2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/197458We introduce a simple coordinate system covering half of de Sitter space. The new coordinates have several attractive properties: the time direction is a Killing vector, the metric is smooth at the horizon, and constant-time slices are just flat Euclidean space. We demonstrate the usefulness of the coordinates by calculating the rate at which particles tunnel across the horizon. When self-gravitation is taken into account, the resulting tunneling rate is only approximately thermal. The effective temperature decreases through the emission of radiation.LaTeX, 10 pages; v2. references added; v3. minor sign errors fixed, reference added, journal versionHigh Energy Physics - TheoryGeneral Relativity and Quantum Cosmologytext