New results coming from the Large Hadron Collider suggest that the hunt for the Higgs Boson, the particle that gives matter mass and holds the physical fabric of the universe together, really is over.

One Higgs-hunting team at CERN on the Swiss-French border reports a "5.9 sigma" levels of certainty it exists.

In laymans terms that equates to a one-in-550 million chance that the Higgs does not exist and the results are statistical flukes.

Particle physics has an accepted definition for a "discovery" which is a five-sigma level of certainty or above.

The number of standard deviations, or sigmas, is a measure of how unlikely it is that an experimental result is simply down to chance rather than a real effect

Similarly, tossing a coin and getting a number of heads in a row may just be chance, rather than a sign of a "loaded" coin

The "three sigma" level represents about the same likelihood of tossing more than eight heads in a row.

Five sigma, on the other hand, would correspond to tossing more than 20 in a row.

Now that two sets of results seem to confirm its existence it is becoming more of a certainty.

Accelerators like the LHC smash together particles at extraordinary energies in a bid to create a Higgs, which should exist only for a fleeting fraction of a second before decaying into other particles or flashes of light that can be caught and counted.

The findings only shore up a result that, as far as physicists were concerned, had already passed muster for declaring the existence of a new particle.

However, many questions remain as to whether the particle is indeed the long-sought Higgs boson; the announcement was carefully phrased to describe a "Higgs-like" particle.

More analyses will be needed to ensure it fits neatly into the Standard Model - the most complete theory we have for particles and forces - as it currently exists.

Last month's result had a 5 signma which meant they were 99.999% sure they have found a new particle.

Finding the Higgs plugs a gaping hole in the Standard Model, the theory that describes all the particles, forces and interactions that make up the universe.

If the particle was shown not to exist, it would have meant tearing up the Standard Model and going back to the drawing board.

The Higgs boson is the final piece of the Standard Model of Particle Physics, a theoretical model which describes the fundamental particles and forces that control our Universe.

It was first theorised in the 1960s by Edinburgh-based physicist Peter Higgs, amongst others, and is credited for giving all other particles mass. But until now, it has proved impossible to pin down.

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An evolutionary "loophole" might explain why males of many species live shorter lives than their female counterparts, a new study finds.

The loophole lies in the mitochondria, the energy-generating parts of our cells. The mitochondria have their own DNA, separate from the DNA that resides in the nucleus of the cell that we usually think of when we think of the genome. In almost all species, the mitochondria DNA is passed down solely from mother to child, without input from dad.

This direct line of inheritance may allow harmful mutations to accumulate, according to a new study detailed today (Aug. 2) in the journal Current Biology. Ordinarily, natural selection helps keep harmful mutations to a minimum by ensuring they're not passed down to offspring. But if a mitochondrial DNA mutation is dangerous only to males and doesn't harm females, there's nothing to stop mom from passing it to her daughters and sons.

"If a mitochondrial mutation pops up that is benign in females, or a mutation pops up that is beneficial to females, this mutation will slip through the gates of natural selection and go through to the next generation," said study researcher Damian Dowling, an evolutionary biologist at Monash Univeristy in Australia.

The result: a load of mutations that don't harm females, but add up to a shorter life span for males.

Mother's Curse

Dowling and his colleague tested this idea — dubbed "Mother's Curse" — in fruit flies (Drosophila melanogaster). They took flies with standardized nuclear genomes, meaning all had the same cellular DNA, and inserted mitochondrial DNA from 13 different fruit-fly populations around the world. [Global Life Expectancy (Infographic)]

"The only genetic difference across the strains of flies lay in the origin of the mitochondria," Dowling told LiveScience.

The researchers then recorded how long each strain of flies lived. Their findings revealed a big difference for males, but not for females.

"There was a lot of variation in terms of male longevity and male aging, but almost no variation in the female parameters of aging," Dowling said. "This provides very strong evidence that there are lots of mutations within the mitochondrial genome that are having an effect on male aging, but are having no effect whatsoever on female aging."

Explaining the gender gap

This finding bolsters the Mother's Curse hypothesis, Dowling said. And the results suggest that the age gap between males and females does not come down to just a few genes.

"In some ways this is bad news for medical biologists, because we're not looking for the mutation that causes early male aging, we're actually dealing with a whole lot of mutations within this genome that are teaming up to shorten male life span," Dowling said. [5 Reasons Aging Is Awesome]

The genetic inheritance of mitochondrial DNA is the same across species, so Dowling said he'd expect to see the same results in human males. There is speculation that women outlive men because men are generally bigger risk-takers or perhaps because testosterone, a hormone men have more of, has deleterious effects on life span, he said. But insects don't have testosterone or a tendency to drive too fast while not wearing a seatbelt, making them a good place to start looking for genetic underpinnings to the gender gap.

Males may not be entirely doomed, however, as evidenced by the fact that they haven't gone extinct yet. It's possible that the nuclear genome — the DNA we inherit from both of our parents — might be compensating for the mitochondrial handicap in men. In other words, men whose genomes can counteract the nasty effects of mitochondrial mutations might do better and pass on their genes more effectively.

"We're looking to uncover those genes now," Dowling said.

Follow Stephanie Pappas on Twitter @sipappas or LiveScience @livescience. We're also on Facebook & Google+. 

• Extending Life: 7 Ways to Live Past 100
• Busted! 6 Gender Myths in the Bedroom & Beyond
• 7 Ways the Mind and Body Change With Age

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If most people know one thing about black holes, they probably know that nothing can escape from them, not even light.

Yet this most basic tenet about black holes has actually been disproven by the theory of quantum mechanics, explains theoretical physicist Edward Witten of the Institute for Advanced Study in Princeton, NJ, in an essay published online today (Aug. 2) in the journal Science.

Black holes, in the classical picture of physics, are incredibly dense objects where space and time are so warped that nothing can escape from their gravitational grasp. In another essay in the same issue of Science, theoretical physicist Kip Thorne of Caltech describes them as "objects made wholly and solely from curved spacetime."

Yet this basic picture appears to contradict the laws of quantum mechanics, which govern the universe's tiniest elements.

"What you get from classical general relativity, and also what everyone understands about a black hole, is that it can absorb anything that comes near, but it can't emit anything. But quantum mechanics doesn't allow such an object to exist," Witten said in this week's Science podcast.

In quantum mechanics, if a reaction is possible, the opposite reaction is also possible, Witten explained. Processes should be reversible. Thus, if a person can be swallowed by a black hole to create a slightly heavier black hole, a heavy black hole should be able to spit out a person and become a slightly lighter black hole. Yet nothing is supposed to escape from black holes. [Photos: Black Holes of the Universe]

To solve the dilemma, physicists looked to the idea of entropy, a measurement of disorder or randomness. The laws of thermodynamics state that in the macroscopic world, it's impossible to reduce the entropy of the universe—it can only increase. If a person were to fall into a black hole, entropy would increase. If the person were to pop back out of it, the universal entropy tally would go down. For the same reason, water can spill out of a cup onto the floor, but it won't flow from the floor into a cup.

This principle seems to explain why the process of matter falling into a black hole cannot be reversed, yet it only applies on a macroscopic level.

Physicist Stephen Hawking famously realized that on the microscopic, quantum mechanical level, things can escape from black holes. He predicted that black holes will spontaneously emit particles in a process he dubbed Hawking radiation. Thus, quantum mechanics refuted one of the basic tenets of black holes: that nothing can escape.

"Although a black hole will never emit an astronaut or a table or a chair, in practice, it can definitely emit an ordinary elementary particle or an atom," Witten explained.

