Laughing with friends releases feel-good brain chemicals, which also relieve pain, new research indicates. Until now, scientists haven't proven that like exercise and other activities, laughing causes a release of so-called endorphins.

"Very little research has been done into why we laugh and what role it plays in society," study researcher Robin Dunbar, of the University of Oxford, said in a statement. "We think that it is the bonding effects of the endorphin rush that explain why laughter plays such an important role in our social lives."

Chuckle it up

Dunbar and colleagues thought our guffaws might turn on the brain's endorphins, a long debated, but unproven idea. These pain-relieving chemicals are created in response to exercise, excitement, pain, spicy food, love and sexual orgasm, among other things.

In addition to giving us a "buzz," these endorphins raise our ability to ignore pain. So the researchers used the endorphins' pain relief to determine if laughter causes an endorphin release. They first tested participants for their pain threshold, then exposed them to either a control or a laugh-inducing test, and then tested pain levels again.

The tests included humorous videos (clips of the TV shows Mr. Bean and Friends) and a live comedy show during the Edinburgh Fringe Festival. Because laughter is such a social activity (it's 30 times more likely to happen in a social context than when alone), the participants were tested both in groups and alone.

The lab-based pain tests included wrapping a participant's arm in a frozen wine-cooling sleeve or a blood-pressure cuff. The pain tests were administered until the patient said they couldn't take it anymore. At the live shows, the researchers tested pain by having participants squat against a wall until they collapsed.

Icy body Dione may have dilute layer of oxygen air, study says.

Saturn's icy moon Dione has an atmosphere, albeit a thin one, astronomers have discovered.

NASA's Cassini spacecraft revealed Dione's atmosphere during a recent close flyby of the Saturnian satellite.

Cassini's data showed that Dione leaves behind "fingerprints" as it sweeps through Saturn's huge magnetic field.

"If a moon did not possess an atmosphere at all - if it was simply an ice ball - the magnetic field lines wouldn't be disturbed at all upstream of the moon, because you need conductivity to disturb the field," said study co-author Sven Simon.

A six tonne NASA satellite is set to fall uncontrolled out of orbit, potentially raining debris over swathes of the planet including Britain, the US space agency has admitted.

The $750 million (£468 million) Upper Atmosphere Research Satellite (UARS) satellite, launched 20 years ago to study climate change, is set to breach the atmosphere within weeks.

In a new alert issued this week, officials warned pieces could land in densely populated areas on six continents including parts of Britain, Europe, North and South America and Asia.

Nasa claimed the risk to public safety from the "dead" satellite - which is orbiting just over 155 miles above the earth with an inclination of 57 degrees - was "extremely small".

But senior space agency officials admitted they were "concerned" about the risk to billions of people when it starts falling uncontrolled out of orbit at any stage from later this month.

When British amateur astronomers Richard Carrington and Richard Hodgson independently saw a brightening of a small region of the Sun about 150 years ago, in 1859, they saw a very powerful event now called a solar flare. Since American astronomer George Ellery Hale discovered about 100 years ago that sunspots are regions of strong magnetism on the Sun, astronomers have linked magnetic storms on Earth to sunspots and to the solar-activity cycle. For roughly the last 50 years, solar flares have been categorized and detected by the x-rays they give off. The current classification of flares goes, in increasing power at their peak, A, B, C, M, X.

Last Wednesday, scientists reported that they haven't been noticing most of the solar flares' energy. In a NASA Press Conference, held simultaneously with the release of a paper online in The Astrophysical Journal, they reported on new results based on observations with NASA's Solar Dynamics Observatory. Since its launch on February 11, 2010, SDO has detected over a couple of hundred solar flares with its extreme-ultraviolet measuring instrument and with its cameras that take images also in that part of the spectrum beyond the violet, the ultraviolet. (Far into the ultraviolet is known as the extreme ultraviolet.) Several analyses have now shown that at least a group of the most powerful flares, which are detected in x-rays by satellites such as the GOES (Geostationary Operational Environmental Satellite) series of the National Oceanic and Atmospheric Administration, give off more energy about 90 minutes later than the x-ray peak than occurred in that first detected peak. This hitherto undetected second peak may not be quite as powerful at its maximum as the first peak but covers a somewhat longer time, rising to its peak and falling more slowly than the x-ray peak. It can thus contain more energy than the first peak.

A sophisticated new camera system can detect lies just by watching our faces as we talk, experts say.

