Wednesday, April 25, 2007

The Physics of Sex Widget Game

In the tradition of physicists through the ages, I've attempted to make a very simple model of a complex system.

This image is screen shot from a game that simulates some of the feedback issues involved in sex. It's the Physics of Sex equivalent of a spherical cow.

To play the game, you have to stimulate the floating ball with your mouse. If you do it properly, the meter on the left will show your progress. Ultimately the meter will top out and the ball will turn red and throb. I'm not going to tell you exactly how to stimulate the ball. Just like learning about the birds and bees in real life, you'll have to discover some of the details on your own. Also just like real life, it's not that hard to figure out.

If you want to give it a try, click the image to download the Widget file. If you've never installed a Widget before, you'll first have to install the free Yahoo Widget 4 engine. It should work automatically on a Mac.

The game is a bit simple and not too challenging at the lower levels(although I haven't beaten it at Level 12 yet), but it illustrates three things about sex

1. Positive feedback (provided by the level meter) helps you achieve the ultimate goal.

2. Negative feedback is necessary to help you follow the ball and apply the appropriate stimulation at the apprpriate place. That is, when the mouse cursor is too far from the ball you adjust by bringing it back.

3. The simplified orgasms simulated by playing the game, which I claim are similar to the type that men have most of the time and women have at least some of the time, are essentially the result of integrate-and-fire circuits.

The first two points are probably familiar to most folks, but integrate-and-fire circuits are a bit more obscure. Basically, this type of circuit measures some input and when it reaches a trigger point it fires.

Avalanches look a lot like integrate-and-fire circuits - snow builds and builds on a mountain until it's unstable, then the slightest disturbance can send it careening down the slope.

Neurons are often described as leaky integrate-and-fire circuits. That means that the correct input can push the neuron toward firing, but if the stimulation stops the neuron will gradually lose memory of the stimulus and return to its resting state.

Picture it in terms of a leaky balloon. If you blow it up far enough, it will eventually pop. But if you take a break before it blows, the air will slowly escape and the balloon will deflate.

I made my widget leaky too. If you stimulate the ball, the meter will climb, but stop for a while and the meter will slowly drop back to zero.

Another aspect of integrate-and-fire circuits is the fact they often experience a refractory period after firing. During that time, they don't respond to any stimulation at all. If you blow up a leaky balloon until it pops, the refractory period corresponds to the time it takes you to find another balloon. Men are intimately familiar with the refractory period that follows sex, and older men know that it seems to take longer to find their balloons with every passing year.

I added a refractory period to my model as well. If you manage to get the ball to throb, you have to wait a few moments before it's ready for you to start again.

I adapted the game from an even simpler game called Focus developed by Aaron McBride of MIT.

Check out the thousands of other widget in the Yahoo gallery. Lot's of them are as useless as the Physics of Sex widget, but plenty of them are handy and/or cool, and most are made by amateur programmers with an idea and a little free time.

Read the rest of the post . . .

Friday, March 23, 2007

A Climactic Hiccup Cure (and your chance to help test it)

"Sex is good for lots of things - now it seems we can add hiccup cure to the list."

If you follow the annual presentation of the tongue-in-cheek Ig Nobel Prize, then you already know that modern medicine has come up with at least one promising hiccup cure. As is often the case for the Nobel Prizes that the Ig Nobel parodies, the recognition of Francis Fesmire's work came much later than it should have.

Back in 1988 Fesmire published a revolutionary paper entitled Termination of intractable hiccups with digital rectal massage in the journal Annals of Emergency Medicine (annals . . . that's funny).

Listen to the podcast with our new roboreader Sangeeta. Or

Skip to the Tip in this week's post.

I've heard jokes about how he might have discovered the effect, but it's not really such a stretch. The key to Fesmire's discovery may be stimulation of the vagus nerve. Other researchers have noted the connection between the vagus nerve and hiccups. Unlike most of the nerves that make their way from your brain to other parts of your body through the spinal column, the vagus nerve is a major nerve bundle that starts at your brain stem and winds its way through your abdomen. In fact the FDA has approved an implantable vagus nerve stimulator for controlling hiccups with electrical bursts.

Personally, I think Fesmire's discovery is a much cleverer way to stimulate the nerve. It makes sense because, among other things, the vagus nerve connects to the sphincter muscles of the gastrointestinal system (including the anus) as well as many muscles and organs involved in hiccuping.

For those of you uncomfortable with the massage, there's an alternative. In 2000, Roni and Aya Peleg published a case report in The Canadian Family Physician journal reporting their observation of sexual intercourse as potential treatment for intractable hiccups.

Sex is good for lots of things - now it seems we can add hiccup cure to the list. That's cool, but it begs the question as to why (and if) sex has anything to do with hiccups.

Now, I consider myself to be a skeptic as a rule. But I also try to be open minded, so I've been withholding judgement on these particular cures until I could see further data. As it happens, I came down with a heavy duty case of hiccups a few days ago . . .

Naturally, I thought I would try one of the cures myself. The massage thing seemed a bit involved and messy, so I went with the alternative. Considering the fact that I was in a rush to try it before the hiccups ended on their own and I didn't want the confounding complication of involving anyone else in the experiment, I went solo.

It worked perfectly. At the climactic moment, my hiccups ceased.

As a result, I was inspired to see if any physicists had taken a look at hiccups and whether they had anything useful to say about the phenomenon.

It turns out that in 1995 W. A. Whitelaw of the University of Calgary, along with Parisians J.-Ph. Derenne of the Groupe hospitalier de la Pitié-Salpêtrière and J. Caban of the Hopital St. Antoine published a paper in the physics journal Chaos titled Hiccups as a Dynamical Disease."= They concluded that hiccups are produced by a central pattern generator (CPG). A CPG is a neuron circuit that generates a signal, which causes an action that in turn stimulates another signal, and the pattern repeats, sometimes indefinitely. Similar circuits apparently handle numerous other repetitive actions such as breathing and walking

The Hiccup Generator as a "Black Box"

Just what all the components are in the hiccup CPG isn't entirely clear. What's more, it doesn't really matter. Instead the researchers treated the hiccup CPG as a black box. To an engineer or scientist, a black box is a system that's studied in terms of what it does, rather than what it's made of. In other words, the physicists studied the behavior of the biological system that causes hiccups without worrying too much about the individual pieces that go into it. The work led to some interesting insights, including the fact that the rhythms of hiccups seem to be tied to breathing rates and heartbeats, but it didn't do much in the way of offering any new cures.

As I see it, the most important aspect of the research is the simplified perspective on hiccups. We have a hiccup black box in our bodies that normally is in the 'off' state. Any number of disturbances can turn it on: eating too quickly, coughing, drinking a hot liquid, drinking a cold liquid, a sudden shock, a sneeze, acid reflux, or even (though, thankfully, rarely) tumors, renal failure, or chemotherapy.

Many causes of hiccups (that aren't related to diseases, anyway) involve a chemical or physical shock that kicks the hiccup black box out of its resting state and into its annoying active state.

A simple way to generally illustrate this sort of thing is to imagine a bunch of kids playing soccer (football for those of you outside the US) at the bottom of a valley. When one of the kids kicks the ball hard enough, they might knock it over the ridge of the valley wall and into a neighboring valley. If the valley next door is not as deep, the kids over there will soon kick the ball back over the ridge to the soccer game. How long that takes depends in part on the height of the ridge between the valleys, and in part on the random chance that some kid kicks the ball hard enough to clear the hill.

