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You can now read the best of the Physics of Sex in the eBook from Amazon.It's chock full of tips and tidbits from the blog as well as more information that you won't find anywhere else.There are eBook versions for Kindle, iPad, iPhone, Android, Blackberry, and Mac operating systems. Each for only $3.99!The paperback version will be available soon on Amazon for about $12, in case you're looking for a holiday present for that special, open-minded, friend.The Amazon preview isn't up yet, but you can check out a preview of the entire book on Lulu.

Different types of love feel different. The love I have for my partner, my children, my parents, and even my dog are similar in some ways, but are very distinct in others. Thanks to fMRI images of the brains of people experiencing various types of love, scientists can now explain where the similarities and differences originate.The topic isn't a new one in sexuality research circles. A Rutgers study comparing maternal and romantic love, which produced the image above, took place in 2004. The study showed that there are distinct parallels in brain activity between people experiencing the two types of love. A number of researchers turned to fMRI and other brain imaging techniques years earlier in hope of finding ways to identify the brain activity characteristic of sexual deviants like rapists and pedophiles, potentially to both reform them and prosecute them, as the case may be. But the brain is complex. It's proven too difficult to tease out sexual criminals from the general population in a reliable way. However, a recent review paper that compares all known fMRI studies of brains in love has at least brought a few interesting aspects to light.For one thing, love is complicated. Regardless of the type of love we're talking about, they all involve several distinct portions of the brain, including the higher-order portions typical of big brained creatures like humans. That suggests that love as we know it may not even be possible for creatures with less developed brains. Lizards and birds, it seems, are probably limited to friend-with-benefits sorts of relationships, rather than full blown love.Not only can we love, but researchers have specifically studied three different types of love: romantic love between sexual partners, maternal love between a mother and child, and compassionate love for vulnerable strangers. All three types lead to increased blood flow, and pr...

It's not clear whether anyone has had actual sex in space, but that hasn't stopped filmmakers from giving us a preview. I'm confident that it's possible, physically speaking, and will soon be an option for anyone with a few tens of thousands of dollars to blow on a trip aboard Virgin Galactic. (It seems they're already booking short flights, but it doesn't look like there's going to be much privacy on the early trips.)In the meantime, check out the fascinating, NSFW article on io9.com compiling the greatest zero gravity sex scenes of all time. It's hot and inspiring. I can hardly wait to give it a try.

Thank goodness CNN is on the job, letting us know that oral sex seems to be a precursor to sexual intercourse among teens. The original study by researchers at the University of California, San Francisco is available online in the Archives of Pediatrics and Adolescent Medicine. From looking at the comments that readers have posted on CNN, reactions to the report tend to fall into one of three categories . . .1. OMG, we have to stop kids from having sex! Now it looks like we can do that by stopping them from having oral sex first. 2. Duh, what a waste of money. Kids have sex in high school. Many have oral sex first, many don't. Why is anyone paying for this research?3. Wow, that's good to know. Let's teach them how to be safe, because they're going to do it no matter what we say. Besides. exploring your sexuality as a teen is completely natural.The researchers themselves seem to agree with answer number 1, judging by the conclusion they draw from the study. Specifically, they say "The first 2 years of high school may be a critical age period for adolescents' vulnerability to vaginal sex initiation via oral sex behaviors. Comprehensive evidenced-based interventions and provision of preventive services aimed toward reducing sexual risk should be expanded to include the role oral sex plays in adolescent sex behavior."I love science and scientists as a rule, but phrases like "vulnerability to vaginal sex" give me the creeps. People aren't "vulnerable to sex," like it's a disease, a drug or a crime. Other than cases of rape, which are not the focus of this study, high school students either choose to have sex or they don't. It sounds to me like the folks who did this particular study have a bias against sex among teens. That's OK. Everyone has a right to an opinion, but published scientific research is not the place to push an agenda, especially one as loaded and sensitive as this one.I tend to fall into the third camp. But even if you're more like the the people who share the first or second point of view, take some comfort from the fact that sexual activity in high school te...

Prepublication edition now available, with free online preview!I'm still making a few edits. It's 99% proofed, but not perfect yet. If you like being first more than you like perfection, you can buy it today.If you're not interested in buying now, you can still preview the entire book absolutely free by clicking the "Preview" link on the Lulu order page.If you have any comments or suggestions, please email me. I try to answer as many emails as I can.Thanks,J.M.

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 caree...

"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...

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.) <br ...

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 includeAngular MomentumandThe Romatic Drama EquationIn 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 xkcd.com.

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...