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Five glassy mysteries we still can’t explain
- ggm 4y agoThe "slumping glass" meme is surprisingly old: my mum passed it on to me, she a trained architectural historian. Metals as glass, sintered metal objects, glass as a state not a chemistry (recipe) per se, fascinating stuff. "Transparent aluminium" wasn't so movie crazy after all
- LeoPanthera 4y agoAluminium oxynitride, which is in fact transparent, was dubbed "transparent aluminum" after Star Trek. Fun stuff. I wonder how many inventions are inspired or named after that show. "The Next Generation" particularly featured touch screens and tablet computers long before those things were common. And original series communicators bear more than a passing resemblance to cellphones.
- shkkmo 4y ago> "The Next Generation" particularly featured touch screens and tablet computers long before those things were common And called them PADDs amusingly enough.
- Izkata 4y ago"Personal Access Display Device" for the mildly curious.
- kurthr 4y agoIt's kinda weird they didn't just use sapphire as "transparent aluminum". AlOxNy is actually somewhat harder (and more difficult to etch) than sapphire, but weird any way.
- moron4hire 4y agoStar Trek's PADDs are also interesting for what they don't show. You'll see many instances of characters giving PADDs to each other. There's one particular scene in an episode of DS9 where Sisco has a whole stack of PADDs on his desk, and he laments the workload. Star Trek figured out touch screens and personal data devices, but didn't figure out basic networked data communication, i.e. email attachments. At a time when email existed! I think of this every time I hand my phone to my wife to show her some stupid joke on Twitter or in a text message thread with my friends.
- ncmncm 4y agoTry to imagine how you would visually indicate a big workload without the stack. Kinda dumb, but dramatically effective, in its way.
- noizejoy 4y agoNot that dumb? https://en.wikipedia.org/wiki/Skeuomorph https://en.wikipedia.org/wiki/Skeuomorph
- krapp 4y ago>Star Trek figured out touch screens and personal data devices, but didn't figure out basic networked data communication, i.e. email attachments. At a time when email existed! I think it's more that they wanted to convey, to the viewer, that information was being passed from place to place, or have stacks of PADDs serve as easy visual metaphors for "piles of paperwork" or what have you. Star Trek isn't actually trying to extrapolate realistic future technology, it's telling dramatic stories In Space, and the needs of the narrative always come first.
- exar0815 4y agoSome small tidbit as well: The process of bending and shaping glass, especially single-layer safety glass, e.g. used in automotive rear and side glazing, is still an iterative process for every new model of car, relying mostly on the gut feeling of the operators of the bending and tempering ovens. No hard and fast rules exist, and a lot is just passed on by experience.
- tomcam 4y agoWow. I just sort of imagined they were somehow molded or vacuum formed in some sort of automated fashion by now.
- btilly 4y agoThe Feynman Lectures on Physics offers a simple dimensional argument for why friction acts like it does, and then says that the details of the coefficient of friction are beyond our ability to estimate from first principles. It then offers a simple experiment to illustrate that the properties have to do with surface impurities. If you slide glass over dry glass, it slides easily. Do the same with wet glass and you can feel a "gritty" motion. This is due to the water lifting the impurities off of the glass and allowing a direct glass on glass contact, at which point they fuse and have to be broken. You can see where this happened because it leaves visible scratches. I found this unbelievable and had to test it. My mother was not thrilled to see that her good crystal got visible scratches on it...
- morpheos137 4y ago>This is due to the water lifting the impurities off of the glass and allowing a direct glass on glass contact, at which point they fuse and have to be broken. I don't believe this. I think it is more due to dirt on the glass that gets mobilised by the water. occam's razor...
- btilly 4y agoThat was his explanation. Not sure how your idea causes scratches to be left on the glass.
- somewhereoutth 4y agoMy first mystery for glass, is why is it transparent? Surely random as opposed to crystalline ordering would be better at stopping photons? Turns out it is about electron excitation levels in glass - the gaps between levels are too large to absorb the energy from a photon, so they pass right through!