We see lots of situations like this in physics; an electron in its lowest orbit in a hydrogen atom can absorb a photon and get kicked into a higher orbit; an atom possessing a characteristic called spin can be flipped from one orientation along a magnetic field to the opposite orientation (this is critical for magnetic resonance imaging); and some types of glass that radically change state when heated in certain ways (a technology based on these glasses may eventually lead to novel data storage chips), to name just a few of the countless examples.

Often in physics we see systems that have been knocked from their ground states (the states they naturally prefer to be in) to higher states, which spontaneously drop back some random amount of time later. If you don't feel like waiting, hitting a system with another shock that's similar to the one that bumped it out of its ground state often knocks it back. In the case of an electron in a higher orbit around its atom, this is called stimulated emission. It takes a photon to get the electron up there in the first place, and another photon can induce the electron to fall back to the ground state immediately instead of randomly.

Hiccups work essentially the same way - a shock to your system bumps the hiccup CPG into its active state. Simply waiting will often be enough that the bout stops on its own as the CPG randomly returns to its resting state. But if you're impatient, any number of hiccup cures that rely on physical or chemical shocks to your system may do the trick immediately.

Trying to scare the hiccups out of someone is obviously a physical shock. The spoon full of sugar cure is a chemical shock to your mouth, throat, and stomach. Holding your breath, breathing into a paper bag, and related asphyxiating cures cause a chemical shock through a relatively rapid build up of carbon dioxide. I could keep going down the list, but as far as I know just about every folk cure involves the equivalent of stimulated emission to kick your CPG to its resting state.

The interesting thing about Fesmire's digital massage is that he is taking advantage of the fact that while we know very little about what's inside the hiccup black box, we know about one thing in there - the vagus nerve. (Remember, the vagus nerve stimulator implant is the only FDA approved hiccup cure.)

The other thing we know about the vagus nerve is that it's involved in orgasm. This was shown in recent studies with paraplegic women who had lost sensation in their lower bodies as the result of back injuries. The startling outcome of the experiments was that they could still experience orgasm from stimulation of their genitals. The researchers believe that the orgasms must involve the vagus nerve because it's the only intact nerve pathway back to their brain stems.

Some folks might prefer Fesmire's massage, but I'm guessing that most people would choose the orgasm stimulation to tickle their vagus nerves and kick the hiccup CPG back to its resting mode.

Do Your Part for Science

As most scientists will tell you, anecdotal evidence is pretty unreliable. And even though I experienced the cure myself, I'm willing to accept the possibility that the success was coincidental. The Pelegs’ case study adds to the evidence, but that's still only two tests.

We need more data. I'm willing to try again, but I don't get hiccups very often.

I'm hoping that you will help test the cure. The next time you get hiccups, and have enough time and privacy to do the experiment, have an orgasm (alone or with a friend) and write to me to let me know whether or not it cured the problem.

I'll compile the data and report back as soon as we have a clear answer one way or the other.

You can post your results in the comment section of this post or email me the results at "BuzzSkyline at gmail dot com."

Read the rest of the post . . .

Thursday, March 22, 2007

Woman on Top: Closing the Feedback Loop

When I was on Tiffany Granath's show a few weeks ago, we took several questions from listeners who called in. A few of the topics lay at the very edge of the domain of physics as it applies to sex, but most were excellent questions that I was pretty comfortable dealing with.

One fellow in particular said that he and his wife have a good sex life, but she's only fully satisfied if she's on top when they make love. He was wondering why that is and what he could do to add some variety without neglecting her needs.

My guess (given the caveat that I was working with a minimum of data) was that he should take into account his wife's sexual feedback loop.

In physics, engineering, and other sciences, we often think of experimental systems as being open loops or closed loops.

An open loop system is one that has a control, which is also known as an input (think of a volume knob on your radio, or the handle on your water spigot), and an output (the radio volume or the amount of water flowing through your garden hose), but no feedback. That is, the person adjusting the radio volume is deaf and cannot hear when the sound level is correct, or the garden hose extends around a corner and you can't tell how much water is pouring out of it.

Alternatively, a closed system sends some information about the output back to the input. In other words, you turn the knob on the radio until the volume is correct, and then you either stop turning or turn it back a bit. By watching the spray coming from your sprinkler, you know whether you have turned the spigot handle as far as you need to in order to water your yard. In either case you're using information about the output to adjust the input.

Open loop systems work fine for lots of applications, and are particularly handy if you just want to turn something all the way up or entirely off. (In electronics, a common jargon for open loop amplifiers is to say that they "go to the rails," which means they can either put out the lowest voltage or the highest voltage that the power supply can handle, but they don't provide any intermediate voltages.)

If you need some reasonable amount of control over an output, you must have feedback. Sexual response can be considered one of nature's closed feedback loops. The input of of sensual contact leads to pleasurable signals passed through the nerves to the brain. In order to work well, information about the pleasurable signals have to make it back to adjust the sensual contact.

If you're masturbating, you don't need any help figuring it out - you just do what the feedback from your nerves tells you feels good. When you're making love with another person, feedback is a lot trickier. You can't share your partner's sensations directly, so you have to rely on secondary clues - by observing the way they're moving or the sounds they.remaking. The loop is more or less closed, but the feedback is relatively tenuous.

A woman who is on top during intercourse, however, can take advantage of her own strong sensory feedback to ensure that the right spot is being stimulated in the right way.

That is, it may not be the woman-on-top position itself that satisfied the caller's wife. It may instead be an issue of closing her feedback loop.

There are numerous ways for the caller and his wife to attempt to get the same result while making love in other positions. For one thing, he could work harder to interpret his wife's responses to his actions. Studying her movements or the sounds she makes during sex may strengthen the feedback enough to close the loop. Of course, it's important for the woman to broadcast her pleasure as much as possible as well. It can be very difficult to satisfy a woman who is too shy to communicate what she needs and enjoys.

Simply holding relatively still while she sets the pace may be enough to help the caller out. It's possible to accomplish this even in the traditional missionary position, if the man supports himself a bit as the woman thrusts her hips rhythmically. Placing a pillow under the woman's buttocks to raise her hips may make this easier to accomplish. It's worth experimenting with other sexual positions - any position that limits the man's motion while leaving his partner free to take charge will shift the focus and the feedback into the woman's control.

Another possibility is to encourage her help out by stimulating her clitoris or nipples to let her strengthen the sensory feedback loop herself, regardless of the sexual position they are using.

One advantage to focusing on your partner's feeback loop is that it often comes at the expense of your own feedback. That can help slow things down if you tend to finish sooner than your partner would like.

You'll get similar advice from traditional sex therapists and experts, but they usually talk about things like communication and sensitivity to your partner's needs. That's all good, but personally, I feel it's easier to think in terms of feedback loops. Of course, I'm just a physics nerd, and I tend to consider sex in terms of the little diagram you see here. If you click the picture, you can visit the Wikipedia entry that explains (in engineering jargon) the meaning of the components in the schematic.

Read the rest of the post . . .

Monday, March 19, 2007

Physics, Sex, and Comics

I wasn't surprised to learn that other people have already noticed the intimate connection between sex and physics, but I was amazed to see how well Randall Munroe portrays the connection in comic strip form.

