We all know how hard it can be to swat flies, but nobody knew how they pull off their incredible evasive manoeuvres. Now high-speed photography reveals that flies steer like helicopters, despite not having rotors.

Using cameras operating at 7500 frames a second, plus a winged robot, of the University of Washington in Seattle and his colleagues studied how flies respond to approaching threats. First they presented fruit flies () with an expanding dark circle on a screen, simulating a looming predator. The flies made rapid banked turns with just a few wingbeats.

“Astonishingly quickly, flies can compute where a threat is coming from and, like an aircraft, generate an evasive manoeuvre in the right direction,” says team member , also at the University of Washington. “They do this by very tiny changes in wing motion.”

Turn turn turn

Whereas aeroplanes can steer by swivelling about an axis that runs from nose to tail, almost like a car, flies do something different. They simultaneously roll their body and angle it either up or down while accelerating to make a speedy getaway.

It resembles how helicopters steer, says Dickinson. To turn, a helicopter tilts itself in the intended direction of travel. Aeroplanes also do this when they bank.

To confirm that they had understood what the fruit flies were doing, the team programmed a winged robot to mimic the flies. Its wing movements created the same turning forces as flies generate.

“Fruit flies turn to avoid fast-approaching objects in the same way as any air or space vehicle,” says of the University of Oxford, who was not involved in the research. “What’s remarkable is the rapidity of the response, and the subtlety of the changes the flies make to their wingbeat when turning. The flies start turning away from approaching threats in half the time it takes you to start blinking at a camera flash, and finish throttling up in one-fiftieth of the time it takes you to complete that blink.”

So what is the best way to swat a fly? “It’s quite simple,” says Dickinson. “You just have to be very fast.”

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Could you tell a new violin from a 300-year-old Italian Stradivarius? If not, you’re in good company: neither can the very best violin soloists.

Many musicians regard vintage violins as superior, especially those by the master builder Antonio Stradivari. His instruments are considered to have exquisite tone, perhaps a result of the wood preservation techniques used in 17th- and early 18th-century Italy.

and colleagues at the Jean Le Rond d’Alembert Institute in Paris wanted to test whether Stradivariuses really are superior.

They presented 10 musicians with six new and six old violins, including five by Stradivari. While wearing modified welder’s goggles and under dim light, the musicians played each violin in a rehearsal room and a 300-seat concert hall. The new violins were also given antique touches to disguise them. Each test lasted 1 hour and 15 minutes.

More playable

Asked to choose a violin to replace their own for a hypothetical concert tour, six of the musicians selected new ones. The whole group did no better than chance in picking out which violins were old and which new, but tended to rate newer ones as more playable.

“Even though soloists readily separated violins they liked from those they did not, they couldn’t reliably tell old from new,” says , a modern-day violin maker based in Ann Arbor, Michigan. “This implies whatever tonal qualities top players happen to be looking for, they don’t seem to be related to an instrument’s age or country of origin.”

The results build on a that took place in a hotel room in Indianapolis, Indiana. This time around the musicians were top-level soloists and had more time to test a wider selection of violins, in more relevant settings.

Fritz is cheered by the findings as she says it vindicates the skill of present-day violin-makers. “It also allows young soloists to be recognised by how they play, rather than what they play,” she adds.

Final word?

It’s unlikely to be the final word. Joseph Nagyvary, a professor emeritus at Texas A&M University in College Station who studies the chemistry of violins, isn’t convinced. He says that players need to play a violin for weeks to evaluate it fully, and that the study did not take into account that Stradivariuses vary in tone. “Experts know well that the 600 or so extant Strads vary vastly in their tone quality due to their playing and preservation history,” says Nagyvary, who is also a maker of modern-day recreations of Stradivarius and Guarnerius violins.

However, , one of the musicians who took part in the study, says he doesn’t believe it was biased. “One can argue that the old instruments selected were intentionally ‘weaker’ than the new ones chosen, or that the new instruments were set up optimally versus the old, which were ‘tired’,” he says. “But I think these are elements that players face each time they walk into a violin shop.”

Fritz says some soloists were frustrated that they did not get to see the violins at the end of the study, and were surprised to learn that their favourite violins were new ones.

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(Image: Ben Birchall/PA Wire/Press Association Images)

Relax, puny humans – it may look like a prototype evil Terminator, but this android has come to help. Its job is to test equipment for the UK’s armed forces.

The robot, Porton Man, is named after the home of the in Porton Down in southern England. It possesses an impressive range of movement – Porton Man can march, run and lift its arm to sight a weapon, just like an infantry soldier.