However, scientists have yet to observe Hawking radiation.

"Unfortunately, the usual astrophysical black holes, formed from stellar collapse or in the centers of galaxies, are much too big and too far away for their microscopic details to be relevant," Witten wrote.

Witten's essay is one of five new papers in Science this week summarizing the state of black hole research.

Follow Clara Moskowitz on Twitter @ClaraMoskowitz or SPACE.com @Spacedotcom. We're also on Facebook & Google+. 

More From Space.com:

• The Strangest Black Holes in the Universe
• Black Holes: Warping Time & Space
• What's at the Center of Black Holes?

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An antiques dealer has admitted interfering with an investigation into the illegal sale of rhino horns, the Manhattan U.S. Attorney's Office said Wednesday (Aug. 1), describing how the dealer used a pair of fake horns to try to double-cross investigators at one point.   

David Hausman pretended to aid the probe into the illegal sale of a black rhinoceros' head and instead tried to buy the head for himself, U.S. Attorney for the Southern District of New York Preet Bharara said in a statement.

In a plea deal, Hausman, 67, admitted in federal court on Wednesday (Aug. 1) to obstruction of justice and falsification of records in relation to the sale of the head of another black rhino. [See photos from the bust]

According to a court document, Hausman alerted the U.S. Fish and Wildlife Service in December 2010 that a taxidermied two-horned head had been illegally sold by a Pennsylvania auction house. However, when he learned the sale was not finalized, Hausman enlisted the help of a collaborator to covertly purchase the head. To keep investigators in the dark, Hausman made a pair of fake but realistic-looking horns, mailed them to the collaborator and asked her to attach them to the rhino head. [Faux Real: A Gallery of Forgeries]

But this wasn't the only incident, the court document recounts:

In September 2011, Hausman sought to purchase a different two-horned, black rhino head from an undercover federal agent posing as a seller. Before purchasing it, Hausman directed the seller to falsify documents to make the sale appear legal.

Not all sales of rhino horns are illegal in the United States; it is legal to sell horns as antiques when they are over a century old. However, Bharara's office said Hausman believed this head was 20 to 30 years old, and he asked the seller to create a document stating the head was older than 100 years. 

After watching Hausman buy the black rhino head at a truck stop in Princeton, Ill., federal agents followed him and saw him sawing off the horns in a motel parking lot, the U.S. Attorney's Office said.

When agents raided his Manhattan apartment in February of 2012, they found four mounted rhino heads, including three with no horns and one with fake horns, as well as three sets of horns and several items carved and partially carved from horn, the court document states. 

The U.S. Attorney's Office and Ignacia Moreno, assistant attorney general for the Environment and Natural Resources Division of the Department of Justice, handled the case.

The international black market is a serious threat to rhinos, large plant-eaters that live in Africa and Asia. Poaching is the main threat to the black rhinoceros, according to the International Union for Conservation of Nature and Natural Resources, which lists that species as critically endangered. A relative, the western black rhino, is now extinct.

The Convention on International Trade in Endangered Species of Wild Fauna and Flora, a treaty signed by 175 nations, prohibits nearly all commercial trade in rhino horns and parts of other species threatened with extinction. In addition, signatories, which include the United States, have committed to regulating trade within their borders.

This arrest was part of Operation Crash, a crackdown on the illegal trade of rhino horn in the United States.

Follow Wynne Parry on Twitter @Wynne_Parry or LiveScience @livescience. We're also on Facebook & Google+.

• Bounds of Biodiversity: Photos of Wildlife At Risk
• In Photos: Top 10 Deadliest Animals
• Up and Away! Photos of Rhinos in Flight

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Sir Lancelot had the Holy Grail. Captain Ahab had Moby Dick. For scientists who study learning, the ultimate quest is to unlock the secrets of engagement. How do we engage students in learning, and then keep them in that state? So ardent is their search that it can lead them down paths that may seem, to the uninitiated, a bit silly — as demonstrated by two recent developments.

Last month, it emerged that the Bill and Melinda Gates Foundation, which has directed millions of dollars into educational research, has awarded grants to study the use of galvanic skin response sensors in the classroom. Immediately dubbed “mood bracelets” and “educational pedometers” by critics, these are small devices worn around the wrist that gauge the user’s physiological arousal by measuring the amount of sweat on the skin. The idea is that a teacher instructing a roomful of students wearing the devices would instantly know who was engaged and who was bored or distracted. The problem is that the sensors are inexact indicators of the wearer’s mental state: a student’s nervous system might be active because there’s test coming up next period — or because there’s an attractive classmate one desk over.

Then last week, a professor of physics education at Kennesaw State University in Georgia reported the results of a pilot study using special glasses that track where and how long wearers direct their gaze. After analyzing the data produced by undergraduates who wore the glasses during lectures, professor David Rosengrant concluded that it was not the case, as many teachers believe, that students were most engaged for the first 15 minutes or so of class, after which their attention gradually slacked off. Rather, he said, student engagement ebbed and flowed over the course of the 70-minute lecture, and spiked whenever the professor used humor, stood close to the student, or talked about material that was not included in the Power Point presentation projected on a screen at the front of the room. Rosengrant also determined that cell phones and the web — especially Facebook — were the greatest obstacles to maintaining students’ engagement in the classroom.

Interesting, but hardly revelatory. Clearly, such devices have a long way to go before they can offer real insight into students’ thoughts and feelings. The irony is that, after many years of investigation, scientists already have a pretty good idea of what captures the attention of an audience — whether it’s students in a classroom, a group of coworkers at a meeting, or a gathering of guests in front of whom you’re making a toast. Follow the strategies below, and you won’t need a sweat sensor or special glasses to know that your listeners are fully engaged.

1. Stimulate curiousity

“Sometimes I think that we, as teachers, are so eager to get to the answers that we do not devote sufficient time to developing the question,” notes Dan Willingham, a cognitive scientist at the University of Virginia. “But it’s the question that piques people’s interest. Being told an answer doesn’t do anything for you.” Take the information you want your audience to know by the end and frame a question that will direct your listeners toward that answer.

2. Introduce change and surprise

Human beings quickly become habituated to the status quo. When something in our environment shifts, however, we start paying attention again. A good rule of thumb is to switch things up every 15 minutes or so — tell a joke or a story, show a picture, address your topic in a different way.

3. Stress relevance and concreteness

The human mind can’t handle too much abstraction. Bring your ideas down to earth by explaining how they connect to your listeners’ lives, and by embedding sensory details — what things look, sound, feel and taste like — into your account.

4. Tell stories

Researchers who study human cognition say that stories are “psychologically privileged” — that is, our minds treat them differently than other kinds of information. We understand them better, remember them more accurately, and we find them more engaging to listen to in the first place. When planning your presentation, think about how to capture your ideas in a narrative. And remember, good stories usually have strong characters, a conflict — the main character can’t get what he wants — and complications on the way to overcoming that conflict. Come to think of it, a lot like the stories of the Holy Grail and Moby Dick.

This article originally appeared at TIME.

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In September 2011, 163 dead harbor seal pups mysteriously washed up on the shores of New England, and scientists have finally figured out why.

The seafaring mammals had come into contact with a new strain of virus closely related to a kind of bird flu.

But perhaps most worrisome about this newly dubbed "seal flu" is that it could eventually impact humans if it continues to evolve.

Here, a concise guide to the flu strain:

How did the seals get it?
The flu in question evolved from H3N8, a strain that was first isolated in North American ducks in 2002.

