AP file

Elvis Presley performs in Providence, R.I., on May 23, 1977, three months before his death. Presley's doctor says that an enlarged and impacted colon played a role in the death of "the King."

In her latest book exploring the science that surrounds life's unmentionables, Mary Roach goes for the gut. Literally.

Roach has already taken on sex ("Bonk"), death ("Stiff"), the afterlife ("Spook") and the final frontier ("Packing for Mars"). In "Gulp: Adventures on the Alimentary Canal," she surveys centuries' worth of weird and wonderful discoveries about our digestive system, from the lips all the way down to the anus (which Roach says has some of the most densely innervated tissue on the human body).

In the course of exploring the alimentary canal, Roach addresses questions about our body's oddities (What keeps our stomach from digesting itself out of existence?) as well as the chemistry of digestion (How does Beano fight flatulence? How does Devrom stop the stink?).

One of the most fascinating tales has to do with the curse of Elvis Presley's colon: He died in 1977, while straining on the stool — and through the years, experts have pointed to drug abuse as well as a bad heart as contributing causes. But Roach concentrates instead on constipation, a problem that apparently plagued Presley for much of his life. The autopsy showed Presley had an enlarged "megacolon," horribly impacted with claylike material from a barium X-ray procedure that the King went through four months earlier.

It turns out that other folks have suffered fatal cases of constipation, but there's so much ickyness surrounding the subject that you don't hear much about it.  "I doubt you'll be seeing bus posters about defecation-associated sudden death any time soon," Roach writes.

There's a similar ick factor about many of the topics touched upon in "Gulp" — but fortunately, Roach has a knack for turning the "ick" into "ooh!" "wow!" and "really!?" In an interview last week, Roach discussed the ick factor and listed some of her favorite "Gulp" moments. Here's an edited transcript of the Q&A:

W.W. Norton

"Gulp" answers questions ranging from Elvis Presley's cause of death to the frontier of fecal transplantation.

David Paul Morris

Mary Roach is the author of "Stiff," "Spook," "Bonk," "Packing for Mars" and now "Gulp."

Cosmic Log: Tell me how the book got started. How did you get into "Gulp"?

Mary Roach: Well, a couple of things: One of them was something I stumbled onto when I was writing "Packing for Mars." I came upon a rather bizarre space nutrition study at the University of California at Berkeley back in the '60s, where they were testing bacteria as an entree. Dead bacteria. They actually had subjects go into a metabolic chamber and they sat them down, and they served them a slurry of bacteria of different varieties. And it was a terrible fiasco, of course.

That got me thinking about eating, and how it's a sensual thing and something that involves the mind, something we look forward to. But underneath all that, it's a basic biological need, and a process. We have a food processor, but we don't like to think about that. So I thought, maybe I'll think about that. Maybe I'll go down the alimentary canal and have a look.

Q: You talk a lot about the taboos that are associated with eating and digestion. Could you put your finger on the silliest taboo you came across? Is there some attitude toward eating that really makes no sense?

A: The first one that comes to mind is saliva. Saliva is something that's a highly taboo substance. Once it's outside your body, your own saliva is a source of disgust. Which is quite bizarre, because you're swallowing it all the time. You generate two to three pints of it, right there in your mouth. And yet, once it leaves the body, it's an object of revulsion. It's fascinating — something that has to do with the boundaries of the self.

Q: You debunk a lot of myths in the book, too. Is there particular bit of accepted wisdom that you're proudest to show is not really true?

A: The myth that I had the most fun with was the Jonah myth. Some people take the Bible literally, and try to make the case that a human being could survive in a whale's stomach. So I looked into this and tried to figure out which whale. A sperm whale would be the most likely candidate, because it's got a big enough gullet, and it doesn't have gastric acid. What it does have, though, is a very powerful stomach that crushes whatever is in its gut. You would be tumbled around and probably have some broken bones if you were inside a sperm whale.

Q: Is there something in the book that people really should know, that they probably don't know? For example, if I ever feel like my stomach is full to bursting, I'm definitely not going to load up on bicarbonate of soda.

