Laser-scanning technology reveals that the Cambodian lost city of Mahendraparvata, dating back to a time before Angkor Wat, was much more extensive than previously thought. The latest word about the high-tech hunt for hidden ruins came over the weekend in an on-the-scene report from Australia's Fairfax Media.

Archaeologists have known about the Hindu-Buddhist-influenced city, situated about 25 miles (40 kilometers) north of the better-known Angkor Wat temple complex, for decades. Some of the ruins rank among the tourist attractions on the holy Khmer mountain known as Phnom Kulen ("Mountain of the Lychees"). However, experts weren't sure how extensive the site was ... until now.

"We're talking about a city that is more than 1,000 years old and is all underground. If you didn't know, you might think it's natural," Stephane De Greefe, the archaeological project's lead cartographer, told Cambodia Daily. 

The Khmer Archaeology Lidar Consortium set up an aerial survey of the Mahendraparvata site and its surroundings, using a technique known as lidar (short for "light detection and ranging"). The process involves flying an instrument-equipped helicopter over the area, bouncing pulses of laser light off the ground below, and then analyzing the scattered light readings to produce a 3-D map of the terrain beneath the jungle's vegetation.

Billions of data points and about 5,000 digital photographs were collected during a week's worth of aerial surveys, taking in an area amounting to 143 square miles (370 square kilometers).

'Eureka moment'
University of Sydney archaeologist Damian Evans told Fairfax Media that seeing the map displayed on a computer screen marked the "eureka moment" in a years-long search. The readings revealed dozens of temple sites, hundreds of mysterious mounds that may represent burial sites, and traces of canals and roads criss-crossing the area.

An on-the-ground expedition followed, during which the team came across two temple sites that may still be intact, and a cave with centuries-old carvings that may have been a refuge for hermits during the Angkor period.

Phnom Kulen served as a center of the Angkor civilization between the ninth and the 16th centuries. Tradition has it that Mahendraparvata was where the founder of the Khmer Empire, Jayavarman II, celebrated his people's freedom from Javanese control in the year 802. Angkor Wat was built nearby more than 300 years later.

How a city got lost
Why did Mahendraparvata fade away? "We see from the imagery that the landscape was completely devoid of vegetation" at some point during the site's history, Evans told Fairfax Media's Lindsay Murdoch. "One theory we are looking at is that the severe environmental impact of deforestation and the dependence on water management led to the demise of the civilization. ... Perhaps it became too successful to the point of becoming unmanageable."

Some reports have made it sound as if Mahendraparvata was only now being discovered, but Evans told Cambodia Daily that the real point behind the research has to do with how lidar resolved the debate over the lost city's extent. Lidar surveys are becoming a routine part of "lost city" quests — including the discovery of centuries-old ruins in Honduras that may be linked to the legendary city of Ciudad Blanca, and an extensive survey of Caracol, a Maya center in Belize.

Details about the Cambodian project are to be published in the Proceedings of the National Academy of Sciences.

Update for 6:30 p.m. ET June 17: The Proceedings of the National Academy of Sciences just sent journalists a pre-publication draft of the paper submitted by Evans and his colleagues — suggesting that Mahendraparvata as well as Angkor Wat were part of a vast urban network.

"We identify an entire, previously undocumented, formally planned urban landscape into which the major temples such as Angkor Wat were integrated," the researchers write. "Beyond these newly identified urban landscapes, the lidar data reveal anthropogenic changes to the landscape on a vast scale, and lend further weight to an emerging consensus that infrastructural complexity, unsustainable modes of subsistence and climate variation were crucial factors in the decline of the classical Khmer civilization."

The researchers say their mapping reveals a pattern of regular "city blocks," within which mounds and ponds were built to create temple precincts. Such cityscapes existed in ancient Angkor as well as the Phnom Kulen region and another area farther northeast, known as Koh Ker.

"These 'urban temples' are not isolated; rather, they are nodes in an increasingly concentrated medieval cityscape," they said.

Evans et al. / PNAS

A map of northwest Cambodia provides an overview of the areas where lidar imagery was acquired, indicated with yellow shading. The background data is from NASA's Shuttle Radar Topography Mission.

Evans et al. / PNAS

Lidar imagery shows the central area of Angkor, with the "walled city" of Angkor Thom above Angkor Wat. Red lines indicate post-medieval features, including roads and canals. The other features are from the Angkor era.

The paper echoes Evans' comments about the potential environmental roots of the Khmer Empire's decline: "The archaeological record shows that episodes of failure were commonplace within the hydraulic infrastructure within the medieval period. ... For several centuries at Angkor, episodic renovation of the water management system offered a series of provisional solutions that were adequate for mitigating the risk of low rainfall on an annual scale. Eventually, however, the civilization was confronted with decadal-scale megadroughts in the 14th and 15th centuries."