The pathogen is capable of making the leap from birds to mammals like horses and dogs, and now it infects young seals, too. (Most of the pups, which were either dead or dying when they washed ashore, were under 6 months old).

Many animals, including seals, bats, pigs, birds, and whales, are susceptible to certain types of the flu that typically originate in birds and then spread to mammals.

The swine flu, or H1N1, outbreak of 2009, for example, was a combination of bird, pig, and human-infecting virus bits coming together,says Wynne Parry at LiveScience. This new variety is considered a relative.

What does this new flu do?
The virus wreaks havoc on the immune system, and, in mammals, binds to cells in the respiratory tract, making it difficult to breathe. Usually it kills infected birds, and it left "horrifying skin lesions" on the seals, "a previously unknown symptom in flu deaths."

What makes these findings especially concerning is that H3N8 mutated to infect a new kind of mammalian host in just a few short years. "Although birds carry a wide variety of flu viruses, which sometimes make the jump into mammals, they almost never acquire the ability to spread from mammal to mammal," says Alexandra Sifferlin at TIME. Researchers have determined that eventually this virus probably could.

But can it really infect humans?
While scientists still aren't certain if this virus could infect humans, the worry is that its alarmingly fast mutation rate may one day allow it to. When a "virus can adapt, evolve, and become more mammalian in phenotype," then "we really need to be concerned," says Dr. Anne Moscana, who edited the report on seal flu.

Although the swine flu outbreak of 2009 killed just 0.002 percent of the millions who were infected, there's a possibility that this new variety could be much deadlier if it progresses. The fact is that "flu could emerge from anywhere, and our readiness has to be much better than we previously realized."

Sources: BBC News, Daily Mail, LiveScience, TIME

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In the silence of space on the approach to Mars a US probe is warming up for an unprecedented act of theatre. Heaters aboard the hurtling spacecraft have begun to glow, thawing thrusters and components ahead of the most daring landing ever attempted on an alien world.

Bearing down on the red planet at more than 8,000 miles per hour, the Nasa ship is carrying the space agency's Curiosity rover, a gangly off-road vehicle with robotic tools to scoop, drill and vaporise the soil and rocks strewn across the dusty landscape. The rover's job is to explore the geology of an enormous crater basin, and uncover whether Mars was ever capable of harbouring life. But first it must touch down safely.

The $2.5bn (£1.6bn) mission blasted off in November on a journey of 300m miles. It is due to land the Curiosity rover at 6.31am (BST) on Monday morning. If all goes to plan, the rover will touch down in the vast Gale crater, around six miles from Mount Sharp, or Aeolis Mons, which rises more than 5,000 metres from the crater bed. The rover's first port of call is what looks like an alluvial fan, a pattern of sediments thought to be created by flowing water, perhaps billions of years ago.

"We expect to land downslope of the alluvial fan, and since water flows downhill, we're optimistic we'll find evidence for an ancient watery environment there," said John Grotzinger, a geologist and project scientist on the Nasa mission. "If there was ground water, or a lake there, then it's possible this was once a habitable environment."

Powered by a lump of radioactive plutonium and lithium-ion batteries, the Curiosity rover is due to explore the Gale crater and its huge central mountain for one Martian year, or 687 Earth days. Much of the mission will be spent trundling up and down the gentle flanks of Mount Sharp, sampling rocks, and following a path scientists plotted on maps compiled from images snapped by Mars orbiters.

Scientists are banking on the mountain being key to the planet's geological past. The rocks at the bottom may be more than 3.5bn years old, while those higher up formed more recently, and so get progressively younger the higher the rover climbs. Curiosity can reach out with a robotic arm, to scoop, drill and hammer rocks, and analyse their make-up with onboard instruments. On a mast protruding from the centre of the rover is a laser that can vaporise rock surfaces and analyse their elemental constituents from up to nine metres away.

"What we see from orbit are the kinds of rocks we think form in the presence of water," Grotzinger said, "and those will be revealed by the clay minerals we find with Curiosity. If the minerals were formed in water, we can infer that maybe there was a habitable environment there. We'll be looking for evidence that maybe there was water flowing on the surface that transported muds that came to rest in these deposits. Maybe the water was there for sufficiently long periods of time that it could have sustained life, had it ever evolved."

Water is only part of the story. The roving laboratory will also look for molecular chains of carbon that are bound to hydrogen, another apparent prerequisite for life. "There's no one feature that says it's a habitable environment; you are looking for a preponderance of evidence," Grotzinger added.

Though Curiosity might find signs that Mars was once habitable, the rover is not designed to find direct evidence of alien life, for example, in the form of fossilised micro-organisms. This is a prospecting mission, aimed at scouring the Gale crater for sites where future rovers, or even human explorers, might one day find concrete evidence of past life on the planet.

But before the science can begin, the three-metre-long rover must touch down on Mars. The size of a family car, this is Nasa's largest rover yet, and tried and tested means of landing on the planet are not sufficient to cushion the rover on impact.

"She's a beast," said Ann Devereaux, an engineer who works on the crucial Entry, Descent and Landing, or EDL, team of the mission. "The fact that we're doing this crazy landing sequence allows us to pinpoint a target on the ground, but the previous ways we've landed on Mars, with airbags, parachutes and even retrothrusters, simply wouldn't work with this rover. Going this big changes things."

Mission controllers will stop talking to the spacecraft two hours before it reaches Mars. At that time, everything the probe needs to get to its landing site will be programmed into the ship's computers. The manoeuvres the spacecraft must execute are so fine and complex that the slightest mistake could notch up another grim statistic in the history of failed missions to the planet.

Ten minutes before the spacecraft arrives, it will jettison its cruise stage and fire thrusters to swing the probe's heat shield into a forward position. Explosive charges then release two 75kg blocks of tungsten, to shift the balance of the probe so it can fly through the tenuous Martian atmosphere. As the probe streaks through the sky, the heat shield will reach more than 2,000C.

Guided only by an onboard computer, small thrusters will steer the spacecraft through the Martian sky, and pull a series of "S" turns to line it up with its landing spot in the Gale crater. After more tungsten weights are shed, the probe deploys a parachute and blasts the heat shield free, revealing a video camera to record the landing.

One mile above the ground, the spacecraft cuts the parachute loose, and begins to fall, until eight retrorockets fire up to control its descent. As it nears the surface, the probe begins what Nasa calls a Sky Crane manoeuvre that lowers the Curiosity rover down on nylon ropes. When the rover hits the ground – hopefully gently – the spacecraft flies to one side and crash lands a short distance away.

Through the entire descent, there is nothing the mission scientists can do from their offices at Nasa's Jet Propulsion Laboratory in California, but wait for the rover to call home. No wonder Nasa staff have hit on the phrase "seven minutes of terror" to describe the probe's descent.

Mission scientists are hopeful that Curiosity will build on the success of Nasa's two recent Mars rovers, Spirit and Opportunity, which touched down in 2004. Their missions were planned to last three months, but Spirit continued to explore the Martian surface until 2010. Opportunity is still operational.

"We've had fantastic results with Spirit and Opportunity, and we hope Curiosity will follow in her cousin's footsteps," said Devereaux. "We just have to get her down to the ground safely. I can't even envisage what she might find, or how far she might go, but it's a big step just to get her down."

Grotzinger confesses to having "blind faith" in the team who drew up plans to land the rover on Mars. "The landing is complicated. It looks improbable, but the guys who built it have very high confidence in it, so I must as well," he said. "Everything I've done for the last five or six years, everything we've done as a team, comes down to those seven minutes."

