National Weather Service

This map shows the track of a tornado on May 3, 1999, in green; and the track of Monday's tornado in red. The similarity of the paths is coincidental, but the larger patterns of storm activity in "Tornado Alley" are due in part to the region's geography.

Do tornadoes follow well-worn tracks? Where do the deadliest twisters hit? Will climate change make such storms worse? Monday's devastating tornado in Oklahoma raises some questions for which scientists have ready answers, and others that could puzzle them for years to come:

Was this tornado a repeat of a famous twister in 1999?

For a time, Monday's storm followed a track that was similar to the path of a tornado with the fastest wind speed ever recorded, 318 mph (512 kilometers per hour), which occurred on May 3, 1999. That twister was one of 74 tornadoes that touched down in Oklahoma and Kansas in less than 21 hours, according to the National Severe Storms Laboratory. The 1999 outbreak of severe weather caused 46 deaths and nearly $1.5 billion in property damage.

The tracks weren't all that similar, however: Monday's tornado took a more southerly route as it moved east. And there's nothing unique about the area's geography to make it a magnet for super-powerful twisters, according to Bob Henson, a tornado expert with the National Center for Atmospheric Research in Boulder, Colo.

"If there were geographic features, that would tend to cause multiple tornadoes every few years," the meteorologist and writer told NBC News. "Well, why has this been happening only since 1999?"

The similarity in the tracks of these devastating storms is "a good example for how weather events can be clustered in ways that are striking yet ultimately coincidental," Henson said.

A classic example of this phenomenon, he noted, is Codell, Kan., which was hit by tornadoes on the same day — May 20 — in 1916, 1917, and 1918. The third tornado killed 10 people and destroyed a part of the community. "That's a good illustration of how sometimes things like this can just happen in clusters," he said.

NOAA SPC

The purple streaks on this map from the National Oceanic and Atmospheric Administration's Storm Prediction Center stand for tornado tracks from 1950 to 2011. The dark blotches indicate population densities.

But isn't Tornado Alley more prone to deadly twisters?

On a wider scale, the geography of America's midsection makes it more prone to tornadoes than any other region on Earth. That's because the Rocky Mountains tend to impede the eastward flow of moist air, while the Great Plains allow frigid Arctic air to stream southward from Canada and meet up with warm, humid air from the Gulf of Mexico. It's the collision of that warm and cold air that breeds powerful twisters.

"Tornado Alley" generally refers to the region centered in Texas, Oklahoma, Kansas and points north, where tornadoes are most frequent — but multiple studies indicate that the deadliest twisters occur to the east, in a region that's come to be known as "Dixie Alley." The reasons for that have to do with geography and demographics as well as meteorology in the southeastern United States: Storms tend to move faster, and they're more likely to strike at night. There are more trees and other obstructions to raise havoc. Population densities are generally higher, and the region has many manufactured homes that lack basements in which to take shelter.

The United States has the highest incidence of tornadoes, with an average of more than 1,000 every year, according to the National Climatic Data Center. But other regions of the world have twisters as well. Canada is No. 2 with about 100 per year, followed by northern Europe, western Asia, Bangladesh, Japan, Australia, New Zealand, China, South Africa and Argentina. Britain has more tornadoes than any other country, relative to its land area. "Fortunately, most UK tornadoes are relatively weak," the data center says.

Why do these tornadoes seem to be hitting all of a sudden?

After a relatively quiet start to the tornado season, tornadoes have been erupting from Texas to Minnesota over the past week. A cold front advancing to the east appears to be to blame. That pocket of cold air has run into warm air from the Gulf, causing the warm air to rise and spawning powerful thunderstorms. "It's kind of like the perfect setup," Jeff Weber, a scientist with the University Corporation for Atmospheric Research, told LiveScience.

The earlier calm was due to the fact that jet stream had been dipping farther south than usual for this time of year. That kept the Gulf's warm, moist air from advancing into Tornado Alley. Now that warm air is pushing northward, and the cold front has moved on to Minnesota and Wisconsin. As a result, the storm system that created Monday's big tornado should soon weaken, Weber said.

Will climate change make tornadoes worse? More frequent?

"The short answer is, we have no idea," Michael Wehner, a climate researcher at the Lawrence Berkeley National Laboratory, told NBC News. For years, Wehner has been studying the climate models for extreme weather, and he's a lead author for the next report from the Intergovernmental Panel on Climate Change as well as the federal government's latest national assessment on climate change.

One problem is that the observational record for tornadoes has not been uniform over time. "It has a bias to it, because more people are living where tornadoes occur, and more people are out looking for them," Wehner said. That contributes to the perception that tornadoes are happening more frequently than they used to.

The other big problem is that current climate models don't have the resolution that's needed to simulate the localized, violent activity of a tornado. Currently, global models are built up from atmospheric interactions on a scale of 100 kilometers (62 miles). Improvements in computer power could soon bring that down to a scale of 25 kilometers (16 miles). That should make it possible for scientists to simulate the weather phenomena that give rise to tornadoes, but not the tornadoes themselves, Wehner said.

On a larger scale, extreme weather events are expected to become more frequent in a warmer world, Wehner said. "The metric that I like to look at is the daily amount of rain for a storm that happens once every 20 years," he said. "That storm, in a much warmer world, would happen more frequently." For example, if the world follows a "business-as-usual" scenario, he projects that the average temperature would rise 11 degrees Fahrenheit (6 degrees Celsius) by the end of the century, and that a once-in-20-years rainstorm would come around every five to 10 years on average.

