A magnetic masterpiece nearly 360 years in the making.
Now if you hold a compass at Greenwich in London- the site of the prime meridian -it will finally point to true north as it and magnetic north converge.
(SOUNDBITE) (English) DR LOUISE DEVOY, SENIOR CURATOR, ROYAL OBSERVATORY, GREENWICH SAYING: "It's just interesting because it aligns with this historic meridian.
In some ways, it's a human construct.
The meridian was chosen here but it could have been anywhere else.
So it's just a nice coincidence really." The earth's magnetic field is caused by huge quantities of liquid iron deep in the planet's core which moves around 12 miles every year because of the rotation of the planet.
The Royal Greenwich Observatory was established in 1676 and helped establish the definition of zero longitude, paving the way for a global reference system for maps and navigation that we know and use today.
The last time Greenwich had zero declination, King Charles II was on the throne, coincidentally it was Charles who established the Royal Observatory at Greenwich in 1675.