This article originally appeared on guardian.co.uk

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Mankind could only be a decade away from walking on Mars, a Nasa scientist has said, as the US space agency makes its final preparations to land a one-tonne exploratory rover – the largest yet – on the barren planet.

A probe the size of a small car will hurtle through the Martian atmosphere at 13,000mph early on Monday morning using engineering which, if successful, could lay the path for the first manned Mars landing.

Using a giant £1.67bn heat shield, the world’s biggest supersonic parachute and eight rocket thrusters, scientists hope Curiosity, a super bot kitted out with 32 cameras and dozens of sampling instruments, will be the test of technological prowess needed to prove an astronaut could eventually descend on the Red Planet in the future.

“If we had the motive, if it was important enough I would say within 10 years we could be there,” Adam Steltzner, the lead mechanical engineer for the entry, told The Daily Telegraph.

“Putting men on Mars is not unachievable. It is just really hard and expensive. So if the world were to find itself with enough resources and the motivation, we could do it.”

Scientists will use a “guided entry” system to land the Curiosity rover, with jet boosters firing at the back of the craft to help her steer through the atmosphere towards the Gale crater landing site.

The descent is expected to reach more than 10 Earth Gs.

It will take a nail-biting “seven minutes of terror” for Curiosity to land, but 14 minutes until Nasa’s 100-strong team of scientists will discover the fate of the probe and whether a combined three centuries of human investment has paid off.

“There is a little bit of apprehension but you have to be just a little nervous every time you go to Mars,” Doug McCuistion, director of the Mars Exploration Programme, said.

“Everyone is confident that they have done everything humanly possible to make sure that this will work. Now it’s a matter of putting it all together.”

Technicians have installed sensors on the heat shield, which is designed to detach as the parachute is deployed, to measure pressure levels and thermal impact during the entry phase.

The heat shield designed for Curiosity’s landing is very similar in size and type to the thermal shield on the Orion deep-space capsule, a craft currently in development which will carry four crew members.

Radiation data will also be collected during the descent to test whether man could tolerate emission fluctuations caused by solar storms from inside a capsule.

“We will learn an enormous amount about what it takes on guided entry visual, what the impacts are on the thermal protection systems and what the atmosphere looks like,” Mr McCuistion said.

“This coupled with the RAD (Radiation Assessment Detector) data really pushes us further into the future and the potential to get humans to Mars.”

Experts at Nasa's Jet Propulsion Laboratory said conditions were “looking good” for the Mars landing on Monday morning, scheduled for impact just after 6.30am.

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At 10:31 p.m. PDT on Aug. 5, after nearly nine months of travel, NASA's Mars Science Laboratory mission (with a rover named Curiosity) will arrive at the Red Planet.

The $2.5 billion rover will begin a two-year quest to explore the interior of Mars' Gale Crater and hunt for evidence of an ancient ocean there. But before this hunt can begin, Curiosity has to land.

The Mars Science Laboratory landing sequence has been the topic of much discussion even before the mission launched on Nov. 26, 2011. Nicknamed "seven minutes of terror," the spacecraft's entry, descent and landing sequence will require a lot of things to go perfectly right — all before anyone on Earth receives even a single signal, due to the length of time it takes for information to travel from Mars to Earth.

"By the time we get the first signal that says 'okay, I've now reached the top of the atmosphere,' in reality the rover has already been on the surface for seven minutes," said Steven Sell, deputy operations led for Entry, Descent and Landing at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It's like your kid playing in the big game, and you can only sit there in the stands and watch. It's a nail-biter all the way."

When the Curiosity rover arrives at Mars it will be traveling at a velocity of 13,000 miles per hour (21,000 kph). Within seven minutes, the vehicle needs to get down to a velocity of zero miles per hour — all in one piece, of course, and in the right spot. [Mars Rover's Sky Crane Landing (Infographic)]

Step one

The first step in this process will be a guided entry, during which the entire MSL spacecraft (currently consisting of the rover and descent stage tucked into a protective aeroshell) will adjust its course toward its 12-by-5-mile-diameter landing ellipse — only an eighth the size of the landing targets of previous rovers.

As it impacts Mars' atmosphere at more than 13,000 mph, MSL's heat shield will take the brunt of the frictional heating generated by the deceleration, and will soon glow white-hot with temperatures reaching 1,600 degrees Fahrenheit (870 degrees Celsius). Even through this, MSL will still be physically guiding itself toward Gale Crater, firing rockets to keep it on track.

The atmosphere on Mars, 100 times thinner than Earth's, isn't dense enough to slow MSL down by itself. So at this point a parachute will be deployed — literally the largest supersonic drogue chute ever created — to slow MSL down from 1,000 mph (1,600 kph) to about 200 mph (320 kph), subjecting the spacecraft to 9 Gs of force. (That's nine times the pull of Earth's gravity.)

Then, with the surface of Mars still approaching rapidly, the spacecraft's heat shield will be jettisoned, exposing the actual rover and allowing it to use its radar guiding system to determine just how high it is. This is one of the most crucial parts of the descent, since it's not until then that MSL will be able to check its altitude.

"When the heat shield comes off and the radar turns on, we need to find the ground," said Sell. "When we first eject the heat shield we're too high for the radar to see the ground yet, so we have to wait a very long 20 to 30 seconds, up to a minute, until the radar can get close enough to the ground to be able to see it. Without that solution it doesn't even try to do the rest of the landing."

And once that's all done, it'll really start to get interesting.

Making a touch down

At nearly 2,000 pounds (900 kg), Curiosity is simply too large to land with airbags like previous rovers. Instead, engineers devised a method that's never been attempted before: a sky crane.

When MSL reaches precisely the right altitude, its descent stage, gripping the Curiosity rover within the sky crane structure, will drop from the aeroshell and quickly fire its thrusters, moving it safely away from the falling back shell and slowing it further.

Curiosity will be carried steadily downwards by the descent stage, which will use its Mars Descent Imager (MARDI) camera to maneuver over its target and, once at a height of 20 meters (about 65 feet) use rockets to hover in place while it lowers the rover down to the surface on bridles and an umbilical cord — all three of which are bearing the weight of the rover.

Although the system has been exhaustively tested on Earth using simulations and very advanced computer models, the first time it's going to play out in full will be during the actual landing on Mars.

"It's the ultimate field test," Sell said.

As soon as Curiosity has touched down, the cords will be cut and the descent stage will soar safely off to the side, crashing onto the Martian surface far enough away to pose no danger to the rover. At this point Curiosity, wheels down, is ready to begin its mission.

That is, as long as everything goes exactly and precisely as planned. On the night of Aug. 5, the entire world — not to mention quite a few folks at JPL — will be watching to see how a rover the size of a Mini Cooper can be sent hundreds of millions of miles to touch down on the surface of another planet.

"We've been preparing for this for many, many years … we're excited to get out there and land this thing," Sell said.

Visit SPACE.com for complete coverage of NASA's Mars rover landing Sunday. Follow SPACE.com on Twitter @Spacedotcom. We're also on Facebook & Google+.

• Mars Rover Curiosity: Mars Science Lab Coverage
• Mars Rover Landing: NASA Set for Curiosity's Red Planet Arrival (Photos)
• The Boldest Mars Missions in History

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Much like lizards that ditch their tails in a tussle, some deep-sea squid can sacrifice their glowing arms to distract enemies and swim to safety. Scientists observed this defense mechanism first-hand in the foot-long octopus squid (Octopoteuthis deletron) off the coast of California.

