More science - consider the Muon

My favourite particle: the muon | Mark Lancaster | Science | theguardian.com

 Most cloud chamber trails are caused by muons, a particle about which I had stored next to nothing in the cranial memory banks.

The article linked above is a really good summary of the history of their discovery, along with some background as to what they are.  Well worth reading.  A sample:

There are several hundred muons going through your head every second
minute. Fortunately, their low energies (and high mass) mean they are
harmless. These muons originate from the collisions of cosmic-rays
(primarily protons spewed out by stars) with the atoms in our upper
atmosphere. After their discovery it was observed that the number of
these muons decreased as you got closer to the earth and the natural
(and correct) conclusion was that they were not stable particles like
the electron but a bit fly-by-night (and day), and they decayed to other
more familiar particles (electrons and neutrinos) in about 2 millionths
of a second. At this point it was known what the mass of the electron
was and neutrinos were assumed massless, so by looking at the trajectory
and energy of the electron from the muon decay (or measuring the time
it took for the muon to decay) it became clear the the muon was a bit of
a porker. It weighed in at about 200 times the mass of the electron.

If you want maths with that, you can have a look at this article, which works through the question of why we see so many on Earth's surface if they decay so fast.  The answer is relativity:

The measurement of the flux of muons at the Earth's surface produced an early dilemma because many more are detected than would be expected, based on their short half-life of 1.56 microseconds. This is a good example of the application of relativistic time dilation to explain the increased particle range for high-speed particles.

Fascinating, hey?