Even a broken compass is right once every 360 years: Royal Observatory Greenwich will soon point to ‘true north’ for the first time in more than three centuries
- Royal Observatory Greenwich tracks distance between magnetic and true north
- This is called declination and has long pointed to the west of true north
- It will soon cross over with true north before it starts creeping eastwards
- Declination is changing due to the constantly changing magnetic field of Earth
Compasses at Greenwich are pointing ‘true north’ for the first time in approximately 360 years.
Experts predict that in the next two weeks the compasses at the observatory will register true north as part of the once-in-a-lifetime event.
Compasses contend with ‘true north’ and ‘magnetic north’, with both measured on a compass.
The angle between the two is called the declination and it constantly changes due to flux in Earth’s magnetic field.
Declination has long been negative, pointing west of true north, but it is soon due to cross over the exact right spot.
The correct compass is much like the broken clock analogy – given long enough it will eventually be correct.
Scroll down for video
Pictured: Declination at Greenwich since 1600. Compasses at Greenwich are pointing ‘true north’ for the first time in approximately 360 years — but some parts of the UK could have to wait 20 years for it to happen
Over the past few hundred years in the UK, declination has been negative, meaning that all compass needles have pointed west of true north.
The line of zero declination, called the agonic, is moving westward at a rate of around 12 miles (20km) per year, experts say.
By next month, for the first time in around 360 years, the compass needle will point directly to true north at Greenwich in London before slowly turning eastwards.
The Royal Observatory Greenwich was established in 1676 and, from 1839, hosted the specialised magnetic observatory which made continuous measurements from 1840 onwards.
In 1926 the instruments were moved to Abinger in Surrey, as electrified railway lines had made it impossible to measure the magnetic field.
Dr Ciaran Beggan, a geomagnetism scientist at the British Geological Survey’s Lyell Centre in Edinburgh, said: ‘At some point in September, the agonic will meet zero longitude at Greenwich.
WHAT IS A MAGNETIC FIELD AND HOW IS IT CREATED?
A magnet is any object that has a magnetic field. It attracts ferrous objects like pieces of iron, steel, nickel and cobalt.
These days magnets are made artificially in various shapes and sizes depending on their use.
One of the most common magnets – the bar magnet – is a long, rectangular bar of uniform cross-section that attracts pieces of ferrous objects
A magnetic field is the space surrounding a magnet, in which magnetic force is exerted.
If a bar magnet is placed in such a field, it will experience magnetic forces.
However, the field will continue to exist even if the magnet is removed. The direction of magnetic field at a point is the direction of the resultant force acting on a hypothetical North Pole placed at that point.
When current flows in a wire, a magnetic field is created around the wire.
From this it has been inferred that magnetic fields are produced by the motion of electrical charges. A magnetic field of a bar magnet thus results from the motion of negatively charged electrons in the magnet.
By next month, for the first time in around 360 years, the compass needle will point directly to true north at Greenwich in London before slowly turning eastwards (stock)
WHY ARE THE EARTH’S MAGNETIC FIELDS MOVING?
The problem lies partly with the moving pole and partly with other shifts deep within the planet.
Liquid churning in Earth’s core generates most of the magnetic field, which varies over time as the deep flows change.
In 2016, for instance, part of the magnetic field temporarily accelerated deep under northern South America and the eastern Pacific Ocean. Satellites such as the European Space Agency’s Swarm mission tracked the shift.
‘This marks the first time since the observatory’s creation that the geographic and geomagnetic co-ordinate systems have coincided at this location.
‘The agonic will continue to pass across the UK over the next 15 to 20 years. By 2040, all compasses will probably point eastwards of true north.
‘It is, at present, impossible to predict how the magnetic field will change over decades to centuries, so the compass may well point east of true north for another 360 years in the UK.’
However, the experts have stressed that zero inclination will have no impact on daily life.
Dr Beggan added: ‘Compasses and GPS will work as usual – there’s no need for anyone to worry about any disturbance to daily life.’
The agonic line is crossing from east to west.
It arrived at East Anglia and Kent in 2017 and is now passing slowly across the British Isles.
WHAT COULD HAPPEN TO EARTH IF ITS POLES FLIPPED?
The Earth’s magnetic field is in a permanent state of change.
Magnetic north drifts around and every few hundred thousand years the polarity flips so a compass would point south instead of north.
The strength of the magnetic field also constantly changes and currently it is showing signs of significant weakening.
Life has existed on the Earth for billions of years, during which there have been many reversals.
There is no obvious correlation between animal extinctions and those reversals. Likewise, reversal patterns do not have any correlation with human development and evolution.
It appears that some animals, such as whales and some birds use Earth’s magnetic field for migration and direction finding.
Since geomagnetic reversal takes a number of thousands of years, they could well adapt to the changing magnetic environment or develop different methods of navigation.
Radiation at ground level would increase, however, with some estimates suggesting that overall exposure to cosmic radiation would double causing more deaths from cancer. ‘But only slightly,’ said Professor Richard Holme.
‘And much less than lying on the beach in Florida for a day. So if it happened, the protection method would probably be to wear a big floppy hat.’
The movement of the Earth’s magnetic poles are shown in this animation at 10-year intervals from 1970 to 2020. The red and blue lines sjpw the difference between magnetic north and true north depending on where you are standing. On the green line, a compass would point to true north. Credit: NOAA National Centers for Environmental Information
Electric grid collapse from severe solar storms is a major risk. As the magnetic field continues to weaken, scientists are highlighting the importance off-the grid energy systems using renewable energy sources to protect the Earth against a black out.
‘The very highly charged particles can have a deleterious effect on the satellites and astronauts,’ added Dr Mona Kessel, a Magnetosphere discipline scientist at Nasa.
In one area, there is evidence that a flip is already occurring. ‘The increasing strength of the South Atlantic anomaly, an area of weak field over Brazil, is already a problem,’ said Professor Richard Holme.
The Earth’s climate could also change. A recent Danish study has found that the earth’s weather has been significantly affected by the planet’s magnetic field.
They claimed that fluctuations in the number of cosmic rays hitting the atmosphere directly alter the amount of cloud covering the planet.
Henrik Svensmark, a weather scientist at the Danish National Space Centre who led the team behind the research, believes that the planet is experiencing a natural period of low cloud cover due to fewer cosmic rays entering the atmosphere.
Source: Read Full Article