A: Yes, the human stomach is surprisingly resistant to bursting. It has a couple of emergency ditching maneuvers. You burp, or you regurgitate. This is your stomach's way of saying, "OK, we don't want to burst, that would be fatal. So let's get rid of some stuff." The only time a human being suffers a case of a burst stomach tends to be somebody who ate a huge meal, and then felt uncomfortable and took a whole bunch of bicarbonate of soda. A little bit of gas makes you burp, and then you feel better. But a lot of gas, generated quickly, can outpace the body's safety mechanisms and burst your stomach. So after eating a huge meal, I don't recommend a large dose of bicarbonate of soda. Proceed with caution.

Q: "Gulp" includes lots of historical tales about those who have studied the alimentary canal. Is there one story you'd point to as deserving of more attention than it usually gets?

A: One of the people that impressed me was the very first experimenter to study and document human intestinal gas. This was in 1816. A Parisian doctor, Francois Magendie, had the opportunity to dissect a couple of guillotined prisoners. Because the prisoners had a last meal, and he knew what the last meal was, he could run a controlled experiment, if you will. He knew how long they'd been digesting. So he looked at what types of gas were in what part of the alimentary canal. He even figured out the hydrogen sulfide component, which is usually only 0.2 to 0.3 parts per million. It's a trace gas, but the human nose is quite sensitive to it, so it's possible he just used, uh, his nose. That was a novel approach to studying human intestinal gas. For originality, I give Magendie a lot of points.

Q: And when it comes to the scientific frontiers for studying the alimentary canal, a lot of people talk about fecal transplants. That's something that you address in the book.

A: Yes, if you have a certain type of bacteria called C. difficile, C. diff for short, it tends to set up camp in little pockets along the intestine, and it can be difficult to get rid of. It can be a kind of lingering infection that leads to inflammation and diarrhea. It's a quite serious condition, sometimes fatal.

If you take someone else's waste, and you use a colonoscope, you can put that material in and basically "seed" the patient's bacteria with a whole different set of bacteria that takes over. You take it from a healthy person, obviously, not from someone else who has C. diff. You take it from the waste material, which is one-third bacteria by dry weight. There's a lot of bacteria in human waste. Tons! That was a surprise to me. You don't really know what that stuff is, but a lot of it is bacteria.

This has about a 90 percent cure rate for chronic C. diff infection, and there's no real down side. It's rare that medicine comes up with something that simple, that effective, and with no side effects. The problem with it is just the ick factor. It's been slow to catch on, probably because there's no device maker or drug company to push a drug through. It has to be the hard work of M.D.'s who are just trying to get it into the system. They don't even know how to bill for it, so they bill for a colonoscopy.

Now people are starting to look at bacterial transplants of different kinds, as possible treatments for everything from weight loss to chronic ear infections. There's someone looking into it as a treatment for gum disease, by taking someone else's oral bacteria and giving them a dose of that. There's not a lot of down side, other than the ick factor.

Q: It strikes me that the ick factor, and how to deal with that, is a theme that runs through the book. Have you drawn any lessons about how to get over the ick factor when it hurts us rather than helps us?

A: This is one of those rare and wonderful cases where the media's fascination has been helpful. There have been a lot of articles written about fecal transplants, and that's partly because it's headline-grabbing. "Yeah, they put someone's crap in somebody else!" It gets people's attention, and they read it. But it's gotten so much coverage that now people are used to the notion of doing it, and they know that it's effective, and they know that it's useful. It's not such an intuitively horrific thing. The more people talk about it, the more they'll get used to it, and the more the ick factor dissolves. Then people with a problem feel free to go to their doctor and say, "Hey, I heard about this fecal transplant, and I wonder if maybe we can try that."

The fact that it's getting a lot of coverage, and a lot of people are talking about it, is making it OK to speak about it. And that's always a good thing.

Q: Do you feel as if "Gulp" actually serves that purpose? I realize every author feels as if his or her book is a boon to humanity, but is this a special case?

A: [Laughter] With my books, it's a little hard to make the case. But if I were to make the case, it would simply be that: I am encouraging people to talk about what's going on in the whole human food processor, from mouth to anus. It's a miraculous machine, and we owe it a little respect, instead of shame and embarrassment. I would love to see people having dialogues about it without feeling funny.

More cool facts about our food processor:

• Passing time by passing gas
• Can eating too much make your stomach burst?
• Diet and nutrition on the Body Odd blog

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.

This story was originally published on Fri Mar 29, 2013 3:33 AM EDT

When you click a "like" button on Facebook, you could be telling the world whether you're gay or straight, liberal or conservative, intelligent or not so much — even if you don't intend to. That's what researchers found when they ran tens of thousands of Facebook profiles and questionnaires through a computer algorithm to find the obvious as well as not-so-obvious connections.

