Earth's tectonic plates have doubled their speed

SO MUCH for slowing down as you age. Earth's tectonic plates are moving faster now than at any point in the last 2 billion years, according to the latest study of plate movements. But the result is controversial, since previous work seemed to show the opposite.

If true, the result could be explained by another surprising recent discovery: the presence of more water within Earth's mantle than in all of the oceans combined.

Plate tectonics is driven by the formation and destruction of oceanic crust. This crust forms where plates move apart, allowing hot, light magma to rise from the mantle below and solidify. Where plates are being pushed together, the crust can either rise up to form mountains or one plate is shoved under the other and is sucked back into the mantle.

The planet's inner heat powers plate tectonics. That heat is ebbing away as Earth ages, and this was expected to slow plate motion. A study last year by Martin Van Kranendonk at the University of New South Wales in Sydney, Australia, and colleagues measured elements concentrated by tectonic action in 3200 rocks from around the world, and concluded that plate motion has been slowing for 1.2 billion years.

Now Kent Condie, a geochemist at the New Mexico Institute of Mining and Technology in Socorro and his colleagues have used a different approach and concluded that tectonic activity is increasing. They looked at how often new mountain belts form when tectonic plates collide with one another. They then combined these measurements with magnetic data from volcanic rocks to work out at which latitude the rocks formed and how quickly the continents had moved.

Both techniques showed plate motion has accelerated. The average rate of continental collisions, and the average speed with which the continents change latitude, has doubled over the last 2 billion years (Precambrian Research, doi.org/vbv).

"We expected to find that the average speed would be slowing down with time, but we didn't get that. Both speeds were going up," says Condie. "It was a surprise."

Condie thinks the mantle's huge store of water could explain the finding. When crust sinks back into the mantle, oceanic water gets sucked down too, and although most comes back to the surface in volcanic emissions, over the aeons the store of water in the mantle has grown vast.

Some of this water forms hydrous minerals that essentially make the mantle more runny, says Condie, speeding up the flow of rock. The effect is strong enough to overcome the stiffening of the mantle caused by the gradual cooling inside Earth, he says.

Peter Cawood at the University of St Andrews in the UK thinks the work is interesting and provocative. "The overall increase in the rate of plate motion with time seems real and believable," he says, and could well be linked to changes in the mantle's water content – although convincing sceptics that plates move faster now will be difficult without more data, he adds.

Van Kranendonk is not ready to change his mind. "Our paper documents a reduction in the rate and volume of crustal recycling for 1.2 billion years, supporting the idea that plate tectonics actually has been slowing down since that time," he says.

This article appeared in print under the headline "Earth's tectonic plates in high-speed controversy"

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Voyager 2's view of solar system's edge will be unique

Earth's second emissary to interstellar space, Voyager 2, is phoning home with new views of the solar system's ragged edge. But what it sees could be very different to what its predecessor glimpsed, revealing new details of the sun's immediate neighbourhood.

Voyager 2 has reached the heliosheath, the beginning of the end of the solar system. If the experience of its twin, Voyager 1, is anything to go by, Voyager 2 is about two-thirds of the way to the heliopause – the outer edge of the sun's influence, also considered to be where interstellar space begins. Voyager 1 crossed this boundary two years ago this week, according to NASA and most Voyager scientists. Not everyone agrees, though, because readings sent back by Voyager 1 left a little room for doubt.

One clue that Voyager 1 had passed the heliopause was that its instruments measured a slowing, sparser solar wind. That's not happening yet for Voyager 2, says Rob Decker at Johns Hopkins University in Maryland.

Windsock-shaped sphere

That could be because the sun's sphere of influence isn't a sphere. Solar radiation blows a bubble of charged particles about 15 billion kilometres in radius, but the sun's motion through the galaxy gives that bubble a windsock shape, with a rounded part in the direction of travel and a tail trailing behind. Voyager 1 is moving in the same direction as the sun, but Voyager 2 – 3 billion kilometres behind – is headed more sideways and down.

In addition to the sun's motion, particles and plasma from interstellar space might be deforming the bubble, Decker says. As a result, it could take longer for Voyager 2 to reach interstellar space – or it could happen sooner, notes Ed Stone, chief Voyager scientist at NASA. Voyager 2 crossed the termination shock, another physical boundary signifying the heliosheath, about 1.5 billion kilometres before anyone expected, he says, so it's hard to make firm predictions about what it will do in the future.

When Voyager 2 does cross the heliopause, its exit will be definitive, Decker and Stone say. Voyager 1's plasma sensor broke down sometime in the 1980s, but the younger probe's still works. The sensor will detect the change between the sun's sphere of influence, which is warm and less dense, to the interstellar medium, which is cold and denser by a factor of 40. That means Voyager 2's observations will be much clearer.

