Travel Reference
In-Depth Information
displays of lighthouse technology and a whaling cannon, you'll see model ships, nautical
paintings, and various salty odds and ends.
Cost and Hours:
Free, daily 10:00-17:00, last entry 30 minutes before closing,
tel. 020/8858-4422,
www.rmg.co.uk
.
The museum hosts frequent family-oriented
events—singing, treasure hunts, and storytelling—particularly on weekends; ask at the
desk. Inside, listen for announcements alerting visitors to free tours on various topics.
• The final sight in town—the Royal Observatory Greenwich—is at the top of the hill just
behind the National Maritime Museum. To reach it, exit the Maritime Museum and follow
signs leading you to a tree-lined uphill path, then follow the crowds as they huff up the
steep hill (allow 10-15 minutes).
The Longitude Problem
Around 1700, as the ships of seafaring nations began to venture farther from their
home bases, the alarming increase in the number of shipwrecks made it clear that
navigational tools had to be improved. Determining latitude—the relative position
between the equator and the North or South Pole—was straightforward; sailors
needed only to measure the angle of the sun at noon. But figuring out longitude, or
their east-west position, was not as easy without a fixed point (such as the equator)
from which to measure.
In 1714, the British government offered the £20,000 Longitude Prize. Two suc-
cessful solutions emerged, and both are tied to Greenwich.
The first approach was to observe the position of the moon, which moves in re-
lation to the stars. Sailors would compare the night sky they saw with the sky over
Greenwich by consulting a book of tables prepared by Greenwich astronomers.
This told them how far they were from Greenwich—their longitude. Visitors to the
Royal Observatory can still see the giant telescopes—under retractable roofs—that
were used to carefully chart the heavens to create these meticulous tables.
The second approach was to create a clock that would remain completely ac-
curate on voyages—no easy feat back then, when turbulence and changes in weath-
er and humidity made timepieces notoriously unreliable at sea. John Harrison spent
45 years working on this problem, finally succeeding in 1760 with his fourth effort,
the H4 (which won him the Longitude Prize). All four of his attempts are on display
at the Royal Observatory.
So, how can a clock determine longitude? Every 15° of longitude equals an
hour when comparing the difference in sunrise or sunset times between two places.
