Without this piece of iron the size of a moon, we wouldn’t exist.


The invisible shield that protects the Earth (and those who live on it) from the bombardment of solar radiation might have disappeared 565 million years ago had it not been for a significant shift beneath the planet’s surface. .

Scientists from the University of Rochester (NY, USA) have found the earth’s magnetic field weakened by ten percent before reaching the strength it is today.

This force is sufficient to keep water liquid on the surface of the earth and to protect the planet from more intense exposure to solar radiation.

And this is probably due to the formation of an inner core of solid iron in an “instantaneous” period of 15 million years.

Why is a magnetic field important?

You can’t see the Earth’s magnetic field – or the magnetosphere – but thanks to your lucky star, it’s there.

Without it, we wouldn’t exist, and having one is considered mandatory for planets wanting to support life.

Earth’s strong magnetic field protects us from exposure to harmful solar radiation, leaving only a small amount to reach populated places.

The magnetic field is also an important defense for Earth’s electrical infrastructure – from the electrical grids that keep the lights on, to the smartphone or computer you’re reading this article on right now.

It is also credited with keeping the Earth flush with surface waters.

This powerful planetary shield is credited with the emergence of life on Earth, unlike Mars and Venus – both of which have relatively weaker magnetospheres.

“The Earth would certainly have lost a lot more water if the magnetic field had not been regenerated,” says Professor John Tarduno of the University of Rochester.

A representation of the Earth, at first without an inner core; second, with an inner core beginning to develop about 550 million years ago; third, with an outermost and innermost inner core, about 450 million years ago. Researchers from the University of Rochester have used paleomagnetism to determine these two key dates in the history of the inner core, which they believe restored the planet’s magnetic field just before the explosion of life on Earth / Credit: University of Rochester illustration/Michael Osadciw

Rock Solid: Inner Core gives Earth the advantage

Earth’s wonderfully powerful magnetic field appears to have been maintained thanks to the emergence of the planet’s solid core 550 million years ago.

Tarduno’s team was able to pinpoint these dates through studies of the magnetism of ancient rocks and minerals.

Rocks that have been migrating to the surface for millions of years have been in a magnetically locked state since their initial formation, allowing scientists to determine the nature of Earth’s magnetic field when they first cooled and hardened .

This branch of science is known as paleomagnetism and has allowed Rochester researchers to determine (at least in geological terms) when Earth’s magnetic field began to strengthen to its modern level.

It also allowed a better understanding of the structure of the inner core.

“The inner core is extremely important,” says Tarduno.

“Just before the inner core started growing, the magnetic field was about to collapse, but as soon as the inner core started growing, the field regenerated,” Tarduno says.

It is believed that the decreasing strength of the magnetic field was due to heat loss in the liquid core.

But the solid iron core formed about 15 million years later, Earth’s magnetic strength was restored – a moment that seems pivotal to the arrival of our ancestors.

The Cambrian “explosion” occurred just tens of millions of years after the formation of the Earth’s inner core – in relative terms, just a few heartbeats in the planetary clock – and saw the first appearance large groups of animals in the fossil record.

“This research really highlights the need to have something like a growing inner core that maintains a magnetic field for the lifetime – several billion years – of a planet,” Tarduno says.


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