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Decaying of muons

  1. Jun 24, 2013 #1
    I know that muons have an average lifespan of 2.2µs. What I'm curious about is given that we do not yet know of relativity and time dilation how were they able to know that in a frame at rest with the muons thats their life span. Or is it that we only knew of their actual life span after the advent of relativity, that by measuring the speed and the time interval of the two events of muon creation and decay we were able to find their proper life span ?
    Last edited: Jun 24, 2013
  2. jcsd
  3. Jun 24, 2013 #2


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    It is possible to produce slow muons, so their rest half life can be effectively measured.

    The rest of your comment is unintellible. A half life does not determine the life span of an individual muon; the life expectancy of a human population does not determine the life span of an individual.
  4. Jun 24, 2013 #3


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    Easy... We measure the lifespan of slowly moving muons.

    We point to muons as an example of relativity at work because of three happy coincidences:
    1) It's easy to produce slow-moving muons so we know what their lifetime is when they aren't moving at relativistic velocities.
    2) We also have an abundant source of high-energy relativistic muons from cosmic rays to compare with.
    3) The muon lifetime is short enough that we can observe them decay. If they lived much longer, they wouldn't need time dilation to live long enough to reach the ground.
  5. Jun 25, 2013 #4


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    I think what you are asking is how scientists explained the long life of muons entering the atmosphere prior to the theory of relativity but since muons were not discovered until 1936, the issue never came up.
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