Five out-of-the-way places — an Appalachian hollow, a sheep paddock, a Cheshire field, a wooded German valley and a limestone sinkhole — each picked for its quiet, and each now holding one enormous ear turned on the sky.
The Robert C. Byrd Green Bank Telescope, dedicated in 2000, is the largest fully steerable radio telescope on Earth — a 100-by-110-metre dish with more than two acres of collecting surface. The valley sits inside the 13,000-square-mile National Radio Quiet Zone, and it was here in 1960 that Frank Drake ran Project Ozma, the first modern search for signals from another civilisation.
The 64-metre CSIRO dish opened in 1961 and was renamed Murriyang — 'Skyworld' — by Wiradjuri Elders in 2020. Its Apollo 11 pictures went to Houston and on to an audience estimated at 600 million, a story retold in the 2000 film 'The Dish'. It also logged strange millisecond radio bursts for seventeen years before staff traced them, in 2015, to the site kitchen's microwave oven being opened before its timer ran out.
The Lovell Telescope was the largest steerable dish in the world when it was completed in 1957 and is still the third largest, behind Green Bank and Effelsberg. The observatory was inscribed as a UNESCO World Heritage Site in 2019 and now hosts the global headquarters of the SKA Observatory.
The Max Planck Institute for Radio Astronomy's 100-metre dish held the record as the world's largest fully steerable radio telescope from 1972 until the Green Bank Telescope overtook it in 2000. It still works as a node of European VLBI networks, combining with dishes across the continent to act as an instrument effectively the width of Europe.
FAST — the Five-hundred-metre Aperture Spherical Telescope — fills the Dawodang sinkhole with 4,450 panels, of which a 300-metre patch is pulled into shape by cables to aim at a target. It has been the largest filled-aperture radio telescope in the world since it was completed in 2016 — four years before Arecibo, the dish it dethroned, collapsed — and by late 2024 it had found more than a thousand new pulsars, more than every other telescope on Earth managed over the same span.
Think you'd have found them? Play today's expedition, or replay this one from the archive.