Greenwich visit marks perspective on Time
By Amanda Jermyn

British astronomers have had a significant influence on how we view the world today. Every place on Earth is measured in terms of its distance east or west of the Prime Meridian Line at Greenwich, England, an imaginary line that runs from the North Pole to the South Pole. This line defines zero longitude. By convention, it runs through the main telescope at the Royal Observatory in Greenwich where a line on the ground indicates the path it takes. I recently had the honor of straddling this line in person.

In contrast, the equator, at zero degrees latitude, separates the northern and southern hemispheres, and is determined by the Earth’s axis of rotation, while the Prime Meridian Line of longitude is entirely arbitrary. The ancient Greek mathematician and astronomer, Eratosthenes, first developed the concept of a Prime Meridian, and through the ages, various lines, dividing the eastern and western hemispheres, were used as a guide to navigation. All of that changed at the International Meridian Conference held in 1884 in Washington, D.C. where 22 countries voted to adopt the Greenwich Meridian as the standard or Prime Meridian of the world.

Our system of time zones is linked to the Prime Meridian, with Greenwich Mean Time as its center. Here in New England, Eastern Standard Time is five hours behind Greenwich Mean Time, while Western Europe is one hour ahead of it. On the exact opposite side of the Earth from the Prime Meridian is the International Date Line.

Close to the Royal Observatory at Greenwich is the National Maritime Museum that currently showcases an exhibition of stunning space photography called “Visions of the Universe.” The Observatory itself houses a science museum, planetarium, and John Harrison’s collection of 18th century sea clocks, or marine chronometers, devices used in the past to solve the problem of establishing the longitude or east-west position of a ship at sea.

One of those present at the 1884 International Meridian Conference was Britain’s representative, John Couch Adams, an astronomer best known for having predicted the position of the planet later named Neptune. In 1845 Adams in Cambridge and Urbain Le Verrier in Paris independently made these predictions, and the planet’s existence was confirmed by telescopic observation in 1846 by Johann Gottfried Galle and Heinrich Louis d’Arrest in Berlin.

Adams became director of the Cambridge Observatory in 1861. This observatory later became part of the Institute of Astronomy, currently involved in cutting edge research, as well as a treasure trove of astronomy history. As a relative of mine works there, I recently had the privilege of a private tour of the facilities and telescopes.
While astronomers have been resident in Cambridge since medieval times, one of the most famous to study there was Sir Isaac Newton who, as a Fellow of Trinity College, compiled his “Principia Mathematica,” published in 1687. The Cambridge Observatory was established in 1823. Its 12” Northumberland Telescope, dating from 1838 was, for some years, one of the world’s largest refracting telescopes. It remains in use for public observing and for visual observations by members of the University Astronomical Society. The 8” Thorrowgood Telescope, also in use at the Observatory, dates from 1864. Double star measurements are currently made with this instrument, and it is also used by the University Astronomical Society and for public observing. Most current observations, however, are made using modern mountaintop or space telescopes.

The Cambridge Observatory building includes a library with astronomical books dating back to 1514 A.D., and was also home to the early observatory directors. One of these was Sir Arthur Eddington, famous for proving Einstein’s theory of relativity correct with his 1919 eclipse expedition. In fact, Einstein came to stay with Eddington at the observatory in 1930, and there is a photo of the two of them on display taken during that visit. In the director’s house is a bust of astrophysicist Subrahmanyan Chandrasekhar, for whom the Chandra Space Telescope is named.

Strolling in the grounds outside, we observed astrophysicist Donald Lynden-Bell, known for his theories that galaxies contain massive black holes at their centers. On the lawn we passed a stylish bench depicting the constellations. On the door to one of the observatories was a sign that read: “Bird nesting. Please do not disturb/move dome.”

The Institute of Astronomy was created in 1972 when the Cambridge Observatories merged with the Institute of Theoretical Astronomy, the latter founded by Sir Fred Hoyle. It was Hoyle who coined the term “Big Bang,” despite opposing the theory vigorously. The illustrious Stephen Hawking and Sir Martin Rees, Britain’s Astronomer Royal, are both associated with the Institute which now has about 140 astronomers involved in areas of research including cosmology, gravitational lensing, X-ray astronomy, galaxies and stellar physics.

In other news, in last month’s column I mentioned that this year’s Connecticut River Valley Astronomers’ Conjunction was likely to be the last. I have, however, been advised that news of its demise is premature. Long live the Conjunction!