100-year-old physics problem has been solved | Hacker News Reader

100-year-old physics problem has been solved

m.phys.org

192 pointsc51740238 comments

Apparently the same scientist published the description of these materials 10 years ago in Nature:

https://www.researchgate.net/profile/Kosmas_Tsakmakidis2/pub...

Wasn't that a concept paper? They did analysis then; they produced no actual material or device. Now they have. 10 years seems like about the right delay between conceiving of a material, and creating it?

Right. That's what I was pointing out. The description / concept came 10 years ago.

Point was he's been working on it for 10 years.

I haven't studied both the original link and your link in detail, but at a quick look: They are different things.

Metamaterials usually are periodic combinations that exhibit interesting properties. So-called "photonic bandgap materials" are an example. The paper you linked shows that strange things can happen to the group velocities in these types of materials.

The phys.org link (based on a Science paper [1]) is about a cavity utilizing non-reciprocal materials. Normally systems involving Maxwell's equations are reciprocal; you can switch the input and output and expect the same behavior. For a basic example, if you look through a tube and see me at the other end, then I will be able to see you as well.

In a non-reciprocal system, this property breaks down. Microwave circulators are a good example: A device with three ports A, B, and C can have

energy coming from A going to B,

energy coming from B going to C,

energy coming from C going to A.

This device is handy if you don't want reflected E&M power from your antenna coming back into your generating circuit. It was well known to guys working on radar, for example.

The real miracle in this paper is that no one put it together sooner: Non-reciprocal devices have been around forever, and resonators more so, but that the combination might be useful has not occurred to anyone? Quite amazing. They probably blew all kinds of time researching through old literature to make sure this hasn't already been mentioned by the radar guys in the 40s.

[1] http://science.sciencemag.org/content/356/6344/1260

> That was the very centre of his genius - he invented things that anyone could have thought of, and men who can invent things that anyone could have thought of are very rare men.

- Terry Pratchett[1]

1: https://libquotes.com/terry-pratchett/quote/lbd3a3k

Thanks for the write up -- the description reminded me of the ST:TNG episode where Scotty defeats being trapped on a Dyson sphere by rigging the transporter buffer to cycle in a loop with a reenergization every n cycles

While not transparent aluminum, maybe Scotty really did invent something in the past

Ho. Lee. Shit. I'm in the satellite telecoms domain - this is incredible and will have far reaching consequences after a decade. Unfortunate that R&D and hardware lead times are so long in this industry.

Could you explain it like I'm 5? How will this have huge far reaching consequences?

Explain perhaps?

"For more than 100 hundred years, these systems were held back by a limitation that was considered to be fundamental ... But that limitation is now a thing of the past."

We should bear breakthroughs like this in mind every time someone appeals to fundamental limitations of physics (or any other field).

So many times I hear people object that something can't be done because of some fundamental limit. But research like this proves that limits that are considered fundamental sometimes aren't, and we can't know ahead of time which of these limits really are fundamental and which only appear so.

More importantly, we should be vigilantly suspicious anytime an article says something about breaking a fundamental limit of physics.

It's not really a fundamental law of physics though.. More like an engineering law

> these systems were held back by a limitation that was considered to be fundamental

This is the key distinction: -proven- fundamental is very different from -considered- fundamental.

Overturning Heisenberg's Uncertainty Principle would shatter physics as we know it.

Overturning a misconception is far more mundane.

How do you ever prove something in an empirical science?

There are various levels of how rigorous evidence is. Apparently, the law in question was made based on assumptions about the materials involved, and as someone else pointed out there was a ten year gap between the mathematical explanation and actual implementation, so I guess these materials are quite complex.

Also, this does not invalidate the previous law necessarily; we still use Newton's laws because its assumptions hold under most circumstances.

By building things that work.

How exactly would you distinguish between 'proven' fundamental and merely 'considered' fundamental?

I mean, sure, some laws like Heisenberg's Uncertainty Principle can be proven mathematically from the axioms of a theory, but how exactly would that make it more fundamental than a law that is considered an axiom itself?

I'm not too knowledgeable in these things, but I'd guess it'd really just depend on the same things everything else does in science: supporting data.

Certain things have an immense amount of supporting data.

The famous philosopher of science Karl Popper disagrees, and few disagree with him - science can definitively disprove, but not definitively prove anything.

PS FWIW Heisenberg's Uncertainty Principle isn't understood now as it was then - that principle as it was has been overturned.

