Imagine if, in addition to sharing photos of those muffins you just baked, you could share their delicious aroma, too. That鈥檚 the promise of an AI-assisted device that can transmit smells over the internet. So far, it works on only a small number of scents, including orange, beer and cake, but its creators hope the system will ultimately recreate more smells. The scent of a pine forest or the aroma of coffee, for example, could then add a new dimension to virtual worlds and long-distance communication.

Although it is now routine to communicate sight, sound and even touch sensations electronically, smell is 鈥渟till a very undeveloped sense鈥�, says at the Ohio State University. That鈥檚 partly because odours involve complex chemistry. Whereas vision, for example, can be broken down into combinations of red, green and blue pixels, says Yang, there鈥檚 no simple building block underlying smell. Any attempt to convert aromas into electronic signals has to recognise combinations of very different molecules.

To solve the problem, Yang and her colleagues built an electronic nose, or 鈥渆-nose鈥�, as well as a smell generator, then used machine learning to connect the two. The e-nose consists of arrays of sensors made of metal oxide. When different gaseous components of smells, such as ethanol (from alcoholic drinks) or limonene (found in citrus fruits), bind to the sensors鈥� surface, this changes their resistance, creating different electrical signals.

The researchers then trained an AI algorithm to recognise the distinctive signals created by smells from five different foods or beverages: orange, cake, coffee, beer and red wine. Teaching the AI to correctly recognise the smells was 鈥渢he most challenging part鈥� of the entire study, says Yang, because to generate enough data to train the system, she had to expose the sensors to the various smells hundreds of times.

This information was then sent over the internet to a smell generation device that the researchers are calling 鈥淪centronic鈥�. This part of the system involves miniature containers holding liquids laced with each of the five smells. Above each container is an atomiser that vibrates in response to electric signals, forcing the liquid in the container through a cotton filter and releasing fine droplets into the air, creating the appropriate smell, or combination of smells.

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Yang built several different designs including stringing the atomisers onto a necklace and a wristband, and mounting them on a handheld device. When she tested the handheld device on 14 volunteers, they correctly identified the smells being transmitted to them 73 per cent of the time, on average.

She also built a prototype that reproduces taste, involving a cup of water with electromagnetic pumps containing flavoured liquid fixed around its edge. 鈥淲hen it receives information from the internet, the corresponding liquid will be dropped into the cup.鈥�

Alternative methods to generate smells remotely have been suggested, including to release particular scents, and even to create the experience of smell. But Yang argues her method is both fast and practical. She now hopes to expand the repertoire of the system, to create more complex aromas.

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She suggests the entertainment industry could be first to develop the technology, to create more immersive virtual worlds. But there could also be health applications. For instance, the smell of food transforms the eating experience, so the technology could be adapted to make soldiers鈥� or astronauts鈥� rations more palatable. The Scentronic system could also enable doctors to assess distortions in patients鈥� sense of smell, for example, in post-viral illness or neurodegenerative disease.

The Scentronic system is 鈥渁 great idea鈥� and a step in the right direction, says at University College London, although she points out that recognising a smell and then releasing a matching one from a limited library is very different from the ease with which we can transmit sound and vision. 鈥淭here鈥檚 still a long way to go before we can truly record and replay smell experiences.鈥�

Leap seconds, previously used to keep the world鈥檚 clocks in sync with Earth鈥檚 rotation, are to be abolished. Instead, universal time will be allowed to drift up to an hour from astronomical time before it is corrected. Representatives from 69 countries voted for the change on 15 October at a meeting of the in Versailles, France.

As the gap between clock time and astronomical time slowly grows, the effect will eventually be 鈥渓ike living on daylight saving time鈥�, but permanently, says , curator of time at the Royal Observatory in Greenwich, London.

For most of history, our clocks have been set by the apparent position of the sun in the sky. But in 1967, after the development of super-accurate atomic clocks, physicists defined an international time standard called coordinated universal time (UTC), based instead on the speed of a particular vibration of the caesium-133 atom.

Natural fluctuations in Earth鈥檚 rate of rotation meant periodic corrections were needed to keep universal time in sync with the sky. As the rotation slowed, physicists added extra leap seconds. Twenty-seven have been added to UTC since they were introduced in 1972.

Now, that strategy is to be abandoned. This is partly because technological systems, from stock markets to telecommunications to GPS, have become much more reliant on precise timekeeping. That means introducing leap seconds is more complex, potentially risking the failure of mobile phone networks or electricity grids. Previous leap seconds have caused websites to crash and disrupted airlines鈥� booking systems, says at the National Physical Laboratory (NPL) in Teddington, UK.

