Some 4.53 billion years ago, a Mars-sized impactor slammed into Earth, forming a young, molten moon. But was it a head-on collision or a glancing blow? New computer simulations argue for the former, indicating that the impactor scored a direct hit, crashing into Earth at a steeper angle and with a higher velocity than previously thought.

The resulting smashup would have ejected far more Earth debris into space than other models have indicated, with much hotter temperatures. And that would mean the moon formed from more Earthlike material than previously thought. The origin of the impactor itself remains an open question.

The slow impact velocity of previous models requires it to have originated from an orbit very near Earth, while the new model allows for an origin from more far-flung parts of the solar system, researchers report in an upcoming issue of Icarus.

Sometimes, history really does seem to repeat itself. After the US Civil War, for example, a wave of urban violence fuelled by ethnic and class resentment swept across the country, peaking in about 1870. Internal strife spiked again in around 1920, when race riots, workers' strikes and a surge of anti-Communist feeling led many people to think that revolution was imminent. And in around 1970, unrest crested once more, with violent student demonstrations, political assassinations, riots and terrorism (see 'Cycles of violence').

To Peter Turchin, who studies population dynamics at the University of Connecticut in Storrs, the appearance of three peaks of political instability at roughly 50-year intervals is not a coincidence. For the past 15 years, Turchin has been taking the mathematical techniques that once allowed him to track predator - prey cycles in forest ecosystems, and applying them to human history. He has analysed historical records on economic activity, demographic trends and outbursts of violence in the United States, and has come to the conclusion that a new wave of internal strife is already on its way¹. The peak should occur in about 2020, he says, and will probably be at least as high as the one in around 1970. "I hope it won't be as bad as 1870," he adds.

Turchin's approach - which he calls cliodynamics after Clio, the ancient Greek muse of history - is part of a groundswell of efforts to apply scientific methods to history by identifying and modelling the broad social forces that Turchin and his colleagues say shape all human societies. It is an attempt to show that "history is not 'just one damn thing after another'", says Turchin, paraphrasing a saying often attributed to the late British historian Arnold Toynbee.

Cliodynamics is viewed with deep scepticism by most academic historians, who tend to see history as a complex stew of chance, individual foibles and one-of-a-kind situations that no broad-brush 'science of history' will ever capture. "After a century of grand theory, from Marxism and social Darwinism to structuralism and postmodernism, most historians have abandoned the belief in general laws," said Robert Darnton, a cultural historian at Harvard University in Cambridge, Massachusetts, in a column written in 1999.

Most think that phenomena such as political instability should be understood by constructing detailed narratives of what actually happened - always looking for patterns and regularities, but never forgetting that each outbreak emerged from a particular time and place. "We're doing what can be done, as opposed to aspiring after what can't," says Daniel Szechi, who studies early-modern history at the University of Manchester, UK. "We're just too ignorant" to identify meaningful cycles, he adds.

But Turchin and his allies contend that the time is ripe to revisit general laws, thanks to tools such as nonlinear mathematics, simulations that can model the interactions of thousands or millions of individuals at once, and informatics technologies for gathering and analysing huge databases of historical information. And for some academics, at least, cliodynamics can't come a moment too soon. "Historians need to abandon the habit of thinking that it's enough to informally point to a sample of cases and to claim that observations generalize," says Joseph Bulbulia, who studies the evolution of religion at Victoria University of Wellington in New Zealand.

Goose bumps often turn out to be a skin orgasm of sorts, frequently resulting from an emotional climax stimulated by a "powerful other," according to new research.

A study exploring the scientific and social aspects of goose bumps finds that this common form of piloerection is associated with feelings of awe. This physical reaction also cannot be faked.

The study, published in the journal Motivation and Emotion, helps to explain how a defense mechanism protecting the body from cold also surfaces during moments of wonderment.

"We suggest that goose bumps may be the initial reaction: a blend of fear, surprise and defense, which is displaced by a positive appraisal made even more positive by the contrast from bad to good," co-author Richard Smith told Discovery News.

Goose bumps come at the intersection of our fight-or-flight response, even if the emotional jolt arises from something as seemingly harmless as a musical performance, Smith, a professor in the University of Kentucky's Department of Psychology, explained.

"[The] powerful other has the capacity to harm, but does not, assuming our submissive response," he said. "An initial 'fight' response, after a subsequent positive appraisal, precludes a 'flight' response. This positive response may be made all the stronger by the contrast."

Parents get physical with unruly children far more in public than they do when they know psychologists or other researchers are looking, a new study finds.

In an experiment that involved surreptitiously watching parents discipline their kids in public places such as restaurants, researchers found that in 23 percent of cases, mom or dad resorted to "negative touch" to get their child to comply. Negative touch can include anything from restraining and spanking to pinching and hitting.

The findings suggest that most social science research in parenting misses out on these sorts of incidents, study researcher Kathy Stansbury, a professor of human development and family studies at Michigan State University, said in a statement.

