50 free Prime Meridian trivia questions with answers — geography quiz, new questions added Aug 2026.
This prime meridian trivia quiz covers the imaginary line at zero degrees longitude and the century-long argument over where to draw it. The easy questions cover the London borough it runs through, the observatory on the hill, the hemispheres it divides, the year the world agreed on it and the country that sulked. From there the quiz moves through the history: Ptolemy's Fortunate Isles, the ancient Indian meridian through Ujjain, Cardinal Richelieu's El Hierro, Mercator's globe, Maskelyne's Nautical Almanac and why French translations quietly kept Greenwich figures. The hard end covers the 1884 International Meridian Conference in Washington: who called it, how many nations came, how the vote went, what France proposed instead and when Paris finally gave in. Then the modern twist: why a GPS receiver standing on the brass strip does not read zero, the deflection of the vertical, the IERS Reference Meridian, the countries the line crosses today, Null Island and its Soul buoy, and the prime meridians of the Moon, Mercury, Venus and Mars. Every answer was checked against the encyclopaedia entries for the prime meridian, the Greenwich meridian, the International Meridian Conference, the Royal Observatory and Null Island before publishing, and the supporting sentence is stored with each question. Our geography, maps and time zones quizzes are natural next stops.
30 of 50 questions with answers and explanations. Play the quiz
Q 01What is the longitude of the prime meridian?
Nought
Longitude is defined as 0 there; with its anti-meridian it splits the globe into two halves.
Q 02What long symbolised the prime meridian in the courtyard of the Royal Observatory?
A brass strip
It has since been replaced by stainless steel.
Q 03Which two hemispheres does the prime meridian divide the Earth into?
Eastern and Western
Unlike the equator, the choice of prime meridian is astronomically arbitrary.
Q 04In which year did the International Meridian Conference adopt Greenwich as the world's prime meridian?
1884
Forty-one delegates met that October.
Q 05In which city was the International Meridian Conference held?
Washington, D.C.
Congress had authorised the president to call it by an Act of 3 August 1882.
Q 06Which US president requested the International Meridian Conference?
Chester A. Arthur
Congress had authorised the invitation by an Act of 3 August 1882.
Q 07How many countries voted to adopt the Greenwich meridian at the meridian conference?
22
Forty-one delegates attended in total; the French abstained.
Q 08Which country abstained from the meridian conference vote and kept its own meridian for decades?
France
It argued for a neutral line through the Azores or the Bering Strait.
Q 09In what year did the holdout nation finally adopt Greenwich as the beginning of the universal day?
1911
Even then it refused to say Greenwich, calling it Paris mean time retarded by 9 minutes 21 seconds.
Q 10What phrase did the French use instead of the word Greenwich once they gave in?
Paris mean time, retarded by 9 minutes and 21 seconds
Navigation charts switched to the Greenwich meridian in 1914.
Q 11Which Astronomer Royal fixed the Greenwich prime meridian in 1851 with his new transit circle?
George Airy
Earlier transit instruments, the first bought by Halley in 1721, sat about 43 metres further west.
Q 12How far east of the Greenwich courtyard marker does a GPS receiver place the meridian?
About 102 metres
That is 5.3 seconds of arc, explained by the deflection of the vertical at Airy's transit circle.
Q 13What is the name of the international standard prime meridian adopted in 1984?
IERS Reference
Its plane passes through the Earth's centre of mass rather than following a plumb line at Greenwich.
Q 21Which ancient geographer was the first to use a consistent meridian for a world map, in his Geographia?
Ptolemy
He based it on the Fortunate Isles, comfortably west of Africa because negative numbers were not yet in use.
Q 22With which modern islands are the ancient geographer's 'Fortunate Isles' usually associated?
The Canaries
His maps actually fit the Cape Verde islands better.
Q 23Per the 4th-century Surya Siddhanta, India's ancient zero longitude passed through which city?
Ujjain
The city was then called Avanti; the line also passed through Rohitaka, modern Rohtak.
Q 14Since what year has the Earth-centred reference meridian been the international standard?
1984
Greenwich had held the role for exactly a century.
Q 15How fast does Airy's transit circle drift relative to Earth-centred zero longitude?
About 2.5 centimetres a year
The drift is northeast and measured from observations of satellites and quasars.
Q 16How has the prime meridian been marked across the London night sky since 16 December 1999?
A green laser
The ground marker is now stainless steel.
Q 17How many countries does the Greenwich meridian pass through between the North and South Poles?
Eight
The list runs from England down through the Sahara to the Gulf of Guinea, plus Antarctica's Queen Maud Land.
Q 18Which is the southernmost African country crossed by the Greenwich meridian?
Ghana
After leaving Ghana the line runs down through the Gulf of Guinea and the Atlantic to Antarctica.
Q 19What is 'Null Island'?
The point where the prime meridian meets the equator
It is open ocean about 600 km south of West Africa, and a running joke among mapmakers about bad coordinates.
Q 20What was moored at Null Island until 2021?
A weather buoy named Soul
Every buoy in the PIRATA array is named after a musical genre.
Q 24Which 1494 Spain–Portugal treaty used a mid-Atlantic line where the compass pointed due north?
Tordesillas
The line was settled at 370 leagues west of Cape Verde.
Q 25Which Canary island did Cardinal Richelieu choose as the meridian in 1634?
El Hierro
Delisle rounded its position to exactly 20 degrees west of Paris, making it the Paris meridian in disguise.
Q 26Through which island did Mercator draw the prime meridian on his 1541 globe?
Fuerteventura
His later maps switched to the Azores, following the hypothesis that magnetic north marked a natural line.
Q 27How were longitudes counted in Ortelius's first modern atlas of 1570?
From 0 to 360 degrees
Navigators kept the 360-degree habit well into the 18th century.
Q 28Whose Nautical Almanac, published from 1765, made Greenwich the universal reference point for navigators?
Nevil Maskelyne's
He published 49 issues; even the French translations kept his Greenwich calculations.
Q 29Which clockmaker developed the marine chronometer that transformed the finding of longitude at sea?
John Harrison
His H4 and three earlier timekeepers are on show at Greenwich; Godfrey and Hadley developed the octant.
Q 30Which king founded the Royal Observatory at Greenwich in 1675?
Charles II
Christopher Wren picked the hilltop site of Greenwich Castle and John Flamsteed became the first Astronomer Royal.