Greenwich in Greater London, England, United Kingdom
Bradley’s meridian line
James Bradley, third Astronomer Royal, observed with improved accuracy using the telescope (purchased in 1749) that first defined this line in 1750. Owing to the unequal length of solar days, astronomers measure the time using distant stars. Stars cross the meridian of an observer around every 23 hours and 56 minutes. Astronomers' clocks run slightly faster than normal clocks to show sidereal (star) time.
You are now standing on James Bradley's meridian line (1750). This is still the reference point for Ordnance Survey maps today.
Bradley preferred using this transit telescope (inside the building ahead of you) as it produced a wider range of measurements.
Topics. This historical marker is listed in this topic list: Science & Medicine.
Location. 51° 28.674′ N, 0° 0.093′ W. Marker is in Greenwich, England, in Greater London. Marker can be reached from the intersection of Blackheath Avenue and Great Cross Avenue, on the left when traveling north. Located at the Royal Observatory Greenwich. Touch for map. Marker is in this post office area: Greenwich, England SE10 8XJ, United Kingdom. Touch for directions.
Other nearby markers. At least 8 other markers are within Airy’s meridian line (here, next to this marker); The Greenwich Meridian Telescope (here, next to this marker); Time for everyone (here, next to this marker); The Shepherd 24-hour Gate Clock (a few steps from this marker); William Herschel’s Telescope (a few steps from this marker); Ordnance Survey Bench Mark (a few steps from this marker); Greenwich Meridian Marker, 1750-1851 (a few steps from this marker); The Royal Observatory (a few steps from this marker). Touch for a list and map of all markers in Greenwich.
Also see . . . Royal Observatory, Greenwich on Wikipedia. (Submitted on May 25, 2018, by Michael Herrick of Southbury, Connecticut.)
Credits. This page was last revised on January 27, 2022. It was originally submitted on May 25, 2018, by Michael Herrick of Southbury, Connecticut. This page has been viewed 178 times since then and 92 times this year. Photos: 1, 2. submitted on May 25, 2018, by Michael Herrick of Southbury, Connecticut.