the

Secret of the Prime Meridian

the concept of a spherical earth has

been widely accepted since the 3rd

century BCE around this time

Eratosthenes calculated the

circumference of the earth and the tilt

of its axis both with remarkable

accuracy and also invented the first

geographic coordinate system his three

volume masterpiece cleverly entitled

geography was preserved alongside all

great works of the time at the Library

of Alexandria nopsi okay so his books

were lost to history but the coordinate

system survived and is still in use

today here's how it works

imagine the earth is split in half along

its axis the resulting circulars 360

degrees divided into quarters of 90

degrees the equator is by definition at

zero degrees the North Pole is thus at

90 degrees north and the South Pole at

90 degrees south every other point on

the circle has a comparable angle value

known as a latitude now let's split the

earth perpendicular to its axis the

resulting circle is divided into halves

of 180 degrees the prime meridian whose

location is fundamentally arbitrary is

by definition at 0 degrees all points on

the circle of an angle value known as

latitude with the point opposite being

simultaneously 180 degrees west and east

so far so good but where does the Prime

Meridian go the first person to use a

consistent reference Meridian was

geographer Claudius Ptolemy in his

eighth book masterpiece also entitled

geography Ptolemy placed the prime

meridian along what he called the

fortunate Isles somewhere in the

Atlantic Ocean the point was to place it

west of the known world since negative

numbers were not yet in use this notion

stuck around for the next 1,500 years

with multiple Atlantic meridians used by

cartographers but eventually empires

happened thus many prime meridians used

in the modern era passed through major

cities including but not limited to

Washington DC Philadelphia Lisbon Madrid

London Paris Brussels Amsterdam Florence

Rome Copenhagen Alexandria Jerusalem

Mecca and Kyoto a particular note was

London's Prime Meridian established in

the 18th century as passing through the

Royal Observatory at Greenwich it gained

widespread use as the British

Empire stretched across the world by the

late 19th century over two-thirds of the

world's commerce depended on see charts

that use the Greenwich Meridian still

the world needed a universal prime

meridian to facilitate global navigation

so in October 1884 the International

Meridian conference took place of the 25

countries present 22 voted in favor of

adopting the Greenwich meridian

internationally two countries abstained

from voting including France who

continued to use the Paris meridian for

almost three more decades today the

Greenwich Observatory in London is a

tourist attraction where every year 750

thousand visitors pay 10 pounds just to

stand on the famous line and every day

at sunset a powerful laser shines across

the London sky marking the line where

East meets West except that's not true

you see this isn't actually the Prime

Meridian originally meridians were

defined relative to the spherical earth

geometric center but GPS satellites

orbit the Earth's center of mass which

differs from its geometric centre since

the earth lacks uniform density and

isn't even a perfect sphere what with

all the mountains and deep seas long

story short the real prime meridian is

the International reference Meridian

located 102 metres east of the Greenwich

Meridian but if the Greenwich

Observatory isn't on the meridian then

what is let's find out so that's the

observatory and that's the marking strip

the tourists paid to stand on

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over there we see Canary Wharf one of

London's financial business districts

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and here we are the Prime Meridian as

you can see there is nothing here well

after combing through all of Greenwich

Park it turns out this dog waste bin is

the only man-made object located on the

Prime Meridian you can find it behind

the Ranger's house so if you ever plan

on visiting the Prime Meridian in London

now you know not to waste 10 quid on the

observatory ticket instead get yourself

a free photo of the prime dog waste bee

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