>An ultra-high-energy cosmic ray carries tens of millions of times more energy than any human-made particle accelerator such as the Large Hadron Collider, the most powerful accelerator ever built, explained Glennys Farrar, a professor of physics at New York University.

“What is required is a region of very high magnetic fields — like a super-sized LHC, but natural. And the conditions required are really exceptional, so the sources are very very rare, and the particles are dissipated into the vast universe, so the chances of one hitting Earth are tiny,” said Farrar, who wasn’t involved in the study, via email.

The atmosphere largely protects humans from any harmful effects from the particles, though cosmic rays sometimes cause computer glitches. The particles, and space radiation more broadly, pose a greater risk to astronauts, with the potential to cause structural damage to DNA and altering many cellular processes, according to NASA
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The event triggered 23 of the surface detectors, with a calculated energy of about 244 exa-electron volts. The “Oh My God particle” detected more than 30 years ago was 320 exa-electron volts.

For reference, 1 exa-electron volt equals 1 billion gigaelectron-volts, and 1 gigaelectron volt is 1 billion electron volts. That would make the Amaterasu particle 244,000,000,000,000,000,000 electron volts. By comparison, the typical energy of an electron in the polar aurora is 40,000 electron volts, according to NASA.

244 Exa-eV
The energy limit for cosmic rays is known as Greisen-Zatsepin-Kuzmin (GZK) Limit. At 50 Exa-eV cosmic rays should start interacting with the cosmic background radiation and lose energy through that interaction. (The same would be true for a spaceship moving at those speeds impossibly close to the speed of light- the background radiation would be a resistive force, so at those speeds streamlining the spaceship makes sense even though its flying in a vacuum) …

The GZK limit means that these cosmic rays must be coming from a source that is ‘nearby’ cosmologically speaking…
the Oh-My-God Particle, which was found to possess a record-breaking 3.12×1020 eV (50 joules) of energy (about the same as the kinetic energy of a 95 km/h baseball).