"We're very fortunate to have a second spacecraft," Stone says.

Journal reference: The Astrophysical Journal, DOI: 10.1088/0004-637X/792/2/126

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Emailing angry? Your keyboard feels your pain

FACEBOOK, email, texting, instant messaging – more of our life than ever is lived through our keyboards. Communicating emotion through type can be hard, though.

That could be about to change. By measuring the way someone is typing – the speed, rhythm and how often they use backspace – and then combining that information with an emotional analysis of the typed text, a computer program has been able to predict how they are feeling with 80 per cent accuracy.

Nazmul Haque Nahin and colleagues at the Islamic University of Technology in Bangladesh asked volunteers to type phrases presented to them on a screen, including passages from Alice's Adventures in Wonderland. First they built a model by measuring and recording information on how people type while also asking them how they were feeling – joyful, guilty, disgusted or tired, for example. When the volunteers were asked to carry out the task a second time, the software used this model to predict how a person was feeling as they were typing.

Tested on different emotions, the program successfully detected joy 87 per cent of the time, while anger was identified 81 per cent of the time (Behaviour and Information Technology, doi.org/vbt).

This isn't the first attempt to measure emotions through a keyboard. A team led by Clayton Epp at the University of Saskatchewan in Canada found that anger and excitement were the easiest emotions to detect, because they were only expressed for short periods of time.

"The objective is a good one," says Joshua Feast, CEO of Cogito, a firm that provides behaviour and voice analytics. "These types of tools can provide automated feedback to individuals to increase self-awareness."

Although monitoring typing comes with overtones of surveillance, Feast says there are lots of useful applications, such as alerting people when they are typing an email while angry.

Epp foresees an "emotional instant messaging client": an app that works like a more sophisticated form of emoticon. Subtle cues would alert the recipient to the emotional message's tone, allowing people to communicate more naturally.

This article appeared in print under the headline "Emailing angry? Your keyboard feels your pain"

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Beautiful spiral cracks could be a feature, not a flaw

UNUSUALLY beautiful and uniform cracks that form in high-tech materials could be used to manufacture micro-patterned surfaces.

Joël Marthelot of ESPCI ParisTech in France and his colleagues noticed the cracks when studying thin films of silicate materials, which are used as a coating inside lasers.

If the coating doesn't quite stick to the surface below, cracks can form that spiral around a central point or that etch out regular rows of crescents. Optical effects caused by the film lifting from the surface produce watercolour-like hues.

Other researchers had seen these cracks in similar materials, but no one had studied how they formed. Investigating further, Marthelot and his colleagues realised that a combination of elastic energy within the film and the process of peeling away from the underlying surface makes an initial crack replicate itself an interval that depends on the thickness of the film (Physical Review Letters, doi.org/vb5).

These regular patterns could be useful in processes such as creating microscopic channels for transporting liquids. "Usually fracture is seen as failure and something you have to avoid," says Marthelot, who is now at the Massachusetts Institute of Technology. "We can think about using such cracks as tools to make patterns at small scales."

"It's a nice piece of work, the pictures are beautiful," says Nicolas Vandenberghe of Aix-Marseille University in France. "Maybe cracks will become a useful process to manufacture or design specific things."

This article appeared in print under the headline "Spiral cracks are a feature, not a flaw"

Correction, 28 August 2014: When this article was first published, the affiliation for Joël Marthelot was incorrect.

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Feedback: Tipping the quantum scales

Feedback is our weekly column of bizarre stories, implausible advertising claims, confusing instructions and more

INSPIRED by reports of experiments that show ever-bigger objects demonstrating quantum properties, Andrew Scott would like to propose some further research. The largest object that Feedback is aware of having gone through two points "at once" is a "buckyball", the near-spherical carbon-based molecule that is just visible under a microscope (8 May 2010, p 37).

Andrew is "wondering what would happen if we tried to narrow down the size range for quantum effects", working down from larger objects. He suggests that "we could begin by letting cats wander through two cat flaps towards a wall smeared with catmint and record the points they touch first". Funding, anyone?

"There is a fault with departure screens," read a display at Dewsbury station: "please disregard the information shown." So they were working?

FURTHER, reports of experiments ...

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Let's talk about the weather to revive climate debate

Explaining how climate change is affecting today's weather will be tricky, but it might bring home to the public the everyday reality of global warming

LULL in the conversation? You can safely bring up the weather – no matter who you're chatting with, no matter where in the world you are. Unless you're talking to a climate scientist, that is.

Unlike the rest of humanity, climate researchers have long avoided discussing what's going on outside the window – be it a heatwave or cold snap, drought or deluge. Their studies have revealed that the weather will change dramatically over the long term, but they shy away from what it's doing right now.

