A SELECTION OF MY ARTICLES

A more comprehensive list of articles I have written can be found on Journalisted.com


Tiny membrane converts radio waves to light

05 March 2014

The radio-wave detector in action. (Credit: A Schliesser, T Bagci, A Simonsen and E Polzik)
The radio-wave detector in action. (Credit: A Schliesser, T Bagci, A Simonsen and E Polzik)

A device that detects ultra-weak radio waves by converting them into light signals has been created by physicists in Denmark and the US. The device does not require costly cryogenic cooling and could be put to practical use in a range of applications, from radio astronomy to magnetic resonance imaging. The researchers also believe that the technology could provide an essential building block of a "quantum internet" of the future.

Detecting extremely weak radio waves is at the heart of many modern technologies, including satellite navigation, long-distance communications, radio telescopes and magnetic resonance imaging (MRI) systems. In some detectors, weak radio signals are converted into optical signals that can then be transported long distances via optical fibres. In addition to requiring expensive modulators to convert the electronic signals into optical signals, these converters must be cooled to cryogenic temperatures, making them expensive and inconvenient to operate. ---> Keep reading

Squeeze light to teleport quantum energy

23 Jan 2014

Get back (Credit: Marie Luise Emmermann)
Get back (Credit: Marie Luise Emmermann)

Putting the squeeze on light may be the key to teleporting energy across vast distances. Although the amount of energy that could theoretically be transmitted is tiny for now, it could be enough to power quantum computers that don't overheat.

For years physicists have been smashing distance records for quantum teleportation, which exploits quantum entanglement to send encrypted information. Entangled particles remain linked no matter how far apart they are, and a change to one particle always affects its partner in a particular way. In experiments, for example, a pair of entangled particles is separated and each partner is sent to a different location. When someone measures the particle at point A, its quantum state is decided and that event immediately causes a corresponding change in the particle at point B.

No physical matter is transmitted, and nothing is travelling faster than light. But the person at point B can recreate the photon at point A using only information about the observed changes – effectively teleporting the photon.

Physicists have done this with light and with matter, such as entangled ions. But Masahiro Hotta of Tohoku University in Sendai, Japan, wondered if it would be possible to also teleport quantum energy. ---> Keep reading

Physicists Produce Quantum Version of the Cheshire Cat

22 Jan 2014

This time, the "grin" is the magnetism, and the "cat" - the neutrons
This time, the "grin" is the magnetism, and the "cat" - the neutrons

In Lewis Carroll's famous children's novel Alice's Adventures in Wonderland, Alice meets the Cheshire Cat, which disappears and leaves only its grin behind. Now, physicists have created a quantum version of the feline by separating an object—a neutron—from its physical property—its magnetism. The experiment is the latest example of how quantum mechanics becomes even weirder using a technique called weak measurement and could provide researchers with an odd new experimental tool for performing precision measurements.

In quantum physics, tiny particles can be in opposite conditions or states at the same time, a property known as superposition. For instance, an electron can literally spin in opposite directions simultaneously. Try to measure the spin, however, and that state will "collapse" so that the electron is found spinning one way or the other. That's because quantum theory generally forbids you to measure a particle's state without altering it—at least ordinarily. ---> Keep reading


Ultrafast phase measurements could boost optical computing

17 Jan 2014

Ultrafast laser at the Max Planck Institute of Quantum Optics (Credit: T. Naeser)
Ultrafast laser at the Max Planck Institute of Quantum Optics (Credit: T. Naeser)

Physicists in Germany say they have taken an important step towards the creation of ultrafast computers that use light instead of electrical signals to process information. The team has created the first compact electronic device that can measure the absolute phase of extremely short light pulses. While the device is first expected to find use in laser labs, it could someday play an important role in systems that use ultrashort light pulses to process information.

 

The work was done by Ferenc Krausz and colleagues of the Max Planck Institute of Quantum Optics in Garching. In 2001 a team led by Krausz and colleagues generated and measured the first isolated light pulse lasting only attoseconds – just a billionth of a billionth of a second. Such pulses have since been used to study the motion of electrons inside atoms and they form the basis of the new and burgeoning field of "attosecond physics".

