Where'd all the intelligent comments go? Hackernews used to be a cut above when it came to an intelligent comments section. Where'd all those people go, is there a new place to hang out?
Careful, we shoot the messenger these days.
Twisted graphene has become the big thing in physics
61–70 of 111 posts
Re: Twisted graphene has become the big thing in physics
#62Earlier quoted context omitted.
Ok I see, by "not losing its charge" you meant not wearing down from repeated use. Technically speaking the charge would be the amount of electrical potential energy stored in the device. This system is still subject to the laws of thermodynamics, however. AFAIK ideal superconductivity does not exist outside of theoretical physics, just as ideal platonic solids do not exist in the real world. Things get bumpy close u…
Charge is not amount of electric potential. Charge is a property of matter which causes experiencing a force when placed in an electric field. Strength of the electric field is electric potential. And charges arrange in some form under this field which wouldn't be so in absense of this field and how tight is that form depends on the strength of electric field. And this can be used to perform some work but this is not…
> Charge is a property of matter which causes experiencing a force when placed in an electric field.
From Wikipedia [0]:
"A battery's capacity is the amount of electric charge it can deliver at the rated voltage."
Another way of saying this is that a battery can store potential electric charge which is discharged from the battery during use. The maximum potential electric charge a battery can store is its capacity.
Similarly, a rock raised above your head is not "storing gravity", but it still contains gravitational potential energy.
When we talk about batteries however, we tend to colloquially refer to this electrical potential as "charge" due to the way words like "charger" and "discharge" have entered the vernacular. Phrases like, "How much charge does your phone have left?" has become increasingly common.
This is distinct from the definition of electric charge that you lifted from Wikipedia's page on "electrical charge". It's just the way language has evolved.
> And charges arrange in some form under this field which wouldn't be so in absense of this field and how tight is that form depends on the strength of electric field. And this can be used to perform some work but this is not storing charge as the total charge before arrangement is same as total charge after arrangement there is no new charge added.
We are not measuring the total charge. We are measuring the electrical potential across a circuit. The total "charge" remains the same, but the electrical potential decreases when the battery discharges.
[0] https://en.wikipedia.org/wiki/Electric_battery#Capacity_and_...
Re: Twisted graphene has become the big thing in physics
#63Earlier quoted context omitted.
Superconductivity would revolutionize transportation, low cost medical imaging with MRIs, and weapons. Lots of weapons.
You're forgetting the two most important; energy storage and transport.
Yeah, imagine if we could more or less losslessly transfer electricity over vast distances. Massive renewable energy farms could be built wherever there was sun/wind/rivers whether the energy consumers are close or not. Energy could be sent to pump water into reservoirs as huge centralized batteries. The problem with 'what happens when the sun isn't shining/the wind isn't blowing' could be sidestepped because it's always sunny/windy somewhere, so we just get the power from as far away as needed.
Re: Twisted graphene has become the big thing in physics
#64Earlier quoted context omitted.
You're forgetting the two most important; energy storage and transport.
Yeah, imagine if we could more or less losslessly transfer electricity over vast distances. Massive renewable energy farms could be built wherever there was sun/wind/rivers whether the energy consumers are close or not. Energy could be sent to pump water into reservoirs as huge centralized batteries. The problem with 'what happens when the sun isn't shining/the wind isn't blowing' could be sidestepped because it's al…
People seem to underestimate how efficient regular power lines are.
The continent-spanning european power grid has a total transmission loss of about 6% using 19th century technology (transformers and copper wires). Modern high voltage DC lines can perform even better. The main limitation seems to be that people don't want to have power lines in their back yard. Not something that superconductors are going to sove.
Re: Twisted graphene has become the big thing in physics
#65Earlier quoted context omitted.
That sounds a lot like a slingshot maneuver around a planet to get more momentum. Strictly speaking you're taking energy from the planet/sun to do so. An unchanging magnetic field still exists in the real universe, and I find it difficult to believe that it would be completely unaffected by the interaction. fwiw I'm also no expert edit: I'm taking unchanging to be a practical implementation of say a permanent magnet…
no, what I'm talking about is more like a perfectly circular orbit around the sun, where the direction of the acceleration is always exactly perpendicular to the motion.
But there is no perfectly circular orbit around the sun. The mass of the two bodies causes the center of mass to be slightly off center from the sun, and both the sun and earth orbit around this center of mass in a fashion that AFAIK loses energy.
