Fundamentals
Start here to understand the basics of cosmic ray science.
What Are Ultra-High-Energy Cosmic Rays?
An introduction to the most energetic particles in the universe — what they are, how rare they are, and why they matter.
The Cosmic Ray Energy Spectrum
Understanding the knee, ankle, and GZK cutoff — features that encode the physics of cosmic ray sources and propagation.
Understanding Extensive Air Showers
How a single particle creates billions — the physics of cascades that make cosmic ray detection possible.
What Are UHECRs Made Of?
Protons, helium, or iron? Understanding cosmic ray composition and why it matters for source identification.
Detection Methods & Observatories
The technology behind catching particles from the edge of the universe.
How We Detect Cosmic Rays
From water tanks to fluorescence telescopes — the ingenious methods used to catch ultra-high-energy particles.
Pierre Auger Observatory: A Deep Dive
Inside the world's largest cosmic ray detector — 3,000 km² of Argentine pampa watching for particles from space.
Telescope Array: Northern Eye on UHECRs
The Northern Hemisphere's largest detector, home to the Amaterasu particle and continuing a Utah legacy.
Mysteries & Challenges
The unsolved problems driving cosmic ray research.
The GZK Paradox
Why do we detect cosmic rays that physics says shouldn't exist? The mystery of the energy limit.
The Magnetic Deflection Problem
Why cosmic rays don't point back to their sources — the challenge of tracing particles through cosmic magnetic fields.
Where Do UHECRs Come From?
AGN jets, gamma-ray bursts, starburst galaxies — the leading candidates for cosmic accelerators.
The Oh-My-God Particle and Amaterasu
The two most energetic particles ever detected — and the mysteries they present.
Multi-Messenger Astronomy
Connecting cosmic rays with gravitational waves, neutrinos, and gamma rays.
Cosmic Rays Meet Gravitational Waves
The new frontier — searching for connections between UHECRs and gravitational wave sources.
Gamma-Ray Bursts and Cosmic Rays
The explosive connection — can the universe's most luminous events produce its most energetic particles?
IceCube and the Neutrino Connection
How high-energy neutrinos from Antarctica relate to cosmic ray origins and multi-messenger astronomy.
History
The story of cosmic ray discovery and research.
Resources & Tutorials
Practical guides for exploring cosmic ray data yourself.