The researchers speculate that those megadroughts triggered the doom of Cambodia's megacities. In that, they see a parallel to the classic Maya civilization, which is thought to have gone into decline due to a similar pattern of deforestation and drought. And they include a chilling observation about our own era, attributed to University of Sydney archaeologist Roland Fletcher: "If the infrastructure of low-density cities is inherently liable to be or to become a constraint on the viability of a city’s daily life, then this is an issue of some serious consequence for our engagement with a future of giant, low-density cities."

More about lost cities:

• Scientists share images of Honduran ruins
• Atlantis thought to be found off Spanish coast
• Lost pyramids spotted by space scientists
• Gallery: Seven tales of cities lost and found

The study to be published in the Proceedings of the National Academy of Sciences is titled "Uncovering Archaeological Landscapes at Angkor Using Lidar." In addition to Evans, Fletcher and De Greef, the authors include Christophe Pottier, Jean-Baptiste Chevance, Dominique Soutif, Boun Suy Tan, Sokrithy Im, Darith Ea, Tina Tin, Samnang Kim, Christopher Cromarty, Kasper Hanus, Pierre Baty, Robert Kuszinger, Ichita Shimoda and Glenn Boornazian.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

This story was originally published on Mon Jun 17, 2013 3:45 PM EDT

Suza Scalora / Getty Images stock

Researchers have found ample links between a father's proximity to his children and his levels of hormones associated with nurturing.

The trick to fatherhood has a lot to do with the brain — and how close a dad gets to his kids. At least that's the message from a mounting pile of research into the neurological and hormonal cues that translate into fatherly nurturing. And what better time to keep that message in mind than on Father's Day?

"Mothers have an advantage, in that the hormones of pregnancy give them a head start and get them primed to be nurturing," said James Rilling, an anthropologist at Emory University who specializes in studying the neurological basis of social behavior. "In particular, when women give birth, there's a big surge of oxytocin, and oxytocin is also released during breastfeeding. Fathers don't have that."

Oxytocin has been called the "love hormone," even though its effect isn't always that lovely. It's thought to deepen the bond that a mom has with her newborn. But what about the dads, who don't get pregnant or breastfeed? It turns out that a father's interactions with his children produce a similar rise in oxytocin levels.

Researchers have found that emotionally involved fathers feel other hormonal effects: reduced levels of aggression-promoting testosterone; higher levels of prolactin, a lust-squelching hormone that shows up in women during breastfeeding and in men after sexual climax; and higher levels of vasopressin, a hormone linked to bonding as well as the maternal stress response.

It turns out that fathers get many of the same rushes that mothers do from parenthood — but the payoff depends on proximity and interaction. For example, researchers see the effect if the child sleeps with the parents, if the father recognizes and responds to the baby's cries, if Dad plays with the kids. When that proximity isn't present, the fatherhood effect isn't as strong.

"There seems to be some kind of fundamental social-neurobiological framework that comes into play when fathers interact with their kids," said Lee Gettler, an anthropologist at Notre Dame who worked on the prolactin study.

Why is it that the mothers and fathers come to the same hormonal response through different paths? "It may be that the most parsimonious way to engineer a paternal brain would be to take the circuitry that was already in place for maternal care, and maybe tweak that," Rilling said. "That might be the reason why there's some overlap there."

James Swain et al. / U. of Michigan

This functional magnetic resonance image shows areas of heightened brain activity when a father hears his own child's cries. Notable areas of activity include the frontal cortex, insula putamen, thalamus and superior temporal cortex.

Or it may merely be that when it comes to parenting, familiarity breeds fatherhood. University of Michigan psychiatrist James Swain has been analyzing a huge data set of MRI snapshots to see how maternal and paternal brains respond to the cries of their own babies and the children of strangers. He and his colleagues have found that brain activity patterns don't change as quickly for fathers as they do for mothers.

"I joke that this may be the physiological basis for why a father can roll over in bed when the baby's crying at 3 weeks," Swain told NBC News.

However, by the 4-month mark, "the fathers seem to catch up," Swain said. And there's some indication that the brain patterns for stay-at-home dads are more similar to the changes that moms go through. Swain and his colleagues are still trying to figure out exactly how the parenthood effect works on the neurological level — and how moms and dads get to the same place by different hormonal paths.

Rilling said the study of the fatherhood effect is a "wide open frontier."

"Humans are an alloparental species, which means mothers get help," he said. "In some cultures it's the father, but in other cultures it's the grandmother, the aunts, the older children. Fathers seem to be particularly important in modern developed Western nations like the U.S., because there are so many people who are living in isolated nuclear families, largely separated from their extended family. That limits the number of potential helpers out there. ... It's really important that fathers step up."

More about science and fatherhood:

• How fatherhood made us human
• Mice get less violent when they're dads
• Scientists see why fathers matter

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Asteroid 1998 QE2 turns while its moon zips upward. Credit: Ellen Howell / NASA / Arecibo

The Arecibo Observatory in Puerto Rico has captured the most detailed radar images yet of asteroid 1998 QE2 and its newly discovered moon.