Re: Twisted graphene has become the big thing in physics
#66Earlier quoted context omitted.
Pretty typical of academia. Grad students also don't normally get Nobels
And for good reason. A responsible supervisor will typically give PhD students tasks that he has already "kind-of / sort-of" worked out as feasible. I once read the following recommendation for how to set dissertation subjects, I can't recall by whom. - BSc thesis: what I can do over lunch - Master thesis: what I could do in an afternoon - PhD thesis: what I could do in a week (Here the figures don't mean typing, pro…
Where are you in the world that the level of sophistication of the work being set is such that this heuristic holds true?
I suppose a BSc thesis or design report etc. is supposed to be more of an exercise in demonstrating some understanding and creating something, but beyond that I would expect some fairly novel impact from an MSc and definitely from a PhD.
I'm very surprised by this as the quality of MSc theses and PhD theses at the universities I attended were all fairly novel, and even if the supervisor had suspected the same conclusion, the amount of work to arrive at that conclusion is non-trivial when doing research.
I fear this devalues the contribution of what these young researchers are doing. I know many people who went on to very good research positions and even founded companies based on their Masters or PhD work.
Re: Twisted graphene has become the big thing in physics
#67Earlier quoted context omitted.
Yeah, imagine if we could more or less losslessly transfer electricity over vast distances. Massive renewable energy farms could be built wherever there was sun/wind/rivers whether the energy consumers are close or not. Energy could be sent to pump water into reservoirs as huge centralized batteries. The problem with 'what happens when the sun isn't shining/the wind isn't blowing' could be sidestepped because it's al…
People seem to underestimate how efficient regular power lines are. The continent-spanning european power grid has a total transmission loss of about 6% using 19th century technology (transformers and copper wires). Modern high voltage DC lines can perform even better. The main limitation seems to be that people don't want to have power lines in their back yard. Not something that superconductors are going to sove.
Also the cost of a equivalent superconductor network would be an order of magnitude more expensive that what is essentially room temperature metal cables with very basic technology - transformers, insulation, and switchgear.
Re: Twisted graphene has become the big thing in physics
#68Holy guac, room temperature superconductivity seems almost science fiction-y but just imagine the disruption it would make. I would be particularly excited to experience how much electric motors and energy transfer/storage and conversion would improve.
Apparently they reached superconductivity at 3K. Hardly room temperature.
However this method is completely different and thus might open more options
Re: Twisted graphene has become the big thing in physics
#69Earlier quoted context omitted.
Yeah, imagine if we could more or less losslessly transfer electricity over vast distances. Massive renewable energy farms could be built wherever there was sun/wind/rivers whether the energy consumers are close or not. Energy could be sent to pump water into reservoirs as huge centralized batteries. The problem with 'what happens when the sun isn't shining/the wind isn't blowing' could be sidestepped because it's al…
People seem to underestimate how efficient regular power lines are. The continent-spanning european power grid has a total transmission loss of about 6% using 19th century technology (transformers and copper wires). Modern high voltage DC lines can perform even better. The main limitation seems to be that people don't want to have power lines in their back yard. Not something that superconductors are going to sove.
Increasing power transfer effectiveness by even 1% seems like it would be a huge improvement when you consider the energy demands of a continent. That's potentially a lot of CO2 saved.
Re: Twisted graphene has become the big thing in physics
#70Fairly shocking to me that Yuan Cao received literally a single glancing mention here, but he was clearly the one who actually made the pivotal discovery, and is the first author on the Nature paper ( https://www.nature.com/articles/nature26154 ), and was the one named to the Nature 10 in 2018 for his discovery. Really mind boggling that this entire piece focuses all the attention on his supervisor and almost neglect…
> Yuan Cao ... was clearly the one who actually made the pivotal discovery
Are you saying that based on something external to the paper? In the author contribution section, Cao is not credited with having done anything on his own:
> Author Contributions
> Y.C., J.Y.L., J.D.S-Y fabricated the devices and performed transport measurements. Y.C., V.F. performed data analysis. P.J.H. supervised the project. S.F. and E.K. provided numerical calculations. S.L.T., A.D. and R.C.A. measured capacitance data. K.W. and T.T. provided h-BN devices. Y.C., V.F., and P.J.H. wrote the paper with input from all authors.
The first authorship is an important meaningful thing, but it definitely isn't a guarantee that they key, most noteworthy step was done by the first author, much less the first author alone.