The results were published on Monday in the Proceedings of the National Academy of Sciences, and you can sample the method for yourself at a website called YouAreWhatYouLike.com.

"The main message of the paper is that whether they like it or not, people do communicate their individual traits in their online behavior," said lead author Michal Kosinski, operations director at the University of Cambridge's Psychometrics Center.

Some of the correlations are obvious: For example, If you're a fan of the "I'm Proud to Be a Christian" Facebook page, it's a pretty safe bet that you're a Christian. But others are hard to explain: Why is it that liking the "Curly Fries" page is associated with having a high IQ? Why does the computer model put "Sometimes I Just Lay in Bed and Think About Life" in the category for homosexual females, while "Thinking of Something and Laughing Alone" is linked to heterosexual females?

"These little patterns are really not perceptible to humans," Kosinski said. Sometimes, it takes a computer.

Kosinski and his colleagues conducted their experiment over the course of several years, through their MyPersonality website and Facebook app. More than 8 million people took the MyPersonality survey, which asked participants about their personal details and also had them answer questions about personality traits. About half of the test-takers gave their OK for the researchers to match up their survey results with Facebook likes, on an anonymous basis. More than 58,000 of the volunteered profiles from U.S. respondents were selected for matching.

The results were analyzed to produce correlations in more than a dozen categories, including five widely accepted personality attributes (openness, conscientiousness, extraversion, agreeableness and emotional stability). Those are the attributes analyzed on the "You Are What You Like" website. The other categories included IQ, religion, politics, sexual orientation, age, gender, race, relationship status, alcohol and drug use, tobacco use, life satisfaction, number of friends — and even whether a Facebook user's parents had separated by the time the user was 21.

This PDF file shows you which Facebook pages are the best fit for each of the categories.

YouAreWhatYouLike.com

Researchers set up a website that assesses your personality based on Facebook "likes."

The researchers' computer model did the best at predicting black-vs.-white and male-vs.-female (95 and 93 percent accuracy, respectively). It could distinguish correctly between Republicans and Democrats 85 percent of the time, and between Christians and Muslims 82 percent of the time.

The accuracy rates for predicting sexual orientation were 88 percent for males and 75 percent for females. But don't think reaching that result was as easy as seeing who clicked the "like" button for "Gay Marriage." Less than 5 percent of the gay users were fans of such obvious pages, Kosinski and his colleagues said. The predictions were based instead on inferences from likes for less obvious pages. For example, the computer model associated the fan pages for Kathy Griffin and "Wicked, The Musical" with homosexual males, while heterosexual males were associated with the pages for Bruce Lee and WWE wrestling.

OK, maybe the pages weren't all that much less obvious.

The model wasn't as accurate (60 percent) when it came to predicting whether a user's parents stayed together or separated before the user turned 21. But even that level of predictive power could be "worthwhile for advertisers," the researchers said. "For instance, digital systems and devices (such as online stores or cars) could be designed to adjust their behavior to best fit each user's preferred profile," they wrote.

"I know the paper might sound like we're criticizing Facebook, but not at all," Kosinski told NBC News. "I'm a fan of Facebook."

Kosinski pointed out that an analysis of your credit card purchases, online music preferences, video rentals and Web browsing habits could come up with personal profiles at least as detailed as the ones that he and his colleagues produced. It just so happens that the Facebook likes were accessible enough to yield a vivid illustration of how such analyses work.

"It's possible this will lead some people to say, 'Maybe I shouldn't be using Facebook, or I shouldn't be using Google.' And that could be bad," he said. That kind of technophobia could hamper technological and economic progress, he said. Instead, the research should lead people to think twice about what they share online.

"We hope this information will help users start a discussion with organizations like Facebook, Google, Microsoft, or even policymakers about the rules of the game online," Kosinski said.

Update for 3:55 p.m. ET March 11: Kosinski's two co-authors, David Stillwell of Cambridge and Thore Graepel of Microsoft Research, passed along their comments in a news release from Cambridge. 

"Consumers rightly expect strong privacy protection to be built into the products and services they use, and this research may well serve as a reminder for consumers to take a careful approach to sharing information online, utilizing privacy controls and never sharing content with unfamiliar parties," Graepel said.