While the technology used to create and characterize these pulses has improved over the past decade, it still involves the use of large and expensive pieces of equipment. ---> Keep reading

Nanotubes give Raman spectroscopy a boost

10 Dec 2013

Raman hot spots (Credit: University of Montreal/Nature Photonics)
Raman hot spots (Credit: University of Montreal/Nature Photonics)

Tiny "tags" made of dye molecules stuffed into carbon nanotubes have been used to develop a high-resolution imaging technique based on Raman scattering. Created by researchers in Canada, the tags boost the weak Raman signal of molecules about one million times. The new approach could lead to improved medical diagnostics and treatments, and could even be used to fight counterfeiting.

Raman spectroscopy involves shining a beam of light onto a solid or a liquid to identify its molecular composition. While most of the photons will scatter from the sample with no change of energy, a small number of photons will exchange a tiny amount of energy by causing molecules in the sample to vibrate. This is called Raman scattering, after the Indian physicist Chandrasekhara Venkata Raman who first observed it in liquids in 1928 and won the 1930 Nobel Prize for Physics for his discovery. ---> Keep reading


Hints of cold dark matter pop up in 10-year-old circuit

03 Dec 2013

If we could see it (Credit: Max Planck Institute For Astrophysics/Science Photo Library)
If we could see it (Credit: Max Planck Institute For Astrophysics/Science Photo Library)

Oops. One of the universe's most-wanted particles may have shown its face in a simple tabletop experiment nearly a decade ago – only no one noticed at the time.

"If other experiments confirm the effect, then it could be an immense step forward in our understanding of the matter contents of the universe," says Christian Beck of Queen Mary, University of London, UK.

Beck has reanalysed an unexplained signal in an electrical circuit, first reported in 2004, and says it is just what you would expect to see if dark matter takes the form of hypothetical particles called axions. It's too soon to known if the signal actually is dark matter, but these circuits -Josephson junctions - may present a promising new way to hunt for the mysterious stuff. ---> Keep reading

A Link Between Wormholes and Quantum Entanglement

02 Dec 2013

Credit: Allen McC./Creative Commons
Credit: Allen McC./Creative Commons

This advance is so meta. Theoretical physicists have forged a connection between the concept of entanglement—itself a mysterious quantum mechanical connection between two widely separated particles—and that of a wormhole—a hypothetical connection between black holes that serves as a shortcut through space. The insight could help physicists reconcile quantum mechanics and Einstein's general theory of relativity, perhaps the grandest goal in theoretical physics. But some experts argue that the connection is merely a mathematical analogy.

Entanglement links quantum particles so that fiddling with one can instantly affect another. ---> Keep reading


Viruses breathe new life into batteries

26 Nov 2013

Viral batteries: improved batteries could be used in electric cars (Credit: Dahyun Oh et al.)
Viral batteries: improved batteries could be used in electric cars (Credit: Dahyun Oh et al.)

Research into lithium–air batteries that may in the future power electric cars and other electronic devices has just received a boost – from a virus. Scientists at the Massachusetts Institute of Technology (MIT) in the US have shown that using genetically modified viruses greatly increases the surface area of nanowires that work as electrodes in a battery's cathode, thereby improving the battery's charge-storage capacity.

A typical battery consists of a cathode, an anode (normally made of lithium), an ion conductor (or an "electrolyte") through which charged ions flow easily, and a separator to keep the two ends apart. An electric current is produced as the positively charged lithium ions move from the anode to the cathode during cell discharge. When a battery is recharged, an external current makes the ions flow in the opposite direction, which results in the ions being stored at the anode. ---> Keep reading

Locust eardrum is a tiny frequency analyser

12 Nov 2013

The locust could inspire new ways of processing sound
The locust could inspire new ways of processing sound

Locusts have a highly integrated and miniaturized hearing system that bears little resemblance to either the human ear or an electronic microphone. That is the conclusion of researchers in the UK who have done a detailed study of how the insects detect and process sounds. The insect's hearing system, which makes use of a nanostructured eardrum to discern between high- and low-frequency sounds, could provide inspiration for the development of tiny microphones or systems for processing human speech.