That doesn't necessarily mean tornadoes would be more frequent, however. In fact, the current projection calls for wetter spring weather in the northern U.S., and drier weather in the Southwest — with Tornado Alley right in the middle. "There's some evidence that there might not be a change" in the character of a tornado season, Wehner observed.

Wehner may sound a bit apologetic about the lack of clear answers in the short term, but in the long term, he's optimistic. "The reason I'm optimistic that we can get somewhere on this is that supercomputing technology is driving this very hard," he said. "We're just getting into the sweet spot for these kinds of issues, with the largest mainframes that money can buy."

More about tornado science:

• Why tornadoes seem as if they're on the rise
• Flash interactive: What causes tornadoes?
• Full coverage of the Oklahoma tornadoes

Alan Boyle is NBCNews.com's science editor. Connect with him by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding him to your Google+ circles.

John Roach is a contributing writer for NBC News. To learn more about him, visit his website. 

This story was originally published on Mon May 20, 2013 8:20 PM EDT

Alan Antczak / DVIDS

A trained Atlantic bottlenose dolphin leaps out of the water during a photo session with the Space and Naval Warfare Systems Center Pacific Marine Mammal Team in San Diego.

The U.S. Navy doesn't yet exactly know how a 130-year-old brass torpedo got to the bottom of the Pacific off the coast of San Diego, but they have a couple of dolphins to thank for rediscovering the rare weapon.

The find was so unexpected that the humans didn't believe the dolphins at first.

The marine mammals have been trained by the Navy's Space and Navy Warfare Systems Center Pacific, or SSC Pacific, to hunt for underwater mines and mark their locations. Divers place mine-shaped objects on the sea bottom, and then they teach the dolphins to find them. "It's all part of training to show the dolphins what they're going to be exposed to when they're on real-world missions," SSC Pacific spokesman Jim Fallin told NBC News on Monday.

During an exercise in March, conducted not far from California's historic Hotel del Coronado, the trainers sent a dolphin down to look for the pre-positioned target objects. The dolphin dove down, came back up — and gave the trainers a signal they didn't expect. "It had found something where we knew something shouldn't be," Fallin said.

The training team dismissed that first signal as a false positive. But when the same team went back to the same place with a different dolphin, the location was flagged again, Fallin said. That's when the trainers started taking the animals seriously.

A piece of naval history
SSC Pacific worked with recovery divers and bomb disposal experts to check out what the dolphins had found. At first, they thought the object was merely an old tail section from an aerial drop mine. They quickly changed their minds.

"It was apparent in the first 15 minutes that this was something that was significant and really old," Christian Harris, operations supervisor for the SSC Pacific Biosciences Division, said in a news release. It turned out to be the tail section from one of the first self-propelled torpedoes developed and used by the U.S. Navy, known as the Howell torpedo.

U.S Navy / SSC Pacific

The fins of a Howell torpedo can be seen preserved in water after the object was recovered with the aid of dolphins.

U.S. Navy

The only other Howell torpedo known to exist today is at the Naval Undersea Museum in Keyport, Wash.

More sections were brought up and submerged in water for preservation. Eventually the torpedo will be flown to the Naval History and Heritage Command at the Washington Navy Yard for more thorough study. "What's missing at this point is the nose, and we're not sure where that is," Fallin said.

The 11-foot-long (3.4-meter-long) torpedo was developed by Lt. Cmdr. John A. Howell between 1870 and 1889. The Navy says it was driven by a 132-pound (60-kilogram) flywheel that was spun up to 10,000 rpm prior to launch. It had a range of 400 yards, a speed of 25 knots, and a warhead filled with 100 pounds of gun cotton.

"It was the first torpedo that could be released into the ocean and follow a track," Harris said. "Considering that it was made before electricity was provided to U.S. households, it was pretty sophisticated for its time."

Howell torpedoes were used on Navy battleships and torpedo boats until 1898, when they were replaced by Whitehead torpedoes. Only 50 of the Howells were ever were built. The only other Howell that exists today is sitting inert in the Naval Undersea Museum in Keyport, Wash.

How did the torpedo get there? Fallin said he "can't add any information other than that it was there," he said.

Day of the dolphins
This isn't the first unexpected object located by the Navy's mine-hunting dolphins: Previously, the mammals have detected sunken items including a submerged car and a lobster trap in a place "where a lobster trap wasn't supposed to be," Fallin said. But the Howell torpedo could well rank as the most significant archaeological find for a finny troop that's trained for war.

The dolphins' finest hour came during the Persian Gulf conflicts, when they spotted underwater hazards and served as sentries for the U.S-led coalition's vessels.

"Dolphins remain the pre-eminent capability for the Navy in counter-mine identification," Fallin said. "There's no technology that the Navy has today that replicates the dolphins' natural ability to identify mines ... although our lab is working on those futuristic technologies. We're designing those technologies around the sonar capabilities that are inherent in dolphins. Unmanned autonomous robots have been proven to be pretty capable at this point in shallow water. The technology holds promise."

It's all in a day's work for the dolphins — and for SSC Pacific, an arm of the Navy's Space and Naval Warfare Systems Command that focuses on command and control, communications, computers, intelligence, surveillance and reconnaissance — a group of technologies known as C4ISR. "We represent the nation's only full-spectrum C4ISR laboratory," Fallin said.

