{"id":373,"date":"2021-11-28T05:00:46","date_gmt":"2021-11-28T04:00:46","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=104187"},"modified":"2021-11-28T05:30:12","modified_gmt":"2021-11-28T04:30:12","slug":"earths-magnetic-field-should-we-be-worried-about-the-poles-flipping","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/earths-magnetic-field-should-we-be-worried-about-the-poles-flipping\/","title":{"rendered":"Earth\u2019s magnetic field: Should we be worried about the poles flipping?"},"content":{"rendered":"

<\/p>

By Marcus Chown\n \t\t<\/p>

Published: Sunday, 28 November 2021 at 12:00 am<\/p>

\n\n

What causes Earth\u2019s magnetic field?<\/strong><\/h2>\n

Magnetic fields are generated by electric charges in motion. In a bar magnet, the moving charges are electrons orbiting in atoms. In the Earth, they are electrons ferried around by circulating currents of molten iron.<\/p>\n

The details are not well understood. But, basically, hot material in Earth\u2019s outer liquid iron core expands, becoming less dense than its surroundings, and therefore rises. Cooling and becoming less dense, it should sink back down again. But the Earth\u2019s rotation prevents this.<\/p>\n

Consequently, liquid circulates around the core, and friction between its different layers charges them up \u2013 just like a plastic comb rubbing against a nylon sweater. It\u2019s these moving charges that generate the Earth\u2019s magnetic field.<\/p>\n

The two requirements for planetary magnetism are therefore a liquid core and rotation. We know this because Venus, though roughly Earth\u2019s size, has essentially no magnetic field. The planet has a liquid core but rotates slowly \u2013 only once every 243 Earth days.<\/p>\n

Why do Earth\u2019s magnetic poles move?<\/strong><\/h2>\n
\""Why\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
\u00a9 Alamy<\/span><\/figcaption><\/div>\n

Though the Earth\u2019s magnetic field is very similar to that of a bar magnet, with a north and south pole, it is not as stable because it is generated by complex processes inside the Earth. These cause the magnetic poles to wander.<\/p>\n

Historically, the North Pole has moved at about 15 kilometres per year. But since the 1990s it has sped up, and now is moving at about 55 kilometres per year towards Siberia. It is speculation, but this might foreshadow a \u2018magnetic reversal\u2019 in which the magnetic north and south poles change locations. This has happened 171 times in the past 71 million years \u2013 and we are overdue a flip.<\/p>\n

Models of the Earth\u2019s magnetic field based on satellite observations have shown that the present wandering is the result of a battle between \u2018blobs\u2019 of unusually intense magnetic fields deep inside the planet. As for the flipping of the Earth\u2019s magnetic field, nobody is 100 per cent sure why this happens.<\/p>\n

What would happen if the magnetic field disappeared?<\/strong><\/h2>\n
\""What\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
\u00a9 Getty Images<\/span><\/figcaption><\/div>\n

Scientists discovered magnetic reversals by measuring the magnetic field on either side of mid-Atlantic ridges from which molten rock is extruded like toothpaste from a tube. As it solidifies, its crystals align along the direction of the Earth\u2019s magnetic field at the time, leaving a \u2018tape recording\u2019 of reversals.<\/p>\n

Reversals are believed to take place over 1,000 to 10,000 years, during which time the field shrinks to zero before growing again with the opposite polarity. There were therefore times \u2013 maybe even centuries \u2013 when the Earth had essentially no magnetic field.<\/p>\n

This is dangerous for life since the planet\u2019s magnetic field extends far into space and creates a protective bubble around Earth, shielding the planet\u2019s surface from the hurricane of particles of the Sun\u2019s \u2018solar wind\u2019 and higher energy \u2018cosmic ray\u2019 particles from deep space.<\/p>\n

Normally, these are safely funnelled down at the poles, creating the auroras. Without a protective field, such deadly radiation would increase the mutation rate of living cells, leading to cancers in animals. Nevertheless, life has weathered large numbers of such events before without being wiped out.<\/p>\n

How stable is Earth\u2019s magnetic field?<\/strong><\/h2>\n
\""How\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
\u00a9 Getty Images<\/span><\/figcaption><\/div>\n

The fact that the Earth\u2019s magnetic field depends on electric currents carried by molten material circulating in the planet\u2019s turbulent interior means it is inherently variable, as demonstrated by the present wandering of the magnetic north pole (the magnetic south pole is, surprisingly, not wandering as fast).<\/p>\n

But what is remarkable is that the magnetic field generated by such violent internal convulsions is relatively stable 99.9 per cent of the time. It is the stability of the Earth\u2019s magnetic field, and the reliability of the protection it has provided, that has enabled life on Earth to persist for almost at least 3.8 billion years.<\/p>\n

How do animals use the magnetic field to navigate?<\/strong><\/h2>\n
\""How\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
\u00a9 Getty Images<\/span><\/figcaption><\/div>\n

Many creatures demonstrate remarkable feats of navigation. The suspicion has therefore arisen that they have some kind of magnetic sense, enabling them to detect the magnetic field lines between the poles. Pinpointing the mechanism, however, has proved difficult. But progress has been made in 2021 by Japanese scientists investigating a process discovered many years ago.<\/p>\n

In the 1970s, Richard Blakemore, a graduate student in the US, observed single-celled organisms streaming in a fixed direction in a muddy pond and showed they were responding to a magnetic field. Biologists later discovered that such single-celled organisms contain tiny bags of magnetic iron oxide or iron sulphide.<\/p>\n

Now, Noboru Ikeya and Jonathan Woodward at the University of Tokyo have shown that a magnetic field causes chemical changes that can affect cellular behaviour<\/a>. They achieved this with the aid of a cellular chemical that fluoresces depending on the external magnetic field. When they waved a magnet near cells, the chemical dimmed by up to 3.5 per cent.<\/p>\n

Read more:<\/strong><\/p>\n