A map generated by ESA's Swarm array, detailing changes in the Earth's magnetic field - red is strengthening, blue is weakening. Image: ESA/DTU Space
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Get ready for the Earth's magnetic field to flip over

New satellite data has indicated that the Earth's magnetic field is weakening, ahead of a rare - but regular - event.

It's still somewhat surprising to think that plate tectonics has only been an accepted and established for roughly 50 years. That is, our understanding of the structure of atoms was more sophisticated, earlier, than our understanding of the planet we live on. Though, that's maybe unfair; as much as scientists could infer the existence of plate tectonics from, for example, the similarities between the coastlines of Africa and South America, gathering evidence to prove that the Earth has a crust floating on a molten mantle was somewhat difficult. (And it meant that the person credited as the modern theory's originator, Alfred Wegener, was considered a crank for years before the establishment changed its mind.)

After the Second World War, scientists were given the chance to use submarine-detecting devices for peaceful research missions, mapping the ocean floor. In the early 1960s a series of papers were published on the magnetic properties of the undersea world, with some surprising findings - it appeared that some places appeared to have ocean floor with a magnetic field that was the reverse of the Earth's. This chimed with the experience of fisherman living off volcanic islands, who have known for centuries that some patches of ocean can cause the north point of a compass to suddenly switch and point south; and it was consistent with magnetic rocks on land that also seemed to have the "wrong" magnetic polarisation.

Yet what became clear when those patches of irregularity were mapped, across the whole of the Atlantic and Pacific, was that they weren't randomly allocated patches - rather, it became clear that the ocean floor was laid out in long, symmetrical stripes of magnetism, emanating from faults like the Mid-Atlantic Ridge. It was clear that magma was coming up from inside the planet, magnetised with a certain polarity, and then cooling and forming new rock as two tectonic plates moved apart from each other; and that every time the Earth's magnetic field flipped, it reversed the polarisation of the magma that was becoming new sea floor. It was a key discovery in confirming the theory of plate tectonics.

It might be a surprise to hear that the Earth's magnetic field flips over, but it does - every few hundred thousand years, the field weakens, then suddenly (which is relative in this context, on the order of a few hundred years) what was north-facing becomes south-facing, and what was south-facing becomes north-facing. We monitor the Earth's magnetic field with satellites these days, and the European Space Agency's Swarm array has noticed it weakening more significantly than expected:

Measurements made over the past six months confirm the general trend of the field’s weakening, with the most dramatic declines over the Western Hemisphere.

But in other areas, such as the southern Indian Ocean, the magnetic field has strengthened since January.

The latest measurements also confirm the movement of magnetic North towards Siberia.

Rune Floberghagen, the mission manager for Swarm, told Live Science that this new data could mean that a flip is due within the next few hundred years, contrary to earlier estimates of around 2,000 years from now.

We don't yet know whether this is signifying a "proper" flip like the Brunhes–Matuyama reversal of nearly 800,000 years ago, or a more temporary one like the one that occured roughly 40,000 years ago during the last ice age, but which only lasted for slightly more than 400 years. This is in part because we still aren't totally sure why these reverses even happen at all. The poles wobble anyway, and it could be that the molten core of the Earth is a bit like a spinning top, occasionally changing its pattern of movement and falling over; or it could be because of large chunks of mantle nearer the surface "fall" into the centre periodically, causing turbulence that throws things off.

Regardless, the changing of the magnetic field is not a cause for alarm, even if the magnetic field is largely responsible for protecting us all from the worst effects of cosmic radiation. This is because the magnetic field does not entirely disappear - it just weakens. There are some who theorise that these events have been linked with mass extinction events, but the evidence is tenuous at best.

Ian Steadman is a staff science and technology writer at the New Statesman. He is on Twitter as @iansteadman.

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Autism and gut bacteria – the surprising link between the mind and the stomach

A recent paper has found that autistic-related social patterns can be reversed when one species of gut bacteria is present in the microbiome of mice. 