If you click the image here, you can see one of Munroe's takes on the intersection of passion, sex and physics.

Some of my other favorites include

Angular Momentum
The Romatic Drama Equation

In truth, only some of Munroe's comics are about physics and sex. Many of them touch on computer programming, math, or random topics that interest him, like this interesting supermarket prank.

It's funny stuff. Check out the rest of the 'toons to see what I mean.

Thanks to my good friend Davide the science writer for letting me know about

Read the rest of the post . . .

Friday, March 16, 2007

Part 2 of The Physics Guide to Hooking Up: Why It's Better to Pursue than to be Pursued, or the Trouble with Rule 6

I'm sorry to burst the bubble of any Disney fans out there, but Prince Charming almost certainly lived more happily ever after than Snow White did.

I'm saying this horrible thing because a famous mathematical puzzle known as the Stable Marriage Problem shows that a person who pursues a mate is almost always more satisfied with their spouse than a person who is pursued.

This is a particularly important fact for women who adhere to The Rules, because physics and math suggest that rule number 6 of the top ten rules for women appears to be very, very wrong.

Skip to the Tip in this week's post.

The first analysis of the Stable Marriage Problem was described in a 1962 paper by mathematician David Gale and economist Lloyd Shapley. They were attempting to determine if a set of 100 men and 100 women could pair up in marriages in a way that no one could find a better mate in the bunch who would have them.

They way they set up the problem goes like this . . .

Each man ranks all 100 women from their first choice of potential partner to their last. The women all do the same for the men. Because the reasons one person finds another attractive is often mysterious, Gale and Shapley selected each person's ranking of potential mates at random. As a result, no two rankings were alike and one person's top choice would likely be farther down on any other person's list. Once everyone has their ranked list, the marriage game begins.

Probably because the paper was written way back in 1962, pairings among men and women occur when a man proposes and a woman accepts. To begin with, the first man proposes marriage to the woman at the top of his list. Because it's early in the game and this is the only marriage proposal the woman has gotten, she accepts (remember, it's just a simple model).

Once the first pairing is out of the way, the second man proposes to the top woman on his list. Assuming she's not engaged to the first man, she accepts. If, however, she happens to be the fiancé of the first man, the woman looks at the ranking of her two suitors and chooses to go with the one she ranked highest.

The game continues with each man in turn proposing to women in the order that he ranked them. As he goes down the list, a woman will accept his proposal if she is either unattached or engaged to a man who she ranks lower than him. Any man who has been thrown over for a higher ranking fellow eventually goes back down his list looking for a woman who is single or prefers him to her current fiancé.

Gale and Shapley found that there are always stable solutions to the problem (usually many solutions, in fact), regardless of the number of people involved. Stability in this case means that once everything is sorted out, a man who checks out all the other couples in the group would not find a woman he prefers over his own fiancé who also ranks him higher than her fiancé.

Mathematically speaking, that's a pretty interesting result. But it's not terribly useful or informative for real people like you and me. The truly fascinating revelation, in my opinion, is that something very surprising comes out of the study if you consider the relative satisfaction of men and women in the model. Specifically, if you look at the ranking of the women who the men ended up with, most men got engaged to a woman who was high on their list. Women, on the other hand, were stuck with men who ranked relatively low on their lists.

To put hard numbers on it, in an expanded a study of 1000 stable solutions to the problem when it included 512 couples, men on average hooked up with women who ranked 8th on their respective lists, while women were engaged to men who ranked an average of 80th. That's a huge discrepancy. Bear in mind that the only difference between men and women in the mathematical model is that men always proposed and women only accepted or rejected proposals.

You'd be right to take all this with a grain of salt. Mating in real life is a much more complicated affair. Even a slight modification of the problem, such as adding the potential for degrees of inherent beauty among the men and women, can radically change the numbers of stable solutions and the average degree of satisfaction. (Some realistic details can actually make the problem so complex that it's essentially unsolvable.) Nevertheless, in general when only men made proposals they were much better off than the women.

The world has changed a lot since '62. Back then, the Stable Marriage Problem didn't have a lot of relevance to the actual complexities of dating and mating. These days, there is one situation that pretty closely approximates the bare-bones problem that Gale and Shapley studied - online dating services.

When you join Yahoo Personals or some other matching service, you post your profile and often your picture. You then have a choice; you can sit and wait for invitations (for dates usually, rather than marriage) to come rolling in, or you can check out the profiles of other people and decide who you would like to contact.

If you passively wait for someone to write to you, you mimic the behavior of the women in the Stable Marriage Problem. That is, you sit on your hands waiting for an email or an instant message from a suitor, then you check out their profile and either accept or reject them.

If instead you take the initiative, you act like the men in the Stable Marriage Problem. You perform some sort of ranking and choose the person you want to contact most from all the people who have posted profiles. If the first person you write to rejects you, you are forced to move farther down in your list of possibilities.

According to the solutions of the Stable Marriage Problem, if you take the initiative in asking out the people you're most attracted to you will meet much more desirable people through online dating services than you would if you wait for someone to contact you.

This runs completely counter to rule number six of the top ten rules for women, which reads "When considering whether to use personal ads or other dating services, you should place the ad and let men respond to you."

Don't get me wrong, I think many of The Rules work just fine. Most of the rules will help a woman play a man like a starving trout hooked on a line. But if you ignore rule six and take the initiative in luring a mate, you dramatically increase your odds of landing a trophy catch rather than some loser you'll want to heave back into the pond.

Read the rest of the post . . .

Tuesday, March 13, 2007

Book Review: Sex in Space

It turns out that my family has a tenuous connection to tabloid-headlining astronaut Lisa Nowak. Apparently, she's a few years younger than my uncle and they went to middle school together in the suburbs of Maryland's upscale Montgomery County.

According to my family's lore, one day my uncle was using crutches because of a leg injury, and Lisa kicked one crutch out from under him. He wasn't hurt as a result of the alleged assault, and knowing my uncle I'm pretty sure Lisa had a good reason to do it, assuming it's true (over years of retelling, we tend to embellish and distort stories like this in my clan).

My uncle and Lisa met up again years later when they were both flying in the US Navy. I don't think she attacked or threatened him the second time they crossed paths, but it's possible that they were both wearing diapers (my uncle has applied for astronaut slots on occasion, I'm guessing he might have had to wear the diapers as part of the flight testing process).

The Lisa Nowak love triangle naturally led me to wonder about the status of sex in space. Lisa never flew on a shuttle mission with the astronaut who was the object of her affections, so it seems unlikely that she had a chance to do a zero-g tango. The question is: have any other space travelers attempted sexual relations in orbit or beyond?

There's more to it than simple titillation. President Bush has declared travel to Mars and the establishment of a lunar base to be official goals of our space program. In either case, humans will spend extended periods in low gravity environments. Sex is an important part of human interactions. Whether or not astronauts have attempted to make love during past missions, it's hard to imagine that at least some of them won't try it during excursions lasting months to years.

This raises several concerns. We don't know whether prophylactics will work properly in space. We can't be certain that we can conceive children in low-g. And if we can, we have no idea what effect it would have on the fetus. Is gravity necessary for fetal development, or will space children suffer birth defects? Assuming the lack of Earth-like gravity itself is not a problem, will we find ways to protect sperm, ova and fetuses, not to mention astronaut parents, from the increased levels of radiation in extraterrestrial environments?