"I have used Facebook since 2005, and I will continue to do so," Stillwell said. "But I might be more careful to use the privacy settings that Facebook provides."

More about Facebook research:

• Facebook posts are more memorable than faces
• Facebook's roots go way, way back
• Scientists map 'Facebook for birds'

The PNAS paper, titled "Private Traits and Attributes Are Predictable From Digital Records of Human Behavior," includes a conflict-of-interest statement: Stillwell received revenue as owner of the MyPersonality Facebook app. Kosinski received funding from the Boeing Co. and Microsoft Research.

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.

This story was originally published on Mon Mar 11, 2013 3:02 PM EDT

For millennia, scientists have puzzled over the reason why rubbing two insulators together can produce static cling — and you may be shocked to hear that the standard explanation is wrong.

Static electricity, also known as contact electrification, is "one of the oldest areas of scientific study," researchers from Northwestern University observe in their paper on the subject, published online today by the journal Science. Questions about the phenomenon's cause date back to around 600 B.C., when Thales of Miletus conducted experiments with amber charging against wool.

The traditional view was that electrons were transferred from the surface of one material to another — for example, from a plastic balloon to the strands of hair on a child's head. That would cause one material to carry a slight positive charge while the other material carried a slight negative charge. Because opposites attract, the hair would be drawn toward the balloon, resulting in that cute "bad hair day" look.

To test that explanation, the Northwestern team took an ultra-close look at the static-charged surfaces of plastic material as well as silicon and aluminum, using Kelvin force microscopy. What they found was different from what they expected. The surfaces were actually "mosaics" of electrically charged nanoscale regions, alternating between positive and negative charges. When the surfaces were rubbed together, tiny patches were transferred from one surface to the other.

"It's not just transfer of electrons when two pieces of material come together," principal study author Bartosz Grzybowski, a chemistry professor at Northwestern, told Science in a video clip. "It's about transfer of material that then mediates the buildup of charge."

When those nano-bits of material are torn away from the surfaces as a result of the rubbing, that breaks chemical bonds and leads to changes in the net electric charge of each material. So when you rub a plastic balloon on a child's head, tiny flecks of that balloon are actually being rubbed onto the little one's locks of hair.

"A picture that emerges is that contact electrification is a complex process involving a combination of, at least, bond cleavage, chemical changes and material transfer occurring within distinct patches of nanoscopic dimensions," the researchers write. "The exact relationship between these effects — and possibly also those due to the presence of surface water and local electric fields — remains unclear but prompts several intriguing questions for future research."

Grzybowski and his colleagues point out that contact electrification isn't just a parlor trick: Through the ages, the phenomenon has sparked technologies ranging from photocopying and laser printing to do-it-yourself biodiesel and spray painting. Grzybowski said his research group was already trying to apply what they've learned to come up with better ways to apply coatings to surfaces. So it's nice to know that even after 2,600 years of study, our view of contact electrification isn't ... heh, heh ... static.

More about electricity:

• Power beamed through the air
• Static buildup may explain Martian mystery
• Avoid getting burned at the pump — literally!

In addition to Grzybowski, the authors of "The Mosaic of Surface Charge in Contact Electrification" include H.T. Baytekin, A.Z. Patashinski, M. Branicki, B. Baytekin and S. Soh. For more about the research, check out this report from the Nobel Intent blog.

You can connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. Also, give a look to "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Brian Snyder / Reuters

Tiger Woods hits his tee shot on the third hole during final round play in the 2010 Masters golf tournament at the Augusta National Golf Club in Augusta, Ga., on April 11, 2010.

Back in the noughties, Tiger Woods, dressed in a red shirt, hoisted a trophy on the 18^th green on almost every Sunday that he started out with at least a share of the lead. Science is helping explain how the red shirt helped him — and why it won't do much for the golfer now.

"It made him feel more confident and powerful and made others shrink in fear of this alpha male among us," Andrew Elliot, a professor of psychology at the University of Rochester, told me Tuesday.

We were talking about a new study in the journal Emotion where Elliot and colleagues find that our reactions immediately become faster and more forceful when we see red.

The conclusion stems from data showing that students more quickly and strongly pinched a metal clasp or squeezed a handgrip after reading red, gray and blue numbers and words that were controlled for lightness and saturation.