"If a predator is trying to attack them, they may dig the hooks on their arms into the predator's skin," said University of Rhode Island researcher Stephanie Bush. "Then the squid jets away and leaves its arm tips stuck to the predator. The wriggling, bioluminescing arms might give the predator pause enough to allow the squid to get away."

Setting out to answer why many octopus squid have arms of different lengths, Bush and her team deployed a camera-equipped remotely controlled vehicle in the undersea Monterey Canyon and prodded a squid with a bottlebrush.

"The very first time we tried it, the squid spread its arms wide and it was lighting up like fireworks," Bush said in a statement from the University of Rhode Island. "It then came forward and grabbed the bottlebrush and jetted backwards, leaving two arms on the bottlebrush. We think the hooks on its arms latched onto the bristles of the brush, and that was enough for the arms to just pop off."

Though the squid eventually re-grow their severed arms, the strategy might seem extreme. Bush notes that there is "definitely an energy cost associated with this behavior, but the cost is less than being dead." [See Cool Photos of Squid]

During later experiments, Bush found that some of these deep-sea squid seemed hesitant to let go of their limbs, while some did so after being poked several times, according to the statement. She also tested seven other squid species for the defense strategy and found that none of them jettisoned their arms.

The results of Bush's experiments were published in the July 2012 issue of the journal Marine Ecology Progress Series.

Past research on the octopus squid found they have another ingenious ability: In the deep, dark waters where the squid live, meeting a mate is tough, and when they do come across their own species, the deep-sea gloom means it's tough to tell a gal from a guy. The octopus squid's workaround? They simply mate with any octopus squid that crosses their path.

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• Marine Marvels: Spectacular Photos of Sea Creatures
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Circa 1870, the North fought the South in the Civil War.

Half a century later, around 1920, worker unrest, racial tensions and anti-Communist sentiment caused another nationwide upsurge of violence. Then, 50 years later, the Vietnam War and Civil Rights Movement triggered a third peak in violent political, social and racial conflict.

Fifty years after that will be 2020. If history continues to repeat itself, we can expect a violent upheaval in the United States in a few years.

It sounds like pseudoscience, but it's a published theory. "My model suggests that the next [peak in violence] will be worse than the one in 1970 because demographic variables such as wages, standards of living and a number of measures of intra-elite confrontation are all much worse this time," said Peter Turchin, an ecologist, evolutionary biologist and mathematician at the University of Connecticut.

Turchin has led the development of a field of study called "cliodynamics," in which scientists attempt to find meaningful patterns in history. The endeavor flies in the face of the traditional study of history, which assumes the countless variables interacting within a society lead to chaotic fluctuations in outcomes like violence and social unrest. Massimo Pigliucci, a philosopher of science at CUNY-Lehman College, said most historians believe that "the factors at play are so many and so variable that there is little reason to expect quasi-regular cycles, or a unified theory to explain them."

But Turchin argues there is order in the chaos after all. [Infographic: Cycles of Violence in the U.S.]

In the new study, Turchin, who reported his results in the July issue of the Journal of Peace Research, compiled historical data about violent incidents in U.S. history between 1780 and 2010, including riots, terrorism, assassinations and rampages. The data indicates that a cycle of violence repeats itself every 50 years in America, like a wave that peaks in every other generation. This short-term cycle is superimposed over another, longer-term oscillation that repeats every 200 to 300 years. The slower waves in violence can either augment or suppress the 50-year peaks, depending on how the two cycles overlap.

The longer cycle is "the one which we understand much better, and it is a universal feature of all complex societies," Turchin told Life's Little Mysteries. From the Roman Empire to medieval France to ancient China, scholars have noted that societies swing between 100-150 years of relative peace and 100-150 years of conflict, and then back again. Only some societies exhibit the shorter-term, and less subtle, 50-year-long cycles of violence along the way — the Roman Empire, for one, and if Turchin's theory is correct, the United States as well.

Why 50-year cycles? Turchin explained that a surge of violence begins in the same way as a forest fire: explosively. After a period of escalation followed by sustained violence, citizens begin to "yearn for the return of stability and an end to fighting," he wrote in his paper. The prevailing social mood swings toward stifling the violence at all costs, and those who directly experienced the civil violence maintain the peace for about a human generation—20 or 30 years. But the stability doesn't last.

Eventually, "the conflict-scarred generation dies off or retires, and a new cohort arises, people who did not experience the horrors of civil war and are not immunized against it. If the long-term social forces that brought about the first outbreak of internal hostilities are still operating, then the society will slide into the second civil war," he wrote. "As a result, periods of intense conflict tend to recur with a period of roughly two generations (40–60 years)."

Peaks occurred around 1870, 1920 and 1970. Confounding this pattern, there was no peak of U.S. violence in the 1820s. In fact, historians call it the "era of good feelings." Turchin explained that social variables such as wages and employment were "really excellent at that time, so there was no reason for any violence to get going." The cycle was skipped. [Do Recessions Increase Violent Crimes?]

But we might not be so lucky this time around. If Turchin's model is right, then the current polarization and inequality in American society will come to a head in 2020. "After the last eight years or so, notice how the discourse in our political class has become fragmented. It's really unprecedented for the last 100 years," he said. "So basically by all measures, there are social pressures for instability that are much worse than 50 years ago."

Pigliucci, who writes a well-known blog on pseudoscience and skeptical thinking, says that although he believes Turchin is "moving in the right direction" by applying mathematical models to history, in this case he might be seeing patterns in random data. Violence and other forms of social unrest undoubtedly vary over time within any given society, Pigliucci said, but most historians would say these fluctuations are chaotic.

"The database is too short: the entire study covers the period 1780-2010, a mere 230 years," he wrote in an email. "You can fit at most four 50-year peaks and two [long-term] ones. I just don't see how one could reasonably exclude that the observed pattern is random. But of course we would have to wait a lot longer to collect new data and find out."

Daniel Szechi, professor of early modern history at the University of Manchester in England, agrees that not enough time has passed for patterns to have emerged. However, he believes "cliodynamics" could eventually work, once humanity racks up a few more centuries of good record-keeping. "Maybe 500 years from now we will have sufficient data and sufficient number crunching power to really make use of the data we will have generated and stored in vast quantities since about 1900," Szechi said in an email.

But even if, half a milennium from now, massive data generation and sophisticated programmatic analysis allows predictive history, Szechi asks: "Is this a good idea?" Prophecies of violence pose the danger of becoming self-fulfilling. Another concern is that governments and other institutions could respond to their knowledge of impending violence by taking preemptive measures, which would not always be in the interests of the people.

The heated debate over cliodynamics will continue among historians and scientists. Only time will tell if the cycle of U.S. violence identified by Turchin holds true, and another telltale peak — or lack thereof — is only a few years away.

Follow Natalie Wolchover on Twitter @nattyover or Life's Little Mysteries @llmysteries. We're also on Facebook & Google+.

More From Life's Little Mysteries:

• The 10 Most Destructive Human Behaviors
• Fight, Fight, Fight: The History of Human Aggression
• Math Formula May Explain Why Serial Killers Kill

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Whether you're gay, straight or somewhere else on the spectrum, the truth of who attracts you could be in your eyes.

Pupil dilation is an accurate indicator of sexual orientation, a new study finds. When people look at erotic images and become aroused, their pupils open up in an unconscious reaction that could be used to study orientation and arousal without invasive genital measurements.

The new study is first large-scale experiment to show that pupil dilation matches what people report feeling turned on by, said study researcher Ritch Savin-Williams, a developmental psychologist at Cornell University.

