In continuation with these fun little posts about particles, we direct our sights to the muon! It derives its name from the Greek letter mu (μ), which is used to symbolically represent it. The muon is an elementary particle that is really, really similar to the electron - with an equal negative charge to the electron and a spin of ½. It is classified as a lepton, which is a group of particles that is home to the electron, the tau, and neutrinos. As is the case with leptons, the muon cannot be broken down any further - it is fundamental.
As experiments have shown, the muon is unstable - possessing a mean lifetime of only about 2.2 µs (microseconds). All muons decay into three particles, an electron and two different types of neutrinos. The muon has a corresponding antiparticle as well - the antimuon (also known as the positive muon). Like all antiparticles, the antimuon the same mass and spin as its counterpart, but an opposite charge.
Muons have a mass of 105.7 MeV/c2, which is approximately 200 times the mass of an electron. Since the interactions are very similar, a muon can basically be thought of as a much heavier sister of the electron. Due to their mass, muons do not accelerate as sharply in electromagnetic fields and do not emit as much deceleration radiation, which allows them to penetrate far more deeply into matter than electrons.
P.S: Do you like the picture? Get awesome plush particles from the Particle Zoo!
Why do Fingernails on a Chalkboard Sound so Terrible?
“The latest study, conducted by musicologists Michael Oehler of the Macromedia University for Media and Communication in Cologne, Germany, and Christoph Reuter of the University of Vienna, looked at other sounds that generate a similar reaction — including chalk on slate, styrofoam squeaks, a plate being scraped by a fork, and the ol’ fingernails on blackboard.
Some participants were told the genuine source of the sound, and others were told that the sounds were part of a contemporary music composition. Researchers asked the participants to rank which were the worst, and also monitored physical indicators of distress — heart rate, blood pressure and the electrical conductivity of skin.
They found that disturbing sounds do cause a measurable physical reaction, with skin conductivity changing significantly, and that the frequencies involved with unpleasant sounds also lie firmly within the range of human speech — between 2,000 and 4,000 Hz. Removing those frequencies from the sound made them much easier to listen to. But, interestingly, removing the noisy, scraping part of the sound made little difference.
A powerful psychological component was identified. If the listeners knew that the sound was fingernails on the chalkboard, they rated it as more unpleasant than if they were told it was from a musical composition. Even when they thought it was from music, however, their skin conductivity still changed consistently, suggesting that the physical part of the response remained. That physical response is likely generated by the shape of the human ear canal, which prior research has shown to amplify frequencies in the range of 2,000 to 4,000 Hz. What seems to happen, the researchers reckon, is that when a screech on a chalkboard is generated, the sound is amplified within our ears to painful effect.”
I cringed when I started reading this post..Weird
|—||Richard Feynman (via quantumaniac)|