In a sense, the research documents our intuitive reaction to red. "It's a danger cue. So your body reacts as if it has just seen a threat. What happens when your body sees a threat is it immediately, automatically, mobilizes energy to flee or fight," Elliot said.

This reaction, the researchers speculate, is an evolved response. In great apes, for example, the alpha males are red in color. Other apes see the alpha males as a threat and thus keep their distance. Humans haven't lost this tendency, he explained.

So, what's this have to do with golf and other sports? The current research, Elliot noted, indicates that "seeing red immediately and very quickly in a short time period does make you stronger. But I don't think it lasts. It is a very quick response."

At the most, the effect might help with something such as weightlifting where a brief burst of strength and speed is needed. Otherwise, the effect of red, which the research shows is real, is likely more in the head when it comes to sports.

In previous research, Elliot and colleagues have shown that seeing red on an opponent makes you think the opponent is more dominant and stronger and so you think the opponent is going to do better than you. They have also shown that wearing red makes you feel more dominant.

"In both ways, viewing it on others and thinking that you are wearing it yourself, red is a dominance and power cue that makes you feel that you are stronger and are going to do better in these physical contests," he said.

On Sundays in the noughties, a dominant Tiger Woods put on his red shirt, walked onto the golf course and a handful of hours later walked off with a trophy. He knew he was powerful, and so did the other golfers. 

But a red shirt isn't magic, Elliot noted, not even for Woods, whose is experiencing the biggest slump of his career.

"If he wears red now, where he is no longer that dominant, it is probably not going to have the same effect because it is not really true, it is not an accurate signal," Elliot said.

"I think there's got to be something behind the signal that is accurate if it is going to work. Tiger is out of luck right now."

More stories on the science of colors:

• Seeking Olympic Gold? Wear red 
• Condi Rice knows – winners wear red
• Different colors describe happiness, depression
• Domestication led to horse color explosion

If you're reading this, the Rapture hasn't happened yet.

If it had happened, you might have been taken up to heaven with 200 million other members of the elect. (Or is that 144,000?) The alternative is even spookier: being left behind to face five months of tribulation leading up to the end of the world and Jesus' judgment. (Or is that seven years?)

The prediction that the end times would begin in earnest on May 21, 2011, was made years ago by Harold Camping — the preacher who heads Family Radio, a worldwide religious broadcasting concern. His prophecy is based on calculations so kooky that other end-time prophets say he's giving them a bad name. 

The real question is: Why has there been so much buzz over Saturday's scheduled Rapture?

"Obviously, what could be a bigger news story than the end of the world?" University of York historian Nicholas Guyatt, author of the book "Have a Nice Doomsday," told me. "It's absurd to think the world is going to end on Saturday, but even if there's an infinitesimally small chance that it's true, we should be interested."

One thing that sets Camping apart from most end-timers is that he sets actual dates. That runs counter to the usual Christian interpretation of the end times, which focuses on a passage in Matthew in which Jesus says "you do not know the day or the hour." It also runs counter to the lessons learned from centuries of failed doomsday predictions.

"Even among evangelists who believe in the Rapture,  most of them know we're not supposed to be trying to set dates," said Jerry Jenkins, co-author of the popular "Left Behind" apocalyptic book series.  "For one thing, it's going to make us look foolish on Sunday."

Jenkins jokingly acknowledges he's "one of those kooks who really believes it's going to happen one of these days." The 16-novel series he wrote with minister Tim LaHaye provides a fictional account of the end times, going all the way to the Second Coming. The tale is based on an interpretation of the end times known as pre-tribulation dispensationalism — which starts with some believers instantly disappearing in the Rapture while leaving others to fight it out with the Antichrist and his minions.

"It'd be a horrifying and chaotic event," Jenkins said. "I'm still a little confused whether Camping thinks that's going to happen, or whether there'll be an earthquake."

Nonsense from numbers
Jenkins and many others are also confused over how Camping came up with his prediction. This year-old posting from Church of God News runs the numbers: Saturday supposedly marks 7,000 years since the Noah's Ark flood, and 722,500 days since Jesus' crucifixion. By Camping's numerology, 722,500 represents (5 x 10 x 17) x (5 x 10 x 17), or the square of atonement times completeness times heaven. 

"Now the above is utter nonsense," the Church of God News' Bob Thiel wrote. That sounds about right.

Jenkins says such number-based predictions "happen fairly frequently" in the end-time game. "It's sort of seasonal," he said.