"So if a man says he's straight, his eyes are dilating towards women," Savin-Williams told LiveScience. "And the opposite with gay men, their eyes are dilating to men."

The eyes have it

The link between pupil size and arousal goes way back. In 16th-century Italy, women would take eye drops made from the toxic herb Belladona, which kept their pupils from constricting and was thought to bestow a seductive look.

In fact, Savin-Williams said, the pupils dilate slightly in response to any exciting or interesting stimulus, including a loved one's face or a beautiful piece of art. The dilation is a sign that the autonomic nervous system — the system that controls involuntary actions like pulse and breathing — is ramping up.

Traditionally, researchers have studied arousal and sexual orientation by asking volunteers to watch erotic movies or pictures while attached to instruments that measure blood flow to the genitals. For men, this involves a circumference measurement of the penis, while women use a probe that measures pressure change in the blood vessels of the vaginal walls.

These measurements have drawbacks, Savin-Williams said. Some people can suppress their genital arousal, or simply don't have genital responses in a laboratory environment. And then there's the invasiveness issue.

"Some people just don't want to be involved in research that involves their genitals," Savin-Williams said.

Simply asking people if a given stimulus turns them on or not is equally problematic, as people may be ashamed to admit their desires or even deny them to themselves. It's also difficult to ask direct questions about sexual orientation in many cultures, Savin-Williams said. [5 Myths About Gay People, Debunked]

Measuring arousal

To get around these issues, Savin-Williams and his colleague Gerulf Rieger, also of Cornell University, turned to the pupils. They recruited 165 men and 160 women, including gay, straight and bisexual participants. These volunteers watched separate one-minute videos of a man masturbating, a woman masturbating and neutral landscape scenes. The videos were all matched for brightness so that differences in light wouldn't skew the results.

A gaze-tracking camera recorded the pupils during these videos, measuring tiny changes in pupil size. People also reported their own feelings of arousal to each video.

The results showed that pupil dilation matches the pattern seen in genital arousal studies. In men, this pattern is generally straightforward: Straight men respond to sexual images of women, and gay men respond to sexual images of men. Bisexual men respond to both men and women.

In women, things are more complex, Savin-Williams said. Gay women show more pupil dilation to images of other women, similar to the pattern seen in straight men. But straight women dilate basically equally in response to erotic images of both sexes, despite reporting feelings of arousal for men and not women. [6 Gender Myths Busted]

This doesn't mean that all straight women are secretly bisexual, Savin-Williams warned, just that their subjective arousal doesn't necessarily match their body's arousal. Sex researchers aren't sure why this happens. One theory is that because women have been at risk of being raped throughout history, they evolved to respond with lubrication to any sexual stimulus, no matter how unappealing. This idea holds that women who did so were less likely to experience trauma or infection after sexual assault, making it more likely that they would survive to pass on their genes.

The researchers detail their findings today (Aug. 3) in the journal PLoS ONE. The next step, Savin-Williams said, is to look at pupil measurements and genital measurements at the same time, to test how well they correspond.

Eventually, he said, this technology could be used to conduct cross-cultural studies of sexuality, given that pupil dilation is universal and doesn't depend on labels of sexual orientation that may not translate across all languages. The method could even be used to help people who are confused about their sexuality sort through their desires, Savin-Williams said.

Follow Stephanie Pappas on Twitter @sipappas or LiveScience @livescience. We're also on Facebook & Google+. 

• The Sex Quiz: Myths, Taboos and Bizarre Facts
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George Edwards, a Scottish skipper who spent decades searching for the beast said to inhabit Loch Ness, claims to have finally spotted his elusive quarry and gotten what he calls photographic proof of the monster.

On Nov. 2, 2011, Edwards photographed what appears to be a single hump in the water from the deck of his boat, "Nessie Hunter." Edwards said that "It was slowly moving up the loch towards Urquhart Castle and it was a dark grey color. It was quite a fair way from the boat, probably about half a mile away but it's difficult to tell in water," according to the Daily Mail, which has has posted Edwards photo. He watched the object for five to ten minutes before it slowly sank and did not resurface.

Edwards said he waited to release the photograph until after unnamed experts had examined it. Oddly, he is quoted in the Daily Mail as having had the photograph "independently verified by a team of US military monster experts." In fact, the United States military does not have a team of "monster experts" that it dispatches to investigate huge, unknown creatures around the world. Nor, for that matter, is it clear what "verifying" his photo would mean other than suggesting it was likely a real (i.e., not digitally faked) image of something in the water — though what that "something" might be is, of course, the relevant question. The shape could theoretically be anything from a fish to a floating log to a lake monster.

Edwards' description of his sighting raises more questions than it answers. For example, if he had the object in sight for five to 10 minutes, why is there (apparently) only one photograph of it? That's enough time to capture dozens or hundreds of photographs. And though the unknown object seems large, there's no way to determine its size since we don't know the exact distance to the object (though he's quoted as saying it was a half-mile away), and there's nothing of scale nearby to help judge. Depending on how close it is to the camera, it could be 5 feet long or 50 feet long.

A watery clue to the mystery?

There are many unknowns, but if Edwards' account is accurate, it may provide an important clue as to the "monster's" identity. Other mysterious objects floating in lakes have been known to behave exactly as Edwards described — for example, the most famous sighting of "Champ," the monster said to live in Vermont's Lake Champlain. A woman named Sandra Mansi sighted and photographed "Champ," resulting in what was called the "best photo" of the monster, and indeed of any lake monster anywhere. [Our 10 Favorite Monsters]

That dark, humped "creature" was later revealed to almost certainly be a submerged tree trunk brought to the surface by buoyant gases created during decomposition. It rose to the surface, floated for about five to 10 minutes (during which time it looked exactly like a monstrous hump), then sank back down into the cold water never to be seen again. It is a well-established phenomenon that can — and has — created false lake monster sightings and photographs.

The floating log hypothesis also explains why these images are unusually good: Unlike an animal or wave that appears for mere seconds and creates blurry images, a log remains stationary for minutes, allowing for sharper, clearer photographs. Then they sink back down to the lake floor never to be seen again, having created a monstrous, mysterious "best ever" photograph.

The solution to one famous "best ever" lake monster sighting and photo does not necessarily solve another "best ever" sighting and photo, though Lake Champlain and Loch Ness have many similar characteristics (including wooded shorelines). The similarities are striking, and there's good reason to suspect the same natural hydrologic phenomenon was responsible for both monster photographs.

There is of course a strong economic incentive to promote monsters like Nessie: tourism. Loch Ness is the main tourist draw in the Scottish highlands, and Edwards makes his living guiding visitors who come from all over the world hoping for a glimpse of the famous monster. No one has suggested that Edwards faked the photo, but it's fair to point out that if an ambiguous shape is seen in the waters of Ness, the monster interpretation is far more likely to be accepted than a mundane explanation. If it's a fish or floating log, it's a non-story; if it's a possible "best evidence" of Nessie, it's international news.

The Loch Ness monster first jumped into international notoriety in the 1930s after a photo was widely published showing a serpentine head and neck. That image, taken by a London surgeon named Kenneth Wilson, was touted as the best evidence for Nessie — until it was admitted to be a hoax decades later. [Countdown: The World's Greatest Hoaxes]

Loch Ness itself has been repeatedly searched for over 70 years, using everything from miniature submarines to divers and cameras strapped on dolphins. In 2003 a team of researchers sponsored by the British Broadcasting Corporation (BBC) undertook the largest and most comprehensive search of Loch Ness ever conducted. They scoured the lake using 600 separate sonar beams and satellite navigation. No large unknown creatures were found.