Fortunately, Laura Woodmansee has taken time to investigate the latest wisdom on all these issues and more, and compiled them in a very tasteful book entitled Sex in Space. Woodmansee is a science journalist who specializes in covering the space program. Two of her other books, Women Astronauts and Women in Space: Cool Careers on the Final Frontier specifically focus on the female astronaut contingent.

Although Sex in Space is a brief 136 pages long, Woodmansee covers topics such as whether or not anyone has had sex in space (the official answer is 'no, but the extensive hours that people have spent in space in the past 50 years and the numerous opportunities available to them suggests that there's a strong possibilty that the true answer is 'a few times'), how they might make love if given the chance, the effect of low-g on astronaut libidos, and the future potential for honeymoon trips to space.

OK, I confess, I turned first to Chapter 2 - How to make love in space. Woodmanse includes several instructional diagrams of possible positions, and brings up issues I never thought of - like just how sloppy space sex is likely to be. But once I finished that portion and went back to read the rest of the book, I found there was plenty to learn about space sex that never would have crossed my mind without Woodmansee's guidance.

One thing that didn't surprise me in reading Woodmansee's book is that NASA has not conducted any official studies of sex between humans in space. Large, formal institutions don't deal with sex well, as Nowak's troubles seem to confirm. In my opinion, however, turning a blind eye to a natural and important part of human behavior is nothing short of irresponsible, particularly if they seriously mean to put people into space for long periods.

Even a simple mission to Mars and back is going to take years. During that time, it's highly likely that some astronauts will experiment with sex. Besides, sexual intimacy is probably a good way to maintain a happy and cohesive crew, provided the whole thing is carefully thought out. After all, they will likely spend most of their time cooped up in a craft about the size of a school bus (at best). The intrepid explorers are going to need all the stress relief they can get.

Ideally, I think NASA administrators and scientists should read Woodmansee's book, and then get to work designing a comprehensive study of sex in space. At the very least, it would be a powerful rebuttal to the concerns of critics who feel that the International Space Station is a waste of time and money that could be better spent on unmanned and robotic missions. Robots can do just about everything humans can do in space except help us to anticipate the various aspects of low-g sex and conception.

Whether we like it or not, sex is going to be among the most important issues we will face if we are ever to truly to break free of Earth's gravitational bonds and move out into the vast galaxy that surrounds us. So NASA might as well face the facts and start investigating the science of sex is space.

Read the rest of the post . . .

Friday, March 09, 2007

Those ain't just your daddy's genes (and maybe not your momma's)

You probably get half of your genes from your mother and half from your father, but it's possible that you got some of your genes from someone - or something - else.

A new model proposed by Jeong-Man Park of Rice University in Houston and his colleague Michael Deem (the same guy working on the HIV vaccination scheme I mentioned a few posts back) suggests that much a significant portion of our DNA was donated by viruses and bacteria that infected our ancestors over the ages. Although the chances are slim, it's possible that some of your DNA comes from microbes that infected your mother or father.

Park and Deem were led to the conclusion as they sought a theoretical answer to the question of why evolution proceeded fairly slowy for 2.5 billion years, as simple multi-cellular organisms developed, and then raced ahead for the next billion years to produce you and me and Brad and Angelina.

The answer may be horizontal gene transfer (HGT). When it was first proposed as a mechanism for bacteria to trade chunks of DNA and effectively adapt without reproducing, the idea of HGT was very controversial. By looking at common sections of DNA in species that should not be related, many scientists have come to the conclusion that we must be exhanging DNA through HGT. In fact, it seems to be at least as important for evolution as the passing on of mutations through sexual reproduction. Among other things, it appears that our immune systems arose from a gene transfer that must have occurred about 400 million years ago.

Park and Deem presented their model of HGT enhanced evolution in a paper published in the journal Physical Review Letters in January. In addition, Deem and Jun Sun (also of Rice University) presented a paper at this week's APS March meeting that shows how genes consist of modular chunks that lead to various traits, rather than having the genetic information spread throughout your genes. This modularity could be handy when it comes to swapping useful blocks of DNA.

Read the rest of the post . . .

Thursday, March 08, 2007

A More Modest Security Scanner

At the Physics of Sex blog, we're huge supporters of freedom and tolerance. But part of ensuring those prescious commodities includes protecting personal privacy. Recently, some airports have installed backscatter x-ray scanners that see through clothing, revealing weapons in the very rare case that someone tries sneaking something on board, while giving security staff a gander at the most intimate details of the bodies of terrorists and innocents alike. You can see some examples in this Google image search. In addition, although the risk is low, you have to get at least a small x-ray dose to suffer the indignity.

Tomorrow morning at the APS March Meeting in Denver, Panu Helisto of the Finnish research company VTT will describe a new imaging system that measures some of the heat-radiation your body emits all the time. It is inherently unable to reveal personal details because it simply lacks resolution to produce a picture of anything smaller than several inches across. And yet it measures terahertz radiation (a type of radiation that's somewhere between infrared light and radio waves) that passes through all but the heaviest clothing, to provide enough detail to pick out the shapes of most knives, guns, and other dangerous stuff. Check out the pictures here that Helisto and colleagues at VTT and NIST made with a microbolometer. The shot on the right is a microbolometer image of the guy in the photo on the left. Looks like he's packin' some heat.

The system will be built of detectors called microbolometers that heat up and change electrical properties when light radiation is focused on them. They were initially developed as parts of antennas for imaging faint radiation from space. A bolometer-based radio antenna measured echoes of the Big Bang that started the universe running, and earned a Nobel Prize for Arno Penzias and Robert Wilson in 1978.

Coincidentally, their antenna lacked resolution to produce pictures of small objects like Uranus, and Helisto's system lacks resolution to reveal details of your a. . .

I'm not going to say it, but I bet you can figure out what I was going to type. I'm not being modest, it's just too lousy a joke. (Feel free to use it though, if you need a bad joke for the pub.)

Read the rest of the post . . .

Wednesday, March 07, 2007

An innovative HIV vaccination scheme

I'm currently in Denver looking for Physics of Sex topics at the year's largest gathering of physicists, the American Physical Society's annual March meeting.

Yesterday I saw a presentation by physicist Michael Deem of Rice University. He applies the math of physics (including things like field theory) to look at all kinds of things in biology and medicine.

One of the papers he presented at the conference analyzed the ways that HIV manages to evade the immune response. His research suggests an intriguing vaccination technique that could cope with the ability of HIV to rapidly evolve in the human body.

One of the problems with viruses like HIV is that it mutates after infection and produces of several different virus strains. Your body's immune system develops T-cells to fight each of the strains, but tends to focus on just one variety. That means you are pretty good at fending off only one strain, while the rest of the strains run amock.

Deem's analysis of HIV suggests that once vaccines against the disease are developed, similar problems would arise if we tried to vaccinate against more than one strain at a time with a single shot containing a blend of vaccines - that is, only one of the vaccine varieties would take effect.

In order to counteract the problem, Deem proposes that future HIV vaccines should be given with several shots simultaneously injected at different locations around the body. The reason is that T-cells are produced in the lymph nodes located primarily near your joints (behind your jaw, under your armpits, etc.). Introducing different vaccines near different joints induces lymph nodes at one location to concentrate on fighting one particular viral strain, while leaving other strains to other lymph nodes.