Locusts and other insects are too small to accommodate the kind of highly developed hearing systems that are found in some larger animals. Mammals, for example, first capture sound with an eardrum, then amplify vibrations through middle-ear bones, and finally transmit these to the cochlea, which functions as a frequency analyser. ---> Keep reading


Why locusts don't need airbags

01 Nov 2013 (Print edition)

(Credit: Shutterstock/VAV)
(Credit: Shutterstock/VAV)

Locusts have been the bane of farmers for centuries. One locust can consume its own body weight in vegetation a day, and in a single plague that struck Ethiopia in 1958, swarms of the insects destroyed 167 000 tonnes of grain – enough to feed a million people for a year. But for the neurobiologist Claire Rind, locusts are also an inspiration. The reason? Their incredible talent for avoiding collisions. Research has shown that locusts can avoid fast-approaching objects as little as 45 ms before a collision – nearly 10 times faster than the blink of a human eye. This ability is crucial to their infamous swarming behaviour: a single swarm can contain millions of insects and may fly 200 km in one day, yet somehow the locusts manage to avoid crashing into each other or triggering airborne mayhem. (Full article in Nov print ed.)

 

Ultracold atoms set the stage for Hofstadter's butterfly

28 Oct 2013

The elusive Hofstadter's butterfly could soon be spotted in lattices of ultracold atoms, now that two groups of researchers have independently created the conditions required for a spectacular fractal pattern to emerge from the energy spectra of ultracold rubidium atoms held in optical lattices. Although neither team has directly observed the fractal pattern, they have created physical systems with the right conditions for Hofstadter's butterfly to emerge. The research could also lead to the development of new ways to simulate quantum systems with exotic electric properties.

In 1976 the American physicist Douglas Hofstadter – famous for the 1979 book Gödel, Escher, Bach – first outlined the concept of the butterfly that bears his name. ---> Keep reading


Strength of gravity shifts – and this time it's serious

11 Sept 2013

The gravitational constant might not be that... constant (Credit: Noël Gaspard/Millennium Images)
The gravitational constant might not be that... constant (Credit: Noël Gaspard/Millennium Images)

Did gravity, the force that pins us to Earth's surface and holds stars together, just shift? Maybe, just maybe. The latest measurement of G, the so-called constant that puts a figure on the gravitational attraction between two objects, has come up higher than the current official value.

Measurements of G are notoriously unreliable, so the constant is in permanent flux and the official value is an average. However, the recent deviation is particularly puzzling, as it is at once starkly different to the official value and yet very similar to a measurement made back in 2001, not what you would expect if the discrepancy was due to random experimental errors. ---> Keep reading

Tiny switch toggles the position of a single atom

11 Sept 2013

One atom thick: current toggles this tiny switch
One atom thick: current toggles this tiny switch

A single atom held between two sharp points has been used to create the smallest-ever memory device – according to the international team of researchers that built it. The aluminium atom operates as a two-terminal switch that can be toggled back and forth between two logical states. This is done by passing electrical currents through the atom, which results in tiny shifts in its position. The device could one day be used to create computer memories with extremely high density.

Conventional electronic switches are usually made of transistors that have three electrodes. The current flowing between two of the electrodes is controlled by applying a voltage to the third electrode. Nanometre-sized transistors based on one atom have been made before. ---> Keep reading


An unearthly answer to the lightning enigma

10 August 2013

A. Gurevich thinks that lightning is triggered by cosmic rays
A. Gurevich thinks that lightning is triggered by cosmic rays

Lightning is a natural electrical discharge – but scientists are still scratching their heads trying to figure out what triggers it. Renowned Russian physicist Alexandr Gurevich tells Katia Moskvitch about his theory, which really is out of this world

What don't we know about lightning?
The main problem is that we don't know how a thundercloud gets the spark needed to initiate a lightning bolt. The biggest mystery is that the electric field in thunderclouds is not very large. Years of experimental measurements from aeroplanes and air balloons have shown that the field is about 10 times smaller than what is needed to initiate lightning. It is not clear how a lightning bolt is born, but the idea is that something has to "seed" it first.

What do we know about how lightning works?
In 1749 Benjamin Franklin discovered that lightning was an electrical discharge between a thundercloud and Earth. ---> Keep reading


Gold-diamond duo takes temperature of single cell

31 July 2013

TALK about bling. Miniature diamonds more usually found in quantum computers, combined with fragments of gold, can be used to measure the temperature of individual cells. That could lead to a more accurate way to kill cancers while sparing healthy tissue – and a new way to explore cell behaviour.

There are already ways to take a cell's temperature, using glowing proteins orcarbon nanotubes. However, these lack sensitivity and accuracy because their components can react with substances inside the cell. 

