The Bizarre Behavior of Rotating Bodies

There are lots of university lectures, worked example problems, videos of people demonstrating and teaching every type of manual skill, .... on youtube > those videos are not educational This kind of thing is absolutely “educational” under any reasonable definition of the word [link] [link] [link] [link] [this video] [link] Of course it’s not (and not supposed to be) a substitute for students working problems for themselves, running experiments, conducting interviews, doing research in the stacks, writing papers, writing code, putting each-others’ art through critique, or the like. Nobody “comes away from a Mathologer video thinking they «know math»” (whatever that is supposed to mean).

> Researchers monitored the known repeater FRB 121102 with the Lovell Telescope, a 250-foot-wide (76 meters) radio dish at Jodrell Bank Observatory in England, over the course of five years. They found strong indications of a 157-day activity cycle; 121102 seems to flare up for 90 days and then go silent for 67, the team reported in a new study. > It's unclear what's behind such cyclic activity, though scientists do have a few ideas. For example, periodic flare-ups could be caused by a wobble in the rotational axis of a highly magnetized neutron star known as a magnetar. Or they could be linked to the orbital motions of a neutron star in a binary system. Could this be the Dzhanibekov Effect ? Funny I just stumbled upon it today! [this video] If Earth can maintain a stable axis, such wobbly oscillating axis could be that star's "normal". Just guessing! Or may be am too wrong. I am not a physicist!

More seriously though, rotating habs are more difficult to spin properly than Clarke knew. The Russians discovered this and kept it to themselves. [this video] I personally like the idea of spinning up large asteroids but the Dzhanibekov Effect will cause a lot of sloshing. If I understand it right, you have to spin them along the long axis, not like O’Neill cylinders. Two separate habitats at opposite ends of an air shaft. Clarke rings have to be careful about docking platforms. In fact they might need an inertially separate structure floating near them to handle loading and unloading of cargo, and then ferry materials back and forth across the “air gap” using very small vessels or robotic arms.