The deep universe is littered with violent astrophysical events: exploding stars (supernovae), colliding galaxies, merging black holes tearing the fabric of space-time, crazy fast spinning pulsars, movies by Quentin Tarantino… these events can create powerful shockwaves that kick intergalactic or stellar gas particles to immense speeds and energies. These particles - often simply protons (i.e. Hydrogen atom nuclei), but sometimes also X-rays and atoms like Carbon - attain unimaginably large energies. They are all around us, so energetic that they pass through our bodies and much of the Earth's rock layers. We call them collectively and cryptically "cosmic rays".
Cosmic rays - unlike the neutrinos of my previous post - do occasionally interact with organic matter (i.e. biological cells) and play an important role in the evolution of life on Earth: they can help mutate DNA when they penetrate a cell, and mutations are a key ingredient in the process of evolution. What is quite astounding about cosmic rays is their extremely high energies. Physicists often measure energies in "electron Volts" - some useful unit of energy related to the more familiar ones such as Joules or Calories. To put things in perspective, the largest particle accelerator built by the pitiful human race generates particles with energies around several trillions of electron Volts. Cosmic ray particles have been detected with energies around a million times more… but not much more than that. Lower energy cosmic rays - in the thousands of trillions of electron Volts range - can be detected directly through detectors raised to the edge of the atmosphere with balloons; higher energy ones are seen indirectly through showers of particles they generate when they collide with the Earth's atmosphere. Much is not known or understood about these mysterious visitors from outer space. But in the past few decades, we have started tracking them down actively and aggressively.
The first video features the late celebrated science narrator Carl Sagan and gives a great overview of the subject. The second video is part 1 of a 3 part series that goes into more details.
Posted on Monday, November 8, 2010 at 9:56AM