A microbicide which, it was believed, might protect from HIV, does notIN THE frantic search for ways to stop the spread of the human immunodeficiency virus (HIV), a gel that women apply to their vaginas before having sex, in order to destroy or disable the virus, sounds one of the most desperate. Yet it is not a foolish idea. Unlike the most reliable form of protection, a condom, it is the woman, not the man, who makes the ultimate choice about whether to use the gel. (So-called femidoms, inserted by the woman, have been a dismal failure.) Moreover, such a microbicide, as it is known technically, might simultaneously protect against the virus that causes AIDS, but permit insemination, and thus eliminate objections from both putative parents and some religious authorities to the use of contraceptives to avoid infection.Sadly, the latest test of a microbicide has shown no protective effect—a result more bitterly disappointing because it followed the apparently positive outcome of a smaller trial of the same substance. The substance in question is a naphthalene sulfonate polymer called PRO 2000 which (in the laboratory) blocks the process by which HIV binds to the cells in which it subsequently reproduces. ...

  Underwater robots can help study the world’s shipwrecks, a trove of information about the past, more easily and cheaplyA SHIPWRECK is a catastrophe for those involved, but for historians and archaeologists of future generations it is an opportunity. Wrecks offer glimpses not only of the nautical technology of the past but also of its economy, trade, culture and, sometimes, its warfare. Until recently, though, most of the 3m ships estimated to be lying on the seabed have been out of reach. Underwater archaeology has mainly been the preserve of scuba divers. That has limited the endeavour to waters less than 50 metres deep, excluding 98% of the sea floor from inspection. Even allowing for the tendency of trading vessels to be coasters rather than ocean-going ships, that limits the number of wrecks available for discovery and examination.Moreover, shallow-water shipwrecks are often damaged. Storms reach down to affect them. Seaweeds and corals, which need light to grow, colonise them. Freelance divers, seeking salvage rather than knowledge, despoil them. Archaeologists do sometimes team up with people who have access to miniature submarines (some manned, some unmanned) to explore deeper waters. But such expeditions are expensive—a million dollars a pop is not untypical—and archaeology is not a well-resourced profession. Often, these expeditions are privately financed, speculative ventures which amount to little more than treasure-hunting. ...

  Wild rumours are circulating of the discovery of one of physics’s great unknowns: dark matterAS The Economist went to press this week, physicists were aflutter about an expected announcement from one of the world’s most important experiments searching for dark matter—the as-yet-undetected material that, if models of the universe are correct, is about six times as abundant as the familiar, visible stuff. Physicists working on the Cryogenic Dark Matter Search (CDMS), a large collaboration whose experimental apparatus is located in Minnesota, will be making presentations on December 17th at Fermilab and the SLAC National Accelerator Laboratory in America, and on December 18th at CERN, the European particle-physics laboratory near Geneva. The speculation is that they will announce the detection of the hitherto unknown particles that make up dark matter. The researchers plan to post their results to the arXiv, an online repository of physics papers, on December 17th, with submissions toa peer-reviewed journal following shortly thereafter. Around a quarter of the universe is thought to be made up of dark matter, which, as the name suggests, neither gives off nor reflects light. (The balance, once the small amount of visible matter is subtracted, is made of even more mysterious stuff known as “dark energy”.) However, dark matter does make itself known through its gravity. This, indeed, is why astronomers believe it must be there. Some galaxies rotate so fast that they should be throwing off their outermost stars. Only the gravitational pull of these galaxies’ unseen halos of dark matter holds those stars in. Observations of the bending of light around clusters of galaxies, as well as the way that galactic structures formed in the early universe, also suggest that there is much more to reality than meets the eye. ...

  Stressed mothers spontaneously abort male fetusesIT HAS been known for a while that stressful conditions such as famine result in more girls being born than happens in good times. The shift in the sex-ratio is tiny—around 1%—but in a large population that is still noticeable. A possible evolutionary explanation is that daughters are likely to mate and produce grandchildren regardless of condition, whereas weedy sons may fail in the struggle to have the chance to reproduce at all. In hard times, then, daughters are a safer evolutionary bet. Regardless of why the shift happens, though, it has long been argued that the moment when it happens is conception—or, more probably, implantation. A womb exposed to stress hormones, runs the hypothesis, is less likely to accommodate a male fetus.A recently published study, however, suggests this ain’t necessarily so. According to Ralph Catalano of the University of California, Berkeley, and his colleagues, writing in the American Journal of Human Biology, stress-induced sex selection can take place long after conception and implantation. ...

