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Death from the Skies!

How will the world end? When Hollywood answers that question, the result is often terrifying but completely unrealistic. But the realms of reality can be even scarier than fiction, as astronomer Phil Plait deftly illustrates in Death from the Skies!, which comes out in paperback this week.

Each chapter begins with a movie script-ready scenario of Armageddon. Before delving into the topics of solar flares and coronal mass ejections, for example, there comes the story of a cold winter made worse when an event—prefaced by sunspots but not yet named—knocks out power for half the planet. Without heat, thousands die, and entire countries are driven bankrupt by the catastrophe. Having hooked his reader thusly, Plait then goes on to describe in easy-to-understand language what had caused the disaster, including how we know that such things happen and whether or not we should be scared.

Topics include gamma-ray bursts, black holes and even alien attacks. And a chart near the back of the book handily sums up the risk of each event, level of damage and whether or not we could prevent such things from happening. The most likely scenario is being hit by an asteroid, though we might one day be able to prevent these strikes. Near impossible in our time, thankfully, are the deaths of the sun or the universe. Most worrisome, though, might be the supernovae, which if one occurred close enough to Earth could lead to a mass extinction.

This book should be on the shelf of every disaster flick screenwriter. Perhaps we would then get movies with plots that are even more terrifying for the possibility that they could really happen.

“The Universe is vast beyond imagining, and wields mighty forces,” Plait writes. And for the events in his book, “it’s not a matter of if, it’s a matter of when.” Scary, indeed.

Before Venice, there was Altinum. During its heydey in the first century A.D., Altinum was a great Roman coastal city, home to as many as 20,000 people, where traders would come to do business from across the Mediterranean. But in the fifth to seventh centuries, the people left Altinum, driven by barbarian invasions to the islands that would eventually become Venice. Stones and bricks from Altinum would be used in building Venice, but Altinum would eventually become overgrown. Some parts became submerged beneath the Lagoon of Venice and others are now covered with farm fields.

A drought in 2007 presented a unique opportunity to learn more about the site without having to dig. A group of Italian scientists took the near-infrared aerial photograph above (their study appears in the July 31 issue of Science). Because the landscape was so dry, the scientists could “see” what was buried beneath the crops reflected in the health of the plants. Stones, bricks and compacted soil appear in lighter blue, and depressed features like pits and canals show up in the darker red. With the image, the researchers built a map of the city (below). With this map, they were able to confirm that the city had been partially surrounded by water, just as the ancient Greek geographer Strabo had described in the first century B.C.

Images copyright Science/AAAS. Check out the entire collection of Pictures of the Week on our Facebook fan page.

Without landmarks, we easily walk in circles (courtesy of flickr user helter-skelter)

In the movies, when hikers get lost in the woods, you know that they are well and truly lost by the third time or so that they pass by that big rock or funny-looking tree. And you just know that that would never happen to you. If you set out on a straight line, you would never double back without intending to do so.

Well, you’d be wrong.

People do walk in circular paths when they are lost, according to a study published online today by Current Biology. Scientists from the Max Planck Institute for Biological Cybernetics in Germany started their experimentations by first letting a few volunteers loose in a large, flat German forest and tracking them by GPS. Those who wandered on a sunny day kept to a nearly straight path while participants who trekked on a cloudy day walked in circles. Three of the cloudy day walkers even repeatedly crossed their own paths and without ever realizing what they were doing.

The scientists repeated their experiment in the Sahara Desert in Tunisia. Two people who walked during the day veered a bit off course (not too shocking when every direction looks similar) but the participant who walked at night managed to keep to a straight line only until the moon became covered by clouds.

In another experiment, the scientists blindfolded their subjects, who were then told to walk a straight line. But without anything to guide their paths, they walked in circles.

Throughout the experiments, though, the participants did not favor any one direction. Sometimes they would veer left, at other times, right. This rules out the idea that we walk in circles because we favor one leg over the other due to leg length or strength. Instead, the scientists say, without something like the sun or a mountain around to help us calibrate “straight,” the “noise” in our sensorimotor system sends us off track. However, the scientists note:

In emergency situations, where one’s life depends on the ability to navigate through unfamiliar terrain and reach safety, emotional state (panic) and social factors (group dynamics) may cause these cues and more cognitive navigation strategies to be disregarded, making people walk in circles even in the presence of reliable directional cues.

In the researchers’ next experiment, they will have participants walk through a virtual reality environment on a treadmill that lets a person walk in any direction (video below) to better determine the factors that help a person to walk straight or sets them into circles.

An orchid at the Smithsonian. Photo by Sarah Zielinski

Forget about birds and bees—if you want to learn about the varieties of sexual practices in the wild, study orchids. They’re the most rich and varied family of flowers by far, with about 24,000 species (another estimate is 30,000 species). And many of those species have evolved elaborate tricks to get hapless birds and bees and other pollinators to lovingly embrace their flowers.