鈥淭ime is now so much more important and integrated into these systems,鈥� says Akkermans. 鈥淲hat once worked has become more problematic.鈥�

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What鈥檚 more, Earth鈥檚 rotation has recently begun to accelerate slightly, raising the daunting possibility of needing 鈥渁 first-ever negative leap second鈥�, said , who heads the BIPM鈥檚 committee on time and frequency, in a statement. The practical consequences of such a jump backwards in time are hard to predict.

Physicists have been debating what to replace the leap second with for the past 30 years. At the BIPM meeting, they finally voted for a 鈥渓eap hour鈥�, which means that UTC will be allowed to diverge from astronomical time for up to an hour before being corrected. That should ensure an uninterrupted flow of time for 鈥渟everal centuries鈥�, said Dimarcq. The change will take effect from 20 May 2027.

Time crystals could be used to build accurate quantum clocks

Once considered an oddity of quantum physics, time crystals could be a good building block for accurate clocks and sensors, according to new calculations

Shemar emphasises that the effects involved are very small: 鈥淚t鈥檒l be many hundreds or even thousands of years before a leap hour is needed.鈥� He adds that physicists will still be accurately tracking Earth鈥檚 rotation to provide information for astronomy and celestial navigation.

The leap hour isn鈥檛 the only temporal innovation being planned, though. The BIPM meeting also asked for proposals on a new definition of the second 鈥� needed because optical clocks are now much more accurate than the caesium clock that time is currently based on 鈥� and called on international agencies to start considering how to define a universal time standard for the moon. Overall, the changes 鈥渨ill have a profound impact on future timekeeping both on Earth and other planets鈥�, said Dimarcq.

Microplastics generated potentially harmful molecules when they contacted serum from blood in a lab experiment. This is due to their large surface area enabling such reactions. If this effect occurs within our bodies, it could explain why they have been linked to cell damage and other health concerns.

Several recent studies have linked microplastics, which form when plastics degrade in the environment, to issues such as poor cognition and cardiovascular disease. This seems to be related to the production of destructive molecules called reactive oxygen species, says at Columbia University in New York. These can then react with different molecules inside cells, contributing to issues like inflammation.

But the extent to which common plastics could be causing such problems was unclear. They don鈥檛 always contain oxygen and are therefore not thought to be particularly reactive. 鈥淔rom a pure chemistry point of view, this should be inert,鈥� says Min.

To find out, Min and his colleagues studied the microparticles of a range of commonly used plastics 鈥� including polystyrene, polyethylene and polypropylene 鈥� and found that 鈥渨ater is a key player鈥� in their effects.

They used techniques including fluorescence microscopy and electron spin resonance spectroscopy to show that a type of reactive oxygen species called hydroxyl radicals spontaneously forms at the surface between plastic and water, making the latter 鈥渘ot regular water anymore鈥�, he says.

The team also showed that this effect is linked to electric charges forming at this plastic-water interface. These charges may help strip electrons from OH- ions in water, generating volatile hydroxyl radicals, says Min.

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In experiments, this electric charge attracted biological molecules such as DNA to the surface of microplastics when suspended in water, which appeared to damage both proteins and red blood cells.

The researchers also tested whether hydroxyl radicals were generated when the microparticles were suspended in serum from blood. The effect was weaker, but 鈥渟till detectable鈥�, says Min. Microplastics have been , however, signals of their presence throughout our bodies and false positive results.

If microplastics do enter our blood, laboratory studies have linked them to cellular , all of which can be caused by reactive oxygen species.

The findings could help explain how those molecules are being produced, says Min, although he adds that the potential size of the effect is unclear and other mechanisms could be involved. It may also depend on whether microplastics are disposed of by our bodies. 鈥淗ow much plastic is in a regular human being?鈥� he says. 鈥淲e have no idea right now.鈥�

at the New Jersey Institute of Technology says the results are 鈥渧ery important鈥�, and although they don鈥檛 directly answer how dangerous microplastics might be, they 鈥減rovide a starting point鈥� to help us understand the interaction between microplastics and cells.

at the University of New Mexico describes the results as a 鈥渃ritical building block鈥� for this understanding. The surface area of microplastics is probably key to their effects, he says, pointing out that a half-centimetre ball of plastic could degrade into a quadrillion 50-nanometre microparticles, increasing its surface area 100,000 times.

