The Mathematics of Stonehenge – A Neolithic Computer

Stonehenge was built over 1,500 years starting ~3000 BC. Its alignments track the solstices and possibly lunar cycles. The 56 Aubrey holes may have been used to predict eclipses via the ‘Saros cycle’ (18 years) or the ‘Metonic cycle’ (19 years). A simple counting scheme moving one marker per year predicts lunar eclipses with reasonable accuracy. The geometry is neolithic: they set out circles using pegs and ropes (essentially a compass) and used Pythagorean triples (3‑4‑5) to make right angles. Stonehenge is a computer built in stone.