When HIV vaccines are finally developed, a person at risk might get a shot in each shoulder, one near each hip, and maybe even at the knees or elbows.

In the meantime, Deem thinks the scheme could help in the prevention of dengue fever. Apparently there are vaccines for several strains of dengue fever, but getting the shot for one strain prevents the others from taking effect, and can increase the risk of developing life-threatening dengue hemorrhagic fever. Deem is hoping to get some medical studies started to see of his multi-shot vaccination scheme works against dengue fever, and eventually against HIV.

Read the rest of the post . . .

Friday, March 02, 2007

Monday, February 26, 2007

Tiffany Granath and the Growler

In case you missed it, Tiffany Granath of PlayBoy Radio was a hoot when she interviewed me this afternoon. (I'll post a few snippets of the show on my iTunes podcast in a day or two.) We talked about everything from the reasons humans have sex to the the fluid mechanics of blood flow during arousal to the physics of the nervous system.

Even better, we took a few moments to discuss a sexual technique that I call the Growler. If you listened in, you heard it first on Tiffany's Afternoon Advice.

A Growler is a low frequency hummer. If you've never heard of a hummer, it's just oral sex, except that the person performing it hums as they work. The extra vibration adds spice to the experience, whether you're doing to it a man or a woman.

So, why is it a Growler? Your nerves transmit signals in a way that limits the vibrations you can feel in your hands, feet, genitals, and basically any other body part besides your ears, to a maximum of 500 hertz or so. That's about the pitch of the A note above middle C on the piano. To give a good hummer, you should stick to pitches somewhere lower on the scale.

But as you lower your pitch, the sound turns into more of a purr or growl than a hum, hence the name "Growler." You should play around with the tone to find the right note. I can tell you that it feels great, and women seem to love getting growlers too (perhaps even more than we guys do).

Thanks to Tiffany for letting me explain it on her show!

Read the rest of the post . . .

Thursday, February 15, 2007

The HPV Vaccine

If someone had asked me a few months ago whether there could possibly be an objection to a vaccine that could prevent cancer in thousands of people each year, I would have confidently answered "Absolutely not."

And yet, here we are, facing debates over the morality, cost, and efficacy of an FDA approved HPV vaccine. Human papillomaviruses cause more than ten thousand cases of cervical cancers and four thousand deaths annually in the US alone. The numbers are much worse in developing countries where sex education is inadequate, screening is rare, and cancer treatments are prohibitively expensive.

The new vaccine, which is being actively (and clumsily) marketed by Merck pharmaceuticals, appears to effectively prevent certain virus strains that are responsible for two thirds of HPV-related cancer cases.

I'm sure that no one will be surprised to learn that I support HPV vaccinations. Anything that extends life and reduces suffering gets my support. The fact that it also makes sex safer only strengthens my conviction.

If you've been following the public debate, you've probably noticed that the connection to sex is one of the chief objections that some vocal opponents to the vaccine point to.

One opponent, conservative Jill Stanek, focuses on the immoral origins of HPV cases. "[Like smoking,] HPV is also the consequence of a destructive behavior, sex outside of marriage."

Besides that fact that sex outside of marriage is both widespread and healthy (if you take reasonable precautions), Jill has a pretty odd idea about how HPV is transmitted. I can't imagine that many viruses can distinguish between sex inside and outside of marriage. If your partner or husband or wife carries the virus, you may be exposed during sex.

I suppose a woman could search for a mate who claims to be a virgin, and then take him at his word. Or she could simply get the vaccine and protect herself.

But the biggest issue I see is that vaccines like the Merck HPV vaccine don't just protect the individual, they protect the community as a whole. A Stanford University study from 2004 showed that HPV-related cancers could be reduced by 64% as a result of a vaccination program targeting prepubescent girls. The benefits extend beyond vaccinated girls. Both men and unvaccinated women will be safer as a result of herd immunity, even if as few as 40% of young girls are immunized. (Of course, the greatest protection will go to the vaccinated girls.)

Abstinence-based objections to HPV vaccinations strike me as both unrealistic and antisocial. It's not just about you, Jill Stanek, it's about protecting society as a whole. Stanek points out that an HPV vaccine will not protect us from other STDs. Such reasoning is so absurd that I can't imagine where to start. Were Small Pox vaccinations a bad idea because they didn't also prevent polio?

Another, more frivolous and short sighted objection is the fact that Merck will make a bundle off of the vaccine. I don't trust the altruism of major corporations (they're set up to make money, not save the world), and I certainly think we should look closely at any drug they provide. That's why we have the FDA. But the lack of profit in vaccinations is one reason we are facing a potential crisis the next time a highly-contagious and virulent flu hits our shores. In this case, it looks as though an HPV vaccine will lead both to profits and improved societal health.

Overall, the Stanford study concludes that the additional cost of the vaccine will raise average lifetime medical expenses of people in the US by $245, or about 0.6%, while saving thousands of lives every year. How can a compassionate person possibly object?

Think of all the additional people who will be alive to hear the abstinence messages that folks like Stanek promote.

Read the rest of the post . . .

Tuesday, February 13, 2007

Buzz Skyline on Playboy Radio, Feb. 26

Mark your calendars!

I will be a guest on Playboy Radio's Afternoon Advice with Tiffany Granath on February 26 at 1:00PM PST (4:00PM EST).

The show is on SIRIUS radio's Playboy Radio channel 198. You can call in toll free to ask questions at 1-877-205-9796.

I'm looking forward to hearing from you on the air.

A few months ago, I never would have imagined that physics could be a topic on channel like Playboy Radio. I'm thrilled!

Now, I wonder if I could convince Physics World to include a centerfold model just to bring the whole thing full circle.

Even better, maybe we could raise enough of a public outcry to get science journalist Karen Hopkin to resurrect her Studmuffins of Science wall calendar.

Read the rest of the post . . .

Wednesday, February 07, 2007

Valentine's Day Physics

Science is probably the farthest thing from your mind as you make plans for Valentine's Day next week. But for this popular holiday dedicated to romance, it occurred to me that you should keep a few of the suggestions from earlier Physics of Sex posts in mind.

Listen to the podcast with Text-to-Speech roboreaders Kate and Paul.

If you're a regular reader, suggestion number 5 is a new one that you haven't seen here yet. The rest are taken from earlier posts.

1. Opt for a low fat dinner. Fat from your meal rapidly moves into your blood, making it sticky, thick and more difficult for your heart to pump around. Reduced blood flow dampens erectile vigor (in the genitals of both men and women), and can reduce lubrication in women. So skip the foie gras on the 14th. Salads and other low fat foods are sexier for your Valentine’s Day dinner. See the entry Pumped Up and Ready for Love, part 2 for more information.

2. Tune your bed and body for better sex. Different beds have different rhythms: firm beds are better for faster sex, and soft beds are better for slower loving. For the most versatility, start with a firm bed and add pillows or thick comforters to slow things down. If you want to take even more control of the pace, experiment with sexual positions. You will find that various positions often encourage distinct natural rhythms. See Sexual Rhythms for more details.

