The Joy of Sexual Physics

                                                                        with Dr John

 "Love is a matter of chemistry, sex is a matter of physics"


Q  You see, part of me is riven with jealousy – the thought of some sleaze sneaking about trying to screw my girlfriend and actually managing to get his member inside her, albeit briefly, makes my adrenaline surge. I’m livid. I want to punch him and give her the biggest piece of my mind in the history of time. But on the other hand, I’m really a tad embarrassed. Actually, I think I’m just fearful of appearing intellectually inferior, unable to follow Sally’s eloquent narrative of how this whole situation came about without a graduate education in astrophysics, and consequently rendering myself incapable of assessing her guilt.

As you may have gathered, Sally either is or was my college girlfriend, although I have had reason to doubt this ever since I walked into her graduate lounge one Friday evening only to find her with my buddy Ernst underneath her gyrating pelvis. I wanted to simultaneously cripple Ernst, vomit and call Sally a dirty slapper, but I was subdued by the intellectual confusion that followed when Sally invoked the kinematical theory of the relativity of motion to cast the blame away from herself and on to every other person and thing in the entire Universe.

“Look Isaac, this isn’t what it looks like,” she said. “I know this must be really hard for you to understand, having only studied Newtonian mechanics to stage one and all, but I’ve really been framed by a galactic event which, in the presence of Ernst’s coincidental erection, has given the impression of consenting sexual intercourse, which is something that I would never do with anyone other than you.”

To be completely honest, I was highly skeptical of this argument at first, although she said it with such conviction and eloquence that I felt myself being won over. Her beautiful, exposed cheeks didn’t assist my aspirations of objectivity either, until I noticed again who was beneath them.

“When we say that a body on which no forces act is either at rest or in uniform motion, what do you think this uniform motion is relative to?” she asked.

“To absolute space, or course,” I said.

“Isaac, nice try, honey, but absolute space is a metaphysical concept that was disproved a century ago by the results of the Michelson-Morley experiment. The observation that a body moves can mean nothing more than that it moves with respect to other bodies, just as Ernst’s coincidental erection is moving relative to my body. But who are we to say whose body is in fact moving and whose is stationary when the two scenarios are kinematically equivalent. If you are observing me, your own girlfriend, to be the active participant in this involuntary thrusting, then is it not conceivable and kinematically equivalent that I am in fact stationary and in the wrong place at the wrong time while an inconsiderate cosmic event causes the rest of the Universe to oscillate at the unfortunate frequency, magnitude and direction required to emulate this unfaithful adultery that I would never commit.”

I couldn’t believe it, but that little weasel Ernst had the cheek to support her on this point.

“She has a point, you know,” he quipped. “It’s true that in order to understand the causes of a local inertial event, you need to take a look at the Universe as a whole. For an audience at an ice skating ring, an ice skater will appear to be rotating relative to a comparatively stationary Universe. However, from the perspective of the ice skater, it is the rest of the Universe, including the audience, who are rotating. How else can you explain the fact that the ice skater rotates faster when she brings her arms in without appealing to the skater’s acceleration with respect to more distant galactic bodies - the same bodies that are responsible for this unfortunate scene. I know it’s hard to believe, Isaac, but we’re your friends. We’re on your side. You have to believe us over the rest of the Universe.”

Perhaps it was in some lame attempt to save our friendship, maybe it was an honest opinion, or more likely it was a prop for Ernst to both flatter Sally and boast his extensive knowledge of physics which I couldn’t compete with. I couldn’t blame the guy for his coincidental erection – Sally inspires that reaction in a lot of passers by – but this response really threw me. You see, I don’t really think it’s fair to steer a relationship argument into the unanswered controversies of theoretical cosmology. So now I’m confused and devastated, not knowing what to make of this dilemma and I was wondering whether you could offer me some insight to help me through this battle of intellectual elitism.


A  I must say that I’m not convinced, although Sally clearly does have quite a brain on her and might be worth holding on to so that you may pass this trait on to your children (it seems they may be slightly impaired by you contribution). That said, if OJ Simpson can prove his innocence in a court of law, I’m sure that Sally also could, in America. These days you can even cut off a penis and blame it on its owner.

Have you ever heard of Occam’s razor? Basically, it is the scientific precept that the simplest answer tends to be the right one. It would suggest that it is more likely that Sally was gyrating on top of Ernst when you walked in, and less likely that a cosmic event caused the heavens to swarm in confusion while far-flung galaxies pulled the rest of the Universe along with them, all except for your pretty, little, innocent girlfriend Sally, who remains conveniently ‘stationary’ throughout the whole ‘galactic framing’ miracle. Occam’s razor would say “maybe, but probably not, nice try though.”

Biochemistry and musculoskeletal physiology would be suspicious that actin-myosin muscle filaments within Sally’s beautiful exposed ass were not contracting in synchrony with her gyrations under the command of motor neuron signals originating in her cerebellum. A person of modest cerebral volume would enquire as to why both Sally and Ernst had their pants down at the time of the galactic catastrophe.

Neo-Kantian philosophers would refute Ernst’s appeal to explain inertial events through acceleration relative to distant galactic bodies on the basis that it ignores the differences between kinematic and dynamic ways of consideration.

And astronomy as a whole would concur, while quietly relishing the fact that finally somebody has attempted to explain their relationship dilemmas with a discipline more reputable than astrology, even if the argument is as factually cringe worthy as a horoscope in Cleo magazine.

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Pour it all out to John.
Since the end of the twentieth century, Dr John Marshall, Ph.D. Sexual Physics has been a sex and relationships writer taking the little-known sexual wisdom from the ivory tower realm of the theoretical physicist to the layperson.
Feel free to write to him at [email protected] or you can visit his webpage at

© John Marshall, 2003