More about dolphins intelligence:

• Dolphins appear to do nonlinear mathematics
• Are dolphins the world's second-smartest animals?
• Dolphins sought to protect against terrorists

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.

There's been a groundswell of 17-year cicadas in Virginia and other southern states, as revealed by a fresh wave of photos and eyewitness reports. In some areas, the outbreak has been accompanied by the insects' loud chorus call. And that's music to the ears of University of Connecticut entomologist John Cooley.

"That's where I'm heading," Cooley told NBC News. The weather is still too cool in New England and the New York City area for a full-blown Brood II emergence, so Cooley is planning a field trip to watch the insects rise up in Virginia.

This is the big year for Brood II cicadas, which are expected to emerge from the ground in the billions over an area of the East Coast ranging from North Carolina up to Connecticut. The bugs are hard-wired to spend 17 years underground, feeding on the fluid from plant roots, and then pop up during the appointed spring when the soil temperature reaches 64 degrees Fahrenheit (18 degrees Celsius).

For weeks, bug-watchers have been posting their sightings (and soil temperature readings) to websites such as Cooley's Magicicada.org and RadioLab's Cicada Tracker. Another website maintained by the Sutron weather information network tracks the soil temperature in Washington, D.C. 

When the winged cicadas throng, they can cover trees and buildings — and raise a din as loud as a lawnmower or jet engine (90 decibels). Over the course of four to six weeks in May and June, the bugs mate, lay their eggs and die, setting the 17-year life cycle in motion once again. (Scientists theorize that there are evolutionary advantages to the long, odd-numbered cycle.)

Although the cicadas have been patiently waiting for 17 years, some cicada-watchers up north are getting impatient with the pace of the emergence. Cooley said the relatively slow pace may be due to this spring's cool temperatures. In order to bring the soil up to 64 degrees F, air temperatures have to get significantly higher than that on a consistent basis.

"I want 80s and 90s," he said, "and so do the cicadas."

Dave Ellis / The Free Lance-Star via AP

Brood II cicadas emerge in the Leavells Crossing neighborhood in Spotsylvania, Va., on May 16.

Carol via Twitter.com/oikwtm_

Cicadas throng near a house in Fredericksburg, Va.

Carol via Twitter.com/oikwtm_

A cat looks through a screen door as cicadas swarm outside a house in Fredericksburg, Va.

Slideshow: Return of the cicada

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

Launch slideshow

More about the cicada outbreak:

• Cicadas crawling out of the ground in droves
• 'Swarmageddon' comes to North Carolina
• Bug-watchers see cicadas on the rise
• Cicada emergence sparks early buzz

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.

LEOzoo.org

Archie the anteater nestles on his mom at the LEO Zoological Conservation Center in Greenwich, Conn.

Is it a case of anteater virgin birth, a hormonal quirk or just some desperate hanky-panky? Whatever it is, Armani the anteater's surprising pregnancy has sparked a debate over what animals are capable of when it comes to sex.

The story unfolded at the LEO Zoological Conservation Center in Greenwich, Conn.: Last month, Armani gave birth to a cute baby pup named Archie. The only problem was, Archie wasn't supposed to exist.

Armani already had given birth last August to a female pup named Alice, fathered by a male anteater at the center named Alf. Anteater dads have been known to kill off their progeny, so Alf was put in a separate pen for several months. Marcella Leone, the nonprofit center's founder and director, said Armani and Alf shouldn't have had the opportunity to conceive little Archie.

"It is our protocol that that should not happen, so it's a mystery," Leone told NBC News.

NBC Connecticut: Birth of anteater has zoo staff puzzled

Leone speculated that the "virgin birth" may have been a bizarre case of delayed implantation, also known as embryonic diapause. Some species are able to hold up hormonally on having their fertilized eggs attach to the uterine wall and start developing, apparently as a stress response. That's known to happen to armadillos, which are in the same scientific superorder (Xenarthra) as anteaters. "It's been presumed that giant anteaters can do this as well," Leone said.

Could that be what happened to Armani?

"Given the paucity of literature, it wouldn't surprise me," said Bruce Murphy, director of the University of Montreal's Reseau Quebecois en Reproduction (Quebec Reproduction Network).

Diapause or desire?
Murphy is no expert on anteaters, but he is an expert on diapause. A paper on the subject that he and his colleagues published in the journal Open Biology is featured this week as an "editor's choice" in the journal Science.

A cross-species study published by a different set of researchers in PLOS ONE suggests that Armani may well have been capable of adjusting the dials on the standard six-month gestation period. "Their conclusion, and I think it's a good one, is that maybe every species has a capacity for diapause, if uterine conditions are appropriate," Murphy told NBC News.

Bob Luckey / Connecticut Post

Marcella Leone, founder and director of the LEO Zoological Conservation Center, watches over Armani and her baby, Archie, clinging to her back, on May 10. For more pictures, check out the Connecticut Post's report.

However, it may not be necessary to turn to diapause, or to a different kind of "virgin birth" known as parthenogenesis, for an explanation. Despite the best efforts of the conservation center's staff, it's conceivable that Armani and Alf found a way to couple through the enclosure's high-tensile fence. They may have even indulged in a brief encounter while they were being moved around.

