explosions and supernovas far beyond the range of our telescopes.
The complexity required to observe neutrinos is why physicists are being extremely cautious about this new “faster than light” hypothesis.
Does this really explain what a neutrino is? Perhaps I should just leave it at the description by Frederick Reines, telling us that a neutrino is “the most tiny quantity of reality ever imagined by a human being.”
- Source: All About Neutrinos – IceCube South Pole Neutrino Detector