A sequence of pictures released on Friday shows the 1.9-mile-wide (3-kilometer-wide) asteroid rotating in outer space while its 2,500-foot-long (750-meter-long companion zips around it. The asteroid and its moon sped past Earth harmlessly at a minimum distance of 3.6 million miles (5.8 million kilometers) on May 31.

"Asteroid QE2 has no chance of hitting Earth," Michael Nolan, head of the 1,000-foot-wide (300-meter-wide) telescope's asteroid radar group, said in a statement from the Universities Space Research Association, or USRA.

The Arecibo Observatory, sponsored by the National Science Foundation, is the world's largest and most sensitive single-dish radio telescope. Astronomers have been using Arecibo and NASA's Goldstone radar installation in California to track the movements of 1998 QE2 and its moon after its close encounter. Radar readings have revealed craters on the surface of the large rock.

Scientists estimate that one-sixth of all near-Earth asteroids have moons. "QE2's moon is roughly one-quarter the size of the main asteroid," said Patrick Taylor a USRA research astronomer at Arecibo. "Similarly, our moon is also approximately one-fourth the size of our planet."

Analyzing the motion of QE2's moon will help scientists determine the mass of the main asteroid.

"Being able to determine its mass from the moon helps us understand better the asteroid's material," said Ellen Howell, a USRA research astronomer who captured radar images of the asteroid at Arecibo and optical and infrared images using the Infrared Telescope Facility in Hawaii. The optical images can provide spectral data, revealing what the asteroid is made of.

"What makes this asteroid so interesting, aside from being an excellent target for radar imaging, is the color and small moon," Howell said in the USRA statement. "Asteroid QE2 is dark, red, and primitive — that is, it hasn't been heated or melted as much as other asteroids. QE2 is nothing like any asteroid we've visited with a spacecraft, or plan to, or that we have meteorites from. It's an entirely new beast in the menagerie of asteroids near Earth."

1998 QE2 gets its name from the timing of its discovery. The "QE2" refers to the order in which the asteroid was found during the latter half of August 1998. For what it's worth, 1998 QE2's diameter is nine times the length of the ocean liner Queen Elizabeth 2.

More about asteroids:

• Huge asteroid's flyby captured in new video
• 1998 QE2 sails past earth, leaving lessons behind
• Cosmic Log archive on asteroids

USRA's Michael Nolan led the radar observations of QE2, along with Ellen Howell, Patrick Taylor, Alessondra Springmann, Sean Marshall of Cornell University, and Mariah Law of Embry-Riddle Aeronautical University, in collaboration with the Near-Earth Object radar team at NASA's Jet Propulsion Laboratory and Goldstone Observatory in California. Observations continued through Thursday morning.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA file

A photo from the Apollo 17 mission to the moon in 1972 shows a makeshift fender on the crew's lunar rover, constructed from laminated maps and duct tape. "Just call me the little old fender maker," mission commander Gene Cernan said.

Over the past half a century, duct tape has been keeping NASA's astronauts alive, putting airplanes back together, making race cars speedier and patching up millions of fix-it projects. It's even been used to remove warts. But the makers of duct tape aren't resting on their sticky, gray laurels: On the contrary, engineers and designers are adding some new twists to the decades-old standby.

"Ten years ago, I used to hear kids say, 'Oh, my dad uses that to fix everything,'" Scott Sommers, director of marketing for ShurTech Brands, told NBC News. "Now I hear the dads say, 'Oh, my kids make everything out of that stuff.'"

ShurTech makes one of the best-known brands of duct tape, known as Duck Tape, and is the motive force behind this weekend's Duct Tape Festival in Avon, Ohio, the company's corporate headquarters. The annual event is scheduled to coincide with Father's Day — which is apt, considering how many dads have gotten out of a tough fix thanks to those silvery rolls of adhesive.

"I hope that women never find out about duct tape," humorist Dave Barry joked, "because once they do, men will no longer serve any useful purpose."

NBC News Travel: Thousands rock the roll at Duct Tape Festival

Duct tape's triumphs add up to a list that would make TV's MacGyver envious:

• The plastic-coated tape first came into its widespread use during World War II, when the U.S. military used it as a waterproof sealant. During the Vietnam War, it was used to patch up helicopter rotor blades — earning it the nickname "100-mph tape."
• When the Apollo 13 spacecraft suffered a crippling explosion in 1970, ground controllers came up with a plan to have the crew build improvised air filters using duct tape. Without that fix, "the crew would not survive," one of the Apollo engineers said. Two years later, Apollo 17 commander Gene Cernan used what he called "good old-fashioned American gray tape" to fix a fender on the lunar rover.
• When an Alaska bush pilot discovered that a brown bear had ripped his plane virtually to shreds, he had to call on friends to help put it back together with sheets of plastic wrap and a case of duct tape. A few days of work made the plane airworthy enough to fly back to civilization. "I think that's as close as you can get to MacGyver without going to outer space," said Jeff Malmer, a member of the research and development team for 3M, which makes Scotch-brand duct tape.
• NASCAR race crews routinely use duct tape to hold things together or modify airflow for peak performance — earning it the upgraded nickname "200-mph tape." It's especially cool if the crew uses color-coordinated tape.
• Some experts have touted duct tape as a wart-removal therapy. Supposedly, the adhesive tape works by irritating the skin and stimulating the body's immune system to attack the virus that causes the warts. Or maybe it just covers up the skin in such a way that makes it less hospitable to the virus. Does it really work? ShurTech's Sommers shies away from the question: "For legal reasons, I can't say we promote it," he said. 

Today, duct-tape manufacturers are reluctant to mess too much with success. "The majority of people who buy duct tape buy it to have around, just in case, and therefore we remain focused on making as much of a universally focused product as possible," Sommers said. But ShurTech is introducing some manufacturing innovations, such as a technique called "co-extrusion" that casts the plastic film at the same time that the rest of the tape (cloth mesh and rubber-based adhesive) is made.

The basic formula occasionally gets tweaked to respond to the marketplace: ShurTech offers different grades of tape for different applications. 3M has its own heavy-duty tape, called "Scotch Tough," as well as transparent duct tape and a type of tape that doesn't leave a rubbery residue when you rip it off.

And then there are the colors and patterns: Both companies have capitalized on duct tape's growing popularity as a craft item. "The kids have started to make fun things, and fashion things," Sommers said. 3M's marketing manager for Scotch duct tape, Laura Maciejewski, told NBC News that "it's really the girls who are using it." ShurTech offers Duck Tape designs with college themes, while 3M has marketing deals for Barbie, Batman and Superman tape.

Is there anything duct tape can't do? Well ... yes.

"What's ironic about duct tape is that it's really not the best product for sealing duct work," Malmer said.

More about sticky science:

• Look out, Spider-Man! Gecko inspires new glue
• The science of stickiness revealed
• Bacteria make world's strongest glue

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

No one expects the Superman saga to serve as a scientific treatise — but the back story for "Man of Steel," the latest reboot of the 75-year-old tale, does play off some of the latest discoveries on the final frontier. And the saga could provide a leaping-off point for future technological advances as well.

Just ask James Kakalios, who literally wrote the book on pulp-comic science, titled "The Physics of Superheroes." Superman's dazzling array of superpowers — ranging from super-strength to X-ray vision and freeze-breath — may be beyond the edge of plausibility, but Kakalios argues that merely musing over how they might work fires the imagination for more down-to-Earth inquiries.

"It's a parlor game reflecting what we do in research anyway — 'what if,' and 'what do I need to have happen for this to exist.' If you do it with superheroes, or if you do it in the real world, it's the same mental muscles that are being exercised," he told NBC News.

Kakalios noted that the first incarnation of Superman, in 1938's Action Comics No. 1, was inspired by Edgar Rice Burroughs' stories of "John Carter on Mars," in which an earthly adventurer took advantage of Mars' lower gravity to leap around and perform feats of seeming super strength. Comic-book writer Jerry Siegel turned that around by imagining that Superman came from a supermassive alien planet called Krypton. "We're the planet that has the weak power," Kakalios said.

So far, so good — but that's not the whole explanation for Superman's powers. The official story is that Superman's body was originally acclimated to Krypton's red sun, and is now able to soak up lots more power from our yellow sun. That gets into shakier ground. "Once you make that argument — that if the dominant wavelength shifts by 80 nanometers, that's enough to enable someone to bend steel in their bare hands and have super-breath — then you've entered the realm of fantasy," Kakalios said.

When it comes to planetology, however, Siegel and "Superman" artist Joe Shuster were ahead of their time: It's only recently that astronomers have come to the conclusion that lots of red dwarf stars may have planets, and that those planets may be as close as 13 light-years. What's more, planet hunters have proposed that super-Earths — that is, terrestrial planets more massive than our own — may well be superior when it comes to fostering life.

At the behest of DC Comics, astronomer Neil DeGrasse Tyson even pinpointed a red dwarf that could serve as a real-life stand-in for Krypton's red sun: LHS 2520, 27 light-years away in the southern constellation Corvus. It's not known whether LHS 2520 has any planets at all, let alone a Krypton-like super-Earth. But at least DC recognizes that exoplanets are no longer the stuff of pulp fiction.

Slideshow: Men of Steel

Getty Images

From comics to movies, the many incarnations of Superman.