Just minutes to do the deed
"I have seen anteaters breed many times, but that doesn’t mean I know exactly what is going on in amongst all that hair," Marie Magnuson, a biologist at Washington's Smithsonian National Zoo, told NBC News in an email. "There is some thought that there is no actual penetration, just a lot of rubbing up together. If that is the case, then his sperm are doing all the heavy lifting on the job, and a fence would not be an insurmountable barrier — as long as it is chain-link and not solid."

It wouldn't take long for anteaters to do the deed, Magnuson said.

"If they were together, it was long enough," she said. "When doing a re-introduction between our breeding pair, we had planned on taking it slow and safe. We were going to put them together for five minutes and then separate them. At three minutes they were copulating."

Leone doesn't totally exclude the possibility that Armani and Alf had a furtive fling. "You can imagine what any man will do to get to his woman," she joked. "This is not our plan, but nature is a very strong force."

The way she sees it, the story is about much more than a couple of amorous anteaters.

"The thing to really focus on is that a plant or animal becomes extinct every 20 minutes," Leone said. "So the point is to learn as much as we can about giant anteaters out of the wild, so that we can apply that knowledge in the wild as well. Ultimately, the most important thing is to save those wild places for wildlife."

More about animal sex:

• Love and lust: Lessons from the animal kingdom
• Gallery: 10 peeks at sex in the wild
• Biologists say animal sex is sensationalized

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.

You'd think that traveling at warp speed to the planet Nibiru would be the coolest thing in outer space, but for the Hollywood types who made "Star Trek Into Darkness," talking with a real astronaut on the International Space Station was way more awesome.

"I'll just act like this is a perfectly normal thing to be happening," Damon Lindelof, a writer and producer for the just-released movie, told NASA's Chris Cassidy during a Google+ Hangout presented on Thursday by the space agency and Warner Bros. "We are literally tickled pink to be talking to you right now."

The other "Star Trek" actors in on the Hangout — Chris Pine (who plays Captain James Kirk), John Cho (Sulu) and Alice Eve (who gets a healthy dose of screen time as Dr. Carol Marcus) — were just as taken. They laughed and hooted like fanboys when Cassidy let go of his microphone and took an upside-down spin in zero-G.

Pine said he loved the idea of mashing up fictional and real-life spaceflight: "It's great that our worlds can meet at some point in the middle and hopefully inspire people to do good things, and to explore."

The feeling was clearly mutual: Astronaut Mike Fincke, who served as space station commander in 2008-2009, said the "Star Trek" TV shows and movies have long inspired scientists, engineers and spacefliers. "We fall for it every time here at NASA," he said.

Fincke appeared in the final episode of the "Star Trek: Enterprise" TV series, and on Thursday he joked that he'd rather be in Hollywood: "Ever since I was 3 years old, I wanted to be a director and writer, but I failed director-writer school. Then I tried acting, and that didn't work out. So now I go on spacewalks." 

If Lindelof has anything to do with it, Fincke won't be the last astronaut to make the crossover to Hollywood. He promised Cassidy that he'd be welcome to a cameo role in a future "Star Trek" movie. "Maybe you could class up the joint a bit," Lindelof said.

Cassidy said the "Star Trek" crew would be welcome aboard the space station as well. He noted that there were currently a couple of vacancies in the U.S. segment of the station — due to the fact that one batch of crew members has just returned to Earth, and their replacements aren't due for launch until May 28. "We got two open beds," Cassidy joked. "The first two here get 'em."

You can watch the whole 56-minute Hangout while you're waiting for the next showing of "Star Trek Into Darkness," but here are a few of the highlights:

• When asked about last week's ammonia coolant leak at the station, Cassidy said he was surprised to see how quickly mission managers were able to plan a spacewalk to fix it. "It's not like you can rescue Spock from a volcano and push a button. It doesn't happen that way up here," he said. Cassidy said the episode illustrated how useful it is to have "garage-tinkerer" types aboard the station.
• Cassidy said ammonia contamination was one of the three emergency threats that the space station crew had to be prepared to deal with, along with an onboard fire or rapid decompression. That led Lindelof to warn the astronaut about the latest "Star Trek" super-villain. "You should watch out for Benedict Cumberbatch," he said. "He's very threatening, I understand."
• Cassidy said the thing that gets him the most about "Star Trek" and other space movies was the ease with which everyone walked around on spaceships, as if artificial gravity was nothing special. Even though weightlessness has its drawbacks, floating around in zero-G would make the movies much more interesting. "Trust me, it's a pretty cool thing to do this anytime you want," Cassidy said.
• The astronauts talked around a question that asked them to name their favorite "Star Trek" captain, but Fincke said his favorite name for a starship would be Enterprise (natch!). Fellow NASA astronaut Kjell Lindgren went with the Starship Endurance, which pays tribute to the ship for Ernest Shackleton's famous Antarctic ordeal in 1914.
• Life aboard the space station tends to give astronauts the same optimistic view of the future that runs through the "Star Trek" saga, Cassidy said. From space, Earth seems so tranquil and peaceful. "There are no borders down there," Cassidy said. "You can't see a little yellow line painted on the green part."
• One of the questions sent in during the Hangout focused on a more mundane aspect of spaceflight: How do spacewalkers handle a sneeze? Cassidy admitted that could be a problem. "Once the helmet goes on, any schmutz that goes on there is just an impediment to seeing clearly," he said. The solution is to incline your head downward before the sneeze, so that the schmutz is directed below the face plate.