Porton Man’s designers used technology from Formula 1 racing cars to give the android tough, lightweight carbon-composite body parts. It carries more than 100 sensors, allowing technicians to study the performance of equipment such as chemical, biological and radiological protection suits.

Future soldiers may have reason to thank Porton Man for better protection against nerve agents such as sarin gas. To find out more about military technology, have a look at the most recent articles in our Topic Guide.

Fragile things can be useful. Earth’s surface is a lively place, made up of shifting plates of rock. Now it seems the surface only moves because it is partly made of flimsy rocks that have been damaged in the planet’s heart.

Uniquely in the solar system, Earth’s crust is divided into several sections. These tectonic plates move over millions of years, throwing up mountains and triggering earthquakes. Often, one plate gets forced under another and sinks into the mantle beneath, a process called subduction. Elsewhere, new material is brought to the surface. If the plates did not recycle themselves like this, our planet might not have such a stable climate, or be so rich in the chemicals vital for life.

So the beginning of plate tectonics is a critical event in our planet’s history. But it is unclear how the plates first started to move, or when. The first subduction seems to have happened about 4 billion years ago, but clear evidence that all the plates were moving and subducting only appears 3 billion years ago.

To explain this delay, of Yale University and of the University of Lyon in France studied how rocks behave on a small scale, and then extrapolated to the planet as a whole.

Crumbling rocks

Bercovici and Ricard modelled what happens to rocks in the upper mantle, just below the plates. There, the strong currents shrink the grains that make up rocks, a bit like the way stirring foam makes smaller bubbles. As a result, weak zones form and grow.

Over time, more and more of these damaged rocks build up in the upper mantle, and eventually are thrust back up to form new sections of plate.

Because these new plates are partly made of fragile rocks, their edges are more breakable, making it easier for one plate to be forced under another.

Bercovici suggests that the first rocks underwent subduction 4 billion years ago, and over the next billion years were gradually damaged in the mantle and got reincorporated into the surface plates. By 3 billion years ago, the plates were fragile enough that subduction could get going in earnest.

Only on Earth

“Their model makes intuitive sense,” says of the University of Bayreuth in Germany. “They take things one step further and show quantitatively that it can work.”

McCammon says that, although we will probably never know for sure how plate tectonics began, Bercovici and Ricard’s model offers a plausible story.

The model could help to explain why Earth is the only planet known to have active plate tectonics. The key is that true plates can only evolve from weak zones in rocks. Venus’s surface atmosphere, for example, is much hotter than Earth’s, so its weak zones heal faster, stopping tectonic activity before it starts.

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(Image: NASA, ESA et al.)

It’s not something in your eye. It’s not smoke from a late-night barbecue. You’re looking at a map of the most massive ancient galaxy cluster ever seen.

Astronomers nicknamed the cluster El Gordo (“the fat one” in Spanish) in 2012, when they estimated its mass. Now, after analysing images from the Hubble Space Telescope, they think it’s 43 per cent fatter still, with a mass as much as 3000 times that of the Milky Way.

Hubble’s images revealed the mass of the galaxy cluster, officially catalogued as ACT-CL J0102-4915, through the phenomenon of gravitational lensing. El Gordo‘s immense gravity warps space – like a distorting mirror at a funfair – and thus also the appearance of background galaxies. The amount of warping tells us how much mass is locked up in the cluster.

Light from the hundreds of galaxies in the cluster began its journey to us 9.7 billion years ago. We know that clusters this big have existed more recently, but El Gordo is the first one seen from such an early time in the universe’s 13.8-billion-year history.

The image above combines Hubble’s visual-light observations with X-ray emissions seen by the Chandra space telescope (in red) and a map of the cluster’s mass (the blue smoke).

Video: Bionic kangaroo bounces on blades

Forget ominous drones and creepy robots, there’s a kangaroo-inspired robot in town and it’s cheerfully bouncing your way.

The BionicKangaroo was developed by , an industrial automation company based in Esslingen am Neckar, Germany. Elastic springs in each leg store energy on landing, just like the tendon in a kangaroo’s leg, allowing the robot to mimic the inexhaustible jumping of the real thing.

The robotic roo weighs just 7 kilograms, stands 1 metre high, and each leap can lift it 40 centimetres into the air and propel it 80 centimetres forward. It is controlled by an armband that lets someone direct it with the wave of an arm.

The BionicKangaroo is the latest member of a menagerie of animals built by Festo for its annual Bionic Learning Network project, which aims to learn from nature to develop better ways of gripping, moving and controlling things in factories.

Past creations include a flying SmartBird, a swimming penguin, a flying object that propels itself by flipping inside out and a robotic elephant trunk that trains itself.