The Field Guide to Particle Physics https://pasayten.org/the-field-guide-to-particle-physics©2021 The Pasayten Institute cc by-sa-4.0The definitive resource for all data in particle physics is the Particle Data Group: https://pdg.lbl.gov.The Pasayten Institute is on a mission to build and share physics knowledge, without barriers! Get in touch.The Particle Data Group's write up on cosmic rays. See Figure 29.8 for a representation of the "ankle" feature in the spectrum.https://pdg.lbl.gov/2019/reviews/rpp2019-rev-cosmic-rays.pdfAnother representation of the power laws can be found in Professor Peter Gorham's Coursework on Ultra High Energy Cosmic Rays: http://www2.hawaii.edu/~gorham/UHECR.htmlNatalie Wolchover has written two great articles in Quanta on Cosmic Rays, both which talk about what might accelerate these particles.The Particle That Broke a Cosmic Speed Limit and Cosmic Map of Ultrahigh-Energy Particles Points to Long-Hidden TreasuresMIT's GameLab has a fun example of how Special Relativity works. See also Gamow's popular science book on Special Relativity. CERN's DIY Cloud Chamber DesignCloud Chamber without Dry Ice (see also references within)Other References:Measurement of muon flux as a function of elevationICRP Paper on Aviation and RadiationRadiation Exposure During Commercial Airline FlightsRadiation from Air Travel as per the CDCCalculate Your Radiation Dose (EPA) Cosmic RaysPart 3 - Cosmogenic Muons and Special RelativityMuons - those heavy, unstable cousins of the electron - are all around us. All the time.On average, every square centimeter of Earth sees a muon about once a minute.  While that might not seem like a lot, if you consider your personal space. Say, about square meter around you - you know, 10 square feet . Over 160 muons pass through your personal space per second! Per second!Those muons coming form the upper atmosphere. They are the debris left over from the constant bombardment Earth experiences from high energy cosmic rays.If only there was a way to see them.Do you remember when I said that a particle physicist will look for particles WHEREVER they can find them? Well, before weather balloons, before particle colliders, there were cloud chambers.Cloud chambers are boxes full of super saturated vapor or some kind. Any little disturbance will cause that vapor to condense, as clouds do up in the sky.High energy particles blasting through a cloud chamber leave tracks. Little clouds form around the path of the particle, just like the contrails of a jet flying through the sky.The muon and the positron were both discovered this way!Cloud chambers are fun because you can build them yourself at home! The main thing you need is a sustained temperature gradient and tiny bit of very pure isopropol alcohol.We’ll link to two great examples of DIY cloud chamber designs in the show notes.Building a cloud chamber at home is a great way to come face to face with the fact muons - the debris from cosmic rays - are passing through us all the time.The Atmosphere as a Muon FilterThe magnetic field generated by the Earth’s core protects us from many incident particles from space. Especially all that plasma in the solar wind.But those high energy cosmic rays blast straight through the magnetic field. It’s just not strong enough to contain them.Our upper atmosphere is our next layer of defense. Cosmic rays collide with its molecules tens of miles above the Earth, creating a shower of debris that itself can be miles across. In some sense, the atmosphere serves as a filter, converting all those particles like protons and pions into muons. Muons comprise the bulk of what we see down here at the surface. Muons are unstable particles. They decay to electrons after about 2.2 microseconds. This means that while many muons make to the ground, not all of them do. The higher you are above sea level, the more muons you’re likely to see.At 10,000 ft above sea level, this number can triple! Given that commercial airline flights t