More about 'Star Trek' and spaceflight:

• Astronauts get a sneak peek at film
• Warp speed! It may actually be possible
• Gallery: Reality check for 'Trek' tech

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.

UTL Scientific

Readings from a laser-mapping system were combined to produce a 3-D map of the Honduran rain forest, and then the vegetation was virtually lifted up from the scene to reveal the ruins of a circular structure.

A high-tech team of scientists and filmmakers shared pictures of what appears to have been a centuries-old civilization in Honduras, one year after they used laser-mapping technology to identify traces of structures in the thick jungle.

The square-shaped and rounded structures, seen in computerized elevation maps of a rugged rain forest, may have been the last vestiges of pyramids, palaces and houses in a fabled settlement known as "la Ciudad Blanca," or the White City.

Tales of Ciudad Blanca have circulated since at least 1526, when the Spanish conquistador Hernan Cortez told King Charles V about a mysterious province called Xucutaco that "must exceed Mexico in riches and equal it in the great size of the towns, the multitude of people and the government thereof." Many explorers have gone in search of the vanished city, driving deep into some of Honduras' roughest and most inaccessible rain forests. Neither riches nor ruins were found.

Nevertheless, the sagas inspired documentary filmmaker Steve Elkins to mount yet another search, this time using an aerial mapping technology known as light detection and ranging, or lidar.

How lidar works
An airplane equipped with the lidar mapping apparatus can bounce laser light off the terrain below, and then gather millions of the reflected readings. Those readings can be interpreted by high-powered software that can produce 3-D maps with an elevation resolution of less than 4 inches (10 centimeters). Such maps can even be "filtered" to peel back the dense vegetation and see the contours of the land below. Using lidar, archaeologists can conduct land surveys that might have required months or years to do on the ground.

"We use lidar to pinpoint where human structures are by looking for linear shapes and rectangles. Nature doesn't work in straight lines," Colorado State University's Stephen Leisz, a member of UTL Scientific's archaeological team, said in a statement from the American Geophysical Union.

UTL / Colorado State University

The left image shows a map derived from lidar readings of rainforest terrain. The readings associated with vegetation have been removed to create the right image, which shows the outlines of a square structure.

UTL Scientific

This lidar focuses on a formation in Honduras' Mosquitia rain forest known as "Structure B."

Archaeologists once thought the rain forests of Central and South America were too rugged to allow for large, highly organized communities like the one described by Cortez. But over the past decade or so, researchers have found evidence to argue that the forests were once much more highly managed by native populations. The idea that the ancient peoples of the Americas created complex cities and roadways in what are now wild forests no longer seems as radical as it once did. That's what inspired Elkins and his colleagues to go ahead with their search.

An 'easy' discovery
A year ago, the team mapped about 60 square miles (160 square kilometers) of Honduras' Mosquitia rain forest, and sent the data back to University of Houston engineer Bill Carter. Carter, who works with the National Science Foundation's National Center for Airborne Laser Mapping, identified the regular outlines of artificial structures after just a few minutes of analysis.

"It was kind of surprising how easy it was to find them," Carter told The New Yorker.

It took months more to map hundreds of ruins at several sites in the target area. On Wednesday, Elkins and his team shared some their images to fellow researchers during a session at a geophysical science conference in Cancun, Mexico, organized by the AGU. The laser images unveiled this week illustrate how structures could be identified beneath the vegetation, but do not show the settlements in a wider context.

"We can't show the overall place because we'd like to protect the site" from treasure hunters and looters, Elkins explained in the AGU's news release.

He said that the UTL Scientific team plans to explore the structures on the ground later this year. (UTL stands for "Under the Lidar".) Eventually, Elkins and fellow filmmaker Bill Benenson, who is underwriting the expedition, plan to produce a documentary about the latest search for Ciudad Blanca.

More about lost cities:

• How lasers helped spot lost city in Honduras
• Lost city of Atlantis may lie off Spain's coast
• Gallery: Seven tales of cities lost and found

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.

Slideshow: Art of Science 2013

Mingzhai Sun and Joshua Shaevitz / Princeton

Click through the top images from Princeton University's Art of Science Competition, which features images of artistic merit created during the course of scientific research.

Launch slideshow

Worms are a source of wonder in this year's crop of aesthetically pleasing scientific images, served up by Princeton University's Art of Science Competition.

"C. instagram," one of the contest's top photos, features a wriggling network of C. elegans worms on an agar plate covered with E. coli bacteria. Ewwww, right? But when Princeton molecular biology student Meredith Wright looked at the scene through a microscope, she had a different reaction: Cooool!

"I found the pattern on this plate particularly lovely, and was able to capture it with my cell phone by holding the lens of my phone's camera up to the microscope eyepiece," she wrote. "I've since shared the photo on social networking sites and have had friends who've never been interested in biology ask me more about my work because of this photo."

Researchers don't do what they do to create beautiful pictures, but beauty often arises amid the search for scientific truth. That's what the Art of Science program is going for: Images produced in the course of scientific research that have aesthetic merit as well.

This year's theme was "Connections." Andrew Zwicker, director of science education at the Princeton Plasma Physics Laboratory, said that some of history's most exciting scientific discoveries have come from making connections between different disciplines.

