Case file · Cosmic event
Al-Biruni's eclipse observation at Kath
On 24 May 997 al-Biruni timed a lunar eclipse from Kath in Khwarezm while Abu al-Wafa timed it from Baghdad, using the difference to work out longitude.
997 CE · 41.69, 60.75 · status: official
The account
The coordinated observation is one of the earliest planned scientific collaborations across distance. Al-Biruni, born near Kath, went on to write on astronomy, astrology and the calendars of many peoples, and was openly sceptical of much astrological prediction.