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Muons from outer space hit our upper atmosphere and begin decaying. The half-life of muons is very short so that even when they are traveling at $99\text{%}$ of the speed of light, very few should be observed by detectors on earth. Nevertheless, surprisingly large numbers of muons are detected.

Which of the following statements is a possible explanation of this observation?

Choose TWO answers.

A

The calculation of the half-life of muons has a large error band so that the observed numbers are reasonable.

B

Time dilation at $99\text{%}$ of the speed of light means that the muons' clocks run more slowly. They reach earth in great numbers within their half-life measured on their clocks.

C

Length contraction at $99\text{%}$ of the speed of light means that the muons measure the atmosphere to be a smaller distance than it actually is. They have less distance to travel to reach earth and can do that within their half life.

D

Muons are produced when the cosmic rays collide with the nitrogen and oxygen in our atmosphere. This does not necessarily happen at the top edge of our atmosphere. More cosmic rays are traveling deeper into the atmosphere before the muons are produced than was originally thought.

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