Let's be clear to differentiate when we're talking about fundamental laws like conservation of momentum or unitarity versus "how much energy can be stored in a fiber", which was really just the derivation someone did on a specific class of fibers and then assumed that every other fiber would be the same thing (some homogenous material, boundary conditions, etc.).

Calling this particular result "breaking a fundamental law" is just typical hyperbolic science PR.

Yeah a more accurate title in these cases is often something like "assumptions of theoretical law don't quite apply in this case or can be otherwise worked around in practice" but that doesn't get clicks.

Another good semi-recent example that comes to mind is the Nyquist–Shannon sampling theorem being "broken" by compressed sensing.

Fundamental limitations reach expiry near the ten thousand year mark, after the civilization, language, and science used to define the limitation have all disappeared into the forgotten past.

Doesn't the time-bandwidth reciprocity fall out of the same math as the Heisenberg Uncertainty Principle? Does this work have implications for HUP "workarounds"?

There are lots of systems that break the reciprocity: https://arxiv.org/pdf/1705.09548.pdf from a few months ago has some descriptions. I think (not having read the Science paper) the issue would be that the underlying fundamental physics has reciprocity as a basic feature by way of Hermitian operators.

If you read the paper, the answer is yes, but you can work around it by basically breaking the symmetry between the "output" of a system and the "input"[0]. For the output and input, they will satisfy basic fourier uncertainty relations, but independently of each other.

[0] I've scanned the paper a couple of times and it's still a little murky for me. I have other things to do, unfortunately. For a clue, see figure 2.

> Doesn't the time-bandwidth reciprocity fall out of the same math as the Heisenberg Uncertainty Principle?

Only loosely. Bandwidth in a traditional cavity is related to the loss in the cavity. (Energy coming out of a laser cavity is loss from the standpoint of the cavity.)

There isn't a Lagrangian where bandwidth is the conjugate "momentum" to time. So not rigorously related to HUP, to my knowledge.

> Does this work have implications for HUP "workarounds"?

Doubtful. Non-reciprocal materials may seem like magic, but they are built out of things that still obey fundamental QM.

But who knows, the world is a strange place.

I read the whole thing with great anticipation. I thought they did some magic math with EM waves in a vacuum.

Then I saw this is actually some fancy material that's required for it to happen. Okay then, nevermind.

> "Other potential applications include ... broadband light harvesting and energy storage, and broadband optical camouflaging ("invisibility cloaking")."

Obviously these sorts of announcements often have hype in them - and that's fine - but could someone really invent a cloaking device with this advancement?

Don't worry, it's a click-bait term for being invisible to low-frequency wavelengths, so not visible light.

The US military has been working on microwave-invisible materials for a while and they've gotten very close. But microwaves have wavelengths on the order of a few cm (10^-2), meanwhile visible light is on ther order of 100's on nm (10^-7).

As the wavelength gets shorter it gets much harder to make "negative-refractive-index" materials - the material that enables to bend light around an object.

Very interesting - reminds me of superconductors. Some quantity which normally cannot be escaped (ie, everything has some amount of resistance, or the Q factor is a finite number) that under certain special conditions can actually hit its singularity. Special conditions which necessitate exotic new theory.

Also, call me cynical but it seems like the natural application is pulsed laser weapons. Now instead of spending infinity dollars on a portable megawatt laser that can gimbal to attack a target, you have a kilowatt laser that charges a waveguide until it has equivalent energy to the megawatt laser and then discharges it as necessary.

This type of laser already exists, they're called solid state lasers. [1].

(Note that these lasers are distinct from semiconductor lasers, which are more colloquially called "diode lasers".)

EDIT: Q-switched laser may be closer to this. [2]

1: https://en.wikipedia.org/wiki/Solid-state_laser

2: https://en.wikipedia.org/wiki/Q-switching

> "The reported breakthrough is completely fundamental —we're giving researchers a new tool. And the number of applications is limited only by one's imagination," sums up Tsakmakidis.

I like the idea of having a new tool available, but don't know why everything has to be sooo revolutionary and unlimited.

Yeah. You can tell the article writer isn't a scientist when they say "the number of potential applications is close to infinite".

- How close?

- Very close ;)

> And the number of applications is limited only by one's imagination," sums up Tsakmakidis.

That's the scientist behind the publication

non-mobile link: https://phys.org/news/2017-06-year-old-physics-problem.html

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