"For example, with physics and biology, everyday there is a new finding showing that the two are connected in the most fascinating and profound way," he said in this year's contest announcement. "In a similar vein, connecting the aesthetics of laboratory images to their scientific importance has transformed how we look at our data and results. With the 2013 Art of Science competition, we are celebrating all manner of connections."

Meredith Wright / Princeton Art of Science Competition

"C. instagram" shows masses of C. elegans worms on an agar plate. The picture was taken with a smartphone camera through a microscope, and shared via Instagram.

The connections between beauty and truth are reflected in this year's three top-rated images. First prize goes to Martin Jucker's visualization of Earth's wind patterns in shades of red and blue. Michael Kosk's photomicrograph of crushed birch wood took second place. And third prize went to a many-branching visualization of online connections for the websites set up by the plasma physics lab and by the Lewis Center for the arts.

"These two embroidery-like figures visually give us an idea of the similarities and differences of a website devoted to science and one devoted to the arts," said the prize-winning webmasters, Paul Csogi and Chris Cane.

The three prize-winners will share $500, divided into shares of $250, $154.51 and $95.49 in accordance with the aesthetically pleasing golden ratio. Another 40 images are included in Princeton's Art of Science 2013 exhibit, which opened on Friday in the atrium of Princeton's Friend Center. The works were chosen from 170 images submitted from 24 different departments across campus.

Click through our slideshow featuring some of the pictures in the exhibit, and then be sure to visit the Art of Science website and the Art of Science Facebook page for much, much more. And don't forget to share. That's precisely what Meredith Wright hopes you'll do with "C. instagram."

"This image represents the simple pleasure of finding something beautiful when you don't expect to," she wrote, "and it shows how easy it is to connect science with new audiences by simply clicking 'share.'"

More artistic science to share:

• Solid science turns into crowd-pleasing art
• Creepy critters and cool close-ups
• How beauty was found in a slimeball

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.

People are getting all twitchy about the bugs that are coming out in New York and New Jersey after a 17-year buildup, but when it comes to cicadas, Billy Tesh is seeing the real deal in North Carolina.

"I was so excited," Tesh told NBC News from Greensboro, where he runs a company called Pest Management Systems. "I've never seen so many in one location in my life. They were on almost every blade of grass."

And this is just the start: Billions of the insects are due to come out over the next few weeks, across a swath of the East Coast ranging from North Carolina to Connecticut.

These particular cicadas have been biding their time underground since the Clinton administration, in 1996. For 17 years, they've been sucking up fluid from plant roots and waiting for their biological alarm clock to ring. The bugs emerge in droves when the soil temperature reaches 64 degrees.

Other species of cicadas break out from the ground every year, but scientists suspect that the 17-year cicadas (and their 13-year kin) adopted a longer life cycle as an evolutionary ploy to overwhelm their predators with sheer numbers and surprise. When the time comes, masses of insects burrow out of their underground homes, shake off the shells of their childhood, unfurl their wings and look around for mates.

This spring's group is known as Brood II — which comes between last year's Brood I in Appalachia and next year's Brood III in the Midwest.

Tesh knows all about the broods: The 53-year-old pest-control specialist has been through several invasions by the red-eyed, loud-humming bugs. Even by his standards, this year's group of cicadas is special. He realized that on Thursday morning when he stopped by a farm in Stokes County, which appears to be one of the first places to experience the full force of this spring's "Swarmageddon."

"This particular brood is extremely large," Tesh said. He's expecting the cicadas to take noisy wing in the next day or two. "They're probably singing tonight."

Billy Tesh

A cicada and its shell sit on pest-control specialist Billy Tesh's hand during a visit to a farm in Stokes County, North Carolina.

Billy Tesh

Red-eyed adult cicadas clump together in a tree in North Carolina.

Billy Tesh

Hundreds of cicadas and their shells hang from dewy spears of grass in North Carolina.

Marc Dennis

Cicada nymphs make their way along a path on Staten Island.

Judging by the reports posted on Magicicada.org and Radiolab's Cicada Tracker, lots more cicadas have been emerging over the past week or so. Sightings have been reported not only in North Carolina, but in areas as far north as New Jersey and Staten Island in New York, which are traditional stomping grounds for Brood II. Those sightings are generating lots of buzz, but University of Connecticut cicada researcher John Cooley says the bugs in the New York metro area appear to be early risers forced out of their holes by wet weather.

Cooley checked out the cicadas that were emerging at New Jersey's Cora Hartshorn Arboretum. "There are nymphs there, and there are lots of them, but I don't think they are ready to come out," he told NBC News. He doesn't expect these early arrivals to do well, and he thinks the nymphs spotted on Staten Island will be in a similar fix. The weather in the Northeast just isn't spring-like enough yet for full-scale Swarmageddon.

When Swarmageddon sets in, Easterners won't need to wonder: The bugs will cover the ground when they crawl, blot out the sky when they fly and generate a mating hum as loud as a New York subway train (90 decibels or more). After a weeks-long mating season, the adults will die off, leaving behind shovelfuls of bug bodies. Meanwhile, a new crop of nymphs will hatch out from their eggs and burrow into the dirt to begin the next 17-year cycle.

Tesh says people have nothing to fear from the cicada invasion. The insects may damage some of the plants that they crowd onto, but they also serve to aerate and fertilize the soil. He's already gotten several calls from concerned customers in the Greensboro area — but so far, no one has asked him to bring out the pesticides. Instead, everyone has been taking his advice: "Just let Mother Nature take its course."

