Dumb question: why is it hard to make something spin really fast?

Simple example: put your frictionless spherical cow on a spinny plate. Make it a very small cow; it's only there to have a point of rotation. Why frictionless? You don't want its butt to catch fire. Why spherical? It'll need to maximize volume dedicated to arm muscles; see below.

Have the cow hold two ropes, each leading to a full-sized cow 10m away. Apply force to those cows (blow on them, or magnetize them and do a solenoid thing, or just make them very gassy cows and orient their spherical butts in opposite directions). Get them spinning at 1Hz. (This is very fast; remember the diameter is 20m.) Now have the middle cow pull the ropes, shortening them to 10cm. It's now spinning at 1Khz. 10mm gives 1Mhz. Conservation of angular momentum, baby.

Do this in a vacuum in microgravity, and you don't need the center cow.

Sure, if you're doing this at a bovine scale, the tension is ridiculously large. What makes it infeasible at a small scale?

Apparently this effect applies to sound waves as well: https://arxiv.org/pdf/2005.03760

So, if you use eddy currents to delay the phase of an exciting field long enough that the object those eddy currents are inside of can spin more than 90 degrees, the response eddy current fields now AID instead of opposing the original field?

This sounds quite a bit like what Steorm[1] was doing years ago. If ultraconductors[2] worked, you could actually build a mechanical device that had losses low enough to actually gain energy once a critical speed were obtained.

[1] https://en.wikipedia.org/wiki/Steorn

[2] https://patents.google.com/patent/US5777292A/en

(Claim 7 is for material with a conductivity of 10^11 S/cm, which is 150,000 times better than copper)

(I didn't understand the math in the paper)

Would this mean that a rotating body in space would eventually slow down? In other words, amplifying EM radiation draws energy from angular momentum?

I keep thinking about all the sci-fi I've seen where a machine with rotating parts opens up a portal or a wormhole...

Could this be used as an engine of some kind? The spinny thing giving off EM waves and those waves are caught by something like a solar sail?

Could it be true for gravitational waves?

The plot in figure 4 looks a lot like the torque/frequency plot of an induction motor.

As someone uneducated in the subject I'm curious what stopped this being discovered earlier? Is the setup particularly challenging?

Reminds me of Kerr-Newman black holes.

Sounds like a crappy Alexanderson alternator.

[flagged]

The experiment provides support to the idea that the Superradiance effect (where waves are amplified when interacting with rotating black holes) may not be pulling energy from the blackhole, but from different dimensions. In theories involving extra dimensions (like those proposed in string theory or braneworld scenarios), rotational effects could alter how energy and momentum are distributed across dimensions, leading to observable phenomena similar to what was demonstrated in the experiment.

If rotation within this higher-dimensional space causes analogous effects to the rotational amplification observed in the experiment, it could imply new ways of energy transfer between dimensions. AKA -- ZPM from Stargate