Cosmic rays are usually protons (but can also be heavier nuclei) which are accelerated by dynamic magnetic fields such as those on the sun, in solar wind, and fields blasted out by supernova explosions in our own Milky Way Galaxy. Cosmic rays can have a wide range of energies, and those with lower energy levels are well understood.

Scientists have various ways of expressing energy levels, but the unit of the electron volt (eV) is used to measure energy possessed by these cosmic particles. (Their energy could also be expressed in more familiar units of energy like calories, BTU, or kilowatt-hours.) These particles could possess energy in the range from 10¹² to 10²⁰ eV. For those not accustomed to using exponents or scientific notation, 10¹² would be equivalent to a 1 followed by 12 zeroes, or 1,000,000,000,000 (one trillion). The weakest cosmic rays have an energy of about 10⁹ eV or 1,000,000,000 (one billion) electron volts, which is about the minimum energy needed for a particle to get from beyond the solar system through the magnetized solar wind. Just a few thousand particles with energy of 10¹² eV would have enough energy to power an ordinary 60-watt household light bulb for an hour.

For the higher energy cosmic rays, there are few existing explanations and there is no scientific consensus about where they originate from. Scientists have built special particle accelerators to duplicate these cosmic ray particles, but the highest energies they have achieved are around 10¹² eV. The Auger Observatory is designed to study particles in the range of 10¹⁹ or 10²⁰ eV, which have around ten million times more energy than the particles produced in particle accelerators on Earth. One of these particles carries the equivalent energy of a baseball being thrown by a professional pitcher, a hockey puck being slap-shot at the net or a soccer ball being kicked at the goal. It does not seem like a great amount of energy to us, but it is packed into an object 100 trillion times smaller than those just mentioned. The Observatory will gather the data needed to solve the puzzle of where they originate - hopefully giving us insight into the process(es) the may create them also. Until it is solved, it will remain one of the greatest mysteries of our universe.