Autism – a developmental disorder that causes impediments to social interactions and behaviour – is usually linked by scientists to abnormalities in brain structure and function, caused by a mix of genetic and environmental factors. Scientists have almost always attempted to understand the way autistic people process the world around them by looking to the mind.

According to the National Autistic Society, “There is strong evidence to suggest that autism can be caused by a variety of physical factors, all of which affect brain development; it is not due to emotional deprivation or the way a person has been brought up.”

Recently, however, a lesser-known link to autism has gained traction. This time, the link is not found in the brain but in the gut.

Reporting their findings in the journal Cell, researchers from the Baylor College of Medicine, Texas, found that the presence of a single species of gut bacteria in mice could reverse many behavioural characteristics related to autism.

In the digestive tracts of humans and other animals, there exists a complex, symbiotically integrated network of trillions of microorganisms known as the “gut flora” or “microflora”. The idea that all these bacteria and microorganisms have taken up a home in our gut may initially seem startling, but they serve a number of beneficial purposes, such as aiding digestion and offering immunity from infection.

The potential link between gut flora and autism arose as researchers identified the increased risk of neurodevelopmental disorders, such as autism, among children born from mothers who were obese during pregnancy. The microflora of obese people is demonstrably different from those who are not obese, and as a result, connections have been made to the gut issues often reported in autistic people.

The senior author of the study and neuroscientist Mauro Costa-Mattioli said: “Other research groups are trying to use drugs or electrical brain stimulation as a way to reverse some of the behavioural symptoms associated with neurodevelopmental disorders – but here we have, perhaps, a new approach.”

To determine what the differences in gut bacteria were, the researchers fed 60 female mice a high-fat diet, with the aim of replicating the type of gut flora that would be found among people consuming a high-fat diet which would contribute to obesity. A control group of mice was fed a normal diet to serve as comparison. The mice in each group then mated, and their eventual offspring then spent three weeks with their mothers while being observed to see how behaviour and microflora was affected.

It was found that the offspring from the mice laden with high-fat foods exhibited social impairments, including very little engagement with peers. Meanwhile, a test called ribosomal RNA gene sequencing found that the offspring of the mice that were fed a high-fat diet housed a very different bacterial gut environment to the offspring of mice fed a normal diet.

Discussing the result, co-author Shelly Buffington was keen to stress just how significant the findings were: “By looking at the microbiome of an individual mouse we could predict whether its behaviour would be impaired.”

In an effort to understand whether the variation in microbiome was the reason for differences in social behaviour, the researchers paired up control group mice with high-fat diet mice. Peculiarly, mice eat each other’s faeces, which is why researchers kept them together for four weeks. The high-fat diet mice would eat the faeces of the normal mice and gain any microflora they held. Astonishingly, the high-fat diet mice showed improvements in behaviour and changes to the microbiome, hinting that there may be a species of bacteria making all the difference.

After careful examination using a technique called whole-genome shotgun sequencing, it was found that one type of bacteria – Lactobacillus reuteri – was far less prevalent in the offspring of high-fat diet mice than the offspring of normal-diet mice.

Discussing the method and finding, Buffington said: “We culture a strain of Lactobacillus reuteri originally isolated from human breast milk and introduced it into the water of the high-fat diet offspring. We found that treatment with this single bacterial strain was able to rescue their social behaviour.”

What the Lactobacillus reuteri seemed to be doing was increasing production of oxytocin, a hormone which is known by various other names such as the “trust hormone”, or the “love hormone”, because of its role in social interactions.

The results of the experiment showing that Lactobacillus reuteri can influence social behaviour are profound findings. Though the work would need to be transferred from mice studies to full human clinical trials to see if this could be applied to autistic people, the impact of adding Lactobacillus reuteri to the gut flora of mice can’t be underestimated. It seems then, for now, that research will go with the gut.