James Gregory’s Meridian Line

James Gregory’s Meridian Line

Natural Philosophy

James Gregory (1638–75) was the first of a great dynasty of Scottish mathematicians and natural philosophers. He became Regius Professor of Mathematics at the University of St Andrews in 1668. In 1672 he mathematically established a meridian line, a line circling the earth from pole to pole along which the time is the same, passing through St Andrews. Currently all time in the world is calculated using a line passing through Royal Observatory at Greenwich. Noon on this line is known as 12.00 GMT (Greenwich Mean Time). As St Andrews is further west than Greenwich, the time at Gregory's meridian is 12 minutes behind GMT. To mark his meridian, Gregory carved it into the floor of his laboratory, now part of the King James Library at the University of St Andrews. In 2014 a brass meridian line and plaque were installed in the pavement of South Street outside the Library to commemorate Gregory's achievement.

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