"I am not enough of a solid-state physicist to judge this proposal,..."
I stopped reading after this confession of the author. So this text is just as good as a opinion of some other random guy.
Superconductor news: What’s claimed, and how strong the evidence seems to be
371–380 of 501 posts
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#372Earlier quoted context omitted.
Do you have a link handy for "we don't know how bikes work" ?
As a bit of an aside, most people don't know how bicycle wheels work. There's a whole section in https://en.wikipedia.org/wiki/The_Bicycle_Wheel that talks about how they actually work. It's not tension at the top, it's compression on the bottom.
Not to appeal to authority, but I wrote my thesis on bicycle wheels. You got it the wrong way around.
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#373This is an extremely useful summarization of the original paper. > The authors believe that the modified/strained structure of their material creates a large number of “quantum wells” between particular lead atoms and the adjacent oxygens of the phosphate groups bound to them, in effect making a two-dimensional “electron gas”. They propose that electron tunneling between these quantum wells, which are between 3.7 and…
> sudden resistivity changes at a critical temperature (bizarrely high though that is in this case) How high? Just wondering if it might eventually be possible to use it in some power/clocking distribution layers of a semiconductor chip without bulky cooling.
> Just wondering if it might eventually be possible to use it in some power/clocking distribution layers of a semiconductor chip
There's an additional obstacle factor here which is that the material has to (a) be "sputterable" onto the surface, which may rule out things with fancy crystal requirements, and (b) not adversely react with the rest of the chip, which is why coppper is ruled out (!) and chips use aluminium for metal layers.
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#374Earlier quoted context omitted.
If it really is as easy as you say then surely every YouTuber with a metal furnace dropped everything to make that 100M view video.
I'm hoping they are. I want to watch them this weekend.
Finally found someone who's liveblogging it: https://nitter.net/andrewmccalip
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#375Earlier quoted context omitted.
Can you explain this part?
like parking tickets for supercars... :) FAA says even superconducting superdrones can't go over 400 feet.
And can you also explain "indefinite levitation" to me? IIRC you can do some levitation over metallic surfaces or magnets, but that would require power, wouldn't it?
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#376If this is real, what about this discovery that made it happen now? Is it a case that some technology is now available that unlocked this? Or is this trying something and seeing if it works? Could this discovery have been made 10-20 years ago?
It could've been made not only 10-20 years ago, but, probably even 100-200 years ago(sure about 20th century, not really sure about 19th).
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#377Earlier quoted context omitted.
Cmon, man
You can write out the equations of motion for a bicycle that will very accurately predict the dynamics. You can put these equations into a numerical simulation and predict motion very accurately. You can change the parameters of the model and do simulations with high confidence. Just because there isn't some neat little equation that says exactly what each parameter change is going to do (without doing the simulation…
You are contradicting yourself:
> You can write out the equations of motion for a bicycle
> there isn't some neat little equation that says exactly what each parameter change is going to do
I mean, if you have the equations you can see what each parameter is doing !
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#378Earlier quoted context omitted.
I'm assuming they mean the balance mechanism, and specifically what allows us to balance. How much is it the rider shifting their weight, how much is micro steering adjusts as we move forward, how much is the gyroscopic forces of the wheels, how much of it has to do with the angle of the handle bars to the wheel verse the center of weight. That said, I'm guessing this one is well understood by experts, but more compl…
We have self-balancing bicycles. We clearly know it well enough to replace the human with a computerized machine. Maybe we don’t know how humans use the bicycle but we know how bicycles balance, we can write programs to balance them physically. 0: https://youtu.be/Ya7iacmVjUM 1: https://youtu.be/2Z67NkvXIF4
You are correct, a lot of forces are canceling out on the long term(instead of instantaneously) it can easily be manipulated into increasing periods of unbalance in one direction until a point is reached then a separate mechanism is used to force it to a balanced state. Conservation of energy is always in effect. Gyroscope effects that bike wheels can be added with other separate gyroscopes. Thus, a self righting bike. The effect called precession is understood well enough.
How a human is able to manipulate it is simply by using the force of gravity from shifting their weight(moving the center of gravity). However, the movement of the center of gravity has to be perpendicular to the wheels axle. The steeper the angle of attack the wheel has to the ground, there will need to be an exponential increase in distance to move the center of gravity. Once the wheel is parallel to the ground, there will be an undefined distance needed to move the center of gravity.
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#379"I am not enough of a solid-state physicist to judge this proposal,..." I stopped reading after this confession of the author. So this text is just as good as a opinion of some other random guy.
I’m not a JavaScript developer, but I can tell if a JS dev is bullshitting or if they know their stuff.
The author has enough relevant experience to be able to safely conclude a similar thing. They are honest that they won’t spot minor issues, but my takeaway from this article is that the original paper authors are not cowboys or bullshitters, and they have a chance at a real finding, subject to regular research bugs.
That’s good enough to be worth an article!
Re: Superconductor news: What’s claimed, and how strong the evidence seems to be
#380Earlier quoted context omitted.
As a bit of an aside, most people don't know how bicycle wheels work. There's a whole section in https://en.wikipedia.org/wiki/The_Bicycle_Wheel that talks about how they actually work. It's not tension at the top, it's compression on the bottom.
what do you mean it's not tension at the top? did you misspeak? bicycle spokes are solely under tensile forces. they can't support compressive forces at all. i'm a hobbyist wheel builder and a once upon a time professional bicycle mechanic during hs & college. if you want to test this take nearly all the pretension out of your spokes and sit on your bike. feel which ones are taught and which ones are completely loose…
This dialogue is reminiscent of rec.bycycles.tech arguments with Jobst, ca 1993.
A bike wheel is a linear elastic system, that can be thought of as a superposition of a uniformly set of tensioned spokes as one state, and a set of spokes in compression in the loaded zone (bottom of the wheel) as the other state. So long as the superposition of the two states obeys the limiting conditions (i.e. spokes in tension) they can be analysed separately.
The size of the loaded zone is related to the relative stiffness of the spokes (axial) and the rim (bending), and can be calculated using beam on elastic foundation methods. For typical rim/spoke combinations, this is approximately 4 spokes.
Outside of the loaded zone, spoke tensions essentially don’t change.