"I have also seen hundreds of kids and their parents in a lab setting, and never once witnessed any of this behavior," Stansbury said.

"Hence, we may justly conclude that the Returns of Comets are much more frequent than is vulgarly reckoned."

There is something truly thrilling about the first-hand accounts of scientists who have homed in on an idea or a fact that is now common knowledge. A few artifacts of such moments -- Darwin's early tree-of-life sketches or the first few minutes of this BBC documentary on Andrew Wiles' work on Fermat's Last Theorem -- convey the emotions and the creativity that surround those discoveries. A paper, published in Philosophical Transactions Vol. 30 (1717-1719) relaying the details of the discovery of a comet as "seen at London on the 10th of June 1717" and now available on JSTOR, does much the same.

Edmond Halley described the events as such:

On Monday, June 10, in the Evening, the Sky being very serene and calm, I was desirous to take a view of the disk of Mars (then very near the Earth, and appearing very glorious) to see if I could distinguish in my 24 Foot Telescope, the Spots said to be seen on him. Directing my Tube for the purpose, I accidentally fell upon a small whitish Appearance near the Planet, resembling in all respects such a Nebula ... The Reverend Mr. Miles Williams, Mr. Alban Thomas, and myself contemplated this Appearance for above an Hour ... and we could not be deceiv'd as to its Reality; but the slowness of its Motion made us at that time conclude that it had none, and that it was rather a Nebula than a Comet.

By way of mechanical stretching, National University of Singapore researchers identify a novel double-stranded DNA structure, thus successfully resolving a 16-year-old scientific debate over the existence of a double-stranded DNA structure.

Double-stranded DNA has often been described as a right-handed helical structure, known as B-DNA. To perform its multiple functions, double-stranded DNA has multiple structures depending on conditions. For example, the melted DNA bubble forms during transcription elongation and the left-handed helical Z-DNA forms hypothetically during transcriptional regulations.

Scientists have been proposing a novel form of double-stranded DNA structure since 1996. Referred to as 'S-DNA', it is produced from stretching the B-form DNA beyond a certain 'transition force' of around 65 pN to approximately 1.7-fold in length (termed as DNA overstretching transition). Its existence has sparked a 16-year scientific debate since it was proposed, as many other evidences suggested that DNA overstretching transition was merely a force-induced DNA melting transition, leading to peeled-apart single-stranded DNA.

At National University of Singapore (NUS), the research was led by Associate Professor Jie Yan, from the Department of Physics, Faculty of Science and Mechanobiology Institute, Singapore. It succeeded in demonstrating the intricacies of the DNA mechanics in highly sensitive single-DNA stretching experiments.

Scientists at the University of Liverpool have discovered that variations in the long-term reversal rate of the Earth's magnetic field may be caused by changes in heat flow from the Earth's core into the base of the overlying mantle.

The Earth is made up of a solid inner core, surrounded by a liquid outer core, in turn covered by a thicker or more viscous mantle, and ultimately by the solid crust beneath our feet.

The magnetic field is generated by the motions of the liquid iron alloy in the outer core, approximately 3,000 km beneath the Earth's crust. These motions occur because the core is losing heat to the overlying solid mantle that extends up to the crust on which we live.

There's been an exciting shift in scientific thinking about life beyond Earth recently. Extraterrestrial-seeking group SETI has started to recognize the importance of detecting alien artifacts along with radio signals. The most viable target for these searches is the Dyson sphere, a massive shell that envelops an entire star. But as Discovery's Ray Villard rightly points out, the difficulty of finding these near-invisible objects could be offset by searching for them in nearby galaxies where their presence would be much more obvious.

Finding a Dyson sphere is not easy - and it's not because we don't know how to do it. As we've discussed before, the trick is to distinguish the infrared signature of a Dyson sphere candidate from natural phenomenon. According to Villard, Dyson hunters have catalogued 17 "quasi-plausible" signatures - but they can't prove one way or another that they're not just, say, stars enshrouded in dust.

Consequently, it will be very difficult to prove that a Dyson sphere exists - at least one that's nearby.

European researchers said Thursday they had developed the world's first real-sized, five-fingered robotic hand able to grasp and manipulate objects with human-like dexterity.
Getting robots to manoeuvre objects with precision has posed many problems for engineers in their quest to build humanoid machines to serve as domestic aides, emergency rescuers or factory workers.

Industrial robotic "grippers" already exist that are able to grasp objects and move them but are unable to handle items as a human hand would -- grasping an egg without breaking it but also lifting heavy, bulky things.

It has also proved difficult to size prototypes on human measurements.

The team from Italy and Germany built a hand using strings that are twisted by small, high-speed motors in five fingers, each with three segments.

What happens when the Sun Earth and Moon line up (in that order)? Do people (or animals) get crazy? Commit more crimes? The Moon always shows us the same face, but there's only one instant when the Moon is truly "Full." @DavidSkyBrody explains.