Editing Time dilation (section)

====Moving particles====

*A comparison of [[muon]] lifetimes at different speeds is possible. In the laboratory, slow muons are produced; and in the atmosphere, very fast-moving muons are introduced by cosmic rays. Taking the muon lifetime at rest as the laboratory value of 2.197&nbsp;μs, the lifetime of a cosmic-ray-produced muon traveling at 98% of the speed of light is about five times longer, in agreement with observations. An example is Rossi and Hall (1941), who compared the population of cosmic-ray-produced muons at the top of a mountain to that observed at sea level.<ref name="Stewart">{{Cite book |last=Stewart |first=J. V. |url=https://books.google.com/books?id=93E_vYuCKHYC&pg=PA705 |title=Intermediate electromagnetic theory |publisher=[[World Scientific]] |year=2001 |isbn=978-981-02-4470-5 |page=705}}</ref>
*The lifetime of particles produced in particle accelerators are longer due to time dilation. In such experiments, the "clock" is the time taken by processes leading to muon decay, and these processes take place in the moving muon at its own "clock rate", which is much slower than the laboratory clock. This is routinely taken into account in particle physics, and many dedicated measurements have been performed. For instance, in the muon storage ring at CERN the lifetime of muons circulating with γ = 29.327 was found to be dilated to 64.378&nbsp;μs, confirming time dilation to an accuracy of 0.9 ± 0.4 parts per thousand.<ref name="Bailey">{{Cite journal |last=Bailey |first=J. |display-authors=etal |year=1977 |title=Measurements of relativistic time dilatation for positive and negative muons in a circular orbit |journal=Nature |volume=268 |issue=5618 |page=301 |bibcode=1977Natur.268..301B |doi=10.1038/268301a0 |s2cid=4173884}}</ref>