radiation. Muons are by-products of cosmic rays colliding with molecules in the upper atmosphere. Muons reach earth with an average velocity of about 0.994c. On earth's surface, about 1 muon passes through a 1 cm2 area per minute (~10,000 muons per square meter in one minute).

Why do so many muons reach Earth?

radiation. Muons are by-products of cosmic rays colliding with molecules in the upper atmosphere. Muons reach earth with an average velocity of about 0.994c. On earth's surface, about 1 muon passes through a 1 cm2 area per minute (~10,000 muons per square meter in one minute).

How do muons reach the ground?

The generated muons rain down at high speed, some of them decaying partway down and others making it all the way to the ground at sea level. According to our knowledge of decay times, we should expect the average distance they travel before decaying will depend on their initial speed.