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 TreasuresColussi & HoffmannIn situ photolysis of deep ice core contaminants by Çerenkov radiation of cosmic originGephysical Research Letters: https://doi.org/10.1029/2002GL016112Guzmán, Colussi & HoffmannPhotolysis of pyruvic acid in ice: Possible relevance to CO and CO2 ice core record anomaliesAtmospheres: https://doi.org/10.1029/2006JD007886A quick primer on Cherenkov Radiation: https://www.radioactivity.eu.com/site/pages/Cherenkov_Effect.htmTheme music "Sneaking Up on You" by the New Fools, licensed by Epidemic Sound.Cosmic RaysPart 4 - Paleoclimatology and MuonsOur atmosphere is one giant filter for cosmic rays. The sparse molecules near the top of our atmosphere begin the process of catching the energy of those energetic particles from space and transferring it into heat or muons. These cosmogenic muons that typically make it all the way down to the surface.Near the surface, the atmosphere is a lot thicker, but it’s still just a collection of ballistic molecules bashing into each other at 1000 miles per hour. Some of those molecules hit us, and some hit the ground. We perceive these molecular impacts as air pressure. By contrast, cosmogenic muons are moving through this mess at over 600 million miles per hour. To those muons, the surface of the Earth is barely noticeable. They fly through a lot of things: hundreds of meters of rock, oceans, plants and animals before colliding or decaying. By contrast, those particles of atmospheric gas typically reflect off the surface of the Earth. Rocks just aren’t that permeable to most gas. As we explained in the ALPHA particle miniseries, helium gas generated from radioactive decay deep within the earth collects underground, trapped by rocks.One thing gas can permeate is surface water.Quite a bit of our atmospheric gases get dissolved into the ocean. Oxygen in the air allows the fish to breathe too, once dissolved into the water so it can be picked up by their gills. Increased carbon dioxide levels also imply more CO2 gets put under water. When the water on Earth’s surface freezes, as it might do near the polar ice caps, it traps some of that dissolved gas with it. This has been happening for millions of years, and until somewhat recently at least, that ice has been compounding. New ice forms above, pushing old ice down. This has resulted in a LOT of ice.In Antarctica there are areas where the ice is over four kilometers deep! That’s miles of ice! Greenland also carries massive glaciers, two to three kilometers deep, built up in same fashion.The gases trapped in that glacial ice is a frozen relic of an older atmosphere. The deeper the ice, the older the dissolved gases. As the mixture of molecules in our atmosphere changes over time, it sets down a record in the glacial ice. The deepest ice, millions of years old, can tell us what the atmosphere was like millions of years ago.Extracting that ice is quite the scientific adventure!This all easy to say in theory - but the practice of Science requires a lot of gory, technical detail. Different measurements