Slideshow: Return of the cicada

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

Launch slideshow

More about Swarmageddon:

• Bug-watchers see cicadas on the rise
• Cicada emergence generates early buzz
• All about cicadas on NBCNews.com

Show us your cicada photos by adding #NBCNewsPics to your tweet or Instagram post, or upload your pictures directly by clicking on this box.

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.

Almost a third of America's honeybee colonies bit the dust last winter, according to a bellwether survey of bee health. But the deaths didn't fit the typical pattern for colony collapse disorder, the mysterious malady that wipes out bunches of bees all at once. Instead, researchers suggest that last summer's drought and other common-sense factors were to blame.

The annual survey of beekeepers, conducted by the Bee Informed Partnership and the Apiary Inspectors of America, found that 31.1 percent of the colonies were lost over the winter of 2012-2013. That compares with a loss of 22 percent during the previous winter, which was exceptionally mild. It's also slightly higher than the six-year average of 30.5 percent in colony losses.

The past winter's bee death rate was roughly as high as it was during the winter of 2006-2007 — when colony collapse disorder, or CCD, was at its peak. But this time, most colonies "dwindled away rather than suffering from the sudden onset of CCD," Jeff Pettis, a U.S. Department of Agriculture bee expert who worked on the survey, said in a news release announcing the results.

University of Maryland entomologist Dennis vanEnglesdorp, who directs the Bee Informed Partnership, listed several likely causes for last winter's spike. One prime reason is the drought that swept over the Midwest last year. "When there's a drought, the bees are in poor shape with the food," California beekeeper Randy Oliver told NBC News in March.

Honeybees may have had to rely on irrigated crops rather than wildflowers for their nectar, which could have increased their exposure to pesticides, vanEnglesdorp said. He said last year's rising corn prices led farmers to replace prairie and shrubs with cornfields, further limiting the bees' foraging areas. And for part of the year, beekeepers lacked an effective treatment for Varroa mites, a type of bee parasite that was cited last week as the biggest factor behind the nation's bee die-off.

VanEnglesdorp said all these factors left bee colonies in a weakened state for the tough winter of 2012-2013. He said the beekeepers who took their hives to California in February to pollinate almond trees suffered especially high losses. Nearly 20 percent of those beekeepers said they lost 50 percent or more of their colonies over the winter.

Pettis noted that the survey stopped tracking losses at the end of April. As a result, "the 31 percent figure likely underrepresents the losses, as we saw many weak colonies that were not actually dead," he said.

Beekeepers rebuild their colonies in the spring, so a 31.1 percent loss rate isn't quite as catastrophic as it sounds. Nevertheless, vanEngelsdorp said high winter losses are changing the way commercial beekeeping is done. "All the money you're going to make in honey goes to replacing dead colonies and keeping your colonies alive," he said. "Any money you make [as profit] will be from pollination."

More about the bees:

• Die-off blamed on combination of causes
• EPA steps up pesticide review
• NBC News archive on the bee crisis

The winter colony loss survey was funded by USDA. The 6,287 U.S. beekeepers who responded to the survey managed nearly 600,000 bee colonies at the start of the survey period, or about 23 percent of the country's estimated 2.6 million colonies. A complete analysis of the survey data will be published later this year.

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.

UWA

The University of Western Australia's Monica Gagliano studies how plants communicate with each other.

Studies show that basil gives a boost to chili peppers, while fennel is a real bummer. The effect has been seen even when the plants are sealed off from each other with sheets of black plastic. So does that mean that the plants are "talking" to each other through subtle vibrations? That's the kind of talk that sparks a debate — not between the plants, but between humans.

The latest study, reported in the open-access journal BMC Ecology, looked at potential communication between basil plants and chili pepper seeds. It's one of a series of experiments conducted by Monica Gagliano and Michael Renton of the University of Western Australia.

"Our results show that plants are able to positively influence growth of seeds by some as-yet unknown mechanism," Gagliano said in a news release from BioMed Central, the journal's publisher. "Bad neighbors, such as fennel, prevent chili seed germination in the same way."

Fennel plants release chemicals into the air and soil that are detrimental to most other plants, including chili peppers. Last year, Gagliano and her colleagues set up mini-gardens to study the interaction between the plants more closely. They were surprised to find that chili seeds germinated more quickly when the fennel plant was sealed off with plastic to block the transfer of those nasty chemicals. It was almost as if the baby chilis sensed that a villainous plant was nearby, and grew up faster so they'd have a better chance of fending off the fennel.

The new study looks at the flip side of plant interaction: Unlike fennel, basil is a "good neighbor" for chili plants because basil plants release chemicals that discourage weed growth. Gagliano and her colleagues found that to be the case for chili seedlings. The seeds germinated at a higher rate, even if the basil plant was sealed off with the black plastic. That led Gagliano and Renton to conclude that the seeds could still sense the presence of a friendly plant when they couldn't get the standard chemical signals.

How could this be?

"We believe that the answer may involve acoustic signals generated using nanomechanical oscillations from inside the cell which allow rapid communication between nearby plants," Gagliano said in the news release.

That surmise seems to fit with other findings on plant communication. Corn roots, for example, give off regular clicking sounds in the range of 220Hz (which corresponds to an A below middle C). Gagliano and her colleagues found that when young corn roots are suspended in water, they tend to lean toward the source of a continuous 220Hz tone transmitted through the water. The researchers suggested that acoustic signals could knit plants into an underground network of friends and foes.