Launch slideshow

Here are a few more examples showing how superpower musings spark real-life science:

Super-suits: The Man of Steel supposedly has a body that's impervious to almost everything except Kryptonite, which led researchers at the University of Leicester to calculate what kind of muscles or skin Superman would need to stop a bullet. Surprise, surprise: The physics don't work out. Even if you could leap tall buildings, your muscles still wouldn't be dense enough to be bulletproof. And in order for skin to stop a bullet, the required density would be "unreasonably high, even by assumed extraterrestrial standards," the researchers reported. Kakalios said it'd be more plausible for Superman to rely on a super-suit woven from graphene, a real-life super-strong substance. "You wouldn't need to be bulletproof if you had something like that," he said.

Fortress of Solitude: In previous movies, Superman's Fortress of Solitude was grown from a crystal — but based on the trailers, the filmmakers behind "Man of Steel" are going for a more organic look this time around, which Kakalios likes. "It almost looks like something from the 'Prometheus' or 'Alien' films," he said. It's more plausible to imagine an organic, nanoscale, self-assembling process that could produce large carbon-based structures — or that graphene super-suit.

Manipulating mass: In a paper titled "A Unified Theory of Superman's Powers," theoretical physicist Ben Tippett proposed that all of Superman's abilities could be explained if you just supposed he had the ability to manipulate inertial mass on scales ranging up from atoms to speeding locomotives and tall buildings. Inertial manipulation is often cited in science fiction as a way to get from place to place at faster-than-light speeds — so that would explain Superman's trip from Krypton to Earth as well. Researchers have been thinking about ways to do this in real life for more than a decade. So far, they're nowhere close to a breakthrough, but who knows? If the Large Hadron Collider's studies of the Higgs boson lead to a deeper understanding of the nature of particle mass, inertial manipulation could become a reality. Or at least become more plausible.

Do you have any musings on the real-life science inspired by the Superman saga? Feel free to weigh in with your comments below.

More about the Man of Steel:

• Super Square must adjust to an 'Iron Man' world
• Rating Hollywood's hunky heroes
• The science of Superman, circa 2006

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

A Chinese spaceship made a successful automated docking with an orbiting module on Thursday, marking one more small step toward full-fledged space station operations.

The Shenzhou 10 spacecraft completed the procedure for docking with the Tiangong 1 module at 1:18 p.m. Beijing time (1:18 a.m. ET),  delivering China's three latest spacefliers to their temporary home, the Xinhua news agency reported.

This was the first docking maneuver of the Shenzhou 10 mission — which was launched Tuesday, representing China's fifth crewed spaceflight since 2003. Tiangong (which means "Heavenly Palace" in Chinese) has been circling the planet for almost two years as a test platform for docking and orbital operations. In 2011, two unmanned, automated dockings were conducted, and the crew of Shenzhou 9 made two test dockings last year.

Three hours after docking, Shenzhou 10's three crew members — including Nie Haisheng, Zhang Xiaoguang and China's second woman astronaut, Wang Yaping — opened the hatch and floated inside the module.

During the current 15-day mission, Shenzhou 10's crew is due to conduct scientific and technical experiments aboard Tiangong 1 and deliver a lecture to students back on Earth. The spacefliers are also scheduled to unhook from the module and come in again for a manual docking.

Tiangong 1 will remain in service for only another three months, Xinhua said. China plans to deorbit the module later this year, and then send up more advanced labs for further testing. Beijing's space strategy calls for the creation of a full-fledged space station by 2020. China is not a participant in the 15-nation International Space Station project, in part because of U.S. opposition.

CCTV / AFP - Getty Images

This still photo taken from China Central Television shows Chinese astronaut Nie Haisheng entering the Tiangong 1 space module on Thursday.

More about China in space:

• Chinese space program continues to improve
• Chinese trio launched for orbital tests

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Brittney Venetucci

A gust-front shelf cloud (or "arcus") looms on the leading edge of a derecho-producing convective system, as seen in Hampshire, Ill., on the evening of July 10, 2008.

They're definitely not tornadoes, but the straight-line windstorms known as derechos can be just as damaging, due to gusts that can reach hurricane force. And they could make their appearance during the bout of severe weather sweeping over the Midwest on Wednesday.

It's been almost a year since a derecho (pronounced "deh-RAY-cho") was last in the headlines: That's when a powerful storm system blasted from Indiana to Maryland — killing more than a dozen people, leaving millions in the dark and shutting down Netflix as well as other online services that relied on Amazon's Cloud servers.

Last June's "Historic Derecho" sparked an assessment by the National Weather Service, focusing on whether more could have been done to anticipate the damage. This time around, forecasters are spreading the word well in advance — although they're using such terms as "localized downdraft/damaging wind threats" instead of the D-word.

Here's what you should know about derechos:

How do derechos differ from tornadoes?

"Derecho" is a Spanish word, meaning "right" or "straight." That's not the kind of word you'd use to describe a tornado, which whirls into action from a spinning storm system. Derechos arise when huge downbursts of cold air hit the ground, spawning winds that spread out in straight lines from the point of impact.