  Loneliness is a contagious diseaseON THE surface, Framingham, Massachusetts looks like any other American town. Unbeknown to most who pass through this serene place, however, it is a gold mine for medical research. Since 1948 three generations of residents in Framingham have participated in regular medical examinations originally intended to study the spread of heart disease. In the years since, researchers have also used Framingham to track obesity, smoking and even happiness over long periods of time. Now a new study that uses Framingham to analyse loneliness has found that it spreads very much like a communicable disease.Feeling lonely is more than just unpleasant for those who yearn to be surrounded by warm relationships—it is a health hazard. Numerous studies show that loneliness reduces fruit-fly lifespans, increases the chances of mice developing diabetes, and causes a host of adverse effects in people, including cardiovascular disease, obesity and weakening of the immune system.Simply being surrounded by others is no cure. In people, the mere perception of being isolated is more than enough to create the bad health effects. However, in spite of its significant impact, precious little is known about how loneliness moves through communities. ...

  A CT scanner and gaming technology opens up a bodyPERFORMING a postmortem on a murder victim can take days, delaying any criminal investigation. Moreover, pathologists sometimes get only one chance to look for clues when dissecting a body. But Anders Persson, director of Linkoping University’s centre for medical image science and visualisation in Sweden, hopes to change that. Along with his colleagues Thomas Rydell and Anders Ynnerman of the Norrkoping Visualisation Centre, they have created a virtual autopsy system.The body needing to be examined is first scanned using a computed tomography (CT) machine, a process which takes about 20 seconds and creates up to 25,000 images, each one a slicethrough the body. Different tissues, bodily substances and foreign objects (such as bullets) absorb the scanner’s X-rays in varying amounts. The software recognises these and assigns them a density value. These densities are then rendered with the aid of an NVIDiA graphics card, of a type used for high-speed gaming, into a 3-D visualisation of different colours and opacities. Air pockets are shown as blue, soft tissues as beige, blood vessels as red and bone as white. A pathologist can then peel through layers of virtual skin and muscle with the click of a computer mouse. ...

  Consumer products and video-gaming technology are boosting the performance and reducing the price of military equipmentVIDEO games have become increasingly realistic, especially those involving armed combat. America’s armed forces have even used video games as recruitment and training tools. But the desire to play games is not the reason why the United States Air Force recently issued a procurement request for 2,200 Sony PlayStation 3 (PS3) video-game consoles. It intends to link them up to build a supercomputer that will run Linux, a free, open-source operating system. It will be used for research, including the development of high-definition imaging systems for radar, and will cost around one-tenth as much as a conventional supercomputer. The air force has already built a smaller computer from a cluster of 336 PS3s.This is merely the latest example of an unusual trend. There is a long tradition of technology developed for military use filtering through to consumer markets: satellite-navigation systems designed to guide missiles can also help hikers find their way, and head-up displays have moved from jet fighters to family cars. But technology is increasingly moving in the other direction, too, as consumer products are appropriated for military use. ...

  Virgin Galactic’s spaceship makes its first appearanceIN THE 1960s Pan Am, an American airline, set up a waiting list for people hoping to fly to the moon. Such was the interest that 80,000 people signed up. In the end, Pan Am died before the space dream did. So when a firm called Virgin Galactic announced in 2004 that it was planning commercial space flights there was, not surprisingly, some scepticism. Cynics thought it was all a publicity stunt by the Virgin Group of companies and its flamboyant British boss, Sir Richard Branson.But on December 7th at the Mojave Air and Space Port in California, Virgin Galactic unveiled its first commercial spaceship, the VSS Enterprise. This is a reusable craft made of composite material, 18 metres (60 feet) long and capable of taking six passengers and two pilots briefly into space before gliding back down to land. Initially such trips will cost $200,000 per person. ...

  The planet’s ability to absorb carbon dioxide is under investigationAS THE world gathers in Copenhagen over the coming weeks to discuss how much carbon dioxide people should be putting into the atmosphere, the Benguela Stream will be docking in the Windward Isles to bring bananas to Europe for Christmas, and doing her bit to help ascertain where a large part of that CO2 ends up. The world’s oceans and plants absorb about 60% of the CO2 emitted as a result of human activities, which has helped keep the extent of climate change in check over the past century or so. But exact figures are hard to come by. Estimates of just how much carbon ends up in plants, in soil and in the oceans are frustratingly sketchy.The oceans suck up CO2 because it is soluble in water. Plants suck it up because they photosynthesise. As CO2 becomes more available, other things being equal, they will photosynthesise more. And a warmer, more polluted, more disrupted world can encourage growth in other ways, too. But none of these things can go on indefinitely. At some point the oceans and plants will have had their fill. ...