That isn鈥檛 necessarily as worrying as it sounds, however. 鈥淚 encourage people to take a deep breath,鈥� says Campen.

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Microplastics have been found accumulating everywhere from our water to our body tissues, but many of the claims have come under fresh scrutiny. Chelsea Whyte cuts through the research to tell you whether you really need to worry

When the researchers added a surfactant 鈥� a chemical that weakens the forces holding the water molecules together 鈥� radical generation was dampened. Some lipids act as surfactants in the body. 鈥淢icroplastics hit your lung and they are surrounded by surfactants immediately,鈥� says Campen. 鈥淚n most situations that I can imagine in a biological system, they will be surrounded by those lipids. The big concern is [whether] this is getting worse over time, and we really need to get a handle on what the health effects are, or could be, so that we can avoid exposures.鈥�

The findings could also help scientists design safer materials, says Min. The researchers found that the most hydrophobic (water-repelling) plastics they tested, such as polyethylene and polypropylene, showed stronger radical-generating activity than more hydrophilic ones, such as PET (polyethylene terephthalate).

Campen notes, however, that the plastics with the lowest activity are also probably the ones that break down more slowly in the environment. 鈥淗ow do you make that trade off?鈥�

Archaeologists have made many stunning discoveries down the years. These have changed our thinking on how our species became the only humans on the planet, how civilisations arose across the world and how international trade first began.

As the world marks the 100th anniversary of one of the most famous archaeological finds of all time 鈥� the unearthing of Tutankhamun鈥檚 tomb in Egypt 鈥� New 精东传媒 asked archaeologists who work at sites scattered across the world, from Greece to Indonesia, to nominate the discoveries they think are even more significant.

Mycenae Grave Circle

In the late 19th century, archaeologist Heinrich Schliemann excavated a circle of six royal graves at the citadel of Mycenae in southern Greece. He found a hoard of golden treasures from the 16th century BC, including the 鈥淢ask of Agamemnon鈥�, which Schliemann believed was worn by Mycenae鈥檚 mythological ruler, who fought in the Trojan war. That is unlikely, but the find 鈥渞evolutionised our comprehension of the Mediterranean鈥�, says at the University of Cincinnati in Ohio, revealing the previously unknown Aegean civilisations that preceded historical Greece.

Terracotta Army and the ancient site of Yinxu

In 1974, workers digging near the city of Xi鈥檃n, China, uncovered a life-size clay soldier poised for battle. Archaeologists soon found an entire terracotta army, guarding the tomb of the 3rd-century-BC emperor Qin Shi Huang. at Harvard University highlights the site along with 聽(see picture at the top of the page). This city, which dates to the late 2nd millennium BC and so is much older than the Terracotta army, revealed a golden age of early Chinese culture, including palaces, a flood-control system and inscribed oracle bones 鈥� the earliest evidence of the Chinese written language. Both 鈥渨ere true discoveries of things and stories that had been long forgotten鈥�, says Flad.

Hand axes of Hoxne

In 1797, antiquary John Frere wrote to colleagues describing sharpened flints uncovered by brickworkers in Hoxne, England. The stones lay 4 metres deep, alongside the bones of enormous, unknown animals and beneath layers apparently once at the bottom of the sea. Frere suggested they belonged 鈥渢o a very remote period鈥� even beyond that of the present world鈥�. His discovery of what we now know are Palaeolithic hand axes 鈥渞evealed for the first time the long-term, deep-time human past鈥�, says at University College London, 鈥渃hallenging the biblical notion that the world was created in 4004 BC.鈥�

Uluburun

This Bronze Age shipwreck, found off the coast of Turkey in 1982, stands as 鈥渙ne of the great underwater discoveries鈥�, says at Lund University in Sweden. Once described as 鈥溾��, it transformed historians鈥� understanding of the era by revealing an astonishing web of trade contacts. The wreck鈥檚 vast cargo represented at least 11 different cultures and included weapons, jewellery, ostrich eggs, resin, spices and copper ingots from as far afield as Egypt, Cyprus and Asia.

The Flores 鈥楬obbit鈥�

The shock discovery of diminutive humans who once lived on the Indonesian island of Flores was the 鈥淛FK moment鈥� of modern archaeology, says at Griffith University in Australia, in the sense that scientists in the field still remember where they were when they heard the news. The tiny bones, discovered in a cave in 2003, showed that individuals (subsequently dubbed Homo floresiensis) grew to just over 1 metre tall and lived alongside giant lizards. For Brumm, 鈥渋t was an electrifying and totally unexpected find鈥�.