"Imagine taking a water balloon and dropping it, where you see the balloon break and splatter on the ground. That's basically how a downburst works. And you can think of a derecho as a large cluster of those downbursts all happening simultaneously," said Ken Pryor, a research meteorologist with the National Oceanic and Atmospheric Administration's National Environmental Satellite, Data and Information Service.

The term "derecho" was coined in 1888 to describe a severe straight-wind storm, in contrast to a tornado (which plays off the Spanish word for a "turning" storm). To be classified as a derecho, the swath of wind damage should extend more than 240 miles (400 kilometers), and the winds should meet the National Weather Service's criterion for severe wind gusts (greater than 57 mph, or 92 kilometers per hour). Derecho winds can range well beyond 100 mph.

What causes a derecho?

Derechos are associated with bands of showers or thunderstorms that assume a curved or bowed shape. The classic atmospheric conditions call for very warm temperatures and a lot of moisture near the ground, contrasted with much colder and drier air higher up. "It's the interaction of the heavy precipitation within a thunderstorm complex with that very dry air aloft that causes very large downdraft energy," Pryor said. "With a large thunderstorm system, the interaction of that dry air with that precipitation will result in numerous downdrafts."

Those pockets of the colder, denser air sink rapidly and hit the ground like a bomb, sparking outward bursts of wind. Within the individual downbursts, there may be intense microbursts that can pose extreme hazards for airplanes. 

NOAA

This map shows the number of derechos recorded from May through August over the 1980-2001 time period.

How often do derechos happen, and where?

The prime season for derechos runs from May to August. "They're typically favored over the Southern Plains and the Lower Mississippi Valley early in the season, and the activity moves north later in the summer," Pryor said. Early-season hot spots are in the Tornado Alley states of Oklahoma, Kansas, Missouri and Arkansas. Later in the season, the action shifts to southern Minnesota, the Great Lakes and the Ohio Valley region. The states in the "bull's-eye" regions might get more than one significant derecho in the course of a year, Pryor said.

Roughly every four years, a derecho breaks out of the Midwest, crosses the Appalachian Mountains and heads for the Atlantic without dissipating, Pryor said. That's what happened last year.

How much warning time can we get?

The National Weather Service issued Wednesday's alerts several hours before the expected onset of strong windstorms. That compares with an average lead time of 13 minutes for tornado warnings. "The lead time with a derecho should be much longer ... because these storms are so much larger and have a much longer lifetime," Pryor said. "There's no reason why you couldn't warn a particular area two to several hours in advance, unless it's the area where the storm is developing." Then the lead time might be an hour or less, he said.

The alerts are generally issued in the form of severe weather watches or warnings. One of the things to watch for is the possibility of "widespread damaging winds."

Last June's derecho was a special case, in that it didn't follow the predicted path. Most forecasters expected the derecho to break up when it hit the Appalachians. They were caught off guard when it didn't, but nevertheless, they "generally did an excellent job issuing warnings," according to the weather service's post-storm assessment. Overall lead times were greater than 30 minutes.

What should be done if there's a derecho threat?

The response should be pretty much what you'd do about approaching tornadoes or other types of severe storms. If there's enough time, "secure loose items outside, bring in furniture and other equipment that could become a missile hazard," Pryor said. Seek shelter in a sturdy structure, and stay away from windows.

"With tornadoes, what you see more in terms of structural damage are homes and other types of structures that are twisted and blown off their foundations. [With derechos] there can be roof damage, window damage, but for the most part the home remains on its foundation," Pryor said. "Straight-line winds have more of an impact on vegetation. They've been known to take down large areas of deciduous trees — that's known as a blowdown."

Keep an eye on the National Weather Service's Storm Prediction Center website as well as The Weather Channel and NBC News' weather coverage for updates as the Midwest storms progress. 

Slideshow: Weird weather

Desmond Boylan / Reuters

Get a look at a sun dog, a haboob, mammatus clouds, dust devils, a derecho and other weird atmospheric phenomena.

Launch slideshow

More about the science of weather:

• From NOAA.gov: All about derechos
• Questions and answers about tornadoes
• Updates from U.S. News on NBCNews.com

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

"How We Do It" may sound like a sex manual, but it isn't: In fact, that's about the only topic you won't find addressed in anthropologist Robert Martin's book-length survey of human reproduction and what we can learn from the animal world.

There's still news you can use, however. For example, how long should mothers breastfeed their babies? The standard advice from the World Health Organization is six months to two years. But Martin, who is the curator of biological anthropology at Chicago's Field Museum, cites evidence suggesting that three years is a more natural length of time.

"Exclusive breastfeeding is probably six months to a year, then for the last two years or so, breast milk is combined with supplementary food," Martin told NBC News.

That estimate is based on comparative studies of other primates, adjusted for the human body size. It so happens that anthropological studies of tooth enamel, going back to 5,000-year-old remains, arrive at a similar estimate. "The earlier you go back, the closer you come to something like three years," Martin said.