If, as seems likely, Edwards photographed a floating log, there will be no way to prove it one way or the other nine months later. Edwards' photograph may or may not be of the Loch Ness monster, but one thing is certain: It is not the first "best ever" photographic evidence, and it won't be the last.

Benjamin Radford is deputy editor of Skeptical Inquirer science magazine and co-author of Lake Monster Mysteries: Investigating the World's Most Elusive Creatures. His Web site is www.BenjaminRadford.com.

• Rumor or Reality: The Creatures of Cryptozoology
• Bigfoot, Nessie & the Kraken: Cryptozoology Quiz
• Top Ten Unexplained Phenomena

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Via Dreamland: Adventures in the Strange Science of Sleep:

The only thing stranger than the need to sleep is what happens when it is ignored. In 1965, a San Diego high school student named Randy Gardner stayed awake continuously for 264 hours, an eleven-day feat documented by a team of researchers from Stanford University who happened to read about his attempt beforehand in the local newspaper. For the first day or so, Gardner was able to remain awake without any prompting. But things went south quickly. He soon lost the ability to add simple numbers in his head. He then became increasingly paranoid, asking those who had promised to help him stay up why they were treating him so badly. When he finally went to bed, he slept for nearly fifteen hours straight. And yet a few weeks later, he was as good as new. To this day, he continues to be a minor celebrity in Japan.

So what's going on under the hood when you stay awake this long?

Within the first twenty-four hours of sleep deprivation, the blood pressure starts to increase. Not long afterward, the metabolism levels go haywire, giving a person an uncontrollable craving for carbohydrates. The body temperature drops and the immune system gets weaker. If this goes on for too long, there is a good chance that the mind will turn against itself, making a person experience visions and hear phantom sounds akin to a bad acid trip. At the same time, the ability to make simple decisions or recall obvious facts drops off severely. It is a bizarre downward spiral that is all the more peculiar because it can be stopped completely, and all of its effects will vanish, simply by sleeping for a couple of hours.

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PASADENA, Calif. — They entered the room like rock stars coming back onstage for an encore, or like heroes returning from a war.

The leaders of the team that put NASA's huge Curiosity rover safely on the surface of Mars received a raucous and lengthy standing ovation as they filed in for a post-landing press conference here at NASA's Jet Propulsion Laboratory (JPL) Sunday night (Aug. 5).

The excitement was understandable, for the team had just pulled off an unprecedented, daring and nerve-wracking touchdown on the Red Planet. In a maneuver that had never been attempted before on another world, a rocket-powered sky crane lowered the 1-ton rover to the Martian surface on cables, then flew off to crash-land intentionally a safe distance away.

After things settled down, NASA chief Charles Bolden said a few stirring and patriotic words, as did White House science adviser John Holdren, who conveyed President Obama's congratulations on a job well done. [1st Images of Mars from Curiosity Rover (Video)]

Landing Curiosity successfully "was by any measure the most challenging mission ever attempted in the history of robotic planetary exploration," Holdren said. "So congratulations again, and long live American Curiosity!"

Then ecstatic chaos reigned again, as Curiosity's entire entry, descent and landing team came in to another standing ovation and chants of "EDL! EDL! EDL!"

Dozens of engineers made a circuit of the room, shaking hands and exchanging high-fives with the luminaries on the podium and the reporters and assorted guests in the crowd. The exuberant display continued for 10 minutes or so before JPL director Charles Elachi pleaded for calm and quiet so the press conference could continue.

The mood then shifted again, to one of reflection and reverence in contemplation of a great achievement. Several speakers stressed the importance of the night's events for NASA's planetary exploration efforts, and for the nation as a whole.

"There are many out in the community who say that NASA has lost its way, that we don't know how to explore, that we've lost our moxie," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate. "I think it's fair to say that NASA knows how to explore, we've been exploring, and we're on Mars."

Adam Steltzner of JPL, the leader of Curiosity's EDL team, seemed to fight off tears several times when the microphone came his way.

"I am terribly humbled by this experience," he said. "In my life, I am and will be forever satisfied if this is the greatest thing that I have ever given."

Steltzner and his wife are expecting a baby girl — their second child — in about three weeks. Steltzner said he won't name her Curiosity, though he was immediately smitten by the name when he read it among a list of schoolchildren's submissions several years ago. (NASA held a naming contest in late 2008, asking students to provide a moniker for the rover more endearing than MSL, short for the mission's official name, Mars Science Laboratory.)

Then Steltzner asked one of the night's special guests to stand up and be recognized — Clara Ma, who proposed the name "Curiosity" as a sixth-grader more than three years ago. Ma rose and smiled shyly, and the crowd went nuts again.

With Curiosity safely on the surface, in the middle of Mars' huge Gale Crater, the mission can now look forward to surface operations. The rover's main goal is to determine if the Gale area is, or ever was, capable of supporting microbial life.

Curiosity will spend at least the next two years trying to answer this question. The mission's chief scientist John Grotzinger, a geologist at Caltech, is thrilled to finally have the keys.

"To me, that was magical. Everything just went so smoothly," he told SPACE.com, referring to the landing. "I'm over the moon."

Visit SPACE.com for complete coverage of NASA's Mars rover landing Sunday. Follow senior writer Mike Wall on Twitter @michaeldwall or SPACE.com @Spacedotcom. We're also on Facebook and Google+. 

• Mars Rover Curiosity: Mars Science Lab Coverage
• NASA's Amazing Mars Rover Curiosity Landing: Best Moments
• Curiosity Rover Lands! - First Imagery From Mars | Video

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1) Get out in nature:

You probably seriously underestimate how important this is. (Actually, there's research that says you do.) Being in nature reduces stress, makes you more creative, improves your memory and may even make you a better person.

2) Exercise:

We all know how important this is, but few people do it consistently. Other than health benefits too numerous to mention, exercise makes you smarter, happier, improves sleep, increases libido and makes you feel better about your body. A Harvard study that has tracked a group of men for more than 70 years identified it as one of the secrets to a good life.

3) Spend time with friends and family:

Harvard happiness expert Daniel Gilbert identified this as one of the biggest sources of happiness in our lives. Relationships are worth more than you think (approximately an extra $131,232 a year.) Not feeling socially connected can make you stupider and kill you. Loneliness can lead to heart attack, stroke and diabetes. The longest lived people on the planet all place a strong emphasis on social engagement and good relationships are more important to a long life than even exercise. Friends are key to improving your life. Share good news and enthusiatically respond when others share good news with you to improve your relationships. Want to instantly be happier? Do something kind for them.

4) Express gratitude:

It will make you happier.

It will improve your relationships.

It can make you a better person.

It can make life better for everyone around you.

5) Meditate:

Meditation can increase happiness, meaning in life, social support and attention span whie reducing anger, anxiety, depression and fatigue. Along similar lines, prayer can make you feel better -- even if you're not religious.

6) Get enough sleep:

You can't cheat yourself on sleep and not have it affect you. Being tired actually makes it harder to be happy. Lack of sleep = more likely to get sick. "Sleeping on it" does improve decision making. Lack of sleep can make you more likely to behave unethically. There is such a thing as beauty sleep.

Naps are great too. Naps increase alertness and performance on the job, enhance learning ability and purge negative emotions while enhancing positive ones. Here's how to improve your naps.

7) Challenge yourself:

Learning another language can keep your mind sharp. Music lessons increase intelligence. Challenging your beliefs strengthens your mind. Increasing willpower just takes a little effort each day and it's more responsible for your success than IQ. Not getting an education or taking advantage of opportunities are two of the things people look back on their lives and regret the most.

