The Gibbons-Hawking effect is named for Stephen Hawking and which physicist?

The Gibbons–Hawking effect is named for Stephen Hawking and Gary Gibbons.

The effect states that a temperature can be associated with a causal horizon in a spacetime satisfying Einstein’s field equations. It extends the thermodynamic intuition of black-hole horizons beyond ordinary black-hole event horizons. For example, de Sitter space has a cosmological horizon and therefore an associated temperature related to its expansion rate.

Gibbons and Hawking developed this work in the 1970s, including their 1977 paper “Cosmological Event Horizons, Thermodynamics, and Particle Creation.” Their analysis helped show that horizon thermodynamics applies to cosmological settings as well as black holes.

This is commonly confused with Hawking radiation, which describes particle emission from black-hole horizons. The Gibbons–Hawking effect is broader: its key idea is that causal horizons, including cosmological horizons, have thermodynamic properties. Gary Gibbons also collaborated with Hawking on Euclidean quantum gravity and black-hole thermodynamics.