The historic Thiruvananthapuram Observatory’s crucial role in understanding Earth’s magnetic field has recently come to light, sparked by the discovery of an old pencil sketch at the National Library of Scotland. This intriguing find, depicting a magnetic observatory once located in Cherthala, prompted a dedicated research team, led by Professor R. Jayakrishnan (the current director), to delve into the observatory’s extensive scientific archives. Their findings, published in the Indian Journal of History of Science as ‘162 years of rendezvous with the Magnetic Equator by the Travancore Observatory,’ meticulously detail the observatory’s monumental contributions to mapping India’s magnetic equator and observing its slow, fascinating drift southward towards Sri Lanka.
This pioneering work began in 1839 when John Caldecott, then director of the observatory, collaborated with T.G. Taylor of the Madras Observatory. Together, they published India’s very first magnetic equator map. Their landmark study pinpointed the magnetic dip equator—a geographical line where the Earth’s magnetic field is perfectly horizontal—at Bolghatty in Ernakulam on the west coast and Manamelkudi in Pudukkottai, Tamil Nadu, on the east coast.
Over Two Centuries of Magnetic Monitoring
Following their initial success, subsequent studies by engineers from the East India Company and scientists at the Trivandrum Observatory, including the renowned John Allan Broun, continued to meticulously track the equator’s persistent migration. Over almost two centuries, the observatory amassed an unparalleled dataset, not only documenting this magnetic shift but also providing rare, invaluable evidence suggesting a potential geomagnetic reversal—a fascinating phenomenon where Earth’s magnetic poles gradually swap places over vast periods.
The observatory’s journey took a new turn in 1961 when, after Travancore became part of India, the Central government took control. Its geomagnetic work was eventually transferred to other leading institutions, first to the National Geophysical Research Institute (NGRI) and later, in 1971, to the Indian Institute of Geomagnetism (IIG). Although the original magnetic facility closed in 1999 and was relocated to Tirunelveli, the Thiruvananthapuram Observatory’s historical archives remain an extraordinary and irreplaceable repository of scientific data.
Professor Jayakrishnan’s team has successfully retrieved around 40 crucial documents from various global repositories, including Munich University. Among these are early almanacs, though the very first one from 1838 is still missing. By carefully compiling and analyzing data from almanacs spanning 1839 to 1941, the researchers made a remarkable discovery: the Thiruvananthapuram Observatory uniquely recorded the magnetic equator’s movement in both southward and northward directions during these 98 years. Professor Jayakrishnan emphasized that this makes the Thiruvananthapuram Observatory the only institution worldwide likely to have documented such prolonged and detailed migration of the magnetic equator directly over its geographical location.