OBSERVED GEOMAGNETIC FIELD INTENSITY IN LONDON

Since 1850 the curve has resumed the steady eastward trend.

If this trend were to continue, the compass would point due north in London in about 2030. The last time it did so was in the 1660s.
NASA Researchers Track Slowly Splitting 'Dent' in Earth’s Magnetic Field

A small but evolving dent in Earth’s magnetic field
The River Thames known alternatively in parts as the Isis, is a river that flows through southern England including London.

At 215 miles (346 km), it is the longest river entirely in England
The ancient religious status of the River Thames is one of London’s greatest prehistoric mysteries.

It’s known that Bronze & Iron Age Britons deposited thousands of prehistoric objects in the river as gifts to its deity or spirits.
The Dynamo Process

A dynamo (or electric generator) is a device converting the energy of motion to that of an electric current.

The concept goes back to Michael Faraday (1791-1867). The son of a poor blacksmith,
Faraday was aware of the possibility of such "fluid dynamos," and accordingly he tried to measure the electric current created by the flow of London's river Thames across the Earth's magnetic field.
FARADAY’S SYNAPTIC GAP

In 1832 Faraday conducted an experiment across Waterloo Bridge.

With this experiment Faraday hoped to observe the electricity generated as the river flowed between east and west across the Earth’s magnetic field.
Waterloo Bridge is a road and foot traffic bridge crossing the River Thames in London,

As the bridge is crossed between the north and south banks of the river, sound results from magnets affecting the left and right ears – as faint electrical signals

Submerged Thought: in the interval where the ears hear their apparatus.

Human ears milled from wood that was taken from the failed foundations of Waterloo Bridge after it was demolished in 1936.
Theoretically, and physically, the sum of space in the human brain where all thought takes place.
Approximate Total Thought: The approximate distance between the pre and postsynaptic neurons, multiplied by a conservative estimate of the number of synapses in the cerebral cortex. https://www.rickmyers.co.uk/work/faradays-synaptic-gap/
William Gilbert, also known as Gilberd, was an English physician, physicist & natural philosopher.

The drawing is from Gilbert's book. The smith is hammering a bar of hot iron, as it cools down while lined up in the north-south direction.
Gilbert noticed that such a bar became weakly magnetized, with the polarity appropriate to its direction, and viewed it as the iron being "reborn" and in the process (like a baby that starts breathing) acquiring the magnetism of its mother, the Earth.
Early in the last century scientists realised that ancient lava flows may tell about variations of the Earth's magnetic field in the past. They were surprised to find some old lavas had the same north-south polarity as the Earth has now, but others had the opposite polarity.
In 1952 Jan Hospers, studying basalts in Iceland, came with convincing proof that there existed long periods in the past, when the north-south magnetic polarity of the Earth was reversed.
Carl Friedrich Gauss, around 1838 devised a method of analyzing the Earth's field mathematically and estimating its strength.

Comparing his observations with recent ones shows that the north-south field of the Earth is weakening by about 5% per century, maybe even a bit faster.
No one knows if the trend will continue for 2000 years, until the poles are reversed. In fact, the field has twists and features that are added on top of the simple two-pole structure, and these seem to be getting stronger.
This suggests that inside the core of the Earth, where flows of liquid iron create the currents responsible for the magnetism of the Earth, the flow pattern can be quite complicated. There may be several independent eddies, & some grow strong, others weak, changing the pattern.
Systems are constructed where the currents of eddy A produce the magnetic field of eddy B, and vice versa, and such systems can in principle create magnetic reversals.

The Sun also has a polar magnetic field, and its polarity reverses in each sunspot cycle, every 11 years or so.
Because of variations in the earth’s magnetic field, the locations of magnetic north, south, east and west with respect to true geographic north, south, east and west have varied considerably through time.
"The World Turned Upside Down" is an English ballad. It was first published on a broadside in the middle of the 1640s as a protest against the policies of Parliament relating to the celebration of Christmas.

Old Public house approx 15min walk from the River Thames and Tower of London... situated on the historical Old Kent Road.
The Civil War and Cromwellian era (17th Century & Oliver Cromwell) are one of the most turbulent periods in English history.

