Duncan Steel (1955- ) is an astrophysicist who has worked in the USA, New Zealand and is currently director of Spaceguard Australia. Dr. Steel has been employed by both NASA and the ESA. In 1995 he suggested that Stonehenge I had been constructed as a predictor of the Earth’s intersection with the path of a comet and its attendant debris, with a 19-year periodicity(a). This controversial idea named Encke’s Comet and the Taurid meteor shower as the principal culprits and dated the first encounters to around 3100 BC. This date coincides with the conclusions of David Furlong and Timo Niroma who note cultural and meteorological upheavals at that same time.
Steel has his own website(b).
(a) https://www.archaeologyuk.org/ba/ba45/ba45feat.html (Offline Mar. 2016) see Archive 2657