That's changing. Thanks to advances in climate modelling, researchers can now assess how much more or less likely climate change has made individual extreme weather events. With enough computing power, this could even become part of your daily weather report (see "And now the weather, featuring climate change blame").

Those driving this effort hope that discussing climate change in the context of today's weather, rather than last year's, will help make it more tangible to a largely confused or indifferent public. Will it? You could argue that when describing a system as complex, variable and chaotic as Earth's climate, it's a good strategy to avoid sweating the small stuff and focus on the big picture: the ample evidence that pumping greenhouse gases into the atmosphere is causing the planet to warm, in turn causing the climate to change – with profound consequences (New Scientist, 7 December 2013, page 34).

The problem, of course, is that this picture has failed to stir much of the public to action: "global warming" still appears far down the list of US voters' priorities, for example. Climate change, as it is usually presented, falls squarely into the category of problems we find it hard to engage with – a seemingly remote threat calling for immediate sacrifices (16 August 2014, page 24).

The effects of the weather, on the other hand, are far more visceral: we don't need much persuasion to take an umbrella out when clouds loom. In fact, in recent years public opinion has been quick to attribute freak weather events to climate change. This may or may not have been warranted, but it does suggest that many people would be receptive to meteorologists revealing human fingerprints on the weather.

How much of this laypeople will really understand is a different question. Talk of climate change "increasing the likelihood" of a weather event, rather than simply "causing" it, is potentially confusing, but blurring the distinction would be disingenuous at best and dishonest at worst.

It will provide fodder for scepticism, too, of both the naive and calculated varieties. The unfair but enduring dictum that the weather forecast always gets it wrong is likely to be aired frequently, while those motivated to deny climate change will seek to highlight "anomalies" in the hopes of muddying the water, just as they gloat meaninglessly over every cold snap now. Lawyers, politicians and businesses will weigh in as and when it suits them.

All this potential for sound and fury should not obscure the value of talking about climate change in everyday contexts. In fact, the potential to reinvigorate the conversation is its value. Empty "debate" over the actuality of climate change has nothing to offer, so it's time to find a fresh topic. How's the weather where you are?

This article appeared in print under the headline "Stormy weather ahead"

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3D-printed books make pictures real for blind children

TIME to get hands-on. A new project is printing Braille picture books for visually impaired children. Each page turns the pictures from the original book into raised 3D shapes alongside traditional Braille text.

"The advantage of 3D-printing is really about making one-of-a-kind objects," says Tom Yeh, who heads up the Tactile Picture Books Project at the University of Colorado at Boulder. Later this year, Yeh's group will work with the National Braille Press in Boston to offer children a copy of Dragons Love Tacos by Adam Rubin that has a page customised with the child's name in Braille.

Over the past few months, the team has used this method to print children's classics like Goodnight Moon and The Very Hungry Caterpillar. Copies were given to children at the Anchor Center for Blind Children in Denver. In the future they hope people can print their own Braille stories on demand.

The 3D-printed books can be rather fragile, says Alice Applebaum, the centre's executive director. But she is excited about the possibility of using Yeh's books to help students learn to read. "Since our children have limited or no vision, having a book that they can feel gives them a sense of what the world looks like," Applebaum says.

This article appeared in print under the headline "3D printed books get personal for blind children"

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A to zinc: What supplements are worth taking?

(Image: Angus Greig)

Vitamins, minerals, fish oils… the list of nutritional supplements you can buy keeps growing. Some are worth it, some aren't. We sift the evidence for you

IN 1911, Polish chemist Casimir Funk made one of the most influential biomedical discoveries of all time. He learned that a disease called beriberi affected those who ate a diet of mainly white rice, but not those who ate mostly brown rice. He isolated a chemical from rice bran, showed it could prevent beriberi, and called it "

We now call that compound vitamin B1. It is one of many essential nutrients that the human body cannot produce in sufficient quantities and that we must obtain from food. Casimir's breakthrough led to similar discoveries, including the compounds that prevent scurvy and rickets. In 1920, the British chemist Jack Cecil Drummond proposed dropping the "e" and using ...

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Taming of the bunny rewrote rabbit genome

When humans tamed rabbits, we changed around 100 regions of their genome. The shifts were subtle, but they may have made domestic rabbits less fearful than wild ones.

Pet rabbits will happily sit in their owner's lap, but wild rabbits are famously timid, fleeing at the slightest hint of a human, let alone a fox or hawk. This tolerance for human company was only bred into bunnies recently: about 1400 years ago in southern France. But it was not clear how this worked at the genetic level. Did domestication make drastic changes to a few important genes, or many subtle alterations?

To find out, Leif Andersson at Uppsala University in Sweden and his colleagues compared the genomes of pet rabbits with those of their wild counterparts (Oryctolagus cuniculus ) from Spain and southern France.