3. Mix it up for sensory bliss. The sensory cells that respond to touch, temperature and other information tune out sensations that don’t change much. (That’s why you may forget about the sunglasses resting on top of your head, for example.) So mix things up in bed – change how and where you touch your lover to keep the sensory cells firing and the excitement levels up. See Sex and Sensibility, part 1

4. Keep going longer with sensory repetition. If you or your lover suffer from premature ejaculation, you may be able to stave off the inevitable with the start-stop method. (The method is essentially the opposite of the suggestion above.) Just as the sensory cells and nerves in your scalp soon forget about the sunglasses stowed there, repeatedly taking a man to the brink of orgasm and stopping briefly makes the sensory system less responsive, and can help him last longer in bed. See Sex and Sensibility, part 1

5. Hum a low pitched tune. Human ears can detect high frequencies, but the nerves in the rest of your body can’t register vibrations much over 500 hertz (roughly the B note above middle C on the piano). So if you give the gift of a hummer this Valentine’s Day, keep the pitch low for the best effect. The details of this suggestion will be in the upcoming post Sex and Sensibility, part2.

6. If you still need to find a Valentine's Day date, try looking the physics way. I can't guarantee results, but researchers have found that some approaches are better than others when it comes to cruising for mates. (Valentine's Day is a week away, so you still have one more weekend to try it out.) The details are in last week's post The Physics Guide to Hooking Up.

Before Valentine's Day gets here, check out other Physics of Sex suggestions in the entry Skip to the Tips.

Read the rest of the post . . .

Saturday, February 03, 2007

Warning: E. Coli Bacteria Can Swim Upstream

Here's a bit of disquieting research news - the bacteria E. coli tend to swim upstream in flowing liquids. The revelation, which appears in a paper to be published Monday, February 5 in the journal Physical Review Letters, could explain how the bacteria manage to make their way far up the urinary tract to cause pyelonephritis, a particularly nasty kidney infection.

Yale University researchers Jane Hill, Jonathan McMurry and Hur Koser collaborated with Ozge Kalkanci of Bogazici University in Istanbul on the work, which they believe is the first observation of the natural tendency of bacteria to swim upstream.

The researchers discovered the phenomenon by filming E. coli being swept along in tiny channels filled with flowing liquid. The bacteria tended to swim to their left (when viewed from above) as they were washed downstream. Eventually, their leftward swimming caused them to move toward the side of the channel, where they promptly turned around to swim back upstream. You can watch the behavior yourself in a video supplement to the paper that the researchers recorded. (The crosshairs in the video highlight the path of one of the bacteria.)

It seems that the leftward swimming and upstream migration result from the mechanical design of the bacteria. E. coli are propelled by whip-like flagella that push the bacteria along by rotating counterclockwise. Their cell bodies rotate clockwise in response to the torque of their twisting flagalla. The combination of motions cause E. coli to swim to the left when they encounter a surface in slowly moving or still fluid - an effect that has been observed in earlier studies.

The surprising result in the recent experiment, however, is that the motions also cause the bacteria to face upstream when they are submersed in a liquid flowing rapidly along a surface, in a manner that the researchers say is "much like a weather vane orienting into the wind."

The researchers suggest that the behavior could explain the incidence of infections in patients fitted with catheters, and could be the cause of the biofilms that form inside some plumbing systems. They even speculate that leaving a running hose in contact with the ground could lead to bacterial migrations out of the dirt and into the toilet tanks and water heater inside your house.

You might wonder what's the Physics of Sex connection to E. coli paddling upstream. Well, if you consider where the largest population of E. coli is in the human body, then you and your partner have yet another excellent reason to use condoms if you happen to practice anal sex. You wouldn't want to give those nasty fellas a chance to swim up anyone's urethra, would you?

Read the rest of the post . . .

Wednesday, January 31, 2007

The Physics Guide to Hooking Up

Another Saturday night is just around the corner, and you're looking forward to cruising for action at the local hot spots.

How'd it work out for you last time? Did you hook up with your dream guy or gal, or did you strike out? Either way, it's possible that you could improve your odds by applying the physics published in the journal Physical Review Letters a few years ago.

Listen to the podcast with Text-to-Speech roboreaders Kate and Paul.

Or, if you're in a rush, Skip to the Tip in this week's post.

In 2002, a group of Spanish and Brazilian physicists looked at two types of search strategy that might be employed by such things as predators in search of prey, bees in search of flowers, or other creatures (like you) in search of mates. They found that the searchers could dramatically improve their odds by tailoring their strategies depending on the distribution and motion of their targets. Theoretically, you should be able to improve your odds of finding that special someone as well.

When you go out on the town looking for love, you have at least two options. For one thing, you could pick a bar and settle in for the night, while doing your best to mingle as you work to attract or seduce someone.

This type of search strategy is called a Brownian random walk. You just bounce around to search randomly for a love connection in some small area, such as the dancefloor of your favorite bar. Eventually, you might drift to another nearby establishment. But in any case, you don't cover a lot of ground over the course of the night.

Alternatively, you could bar hop - drop in on a bar, work the room, and then if there's nothing promising, dash to another bar to do it again.

This second type of strategy is called a Lévy flight search. Lévy flights involve poking around in one location, and then zipping off to poke around somewhere else. Lots of creatures use Lévy flights for searching large areas, when there are sparse distributions of what ever it is that they're after. Bees often hunt for pollen rich flowers this way, and there's a good chance that you look for your lost keys with a similar search pattern. (You might check the dresser, skip down to look through the desk, pop over to the closet to check your coat, etc.)

As the research team ran their simulations, they found that when the targets were relatively stationary and far apart, searchers increased their odds of success by performing Lévy flights from place to place. Picture, for example, groups of eligible singles nestled at bars around town, with the bars far enough apart that you have to drive or walk a long way to get from one place to the next.

If instead, the targets moved around a lot or there were many of them packed in a large area, then searchers were more successful when they avoided Lévy flights and just flitted around randomly in a small area.

The first scenario sounds a lot like the club scene in most major cities, and the second scenario is more like the flowing crowds at Carnival in Rio or Mardi Gras in New Orleans.

At first glance it seems like the best bet is simply to zip from bar to bar with a series of Lévy flights, so long as you're cruising in town. But if you're at a big event with lots of available singles around, you should stay in one place.

Unfortunately, things aren't always so easy. If you're making lots of Lévy flights to search the clubs, and your targets are making frequent Lévy flights as well, then the chances are you're going to miss many of your potential love connections while in transit. When targets are highly mobile the physics model suggests that a searcher, like you, should pick one place and stay there to wait for your potential mate to make a Lévy flight right into your lap. In fact, the faster your targets are moving the less you should stray from your barstool.

In some cases it makes sense to evaluate the traffic flow and adjust your strategy throughout the course of the night. That would've worked best for me when I was in college and I used to head with my buddies into town to meet girls. Early in the evenings, clusters of women would seem to be roaming everywhere. And we were roaming too, occasionally flirting as we were going along. In retrospect we could probably have met more women if we'd settled somewhere and waited for them to come to us.

But as the night progressed and the alcohol kicked in the girls tended to travel less, and many of them eventually took up residence at various bars. That would've been the time to zip from bar to bar looking to hook up. Of course, by then we were usually pretty tipsy too and probably in no shape to walk or drive very far.

If I had it to do over again, I would spend the early part of the evening sipping mild drinks and sodas while attempting to charm the girls who were cruising through one of my favorite hangouts. Then I could've turned to Lévy flight searches from bar to bar, once the women slowed down.