So Mikhail Lukin at Harvard University and colleagues turned to nanodiamonds, which have defects in their structure that mean they sometimes contain extra electrons. The tendency of these electrons to exist in many states at once, a superposition, makes nanodiamonds promising as the bits, or qubits, of a quantum computer, where superposition enables multiple calculations in parallel. However, these states vary with temperature, which is troublesome for computing. --->Keep reading

Schrödinger's 'kittens' made in the lab from photons

24 July 2013

A quantum object that meows? (Image: Ineke Kamps/Getty Images)
A quantum object that meows? (Image: Ineke Kamps/Getty Images)

Erwin Schrödinger dreamed up the famous thought experiment about a cat that is both dead and alive to demonstrate the absurdity of applying quantum mechanics to ordinary objects. Now two teams have made the closest thing yet to a Schrödinger's cat in the lab – by connecting hundreds of millions of photons via the strange quantum property of entanglement.

"It's not the entanglement of something as big as a cat, but it's at least a kitten," says Seth Lloyd of the Massachusetts Institute of Technology, a quantum physicist who was not involved in the work.

The results, which were presented on 23 July at the Second International Conference on Quantum Technologies, in Moscow, Russia, suggest that the rules of quantum mechanics may extend to much larger objects than we thought – and that this could have practical uses. ---> Keep reading


Fingerprint technique with the help of neutrons

16 July 2013

The Rutherford Appleton Laboratory have decided to work with the bare surface between the ridges of a fingerprint
The Rutherford Appleton Laboratory have decided to work with the bare surface between the ridges of a fingerprint

Researchers in the UK and France have developed a new and extremely sensitive method for visualizing fingerprints left on metal surfaces such as guns, knives and bullet casings. The technique utilizes colour-changing fluorescent films and the team says that it can be used to complement existing forensic processes.

The chance that two people will have identical fingerprints is about 64 billion to 1, which is why law-enforcement agencies rely on fingerprint evidence. Despite advances in detection since the 19th century, only about 10% of crime-scene fingerprint images are of sufficient quality to lead to the unambiguous identification of an individual that is good enough to satisfy a court.

Fingerprints are essentially deposits of sweat and natural oils. ---> Keep reading

Atomic Van der Waals force measured for the first time

4 July 2013

Vad der Waals force is so named after the Dutch scientist Johannes Diderik van der Waals
Vad der Waals force is so named after the Dutch scientist Johannes Diderik van der Waals

Scientists in France are the first to make a direct measurement of the Van der Waals force between two atoms. They did this by trapping two Rydberg atoms with a laser and then measuring the force as a function of the distance separating them. The two atoms were in a coherent quantum state and the researchers believe that their system could be used to create quantum logic gates or to perform quantum simulations of condensed-matter systems.

The Van der Waals force between atoms, molecules and surfaces is a part of everyday life in many different ways. Spiders and geckos rely on it to walk up smooth walls, for example, and the force causes proteins inside our bodies to fold into complicated shapes. ---> Keep reading


Plants Use Quantum Physics to Survive

26 June 2013

Tabletop accelerator shoots cheap antimatter bullets

25 June 2013


Quantum mechanics may enable many of life's processes (Credit: agsandrew/Shutterstock)
Quantum mechanics may enable many of life's processes (Credit: agsandrew/Shutterstock)

Humans can't teleport or reside in multiple places at once — but the tiniest particles of matter can.

These eerie quantum effects have traditionally been studied and observed only under the strictly controlled conditions of a physics lab. That is, until some scientists suggested that such weirdness also exists in wet and soggy biological systems.

In recent years, this hypothesis has gained more and more support, with a new study detailed in the journal Science suggesting plants may rely on such physics to survive. ---> Keep reading

The Crab pulsar, an antimatter factory (Credit: NASA)
The Crab pulsar, an antimatter factory (Credit: NASA)

Make way for the antimatter gun. A tabletop device just 10 square metres in size can spit out energetic bursts of positrons as dense as those kicked out by the giant particle-factories at CERN.

Each positron-packed bullet lasts for just a fraction of a second, so don't expect to fill the tank of your antimatter engine any time soon. Instead the smaller, cheaper machine might help labs around the world study deep-space objects such as powerful radiation jets squirted out by black holes.