No genes had been turned off outright, a process that in theory might have helped reduce fear of humans. "Gene loss has not played a prominent role during rabbit domestication," says Andersson.

Instead, the team found that lots of small, pre-existing genetic variations became more common in rabbits as they were domesticated. Most of these variations involved just one letter of DNA code. All in all, about 100 regions were selected to be different in the domesticated rabbits.

Tamer switch

Rather than affecting the genes themselves, most of the DNA tweaks were in regulatory regions of the genome, which control whether genes are switched on or off. "Wild and domestic rabbits do not differ so much in actual protein sequences, but in how gene and protein expression is regulated," says Andersson.

The genetic shifts were often associated with regions of the genome involved in the development of neurons and the brain. That makes sense, says Andersson, considering the differences in behaviour between domestic and wild rabbits.

"Selection during domestication might have focused on tameness and lack of fear," says Pat Heslop-Harrison of the University of Leicester in the UK. "As a farmer, you neither want the animal to hurt you, nor for the animal to die from stress." Keeping lookout and fleeing from potential predators uses up lots of an animal's energy, which humans would rather see turned into meat.

Because rabbits were only domesticated relatively recently, the new sequences are not all present in all domestic rabbits. As a result, Andersson says escaped domestic rabbits could revert to wild-like forms over just a few generations - assuming they survived in the wild.

Journal reference: Science, DOI: 10.1126/science.1253714

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Moving home? Your microbes will make the trip too

You may forget your toothbrush next time you go away but you can't leave your microbes behind. Millions of bacteria hitch a ride with you, making themselves comfortable wherever you go. Within only a few hours, they will have colonised a hotel room; give them 24 hours and they can take over an entire house.

These are just some of the results from the Home Microbiome Study, the first attempt to trace the path of microbes from our bodies to our built surroundings, and vice versa. "We know that some microbes can increase our weight, we know that some can influence our neurological development, we want to know where those bacteria come from," says Jack Gilbert from the University of Chicago, who leads the work.

The cells of our bodies are outnumbered 10 to 1 by the microbial cells that call our bodies home. Every time we breathe, sneeze or cough we leave traces of these microbial hangers-on. Others are left behind as we shed skin cells or touch surfaces. Given how much time we spend there, most of this microbial shedding is done at home. Despite this, we know surprisingly little about the interaction between our bodily microbes and those in our houses.

Microbial censor

To shed some light, Gilbert and his colleagues mapped the microbial signatures of seven human families, including three that were in the process of moving house. The families came from different parts of the US and were from different socioeconomic backgrounds and ethnicities. Over a period six weeks, the team took repeated swabs of the 18 family members' feet, hands and nose. They also took samples from door knobs, floors, light switches and kitchen counter surfaces, as well as from any pets.

By amplifying and sequencing the genetic material in these swabs, the team isolated more than 21,000 different microbial species. Each family had its own distinct microbial signature that could be used to identify them. This signature was quickly transferred to the family's living space, overwhelming the microbes already there. For example, one of the families moving house temporarily stayed in a hotel room. According to Gilbert, it took just 3 hours for their microbial signature to swamp the room, and less than 24 hours after they moved in to their new house for it to resemble their old one microbially.

Unsurprisingly, microbes transfer most commonly between hands and doorknobs, light switches and kitchen counters, and between floors and feet. Floor samples differed most between families. The smallest microbial variation between people was found between those in regular close contact, like couples, or parents and young children. There was greater variation between separate adults, for example, unrelated flat mates, and teenagers and their parents.

Young children, or people whose gut microbiota have been compromised by antibiotic use, for example, readily "accept" the microbes of others. Household pets were particularly good microbe "donors" – which persuaded Gilbert and his wife to buy a dog to increase the exposure of their family to a greater diversity of microbes, because this has been shown to reduce vulnerability to allergies.

The bugs are watching you

Gilbert says the research could be used to chart people's movement around a house, and monitor their interactions. "We could tell how many individuals live there, and the relationship between them," he says.

He recounts one case where a couple shared their home with a male lodger. Through analysis of the microbial samples from different parts of the house, the researchers could tell that the two men shared a bathroom, but the woman used another – a fact confirmed later by the couple. Theoretically, Gilbert says, analysis of microbial swabs could be used to detect a new relationship or uncover a cheating partner. If a database of people's microbial profiles was ever created, a microbial signature or "fingerprint" could perhaps be used to identify criminals.

In the shorter term, such work could be used to recognise the presence of burglars in the house from an influx of unfamiliar microbes, or recognise alien microbes left on the skin of a homicide victim by the perpetrator – something that Gilbert is now working on in collaboration with the police department of Hawaii.

Journal reference: Science, DOI: 10.1126/science.1254529

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