R. Moradi

An avalanche in a sandpile starts with a single grain. No one knows exactly where it will slip or how big the slide will be. But if you keep pouring sand, the pile itself reaches a state where avalanches of all sizes, from tiny trickles to massive collapses, follow the same law.

Two snapshots of the same lighthouse. One is taken from a boat sailing straight into the beam, the other from the shore, where the beam only grazes the edge of the sky. From these two frames, you can reconstruct how the lighthouse light is distributed across angles without ever getting close to it. That is roughly what astronomers did with two gamma-ray bursts they consider twins.