In fact, Camping himself predicted years ago that the world would end in 1994. When the prediction failed, Camping said he got his initial calculations wrong and corrected the figures to come up with Saturday's doomsday date.

Guyatt noted that prophets have been predicting the end times, and getting the dates wrong, for hundreds of years. One of the best-known examples in America is the "Great Disappointment" of 1844. Baptist preacher William Miller predicted that the "Second Advent" would come on Oct. 22 of that year (after a couple of abortive predictions for earlier dates). He attracted as many as 50,000 adherents by the time the big day came. Nothing happened, of course. The result? Derision, church burnings, vandalism, even tar-and-feathering. Miller continued to await the Second Advent until his death five years later.

Miller's theology contributed to the later rise of denominations such as the Seventh-Day Adventists and Jehovah's Witnesses, but those churches did away with the date-setting.

Bart Ehrman, a professor of religious studies at the University of North Carolina at Chapel Hill and author of the newly published book "Forged," notes that the scriptural foundations for modern-day end-time scenarios are shaky. "In the Apocalypse, there's no reference to the Rapture at all," he told me. "The idea of the Rapture comes from the writings of Paul." And many of the details have been "completely made up by theologians, they're not found in the Bible," he said.

Ehrman said he could come up with his own scenario for the end times that would make more sense than Camping's. "What I'm looking for is some very wealthy believer," he joked.

Ah, the money angle. "The thing that's confusing about [Camping's prediction] is that he doesn't seem to be making money off this," Jenkins said.

Funding the Apocalypse
Lots of money is being spent on promoting the Rapture, however. Family Radio's financial records indicate that the nonprofit organization had $122 million in net assets in 2007. The figures for the following year, 2008, show $41 million in expenses, resulting in net assets of $86 million. The 2009 report shows expenses of $37 million and net assets of $72 million. And judging by the billboard ads, bus ads and direct-mail campaigns promoting the Rapture, the spending rate must have risen substantially since those reports were filed. After all, if you're going to heaven on Saturday, why wouldn't you spend it all?

Ehrman noted that this sort of pre-doomsday spending spree has happened before, when he was teaching Bible classes in the 1980s. One of the books that came out back then was "88 Reasons Why the Rapture Will Be in 1988."

"I had students in my classes whose parents literally sold the farm because they didn't need it, and then it didn't happen," he recalled.

Some Family Radio listeners, such as Staten Island retiree Robert Fitzpatrick, have spent tens of thousands of dollars of their own money to promote the Rapture. That worries Jenkins. "There are very well-meaning people who are telling me they're getting rid of their life savings," he said. "I wonder who's going to take care of them when it's all over?"

Gerry Broome / AP file

Allison Warden shows off her car, emblazoned with messages about Saturday's scheduled Rapture. Warden, of Raleigh, N.C., has been helping organize a pre-Rapture campaign using billboards, postcards and other media in cities across the U.S.

The big spending spree is one big reason why this particular date has gotten so much traction. But end-time tales do not live by billboard ads alone. Guyatt says this time in history is particularly well-suited for doomsayers.

"Whenever anything really bad happens, it kind of gives their case a little support," Guyatt said. "So if you think of the turbulent times we've had over the past decade — 9/11, Iraq and Afghanistan — it kind of feeds on that. Maybe it's not formal, but we have an affinity with the view that the world is becoming a more dangerous place, or maybe our days are numbered."

And every Twitter tweet, Facebook update, Rapture party invitation — for that matter, every blog post — turns up the wattage ever so slightly on the doomsday spotlight. "What's given this traction is the billboards and the media," Guyatt said. "At some point the ball is rolling, and we help tip it a bit further, because of you, because of us."

How imminent is 'imminent'?
Leave it to the veteran end-timers, who have been through all this before, to provide perspective. "I applaud the discussion," Jenkins said. "I think people should be thinking about this."

Jenkins' writing partner, Tim LaHaye, has said on many occasions that events such as the Japan earthquake and tsunami are signaling that the end is near. The way Jenkins sees it, the end of the world could well be imminent, but "our definition of 'imminent' is clearly not the same as God's."

"If he waits one more day in his mercy, it could be a thousand years in our time," he said.

So what will Jenkins be doing on Saturday?

"We're just going to carry on with the usual activities," he told me. "One of our granddaughters is going to have a ballgame."

