Astrid Eichhorn

In causal set theory, spacetime is not a smooth sheet but a web of tiny points connected by arrows of cause and effect. A point is linked to another only if the first can influence the latter. In such a web, a black hole is described differently: its horizon, the boundary from which signals cannot return, must be redefined.

Spacetime is often pictured as a smooth fabric. But at the very microscopic level, this fabric might not be continuous; instead, it could consist of individual 'atoms'—events linked by causality. This picture of the world is called causal set theory.

When a grain of sand falls on a table, its impact is predictable. But if you squeezed it down to the size of an atomic nucleus, the familiar laws of gravity would break down — the force of gravity would grow without bound.