Some orchid flowers look just like their pollinators and thereby lure the real thing. In a special issue on orchids in the Annals of Botany this month, an introduction points out that Carl Linnaeus appreciated one superb mimic:

Its flowers bear such a resemblance to flies, that an uneducated person who sees them might well believe that two or three flies were sitting on a stalk. Nature has made a better imitation than any art could ever perform.

(See for yourself here.)  Linnaeus didn’t figure out what the orchid was up to, but Darwin did. The National Museum of Natural History had a gorgeous exhibit of live orchids this spring called Orchids Through Darwin’s Eyes, which Sarah photographed.

Botanists recognized orchids’ visual mimicry first, but lately they’ve uncovered even more interesting scent-based mimicry. Basically, the orchids emit chemicals that smell, to a male insect, just like the sex pheromones emitted by the female of his species. In an interesting twist last year, researchers found that a bee-pollinated orchid produced chemicals that are similar but not identical to a female bee’s scent. It’s not that the orchid is a bad mimic, they researchers conclude, but that male bees are most attracted to a scent that’s not too familiar.

Aside from feeling used, do pollinators suffer from being tricked by orchids? Maybe so. As a paper in the American Naturalist last year pointed out:

While some sexually deceptive orchid species require only pollinator gripping or brief entrapment for effective pollination, other orchid species coerce their pollinators into energetic copulation. Although these copulations are often described as “pseudocopulations,” the vigorous response of pollinators suggests that true matings with ejaculation and costly sperm wastage may indeed occur.

Sure enough, they found that male wasps pollinating Australian tongue orchids do indeed ejaculate, which is a waste of time and energy for the wasps.

For the orchid, the relationship with pollinators is all about sex; but for the pollinators, sometimes it’s about food. A study that comes out in Current Biology later this month shows that a Chinese orchid mimics the scent of a honeybee’s distress signal—a scent that attracts honeybee-eating hornets. Wicked!

But orchids don’t always need pollinators. Sometimes they have sex with themselves. A study a few years ago showed that another Chinese orchid, if no wind or pollinators are around, will twist its pollinia into its own stigma:

Here we describe a new type of self-pollination mechanism in the tree-living orchid Holcoglossum amesianum, in which the bisexual flower turns its anther against gravity through 360° in order to insert pollen into its own stigma cavity — without the aid of any pollinating agent or medium.

Why is there a zombie here? Keep reading. (Courtesy of flickr user Felix42 contra la censura)

August may be a slow news month (especially here in humid, mosquito-filled Washington, D.C., which Congress has fled for more pleasant climes), but it is turning out to be a month for weird science news.

Let’s start with male breastfeeding, a topic that a friend tried to convince me to write an entire post about (though I’m far too creeped out by this to write 300 words on the subject). Male breastfeeding, it turns out, isn’t impossible: men have the mammary glands and pituitary glands necessary for breastfeeding. But aside from a few anecdotal reports of male breast feeding, there’s little evidence that men can produce milk without taking a drug that stimulates prolactin production or having a pituitary prolactin-secreting tumor.

Then there was yesterday’s news that 90 percent of the banknotes in the United States have traces of cocaine, up from 67 percent two years ago. The scientists say that powder from the few bills that are used to snort the drug spreads to all the other bills through handling and bill-counting machines.

Wolfgang Amadeus Mozart died in 1791 at the age of 35. A new study claims that complications from strep throat killed him:

Mozart’s body was said to be so swollen in his dying days that he could not even turn over in bed. And in December 1791, the month of his death, the researchers found oedema [a swelling caused by the build-up of fluid beneath the skin] to be far more prevalent among men of his young age.

This led them to conclude he may have had a simple strep infection, which caused a disorder that destroyed his kidneys.

Or, as they pithily conclude: “Our analysis is consistent with Mozart’s last illness and death being due to a streptococcal infection leading to an acute nephritic syndrome caused by poststreptococcal glomerulonephritis.”

Scientists have created an artificial tongue that is better than a normal human tongue at discerning subtle differences in various sweeteners.

About the size of a business card, the sweetness sensor works by detecting pH changes when a sweet substance mixes with a derivative of the chemical boric acid.

“We take things that smell or taste and convert their chemical properties into a visual image,” chemist Kenneth Suslick of the University of Illinois said in a press release. “This is the first practical ‘electronic tongue’ sensor that you can simply dip into a sample and identify the source of sweetness based on its color.”

A South Carolina social psychologist found a correlation between tough economic times and the election of tall presidents. Apparently McCain never had a chance last year.

And researchers in Canada have carried out a mathematical exercise to show that, in the absence of a quick and aggressive response, a zombie attack would lead to the collapse of civilization.

[The] analysis revealed that a strategy of capturing or curing the zombies would only put off the inevitable.

In their scientific paper, the authors conclude that humanity’s only hope is to “hit them [the undead] hard and hit them often”.

They added: “It’s imperative that zombies are dealt with quickly or else… we are all in a great deal of trouble.”

According to the researchers, the key difference between the zombies and the spread of real infections is that “zombies can come back to life”.