In these times England not only lost a king, and gained a ‘Lord Protector’, but created the first modern republic - and the first modern dictatorship.
It truly was a ‘world turned upside down’.

The English Civil War (1642–1651) was a series of civil wars & political machinations between Parliamentarians ("Roundheads") and Royalists ("Cavaliers") principally over the manner of England's governance & the Three Kingdoms.
If the observed geomagnetic field intensity in London trend continues then the compass would point due north in London in about 2030. The last time it did so was in the 1660s.

On 23 October 1642 the first true battle of the Civil Wars took place,

Families were torn apart as uncles, sons, brothers and fathers took up arms against one another. In total, perhaps 100,000 soldiers and civilians perished during the wars, and 10,000 houses were destroyed.
On the morning of Tuesday 30 January 1649, with one swift blow, Charles’s head was removed by the executioner’s axe: an unprecedented act of regicide hitherto unknown in British history.
For the next 11 years Britain was governed as a republic, with Oliver Cromwell ‘Lord Protector’ as head of a new ‘Commonwealth’.

Between 1649 and 1653 the so-called ‘Rump Parliament’ sat at Westminster.
1649 - 1653 the ‘Rump Parliament’ sat at Westminster, generally loyal to the ‘New Model Army’ of parliamentary forces. Many members were also so called ‘puritans’ who demanded that strict moral behaviour be adopted by the country at large.

http://palatinate.org.uk/debate-has-pol 
"The World Turned Upside Down" is an English ballad. It was first published on a broadside in the middle of the 1640s as a protest against the policies of Parliament relating to the celebration of Christmas.

In 2019 a sculpture by Mark Wallinger titled "The World Turned Upside Down" was unveiled at the the London School of Economics. It is a political globe with the south pole on top. It is 4 metres (13 ft) in diameter & displays the nations and borders of the United Nations.
According to American legend, the British army band under Lord Cornwallis played The World Turned Upside Down when they surrendered after the Siege of Yorktown (1781).
On 3 September 1658 Oliver Cromwell died as a result of pneumonia, and was succeeded by his son Richard. As second Lord Protector, Richard was a weak, indecisive and ineffective leader who failed to win support of the Army.
After just seven months in power Richard Cromwell was deposed by his generals.

Charles II, as eldest son of the executed king, was recognised as the rightful sovereign. The years of bitter civil war were over.
Charles II was held in high esteem by many of his subjects, a position earned through his compassionate responses to the two great disasters that marked his reign: the arrival of plague in 1665 and the Great Fire of London, which devastated the capital the following year.
The fire moved quickly down Pudding Lane and carried on down Fish Hill and towards the River Thames. It spread rapidly, helped by a strong wind from the east. When it reached the Thames it hit warehouses stocked with combustible products.
Around September 9th 2019, compasses at Greenwich pointed true north for the first time in about 360 years.

https://www.google.co.uk/amp/s/amp.theguardian.com/science/2019/aug/30/compasses-to-point-true-north-for-first-time-in-360-years
London calling, yes, I was there, too
And you know what they said? Well, some of it was true

London calling at the top of the dial
And after all this, won't you give me a smile?

Researchers have discovered a small spot on the beak of some other birds that contains magnetite. 

Magnetite is a magnetized rock, which may act as a tiny GPS unit for information about position relative to the Earth’s poles.

https://ssec.si.edu/stemvisions-blog/how-do-birds-navigate
They are so eager to migrate, that they will jump in the direction in which they want to fly, and if you turn a static magnetic field in the horizontal plane they will start to jump in a different direction. https://www.bbc.co.uk/news/science-environment-27313355
Two recent studies discovered that the ability to see the Earth’s magnetic field is a result of a special protein in bird’s eyes. The two papers studied found evidence for an unusual eye protein called Cry4. (cryptochromes)
Cry2 is heavily active in the human retina. Steven Reppert said “It’s beautifully poised to sense light but we don’t know if it has the downstream pathways that communicate magnetic information to the brain. The possibility exists.”
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