Antiparticles have the same mass as their ordinary particle counterparts but carry an opposite charge and spin. --->Keep reading


First glimpse of a single molecule dumping heat

13 June 2013

Gadgets should be sleek and powerful but must not overheat, and that's a big problem for small circuitry. At the nano-scale, weird quantum effects come into play, and uncontrollable temperature fluctuations become seriously limiting.

Now physicists have built a thermometer that can measure the slightest temperature change in circuits the size of a single molecule. The device could help realise the dream of electronics made from graphene, carbon nanotubes and other super-small materials.

The exponential decrease in transistor size seen to date – often referred to as Moore's law – suggests that in one to two decades we should see nano-scale transistors, says Pramod Reddy at the University of Michigan in Ann Arbor.

Without an appropriate thermometer to see how such transistors shed heat, experiments on nanomaterials cannot test theoretical predictions. That makes it hard to control for overheating, which can cause circuits to fail. In the electrical currents that flow in the microcircuits of today's gadgets, the electrons behave like particles and follow classical, predictable laws of heat transfer. But on the molecular scale, electrons are essentially waves, and their behaviour is governed by quantum probability, which makes predicting their behaviour &ndash and thus where they will release heat – much more tricky. Juan Carlos Cuevas at the Autonomous University of Madrid in Spain and his colleagues modified a scanning tunnelling microscope – which allows the manipulation and imaging of atoms – to trap a ring of benzene between the probing tip of the microscope and a flat gold surface. (...) Read original article in full here


Quantum gravity takes singularity out of black holes

 29 May 2013

You might not get turned into spaghetti (Credit: Tom Dymond/Rex)
You might not get turned into spaghetti (Credit: Tom Dymond/Rex)

Falling into a black hole may not be as final as it seems. Apply a quantum theory of gravity to these bizarre objects and the all-crushing singularity at their core disappears.

In its place is something that looks a lot like an entry point to another universe. Most immediately, that could help resolve the nagging information loss paradox that dogs black holes.

Though no human is likely to fall into a black hole anytime soon, imagining what would happen if they did is a great way to probe some of the biggest mysteries in the universe. Most recently this has led to something known as the black hole firewall paradox – but black holes have long been a source of cosmic puzzles.

According to Albert Einstein's theory of general relativity, if a black hole swallows you, your chances of survival are nil. You'll first be torn apart by the black hole's tidal forces, a process whimsically named spaghettification.

Eventually, you'll reach the singularity, where the gravitational field is infinitely strong. At that point, you'll be crushed to an infinite density. Unfortunately, general relativity provides no basis for working out what happens next. "When you reach the singularity in general relativity, physics just stops, the equations break down," says Abhay Ashtekar of Pennsylvania State University.  (...) Read original article in full here

Ultrashort laser pulses squeezed out of graphene

 24 May 2013

Graphene's hexagonal lattice of carbon atoms can absorb laser light like a sponge and then release it in bursts lasting just a fraction of a nanosecond.
Graphene's hexagonal lattice of carbon atoms can absorb laser light like a sponge and then release it in bursts lasting just a fraction of a nanosecond.

Graphene, hailed as one of the thinnest, strongest and most conductive materials ever found, seems to have bagged one more amazing property. Experiments suggest that it can be used to create ultrashort laser pulses of any colour, owing to an ability to absorb light over a broad range of wavelengths.

The discovery could help researchers to build small, cheap and highly versatile ultrashort-pulse lasers, with potential applications ranging from micro-machinery to medicine.

Conventional ultrashort-pulse lasers use a material that absorbs light like a sponge and then releases it back in quick bursts, typically lasting for femtoseconds (one femtosecond is 10−15 seconds, or one millionth of a billionth of a second). These 'saturable absorbers' function only at specific wavelengths, says Roy Taylor, a physicist at Imperial College London. Applications such as monitoring pollutants in the atmosphere need to use multiple wavelengths to detect a range of molecules, so several separate lasers are required.

In 2009, physicist Andrea Ferrari of the University of Cambridge, UK, and his collaborators first showed that graphene —  a one-atom-thick sheet of carbon, with the atoms arranged in hexagons like chicken wire — can act as a light sponge in the infrared spectrum1. More recently, Taylor, Ferrari and colleagues from the United Kingdom and Switzerland have coaxed the material to produce pulses of infrared radiation lasting tens of femtoseconds. (...) Read original article in full here

Quantum trick offers source for mystery cosmic magnets

10 May 2013

The universe is strangely magnetic – and a process of runaway expansion at its birth is to blame. New calculations shore up the idea that cosmic inflation stretched out tiny magnetic fields in the infant universe, leading to the magnetism that now surrounds galaxies, galactic clusters and giant voids in space.

