Are black holes nature’s ultimate particle accelerators?

The most energetic particles ever detected on Earth carry, in a single proton, energy comparable to a tennis ball served by Serena Williams. Where in the Universe such cosmic rays are accelerated remains one of the great open questions of modern astrophysics.

Black holes provide some of the most extreme environments known, driving powerful outflows and jets. In this talk, I will explore how different black hole systems, from nearby “microquasars” in our Galaxy to distant and transient phenomena such as tidal disruption events, may contribute to the cosmic rays we observe on Earth across energy scales, and what this can tell us about the Universe's ultimate accelerators.