Earlier this year there were worries that the Earth’s magnetic poles could reverse. Some claimed changes to the Earth’s magnetic field could leave us exposed to dangerous cosmic radiation. What are the chances of the poles reversing and what would happen if they did?
Earth’s Magnetic Field
Earth’s magnetic field, known as the ‘geomagnetic field’, is generated by the molten metal outer core swirling around the solid inner core.
This field helps protect the Earth from dangerous solar rays and cosmic radiation. It helps humans and animals navigate, as well as protecting sensitive technologies such as telecommunication and satellites.
In early 2018 a story about the disastrous effects of a supposedly imminent reversal of the magnetic poles gained widespread media coverage.
The original article argued that as the poles reverse, the geomagnetic field will weaken in places.
This would weaken the field’s protection, allowing ‘devastating streams of particles from the sun, galactic cosmic rays, and enhanced ultraviolet B rays from a radiation-damaged ozone layer’.
What Could Happen?
Following this theory, if deadly rays and radiation from outer space could reach the planet’s surface unhindered the results would be disastrous. All life on Earth would suffer.
Our reliance on technology would add to the suffering. The energy from solar rays would destroy the fragile electronics of satellites.
In a scenario reminiscent of a disaster movie, this could create a chain reaction, leading to failures in power stations across the world and a global blackout which could potentially last for years.
Has a Pole Reversal Ever Happened?
Earth’s magnetic poles have exchanged places many times.
Cores drilled from lava on the deep ocean floor act as a record of the Earth’s magnetic shifts. The lava’s magnetisation is determined by the status of Earth’s magnetic field when it is deposited.
Scientists estimate the poles have exchanged places hundreds of times over the past three billion years. Known as ‘geomagnetic reversals’, NASA has stated, ‘Reversals are the rule, not the exception.’
The process takes hundreds to thousands of years and is thought to occur due to the convection of molten iron in the Earth’s core.
Are We Due a Reversal?
In the last 20 million years the poles have reversed roughly every 200,000 to 300,000 years. The last pole reversal was about 780,000 years ago.
Since first measured in 1840, scientists have observed the geomagnetic field weakening at the rate of 5% every 100 years.
These two factors, along with a weakening in the geomagnetic field in the South Atlantic, fuelled speculation that a geomagnetic reversal could be coming soon.
Are the Poles Going to Flip?
The good news is latest research shows that the magnetic poles probably are not going to reverse. At least not for a few thousand years.
Scientists studied two previous ‘geomagnetic excursions’, shifts in the geomagnetic field which are not full reversals but still cause significant changes.
The scientists found that the evolution in the geomagnetic field building up to these previous excursions did not resemble current changes.
The data suggests that the current changes in the geomagnetic field will recover rather than signifying a dramatic shift.
Even if a geomagnetic reversal did occur, the doomsday theory about deadly cosmic radiation might be overstated.
The field would weaken during a geomagnetic reversal, but it would not vanish. Furthermore, the Earth’s atmosphere acts as another layer of protection from rays and radiation.
NASA itself discounted the claims of potential dangers, stating:
‘A weaker field would certainly lead to a small increase in solar radiation on Earth – as well as a beautiful display of Aurora at lower latitudes – but nothing deadly.’
So, a geomagnetic reversal is more likely to be accompanied by a colourful display of Aurora rather than the destruction of life as we know it. A comforting thought.