The computerised system uses a simple video camera, a high-resolution thermal imaging sensor and a suite of algorithms.

Researchers say the system could be a powerful aid to security services.

It successfully discriminates between truth and lies in about two-thirds of cases, said lead researcher Professor Hassan Ugail from Bradford University.

The system, developed by a team from the universities of Bradford and Aberystwyth in conjunction with the UK Border Agency, was unveiled today at the British Science Festival in Bradford.

A missing dot in an email address might mean messages end up in the hands of cyber thieves, researchers have found.

By creating web domains that contained commonly mistyped names, the investigators received emails that would otherwise not be delivered.

Over six months they grabbed 20GB of data made up of 120,000 wrongly sent messages.

Some of the intercepted correspondence contained user names, passwords, and details of corporate networks.

About 30% of the top 500 companies in the US were vulnerable to this security shortcoming according to researchers Peter Kim and Garret Gee of the Godai Group.

Getting rid of quantum noise

One characteristic of quantum physics is being used to defeat another, with the aim of making more sensitive gravity wave detectors, in an international project with contributions from the University of Western Australia, the Australian National University, and the GEO600 Gravitational Wave Observatory in Germany.

A problem with trying to detect gravity waves is that they're very, very weak, and there's lots of sources of noise to spoil the experiment. One of those noise sources turns out to be the strangeness of the quantum world.

Near-death experiences are often thought of as mystical phenomena, but research is now revealing scientific explanations for virtually all of their common features. The details of what happens in near-death experiences are now known widely - a sense of being dead, a feeling that one's "soul" has left the body, a voyage toward a bright light, and a departure to another reality where love and bliss are all-encompassing.

Approximately 3 percent of the U.S. population says they have had a near-death experience, according to a Gallup poll. Near-death experiences are reported across cultures, with written records of them dating back to ancient Greece. Not all of these experiences actually coincide with brushes with death - one study of 58 patients who recounted near-death experiences found 30 were not actually in danger of dying, although most of them thought they were.

Recently, a host of studies has revealed potential underpinnings for all the elements of such experiences. "Many of the phenomena associated with near-death experiences can be biologically explained," says neuroscientist Dean Mobbs, at the University of Cambridge's Medical Research Council Cognition and Brain Sciences Unit. Mobbs and Caroline Watt at the University of Edinburgh detailed this research online August 17 in Trends in Cognitive Sciences.

We may have interbred with Neanderthals in the past, but only rarely was that sex successful in producing offspring, scientists now suggest.

Any such dalliances might either have been scarce or only rarely produced offspring, or both, researchers explained.

Recent analyses of Neanderthal genes revealed that many of us have this extinct lineage within our ancestry. Estimates suggest that Neanderthal DNA makes up 1 to 4 percent of modern Eurasian genomes.

To learn more, scientists designed a computer model that estimated how much Neanderthal ancestry would be present in modern humans based on different levels of interbreeding, simulating potential interactions after our ancestors expanded into Neanderthal territory from Africa starting about 50,000 years ago. They next applied this model on the level of Neanderthal DNA seen in modern French and Chinese groups.

Based on this data and model, the researchers discovered the interbreeding success rate was probably less than 2 percent in most scenarios. Assuming that both lineages interacted for about 10,000 years, this means successful interbreeding would have, on average, happened just once every 23 to 50 years, they calculated.

A key source of information about the health of the ozone layer above the Arctic looks set to be choked off.

In a year that saw the first genuine 'ozone hole' appear in the Northern Hemisphere, atmospheric scientists say they are shocked to learn that Environment Canada, the country's environment agency, has decided to drastically reduce its ozone science and monitoring programme.

Its network of monitoring stations provides about one-third of the Arctic's ozone measurements and this year contributed key data showing unprecedented depletion of stratospheric ozone over the Arctic. With regular in situ measurements going back to 1966, Canada also holds the longest-running record of atmospheric ozone levels in the world - an archive that is also threatened.

The Canadian observation network comprises 17 stations - from London, Ontario, in the south to Alert in the high Arctic - which use several techniques to measure ozone (see 'The ozone network'). But atmospheric scientists and research institutes around the world, including Canada, Britain, Switzerland and Germany, have been told, informally, that the network will be shut down as early as this coming winter. This will be the end of in situ ozone measurements, including those made by balloons launched at least once a week from 11 of the stations. "This is devastating for the whole field," says Tom Duck, who conducts atmospheric research at Dalhousie University in Halifax, Nova Scotia.