Interferometry

Interferometry is a measurement technique that extracts information by combining waves — typically electromagnetic — from multiple sources so that their interference patterns reveal properties inaccessible to any single detector. In astronomy, interferometry allows dispersed telescopes to function as a single instrument with resolving power set by the distance between them, not their individual sizes. The technique underlies the Event Horizon Telescope, the ALMA, and the proposed space-based interferometers that may one day image exoplanets directly. It is not merely a workaround for building larger mirrors; it is a different ontology of observation, one in which the instrument is a network rather than an object.