8) Laugh:

People who use humor to cope with stress have better immune systems, reduced risk of heart attack and stroke, experience less pain during dental work and live longer. Laughter should be like a daily vitamin. Just reminiscing about funny moments can improve your relationship. Humor has many benefits.

9) Touch someone:

Touching can reduce stress, improve team performance, and help you be persuasive. Hugs make you happier. Sex may help prevent heart attacks and cancer, improve your immune system and extend your life.

10) Be optimistic:

Optimism can make you healthier, happier and extend your life. The Army teaches it in order to increase mental toughness in soldiers. Being overconfident improves performance.

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Showing off one's playful side is a strategy men and women have developed to make themselves more appealing to potential mates, a new survey suggests.

A team of US academics surveyed 250 undergraduate students and found that both sexes list "sense of humour", "fun loving" and "playful" among the most important characteristics they look for in a potential long-term partner.

The results could explain why humans continue to play throughout their lives, while most other animals stop doing so when they reach adulthood, the researchers said.

Playful behaviour may provide an evolutionary benefit by displaying desirable qualities such as non-aggressiveness or youthfulness to potential long-term partners, they explained.

Lead author Prof Garry Chick, head of the Department of Recreation, Park and Tourism Management at Penn State, said: "Humans and other animals exhibit a variety of signals as to their value as mates.

"Just as birds display bright plumage or colouration, men may attract women by showing off expensive cars or clothing. In the same vein, playfulness in a male may signal to females that he is nonaggressive and less likely to harm them or their offspring.

"A woman's playfulness, on the other hand, may signal her youth and fertility."

The study built on a previous survey which asked participants about 13 different characteristics which people may find desirable in a long-term partner.

They added three new traits – "sense of humour", "fun loving" and "playful" – to the original survey and found that they ranked second, third and fourth as traits that women look for after "kind[ness] and understanding".

Men ranked a sense of humour as the highest priority, with a fun-loving nature third and playfulness fifth, while putting physical attractiveness only ninth, according to the study in the American Journal of Play.

Prof Chick said: "It seems to us that signalling one's virtues as a potential long-term mate through playfulness is not far-fetched.

"Our results suggest that adult playfulness may result from sexual selection and signal positive qualities to potential long-term mates."

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Blue is for boys and pink is for girls, we're told.

But do these gender norms reflect some inherent biological difference between the sexes, or are they culturally constructed? It depends on whom you ask.

Decades of research by University of Maryland historian Jo Paoletti suggests that up until the 1950s, chaos reigned when it came to the colors of baby paraphernalia. "There was no gender-color symbolism that held true everywhere," Paoletti told Life's Little Mysteries.

Because the pink-for-a-girl, blue-for-a-boy social norms only set in during the 20th century in the United States, they cannot possibly stem from any evolved differences between boys' and girls' favorite colors, Paoletti has argued.

Baby books, new baby announcements and cards, gift lists and newspaper articles from the early 1900s indicate that pink was just as likely to be associated with boy babies as with girl babies. For example, the June 1918 issue of the Infant's Department, a trade magazine for baby clothes manufacturers, said: "There has been a great diversity of opinion on this subject, but the generally accepted rule is pink for the boy and blue for the girl. The reason is that pink being a more decided and stronger color, is more suitable for the boy; while blue, which is more delicate and dainty is prettier for the girl."

But this attempt at establishing the rule for retailers and manufacturers clearly did not stick. "There was a 1927 chart in Time Magazine where department stores in various cities were contacted and asked what colors they used for boys and girls. And it was all over the map," Paoletti said. It wasn't until after the Second World War that the modern convention (pink for girls, blue for boys) started to dominate, and even so, it didn't "gel" until the 1980s, she said. [Video: Pink Light Doesn't Exist]

As for why today's strict color-gender norms set in at all, Philip Cohen, a sociologist also at the University of Maryland, thinks they are, essentially, the outcome of a marketing ploy.

"This happened during a time when mass marketing was appearing," Cohen told Life's Little Mysteries. "Being 'gender normal' is very important to us, and as a marketing technique, if retailers can convince you that being gender normal means you need to buy a certain product—cosmetics, plastic surgery, blue or pink clothing, etc.—it just makes sense from a production or mass marketing perspective," Cohen wrote in an email.

As for why one color-gender pairing came to dominate over the opposite pairing, Paoletti argues that the rule we use today may reflect the influence of French fashion. Traditional French culture paired pink with girls and blue with boys (while Belgian and Catholic German culture used the opposite), and because France set the fashion in the 20th century, their tradition held sway.

However, a new letter published July 21 in the Archives of Sexual Behavior questions this widely accepted pink-for-girls, blue-for-boys origin story.

Google book search

Marco Del Giudice, a sociologist at the University of Turin in Italy, says a simple search of all the books published in the United States between 1880 and 1980, which have been scanned by Google, suggests that pink was associated with girls and blue with boys during that entire time. Using the program Google Ngram, he searched for the phrases "blue for boys," "pink for girls," "blue for girls, "pink for boys," as well as the singular versions "blue for a boy," and so on. The rules we abide by (blue for boys and pink for girls) appeared in books from 1880 onward, becoming more common over time, but the opposite rules (pink for boys and blue for girls) didn't turn up in the book search at all.

"Pink seems to have been a feminine color at least since the late 19th century," Del Giudice wrote in an email. "In summary, when inspected closely, the reversal in pink-blue gender coding shows many warning signs of a scientific 'urban legend,' an urban legend that somehow managed to infiltrate the peer-reviewed literature." [Our Favorite Urban Legends Debunked]

If pink has always been feminine and blue masculine, this allows for the possibility that these gender-color associations have some basis in human biology. Do girls inherently prefer pink, and do boys inherently prefer blue? No one knows, Del Giudice said. "I bet the answer will turn out to involve an interplay of culture and biology. For example, in 2007 a study found evidence that males and females may be sensitive to different regions of the color spectrum, but the explanations that have been proposed are still very speculative and leave much to be desired. I think this is an absolutely fascinating question."

However, Del Giudice added, people stopped studying whether there was a biological basis for the gender-color associations because it seemed obvious that there couldn't be, in light of what he calls the "urban legend" that the associations only formed recently. [Your Color Red Really Could Be My Blue]

Back and forth

Paoletti says Del Giudice's book search simply missed most of the visual representations of mixed color-gender associations that she has observed. "I would never think of doing a word search in order to study something visual," she said. The fact remains that baby paraphernalia from the early 20th century followed no single standard when it comes to gender-color associations—a confusion reflected in the magazine articles that Paoletti found.

Cohen adds that despite the new book-search results, all other evidence indicates that, today, we differentiate children by gender much more than we did 150 years ago, when babies of either gender were typically outfitted in white dresses. The recent strengthening of gender-color associations must be cultural, he argues, leaving little room for the notion that each sex has evolved its own color preference. "If you don't have a strong reason why evolution would have dictated this and that, if you don't have a biological basis for this preference, then you're really just making it up," he said.

The debate about how, exactly, we got to the point where something as impartial as the color pink seems infused with femininity, will probably rage on in the pages of academic journals. In the meantime, we're left to ponder the bizarre truth that just a century ago, a magazine asserted, "the generally accepted rule is pink for the boy and blue for the girl."

Follow Natalie Wolchover on Twitter @nattyover or Life's Little Mysteries @llmysteries. We're also on Facebook & Google+.

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