The physicists who ran the search simulation weren't specifically thinking of the singles scene, they also considered things like the relative sizes of searchers and targets. For large creatures in search of small targets - like foxes hunting for rabbits - Lévy flights usually work best. For small searchers on the prowl for large targets - like parasites hoping to latch onto passing horses - it's best to sit tight and wait.

For humans, who are all roughly the same size (from a physics point of view) relative size isn't an issue. We only have to worry about the relative motion and the distribution of the people we'd like to meet.

So the next time you head out to the club scene to hook up, stop to take stock of the situation. If the kind of people you're after are bar hopping, you should stop in one establishment and mingle. If there's not much traffic in and out of the bars, then consider Lévy flight searches. And if you're going to Mardi Gras, pick a location, sit tight, and wait for the prospective mates to come to you.

Read the rest of the post . . .

Monday, January 29, 2007

Book Review: The Science of Orgasm

The Science of Orgasm by Barry R. Komisaruk, Carlos Beyer-Flores, and Beverly Whipple has got to be one of the best science books on sex that you can buy, if you can deal with wading hip deep through medical and biological research jargon.

I learned something new on just about every page, and each fascinating factoid and phenomenon - from the horrific sexual behavior that can result from certain types of brain damage to the question of whether or not orgasms are good for your health - is backed up with citations from top research journals and institutes. The authors themselves are responsible for a significant amount of the original research in the book. It seems pretty clear that that they know what they're taking about.

Still, you have to be awfully determined to plow through passages like this, "The participation of the adrenal cortex as a source of steroids capable of maintaining sexual response in women after bilateral oophorectomy has often been suggested" (page 179).

It can't hurt to have browsers open to Gray's Anatomy (the medical text, not the TV show) and Wikipedia as you make your way through the book, just to keep up with the lingo.

It's interesting that the publisher would choose cover art that resembles a plain brown wrapper, as if you're going to buy a copy to read under the covers while your mom thinks you're sleeping in. No matter how sexy the topic, doctor-speak is hardly a turn on. (Although, I'm sure it works for someone.)

If you read nothing else in this book, I highly recommend the brief section addressing the biological function of the female orgasm (pages 10-15). I have never seen a more coherent and compelling argument that orgasms in women serve some vital, if only partially understood, purpose. It's an excellent counterpoint to arguments claiming that orgasms are critical rewards to induce men to mate, but in women are only evolutionary accidents.

I'm not going to go into details here, but basically the authors point out that women seem to have at least some specialized anatomy that lets them experience types of orgasms that have no male equivalent. (The authors even invented a device to give women orgasms by stimulating only the cervix, which is an exclusively female body part.) The female-only orgasms can't be something left over from male anatomy, they conclude, if they can't exist in male bodies.

I plan to explain things more fully in a future post, but if you can't wait and you think reading the Journal of the American Medical Association is a good way to pass the day, pick up a copy of The Science of Orgasm. If nothing else, it's a good addition to your sexual science reference shelf.

Read the rest of the post . . .

Thursday, January 18, 2007

Is the Select Comfort air mattress good for sex? A PoS experiment

If you're eagerly anticipating part 2 of Sex and Sensibility, we'll have that for you next week.

In the meantime, we decided to send two of our writers, Buzz Skyline and Martica, into the field to do an experiment inspired by a portion of the Physics of Sex post Sexual Rhythms.

Specifically, we wanted them to see what physics could tell us about the Select Comfort brand adjustable bed. We hoped they would learn enough to help you determine if it's the best bed for your love life.

You can listen to roboreader Heather interviewing Martica and Buzz in our latest podcast, or read the transcript below, to find out what (if anything) the Sleep Number bed has to offer for sex.

Skip to the tip in this week's post, if you're in a rush.

In any case, please take part in The Great Physics of Sex Bed Test. We want you to test out your bed and send us the data so that we can figure out, once and for all, what type of bed is best for sex. But don't do it for us. Do it for yourself. Do for the world. Do it for science.


Heather: Welcome to the Physics of Sex podcast. My name is Heather.

If you've been listening to our past episodes, you know we usually give a little lecture about a fascinating aspect of physics, as it applies to your love life. But this week, we decided to try something different.

We sent two of our writers into the field to do a few experiments on an unusual kind of bed, in order to find out how it might affect your sex life. Here to report on what they found out about the Select Comfort sleep number bed, are Martica. . .

Martica: Hi Heather.

Heather: . . . and Buzz Skyline.

Buzz: Hi Heather.

Heather: So guys, you ventured out to test a bed. Did you do what I think you must have done? How'd you keep from being arrested?

Martica: Well, we didn’t actually do anything that's not appropriate in a mattress store. We actually just went and jumped on the bed.

Buzz: Well, we sat and bounced on the bed.

Martica: Exactly.

Buzz: We didn’t stand on the bed.

Heather: OK, well tell us about the bed.

Martica: It’s a Select Comfort Sleep Number bed, which [allows you to] change the firmness of the mattress.

Buzz: You can change the amount of air inside the mattress.

Martica: Right.

Buzz: And they call it the firmness.

Martica: It’s a big air mattress with a pump and a little remote control which you can use to pump the air in or let the air out and that changes the firmness, what they call the firmness, of the mattress.

Buzz: And it basically is just inflating this bladder that’s inside the bed instead of springs.

Heather: So this is the bed Lindsay Wagner promotes on TV. Great. How did you do the experiment?

Martica: We sat on the bed and bounced up and down.

Buzz: At different numbers. We set it for different numbers and we took turns bouncing on it. Martica bounced on it a few times at different settings and I bounced on it at a few different settings, a few different sleep number settings, and the last time . . .

Martica: We sat next to each other and bounced up and down at the same time, which is actually really hard – but fun. (laughs)

Heather: What sort of results did you expect?

Buzz: So, what we thought would happen was we assumed the sleep number really was what you call firmness, which on a spring would basically be the spring constant. It would tell how strong the springs are. And that means that as you turned it up it should increase your resonance frequency- the frequency that you bounce on the bed. And as you turn it down, it should decrease your resonance frequency. And so we started out with Martica on the bed, and what we found was no matter what sleep number we chose, she bounced at about the same rate.

Martica: I was trying! (laughs)

Buzz: It wasn’t her fault. It was obviously the physics. And so we thought there must be something wrong. So I sat on the bed and tried it for several numbers and I also bounced at almost exactly the same rate every time.

Martica: But a little bit more because you’re a little bit heavier than I am.

Buzz: Yeah, I bounced slower than Martica did because I weigh about 50 pounds more. So you would expect it to be a little slower, and it was a little slower, but by the same amount every time than Martica’s bounce was.

Martica: No matter whether the bed was really, really, really firm and full of air or really, really, really soft and the balloon was almost flat.

Buzz: So basically that means that whatever the sleep number tells you, it doesn’t really tell you the firmness in the same way that a bed is firm, it doesn’t tell you how firm the springs are. It’s changing something else.

Heather: All right then, what's going on?

Martica: So what it actually is that’s changing is the damping of the bed. It’s like having a giant pillow that you can compress and make it firmer or make it softer.

Buzz: Yeah. So if you were to open the bed and look at the bag, you would either see that it was completely full at a hundred percent, or a hundred sleep number, but usually it was kind of floppy.

Heather: So the sleep number doesn't matter for sex? You just set it wherever you want and things don't change?

Buzz: Well we did find that there was a change as we turned the sleep number up or down.