  Copying birds may save aircraft fuelBOTH Boeing and Airbus have trumpeted the efficiency of their newest aircraft, the 787 and A350 respectively. Their clever designs and lightweight composites certainly make a difference. But a group of researchers at Stanford University, led by Ilan Kroo, has suggested that airlines could take a more naturalistic approach to cutting jet-fuel use, and it would not require them to buy new aircraft. The answer, says Dr Kroo, lies with birds. Since 1914, and a seminal paper by a German researcher called Carl Wieselsberger, scientists have known that birds flying in formation—a V-shape, echelon or otherwise—expend less energy. The air flowing over a bird’s wings curls upwards behind the wingtips, a phenomenon known as upwash. Other birds flying in the upwash experience reduced drag, and spend less energy propelling themselves. Peter Lissaman, an aeronautics expert who was formerly at Caltech and the University of Southern California, has suggested that a formation of 25 birds might enjoy a range increase of 71%. ...

  The world’s first osmotic power station has just opened in NorwayIT WAS one small movement for a royal finger—but it started a power station of a sort that has never been tried before. On November 24th, when Princess Mette-Marit of Norway pressed the red button, pumps started to hum, pressing freshwater from a river and saltwater from the nearby Skagerrak through an array of white steel cylinders. Then a turbine began to run inside a small, redbrick hall at Tofte, a few kilometres south-west of Oslo, and electric current emerged. The power in question was generated by osmosis. This is the tendency for water to pass through a membrane separating a weak solution from a strong one. This causes a build-up of pressure on one side of the membrane. ...

  Ozone giveth. The greenhouse taketh awayTO SEE the ironic complexities of climate change at their finest, look south. For the past few decades the hole in the ozone layer over Antarctica has been shifting the way in which winds move round the continent, driving them round the Southern Ocean ever faster. This has increased the continent’s isolation from warming in the climate elsewhere, allowing the bulk of it to stay quite cold (though the winds have helped warm the Antarctic Peninsula, which reaches north into the surrounding ocean). But this odd balancing of one human intervention by another cannot last. One of the main conclusions of a report issued this week by the Scientific Committee on Antarctic Research (SCAR), reviewing the possible impacts of climate change on the continent, was that this protection—which will fade as the ozone hole begins to heal—will, over the next century, be swamped by the warming of the continent itself by greenhouse gases. ...

  The world’s largest and most expensive experiment is up and running. AgainSOMETIMES the only way to crack a nut is with a sledgehammer. Such is the case with the Large Hadron Collider (LHC), an experiment so grand that it spans two countries in its quest for subatomic particles so tiny that they are literally almost nothing. It was ingloriously shut down after springing a helium leak in September 2008, before it had even got properly going. If all is well over the next few days, though, it will become the most powerful particle collider in the world.The machine lies 100 metres below the countryside, straddling the Franco-Swiss border outside Geneva. This is where CERN, the European particle-physics laboratory, has its headquarters. The LHC is housed in a circular tunnel some 27 kilometres (17 miles) around. At four points on this circle sit vast experimental halls where beams of protons, circulating at more than 99.99% of the speed of light in a vacuum comparable to that of outer space,will collide at temperatures just above absolute zero. Tens of thousands of physicists from more than 100 countries are watching to see what happens when they do so. ...

  America’s food-waste problem is getting worseIN MANY countries one of the side effects of the second world war was to breed a generation that could not abide waste. Newspapers, jars and string were diligently saved and reused. Glass bottles were returned to their makers. Most importantly, though, food was never, ever thrown away. Leftovers were recycled into new meals, day after day. Fast forward to today and things have changed. There are reports of rich countries throwing out 25-30% of what is bought. Add in what never even makes it to the cupboard or the refrigerator, and the scale of the problem is considerably larger. Reliable data, though, are scarce. Existing reports usually collate small-scale studies of households’ leftovers and rubbish bins and then extrapolate the results across a country. So Kevin Hall and his colleagues at the National Institute of Diabetes and Digestive and Kidney Diseases, in Bethesda, Maryland, decided to look at the problem in a new way. ...