Studies suggest that brain development is better in babies who are breast-fed, probably because of nutritional factors contained in human milk. Martin's point isn't so much that you're a bad mother if you can't breastfeed for three years. "My point is that we should find out what's in human milk that is essential," he said. "If we're going to use artificial milk, we've got to get the formula right."

Basic Books

Robert Martin's book, "How We Do It: The Evolution and Future of Human Reproduction," looks at the myths and realities surrounding reproductive research.

Other chapters delve into the facts and fictions surrounding sex. True or false?

Humans do it faster: True, to an extent. A large-scale study found that human copulation lasts five minutes on average, although it may rarely last as long as 45 minutes. That's much shorter than the 12-hour mating roundsseen in marsupial mice, or the 15-minute couplings for orangutans, but longer than the chimpanzees' eight-second trysts. The males of some species have a bone in their penis, presumably to aid with prolonged mating. (Martin advises doing a Web search for "mountain man toothpick" to find examples.)

Humans are naturally promiscuous:False, at least in comparison with chimps and bonobos, our closest modern-day evolutionary relatives. The evidence for that is in our reproductive system: Chimps' sperm is much stickier than humans', so much so that it forms a "plug" inside the female tract. Scientists believe the plug is part of a strategy known as sperm competition, aimed at preventing other males' sperm from wriggling their way to fertilization. Another tip-off is the relative size of a male chimp's testes: They're bigger than humans, and that's linked to sperm competition. Humans (as well as gorillas, which also lean toward monogamy) lack the genetic machinery for sperm competition. And as for the bonobos ... we all know they sleep around, right?

The rhythm method works: False ... or at least not as true as some people might think. When it comes to contraception, you can't always trust the "egg timer." Researchers found that sperm cells can be stored for days in the womb, probably hidden in crypts in the womb's neck. This means that intercourse leading to conception can occur 10 days or more before ovulation occurs.

Sperm counts are declining: Signs point to "true" ... and that's a worrisome development. Studies from Israel and France, published last year, suggest that average sperm counts have dropped 30 to 40 percent over the past couple of decades. "It's quite obvious that this is going to lead to more cases of infertility," Martin said. The prime suspects include BPA, a chemical found in food packaging and other plastics. Studies have also implicated dairy products, soy products, sauna visits, TV viewing and even trends in male underwear (or the lack thereof).

There's nothing unique about the way we 'do it': Mostly but not completely true. Martin says one of the goals of his book is to "demolish myths of human uniqueness that don't stand up to observation." But when it comes to childbirth and child development, our big brains require special handling. A baby's head has to go through a complex rotation just to fit through the mother's pelvis — and at birth, a human baby's brain is only a quarter of its adult size. In comparison, a newborn chimp's brain is half the adult size. "Our extended period of childhood is really unique," Martin said. "The primary reason for this is that our brains are so poorly developed at birth."

More about the science of sex:

• 10 surprising sex statistics
• Real-life love potion identified
• Love and lust: Lessons from the animal kingdom

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log pageto your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

A little more than a month after this spring's great cicada outbreak began, the stink of dead insects is wafting through the air in North Carolina — even as the bugs' 17-year life cycle is reaching its prime farther up the East Coast.

"It's pretty much over, I'm afraid," said Tommy Joseph, a technology manager at the Greensboro Public Library who was among the first to report cicada sightings in North Carolina in early May.

Billions of periodical cicadas have been rising up from the ground over the past few weeks, after spending the past 17 years underground as immature nymphs. The insects emerge from burrows, shed the shells of their childhood, crawl up trees and buildings (and even legs), take wing and look for mates.

Scientists suspect that so many cicadas emerge at once as part of an evolutionary strategy to overwhelm their predators with sheer numbers. This year's breed is known as Brood II. Other broods of 17-year and 13-year cicadas take their turns in different years, and still other types of cicadas emerge every year.

Buzzing in the North
Brood II has a patchy geographical distribution, extending along the East Coast from North Carolina (and a bit of Georgia) to New York (and a bit of Connecticut). The buzz of the brood's mating call can create a 90-decibel hum — which is about as loud as power tools and lawnmowers. (And in fact, those mechanical sounds have been said to attract the bugs.) In the space of just a few weeks, the cicadas couple up, lay their eggs and die.

Slideshow: Return of the cicada

Take a closer look at the curious 17-year life of the flying bug as the East Coast weathers an invasion.

Launch slideshow

In temporal terms, the cicada outbreak is like a wave, moving northward in May and June as the spring weather warms. John Cooley, an entomologist at the University of Connecticut, said Monday that the outbreak has reached its peak in the north. "They're pretty much out in all the places they're going to be out," he told NBC News.

The current hot spots include northern New Jersey as well as Staten Island and the Hudson Valley in New York. For a nice cicada drive, Cooley recommended Routes 9G and 9H, heading up the Hudson Valley. Throngs of cicadas have been sighted on Bard College's campus, he said.