To create a magnetic field in stars or a planet, the spins of individual electrons in a magnetic material, such as iron, line up in the same direction. If these then rotate, like liquid iron in Earth's outer core, it creates a geodynamo, which produces an electric current and in turn a magnetic field.

But the alignment of interstellar dust grains and measurements from radiotelescopes reveal that primordial magnetic fields surround galaxies, galaxy clusters and even cosmic voids – and these cannot be caused by geodynamos. This magnetic fields are much weaker than Earth's, measuring at most 10-6 gauss, although if you add up all the ones across the universe, it amounts to a lot of energy, says astrophysicist Gianluca Gregori of the University of Oxford.

This magnetic fields are much weaker than Earth's, measuring at most 10-6 gauss, although if you add up all the ones across the universe, it amounts to a lot of energy, says astrophysicist Gianluca Gregori of the University of Oxford. (...) Read original article in full here

Do Cosmic Rays Grease Lightning?

03 May 2013

Bolts from beyond. Radio pulses from thunderstorms might indicate that lightning is triggered by cosmic rays. Credit: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)
Bolts from beyond. Radio pulses from thunderstorms might indicate that lightning is triggered by cosmic rays. Credit: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)

Nobody knows exactly what triggers lightning bolts. Now, two Russian researchers say that these discharges of a billion volts or more could be caused by the interaction of cosmic rays—high-energy particles from outer space—with water droplets in thunderclouds.

Cosmic rays are created deep in space by powerful events such as star collisions, gamma ray bursts, and supernovae. These cataclysms accelerate charged particles—mostly protons—to very high energies. The rays zoom across space, and those that strike the upper atmosphere of Earth generate invisible but highly energetic air showers of ionized particles and electromagnetic radiation.

The idea that these air showers could cause lightning when they pass through a thundercloud has been around for 2 decades. In 1992, Russian physicist Alexandr Gurevich of the Lebedev Physical Institute in Moscow suggested that the high-energy particles produced by a cosmic ray strike ionize the air in thunderclouds, creating a region with a lot of free electrons. The thundercloud's electric field accelerates the electrons almost to the speed of light, boosting them to very high energies. Then the electrons collide with atoms in the air, generating even more electrons as well as x-rays and gamma rays. This avalanche of high-energy particles in the cloud—which Gurevich calls "runaway breakdown"—provides ideal conducting conditions for lightning.

Researchers worldwide have debated Gurevich's idea ever since he introduced it, says Joseph Dwyer, a lightning scientist at the Florida Institute of Technology in Melbourne who was not involved in the study. But Gurevich hasn't found concrete evidence that cosmic rays are the culprits. Radio waves could provide a clue, Dwyer says: Cascades of electrons at the onset of a lightning strike should produce radio waves. "The cosmic ray community has known that cosmic rays make radio waves, and when there are thunderstorms around, it's been seen that you get more of these radio pulses," Dwyer says. "But no one has yet closed the loop and really shown that the air showers going through [a thundercloud's] electric field making these runaway electrons are the things that are doing it."(...) Read original article in full here

Micro-ratchet spins pearls with perfect symmetry

3 May 2013


Mollusc manufacture (Credit: Walter Bibikow/AWL Images)
Mollusc manufacture (Credit: Walter Bibikow/AWL Images)

IT took humans hundreds of thousands of years to invent the wheel, but thanks to microscopic ratchets, molluscs have been turning out flawless spheres for hundreds of millions of years.

Pearls are a mollusc's defence against irritants trapped inside their shells, such as bacteria or a grain of sand. They coat the intruders with layer upon layer of mother of pearl (nacre). Most are oval or shaped like teardrops. Just how they form such radially symmetrical shapes has so far remained a mystery.

Julyan Cartwright of the Spanish National Research Council and his colleagues used electron microscopy to show that the growth layers of nacre overlap to form a tiny step-like structure. The edge of each layer, they say, works like teeth in a ratchet (arxiv.org/abs/1304.3704). The team think that rocking from currents sets the liquid inside the molluscs in motion. As it moves past the pearl, it catches on the layers, making the pearl spin. So a pearl's perfect shape comes from growing in constant rotation. (...) Read original article in full here

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