# How can we know the muon?

Level pending

The muons generated at a height of $$10$$ km from the earth's surface move very fast at a velocity of $$0.99$$ c ($$99$$% of the velocity of light). The muons are unstable subatomic particles with a mean lifetime of $$2.2$$ µs. So, from a classical point of view, they should decay completely before arriving at the earth's surface. But in reality, the muons are found on the earth's surface. Which of the following can explain this phenomenon?

a) Because time passed slowly from the muon's point of view.

b) Because time passed slowly from the earth's point of view.

c) Because the distance to the earth's surface was shortened from the muon's point of view.

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