More about the Rapture rumblings:

• Rapture prophet says he'll be watching the action on TV
• Digital Life: Post-rapture video reveals stunning lack of zombies
• The Last Word: Only hours to go until the (fake) Rapture
• End of Days? Believers enter the final stretch
• End of the world? How about a party instead?
• Slate: 144 scenarios for America's apocalypse
• Pet sitting offered during Rapture
• Doomsday facts (or fictions)

In some parts of the world, it's already Saturday. I'll be blogging about the Rapture hype over the weekend, and you can follow the updates by checking CosmicLog.com/Rapture. You can also connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. And for something completely different, check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Rothamsted Research

Disrupting a mosquito's sense of smell can ward off a bug bite.

Researchers say that they’ve found a new class of chemicals that can drive away mosquitoes by disrupting their odor-sensing system — and the first chemical in that class seems to be thousands of times more effective than DEET.

The compound, called VUAA1, was identified thanks to the kind of high-throughput screening process that is more typically used for drug discovery, said Vanderbilt University professor Laurence Zwiebel, a member of the research team. Zwiebel and his colleagues published their findings online this week in the Proceedings of the National Academy of Sciences.

"This compound is really a first-in-class molecule to do this action," Zwiebel told me today.

A mosquito's olfactory system relies on a variety of receptors spread out on the bug's antennae — known odorant receptors, or ORs. The receptors are tuned to respond to different types of odors, including the smell of sweat and blood, and they activate switches called OR co-receptors (Orcos) to tell the mosquito's brain which scent is being picked up.

Researchers screened almost 120,000 small-molecule compounds to check their effects on human embryonic kidney cells that were genetically engineered to include the OR-Orco complexes.  "It was totally a shotgun approach," Zwiebel said. "Throw the kitchen sink at it and see what happens."

The scientists were surprised to find that VUAA1 consistently activated the odor-sensing complexes, even though it's not actually considered an odorant. "It wasn't something we set out to find. It was an anomaly in our tests," another member of the Vanderbilt team, graduate student David Rinker, said in a news release.

"If a compound like VUAA1 can activate every mosquito odorant receptor at once, then it could overwhelm the insect's sense of smell, creating a repellent effect akin to stepping onto an elevator with someone wearing too much perfume, except this would be far worse for the mosquito," said Patrick Jones, a postdoctoral fellow at Vanderbilt who is the study's first author. 

Zwiebel said that he and his colleagues compared the effectiveness of VUAA1 with that of the widely used DEET insect repellant by measuring how much of each compound it took to repel larval mosquitoes in a petri dish. "The more you use, the more the mosquito moves, as if it's trying to get out of Dodge," he explained. A tiny amount of VUAA1 had the same repellent effect as a concentration of DEET that was tens of thousands of times stronger, Zwiebel said.

However, Zwiebel stressed that VUAA1 isn't yet ready for prime time. "The commercialization of this compound has hardly begun," he said. The chemical still has to be fine-tuned and checked for toxicity, and it's possible that other chemicals in the same class will turn out to be more effective or safer. Vanderbilt University says it has filed for a patent on this class of chemicals and is talking with potential corporate licensees about commercialization, with special focus on the development of products to reduce the spread of malaria in the developing world.

Zwiebel noted that VUAA1 has been found to activate the odor-sensing complexes of flies, moths and ants as well. "Basically, every insect that has an olfactory system has this Orco ion channel," he told me. "We have an expectation that every insect will be affected by this molecule. Now, that's both good and bad."

It's good, because the new class of chemicals may yield new ways to drive away other types of nuisance insects and agricultural pests. But it'd be bad if they also drove away beneficial bugs such as bees and butterflies.

"We've all read 'Silent Spring,'" Zwiebel said. "We don't want to have the same DDT story."

More about mosquitoes:

• Scientists tweak mosquito genes to fight malaria
• A malaria mosquito is quickly becoming two species
• Scientists find natural mosquito repellent
• Researchers studying better insect repellents
• U.N.: Efforts on track to halt malaria deaths

In addition to Jones, Rinker and Zwiebel, authors of "Functional Agonism of Insect Odorant Receptor Ion Channels" include Gregory M. Pask. VUAA1 stands for Vanderbilt University Allosteric Agonist 1. The research was supported by the Grand Challenges in Global Health Initiative, funded by the Foundation for the NIH through a grant from the Bill & Melinda Gates Foundation.

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