The blog Fuck Yeah Fluid Dynamics posted some stills from this video recently. The images were fantastic, but I didn't totally understand what I was seeing. Thankfully, FYFD blogger (and aerospace engineering Ph.D. student) Nicole Sharp was kind enough to answer my questions.
What you're looking at is a rocket engine. The video shows what happens to airflow in the engine as it goes from subsonic to supersonic. In the video and the pictures, you can see a dark red line moving down the tunnel. That's the edge of the shockwave that marks the boundary between subsonic air and Mach 1. You should also pay attention to the little black vortices that whirl away from the edge of the engine wall. Those are pretty important.
Good news, everyone*! If you're tired of being splashed (or splashing others) with your own urine, the Brigham Young University Splash Lab has done the research and produced a series of helpful tips that will enable you to potty without the spotty. Research at the Splash Lab is heavily based on imaging and this video will show you how easy it is to reduce splash-back with simple changes like peeing against a vertical, rather than horizontal, surface.
And by "everyone", I mean "people who pee into urinals".
There are facts that just aren't apparent from our everyday perspective. Sometimes, in order to really get a scientific concept at the gut level, you have to seek out a different way to view the world. Do that, and you'll find yourself emotionally gobsmacked by well-known concepts you'd long ago accepted intellectually.
For instance, watching this video montage of 9 weeks worth of infrared images from NASA’s GOES-East satellite, the lizard-brain part of me was struck with a sudden realization, "Oh my god. Air really is a fluid, isn't it?"