Somber in the South
The story is more somber down south: On the Entomology-Cicadidae discussion forum, Joseph reported that "the stench of death is in the air" in Greensboro. The smell has been "pretty bad over the past week or so," he told NBC News.

"I haven't actually seen a live one in probably two and a half days," Joseph said Monday. "The remains are not quite as prominent as you would have thought. We find wings here and pieces of 'em there, but it's not like giant piles of dead ones."

One potential reason for the dearth of dead cicadas is the fact that they're considered tasty by dogs, squirrels and other species looking for a snack. Even humans are giving the bugs a try. The taste of cooked cicadas has been compared to shrimp, or asparagus, or nuts, or popcorn.

Fabienne Faur / AFP - Getty Images

Biologist Jenna Jadin prepares "Caramelized Brood II cicadas" at her Washington home on May 28, 2013. Jadin specializes in cooking the insect and wrote "Cicada-Licious" when she was a university student. Some of her recipes include: Maryland cicadas with onions, potatoes and corn; Shanghai cicadas with soy sauce, garlic and turnips; or pizza a la cicada, with basil, olives and onions.

In her "Cicada-Licious" cookbook, entomologist Jenna Jadin says it's best to scoop up the bugs by the bagful when they're newly hatched. She has come up with recipes for cupcakes, casseroles, cocktails and candies that incorporate cicadas.

Is it safe? "I don't think the average person who wants to go out and enjoy the cicada emergency by having a meal of cicadas or two [has] anything to worry about," Jadin told National Geographic. But you'd better hurry: The fresh-cicada season is clearly nearing its end.

To keep tabs on the progress of "Swarmageddon," check out Cooley's Magicicada.org website, Dan Mozgai's Cicada Mania blog and Radiolab's Cicada Tracker, as well as the Twitter hashtags #BroodII and #cicadas. If you see something, say something ... in a comment below.

Previous chapters in the cicada saga:

• June 1: Cicadas survive Sandy, but not sprawl
• May 23: Bugfest closes in on East Coast cities
• May 17: Cicada hordes sighted in Virginia
• May 10: 'Swarmageddon' in North Carolina
• May 5: Bug-watchers see cicadas on the rise
• April 9: Cicada invasion generates early buzz

To sample the lighter side of Swarmageddon, check out this New Yorker essay on missed cicada conections.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA via NBC News

A meteor crackles in the night sky. Will the Gamma Delphinids produce sights like this?

The Gamma Delphinid meteor shower hasn't made a splash since 1930 — but astronomers say this just might be another big year for the outburst, due to Earth's changing orbital path.

If the outburst comes, it's expected to last for about a half-hour starting at 4:28 a.m. ET Tuesday, according to Peter Jenniskens and Esko Lyytinen, who specialize in comets and meteor tracking. That would be prime viewing time for observers in the Americas and points as far west as Hawaii. But don't get your hopes up too high.

"No one knows the strength of this display, or whether it will occur at all," Robert Lunsford of the American Meteor Society says in his preview.

On the evening of June 11, 1930, observers reported seeing a flurry of meteor activity even amid the glare of the full moon — but there's not been a repeat of the display since. That led some experts to question whether the original reports were authentic. Jenniskens and Lyytinen think that they were, and they have determined that our planet should be going through the same region of its orbit on Tuesday. If a long-period comet left behind the type of cosmic grit that sparks shooting stars in the upper atmosphere, we should be seeing a similar display this June 11.

The meteors would appear to radiate from the double-star gamma Delphini, which will be high in the southern sky for East Coast observers around 4:30 a.m. Lunsford advises beginning your night's watch a couple of hours before that, just in case the outburst comes early.

"This is not something one can stand outside and try to witness," he says. "Serious observers should be comfortable in a lounge chair and watch for at least an hour. I would not expect strong rates such as that occurred with the Leonid outburst near 2000. Rather, these meteors are more likely to appear a minute or two apart."

NASA

This chart indicates the area of visibility for Gamma Delphini, the double star that is considered the radiant for a meteor shower that may or may not occur on June 11. The green and yellow colors indicate how high the radiant will be in the sky at the expected time of maximum meteors, around 4:30 a.m. ET (08:30 GMT).

While you're waiting, you can click into an online chat with Bill Cooke of NASA's Meteoroid Environment Office at Marshall Space Flight Center from 11 p.m. to 3 a.m. ET. The chat page will also feature streaming video from a telescope monitoring the skies over Huntsville, Ala., in Marshall's neck of the woods.

If you snap a picture of the Gamma Delphinids, please share it with us via NBC News' FirstPerson photo upload page — and be sure to tell the American Meteor Society, too. You can use the AMS online report form or send a note to lunro.imo.usa@cox.net. "Even reports with no activity will help," Lunsford says.

More about meteors:

• Springtime Lyrid shower blooms in the sky
• Flash interactive: The science of meteors 
• Cosmic Log archive on meteors

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.