Victor Hess won the 1936 Nobel Prize for his discovery of cosmic rays by taking an electroscope along on a balloon ride. Hess noticed that the higher he was above the ground the less time it took for his electroscope to become discharged. He believed that particles moving through the air were robbing his electroscope of charge. He proposed that the discharge rate decreased with altitude due to the higher numbers of these particles at altitude. We now call these cosmic rays.
The particles that end up in the QuarkNet On-Line Cosmic Ray Detector are not the same as those that strike the upper atmosphere. Those incident on the upper atmosphere are called primary cosmic rays and have many different origins; many of them are protons. These extremely energetic protons strike the nucleus of atmospheric gases and create new subatomic particles that continue towards Earth's surface. Many of these subatomic particles have short lifetimes and decay into other particles. These 2nd and 3rd generation particles may enter our detector, which is located in an office on the 15th floor of Fermilab's Wilson Hall.
