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Amplification of electromagnetic fields by a rotating body

(www.nature.com)
142 points keepamovin | 1 comments | 13 Oct 24 07:23 UTC | HN request time: 0s | source
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mikewarot ◴[17 Oct 24 20:34 UTC] No.41873484[source]▶
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)

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Terr_ ◴[17 Oct 24 21:20 UTC] No.41873927[source]▶
> If ultraconductors[2] worked, you could

Not familiar with that idea, but this construction sounds a bit like: "If only you had an (infinitely) rigid rod, you could push one end to communicate faster than lightspeed."

Or in balder terms: "If only we had a subtly impossible component, we could make a blatantly impossible machine."

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MadnessASAP ◴[17 Oct 24 21:54 UTC] No.41874203[source]▶
I am somewhat curious where the math on a perfect rigid rod breaks down (that is, where does the 0 end up under the line)
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1. 00N8 ◴[17 Oct 24 23:12 UTC] No.41874752{3}[source]▶
I think the math is fine, but a perfectly rigid rod cannot exist in our universe, so there's no paradox, even though it would let you send messages faster than light. It's like calculating how strong of a hydraulic press you'd need to compress matter into neutronium in your garage, or claiming that if a spaceship could travel at 2x light speed, then it could fly its way back out of a black hole.