By RUDY!
Today, at a lunchtime seminar, a figure came up, and my mind went dirty.

That’s a diagram of stellar orbits in a galactic bar potential. The solid line is called an x1 orbit, the dashed line is called an x2 orbit. The speaker traced the x1 orbit, hovered momentarily at the top, and then highlighted the cusp with a steady circular motion.
Like I said, my mind went dirty. I blame Nicholson Baker’s novel Vox, a voyeuristic peek at a long, sexually-charged conversation between two strangers. A novel who’s genius lies not in its vividly intense descriptions of wet daydreams and bizarre turn-ons, but in the overarching theme of prolonged and delayed gratification and the benefits that follow.
“I can hear your strumming in your voice, you nasty boy.”
“Nastybation. I don’t want to come, though. I’m going to stop.”
“Prudent.”
“Funny.”
It’s totally meta in this respect. Consider this excerpt:
“As I was driving home I was so stiff from owning this pre-enjoyed book that once when I was stopped at a stoplight and I saw a woman in my rearview mirror I made a very small clit-circling motion with my fingers on the roof of my car, despite the bird droppings up there—the idea that she might notice and understand what this motion meant made me feel faint with excitement—but she was expressionless.”
which spurs an alternative interpretation of the slight pause in today’s speaker’s pointer as he is about to describe how shocks can form near the upper cusp as stars on x1 orbits transfer to x2 orbits giving rise to potential sites of star formation in the central molecular zone of our galaxy.