But as Gagliano points out, no one has yet identified the precise mechanism by which one plant hears what another plant is saying. That's one of the reasons why other researchers haven't wholeheartedly embraced the idea that plants are talking to each other.

"Although the idea of plants communicating by sound is intriguing, there is still a long way to go before we know whether, and if so to whom, the woods sing!" the University of Leiden's Carel ten Cate wrote last December in the journal Behavioral Ecology.

Duke University's Dan Johnson, who is studying how trees respond to drought, said it's "too early to tell" whether plants truly respond to each other's sounds.

"We have been detecting these acoustic signals for almost 50 years," Johnson told NBC News. "The idea of using those signals for communication is incredibly interesting, and there is potentially some growing support for it. But we're a good ways away from strong support for acoustic signaling between plants. ... I'm glad that somebody's working on it, but I think it's too early to say."

More about plant communication:

• Hear that sound? That's a thirsty tree
• Listen up: This is your plant talking!
• Plant uses sound to attract bats
• Flowers and bees have electrifying discussions

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.

Slideshow: Return of the cicada

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

Launch slideshow

Backyard bug-watchers are seeing the winged bugs known as cicadas come out of their holes in New Jersey and North Carolina after 17 years of underground slumber — and scientists say a full-scale outbreak may not be far behind.

"There are some pretty convincing reports coming out," John Cooley, an expert on cicadas at the University of Connecticut, told NBC News. "It's fair to say it's starting, but it's still in the very early stages. It certainly isn't going all crazy. ... When it really happens, it's not going to be like this. It's going to be shovel loads of cicadas."

Cooley maintains one of the most closely watched websites for this spring's emergence, Magicicada.org. Little bug logos are popping up on different areas of Magicicada's interactive map, which means a smattering of Internet users are seeing cicadas coming out of the ground. In some cases, they're even seeing the bugs crawling around as adults.

Cooley, however, says that we ain't seen nothing yet. "When it really happens, we expect that website will just light up," he said.

The outlook is similar on other bug-watching sites — such as Radiolab's Cicada Tracker, which is encouraging listeners to put out their own soil-thermometer setups. Those readings are considered key leading indicators for cicada activity, because researchers have found that the bugs emerge en masse when the springtime soil temperature reaches 64 degrees Fahrenheit (18 degrees Celsius). A different temperature tracker set up by the Sutron information network for the Washington area suggests that the nation's capital still has a way to go before the cicadas come out.

Insects are expected to emerge by the billions on the East Coast, across an area stretching from North Carolina to Connecticut. This army of bugs, known as Brood II, spends 17 years feeding on plant roots underground. Sometime between late April and early June, depending on the weather, the insects burrow out of the ground as nymphs. The juveniles shed their outer skins, crawl up trees or buildings, and fly around to find their mates. The females lay their eggs, and then the adults die in droves. All this happens in the course of four to six weeks.

After another few weeks, a new generation of nymphs hatch from the eggs, drop to the ground, burrow into the soil and begin the next 17-year cycle.

Magicicada.org

An interactive map provided by Magicicada.org shows this spring's cicada sightings.

Ron Edmonds / AP

Red-eyed cicadas cluster on leaves in Annandale, VA., during the Brood X emergence of 2004. Like Brood II, Brood X comes out every 17 years - but the timing of the cycle is different.

Brood II is just one of several broods of 13-year and 17-year periodical cicadas: The last big bug outbreak featured Brood XIX, which created a huge buzz in Southern states in 2011. This year's emergence is expected to begin in the South as well, though that's not guaranteed.

"Our expectation has been that we would hear from folks in North Carolina first," said Missy Henriksen, vice president of public affairs for the National Pest Management Association. However, the only cicada sighting she's actually been able to confirm was made in New Jersey. Although the insects tend to swarm in rural or suburban areas, there's a chance they could be sighted in urban enclaves such as New York's Central Park or the Bronx Zoo as well.

Cooley said he expected the pace of sightings to accelerate in the days ahead. "Within a week or so, it ought to really be going," he told NBC News. "Spring can't hold off forever."

When it comes, a cicada emergence can fill the skies with flying bugs, and fill the ears with a hum as loud as a jet engine or lawn mower. Those who have been through the full-frontal buzz say the experience can be disconcerting if you're not prepared for it. But cicadas are not considered a threat to humans. In fact, they can be quite delicious.

For true bug fans, the best response to the emergence is to lie back and enjoy it. "I'm looking forward to it," said Cornell University entomologist Cole Gilbert, who's expecting to catch the trailing edge of the Brood II outbreak in upstate New York. "I think it's pretty cool."

More about cicadas:

• Cicada invasion generates early buzz
• In death, cicadas boost plant life
• Tasty cicadas may sicken pets

Thanks to the rapid rise of crowdsourcing and social media, this year's event is sure to become the most tweeted cicada emergence in history: Cicada Mania suggests using the hashtag #BroodII for the 2013 outbreak, and #Cicadas for general cicada issues. If you want to see the Twitterverse from the cicadas' point of view, just follow @Brood_II. There's a Cicada Mania Facebook page for entomophiles. And if you're an entomophobe, you'll find kindred spirits on the "I Hate Cicadas!!!!!!" Facebook page.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" NBC News Science'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.