Martica: Right, it got harder to bounce on.

Buzz: It was more . . .

Martica: It took more energy because you’re bouncing on a less inflated balloon, basically.

Buzz: You are tuning something. You’re not tuning the spring constant, but we were tuning the damping. It made it harder to maintain a bounce because it was . . . it wasn’t changing the spring constant, but it was sucking energy out of the bed, it was damping the energy. It meant that we had to work harder to bounce when you turned the sleep number down, which corresponds to turning up the damping but not changing the spring constant.

Heather: Do people who actually buy the bed think about this sort of thing?

Buzz: In fact, we had the same question. So I went back when the store was closing and there weren’t any customers to distract the salesman, and I asked him that very question. And this is what he said.

(Mall noise)

Buzz: And so the feature we’re doing is a question of whether or not some beds are better for a love life than other beds.

Salesman: Uh huh.

Buzz: And we’ve gone around and we’ve measured basically the resonance frequency of various beds and . . .

Salesman: Uh huh.

Buzz: . . . things like that to try to understand how they’re different.

Salesman: Huh.

Buzz: So I was wondering – do people ever take that into consideration? When they talk to you when they are about to buy a bed, is that something that ever comes up?

Salesman: Nah, it never comes up. Maybe, maybe they think about it, or maybe they talk to each other about it.

Buzz: So it’s not like a waterbed store where you know what they’re there for . . .

Salesman: Right.

Buzz: This is more for . . .

Salesman: I’ve never, never heard anybody say anything like that.

Buzz: How long have you been sellin’ the beds?

Salesman: Since November.

Buzz: Oh OK, so you haven’t been doing it too long. So some people may think that . . . But if they did there’s not . . .

Salesman: I’ve slept on one. I’ve slept on one for about six years. But my wife and I, we don’t talk about it.

Buzz: You don’t adjust the pressure . . .

Salesman: No.

Buzz: . . . or anything?

Salesman: No no. Nope.

Buzz: Oh OK. (laughs) Alright. Well I know they’re strange questions.

Salesman: No no no. It’s all part of research.

Buzz: Exactly.

Salesman: I’m doing my part for science.

Buzz: OK. Alright.

(Mall sounds fade.)

Heather: So, having put the Sleep Number bed through it's paces, what are your recommendations?

Martica: Well if you already have a sleep number bed then you can turn it up for sex, if you want to make sure you’re getting the most bounce for the energy you put in.

Buzz: With a regular mattress, you can add damping. You can add something like comforters or pillows or something. You have to add additional material to make it softer to make it more comfortable or to change the rhythms of sex. Whereas with the Sleep Number bed you could potentially, with just this one adjustment, quickly go from what’s comfortable for sleeping to what’s comfortable for sex and back again.

Heather: Do you have plans for follow up experiments?

Martica: We plan to go to a mattress discounter store where there will likely be more mattresses with springs inside of them rather than air inside of them, and jump up and down on the beds there as much as they’ll let us. And ask some of the same questions. If maybe people who buy spring beds are looking to see how their sex lives will be changed by these beds. And if we go to a waterbed store, maybe people are even more interested in sex when they come into a waterbed store looking to buy a waterbed.

Buzz: It would be a completely different experience. And we could also consider alternative sleeping surfaces, like futons.

Heather: That's great. You've certainly given us something to think about. Thanks for stopping by.

Martica: Thanks Heather. It was great to talk to you.

Buzz: Bye.

Heather: After the select comfort adventure that Martica and Buzz went on, it occurred to us to ask our listeners and readers, to tell us about your beds. What type of bed do you sleep on? Is yours good for sex? Is it fast or slow? Do you prefer lots of damping or just a little?

We'll post instructions on our website,, to let you know how to send us some data. We'll analyze it and hopefully report back with the results in a few weeks.

Thanks for listening to the Physics of Sex podcast. I'm Heather.

Download us next time for the second segment of last week's show, part two of Sex and Sensibility, the physics of the nervous system.

Bye for now.


The Great Physics of Sex Bed Test

It's this easy.

Send us an email or write in the comments section the information you collect by following these instructions.

1. Tell us what kind of bed you have (spring mattress, waterbed, space-age foam, futon, air mattress, etc.)

2. Estimate the damping on your bed - is it plush (like a pillow top bed), moderately padded, or a plain mattress?

3. Measure your bed's resonance frequency by

a. getting a watch with a second hand

b. sitting on the bed and bouncing at the rate that feels most natural

c. timing how long it takes to bounce 25 times

d. It couldn't hurt to do the experiment a few times, or even get your partner or friends to try it. Be sure to note both the time it takes to bounce 25 times and the weight of the person bouncing. We'll need both numbers to calculate your bed's spring constant.

4. Tell us whether your bed is good for sex on a scale of 1 to 5, where five is Nirvana and one is like doing your taxes.

5. Send the information to us in an email to, or paste it into the comments section for this blog entry.

Read the rest of the post . . .

Tuesday, January 16, 2007

The Physics of Sex Cited Among the Best of Science Blogging

The Physics of Sex post Sexual Rhythms is included in a brand new anthology of the 50 best science blog posts of 2006.

The Open Laboratory: The Best Writing on Science Blogs 2006 was edited by Bora Zivkovic (aka Coturnix of Seed Media's, who is probably one of the hardest working folks in the blogosphere.

Bora chose the entries with the help of a select group of the top science bloggers around. The whole process is detailed on Bora's web page.

Buy the book and find out what wild and wonderful things are out there under the heading of science blogging. (No one at The Physics of Sex is getting a penny for this endorsement, BTW. We just like to encourage initiative like Bora's.)
Read the rest of the post . . .

Wednesday, January 10, 2007

Skip to the Tips

One of the great things about pondering the Physics of Sex is that it naturally leads to tips to enhance your sex life. Several of the posts that you can read here have a physics inspired suggestion or two in them.

Some of the suggestions - such as how to choose a good bed for sex - include information that you may not be able to find anywhere else.

For those of you who don't have time to read the full posts or listen to the podcasts, we have made a list of the tips that lets you jump straight to the good stuff.

You'll see this little icon next to italicized text to highlight the Physics of Sex Tips in each post.

Check out the tips below.

The Physics of Sex Tips (so far . . .)

-> Find the best bed for your sexual style. (from Sexual Rhythms)

-> Take control of your vibe with damping. (from Sexual Rhythms)

-> Choose the right lube. (from Slip, Slide or Stick)

-> Find out how the pinch technique can enhance your erection . . . or how it can be adapted to women. (from Pumped Up and Ready for Love, Part 1)

-> How you should adjust your smoking habits to reduce the negative impact on your sexual function. (from Pumped Up and Ready for Love, Part 2)

-> How losing weight can improve your circulation and make you better in bed. (from Pumped Up and Ready for Love, Part 2)

-> A safer alternative to the dangerous practice of erotic asphyxiation. (from Pumped Up and Ready for Love, Part 2)

-> How minding the negative feedback in your sensory receptors can help you make sex more intense. (from Sex and Sensibility, Part 1)

-> How the "start-stop method" helps you manipulate your sensory receptors to get past premature ejaculation. (from Sex and Sensibility, Part 1)

-> Two ways the physics of sensory receptors can add an extra tingle to sex. (from Sex and Sensibility, Part 1)
Read the rest of the post . . .