Muon
Mu off
2.2 µS
They are or can be created in our atmosphere as a result of collisions between incoming cosmic rays and elements in the upper atmosphere. Amazingly, more of them reach detectors on the ground than would be expected given their extremely short life spans. The reason that they do involves their high rate of speed, a significant portion of light speed. And so, from their perspective, or frame of reference, the distance between their point of creation and the ground is shortened by a phenomenon known as the Lorentz Contraction. And from an earthbound point of view, again, due to their high rate of speed, their internal 'clock' is slowed by a reciprocal known as Time Dilation, allowing them to live long enough to make the trip to the ground. Both of these phenomena are part of Einstein's theory of relativity.