- kurthr 4y agoIf you're intrigued by band gaps... get some cheap synthetic Ruby (you can get a 1.5 carets for $40-50) and see what happens when it gets hot/cold. Ruby is just Sapphire (Aluminum Oxide) with Iron impurities that make it red. It is red because blue light (everything above the band gap) is absorbed! When you cool the ruby (e.g. in liquid nitrogen) it will turn pink/orange as it shrinks and the absorption band moves to shorter wavelengths. When you heat it (e.g. with a propane torch) it will turn deep red to black as the crystal structure expands and the absorption band moves up in wave length from red into the IR. Remove the heat/cold and watch it slowly come back to the ruby color you expect!
- boredemployee 4y agothats a classic matter in materials science and engineering !
- deleted 4y ago[deleted]
- marcosdumay 4y agoYou are not far from the truth. Interatomic forces tend to create energy levels with differences on the infrared band. And glass is pretty opaque on the infrared. But yes, the visible light features are usually caused by electron excitation.
- Sharlin 4y agoSiO2 glass happens to be transparent to visible wavelengths in particular, which is one of the reasons we use it. But it’s not nearly as transparent to UV and also becomes quickly opaque as you go from near IR to longer wavelengths. In "thermal" IR, glass is actually a pretty good mirror.
- swayvil 4y agoTo explain a mystery is to tell a story. A story about a thing that joins up nicely with our stories about everything else. The story is important. More important than the actual thing maybe. I think it's so important because the story can be kept and carried around, like money. And it can be communicated. Translated into the noosphere or whatever. And everybody likes the noosphere.
- SamBam 4y agoThis sounds like it was generated by GPT-3.
- swayvil 4y agoI always get responses like that when I talk like this. Maybe your reply was generated too.
- SamBam 4y agoI guess because it seems so entirely content-free. It's riffing entirely on the title of the post — the words "explain" and "mystery" — and not on the actual subject, which is glass. All the other (human, presumably) commentators responded to the subject, and talked about glass. It's as if I said to you "Guess what? I just landed the job of my dreams!" and you replied "Guessing is an interesting pastime, people have been doing that for thousands of years." To an AI it might seem like your comment followed mine, but a human would walk away from you.
- Gigachad 4y ago
- swayvil 4y agoI think that the popular opinion is that the noosphere (the collective body of ideas) is realer than the physical world. And that the idea about a thing is realer than the thing itself. Opinion to the contrary is offered only by scientists, artists and similar weirdos and social outcastes.
- doodlebugging 4y agoWell, everything was going great in the article until I got to this part in the first "Flowing Myth" example: >At this rate, a piece of common soda-lime glass would take aeons to slowly flow and turn into the more energetically favourable crystalline sodium dioxide – otherwise known as quartz. Quartz is not sodium dioxide - NaO2, it is silicon dioxide - SiO2. Sodium dioxide is probably not stable and after looking it up the most stable form is probably sodium peroxide - Na2O2. This guy forgot all about the sand he used to make the glass. The sodium part of the deal, sodium carbonate or soda ash - Na2CO3, was used to regulate temperature as he described and the lime was produced from local limestone, CaCO3. This is a Physics World article and I would've expected someone to proof-read it specifically for stuff like this. In reference to the Flowing Myth, I first heard that myth in a geoscience classroom and it was stated as a fact that old glass is thicker at the bottoms of cathedral windows because it has slowly flowed. Taking that further, I guess it is a good thing that these cathedral windows were made of many panes of this old flowing glass since the thickening would not dramatically change the graphic display. If they were made of a single pane and it flowed significantly over time, Jesus may have started in medieval times as a finely cut specimen of manhood and ended up in modern times with a noticeable middle-age spread.
- ncmncm 4y agoThat is not all. It repeats the falsehood: The stability of glass is one of its most attractive characteristics, for example in the storage of nuclear waste. Vitrified nuclear waste, immersed, would become porous and friable long before its radioactivity decayed significantly. It also claims that we don't have proof glass doesn't flow in historical time-frames, where in fact we have glass goblets from thousands of years ago. It further attributes tapering in glass in windows as indicating poor quality, where in fact that was just a feature of how flat glass was made. Window makers oriented glass thicker edge down because that was the sturdier way to make things. Until quite recently, flat glass was made by blowing a big bottle, and centering it on a turntable while still soft. Spinning, the mouth widened until the whole thing flopped out flat, with a characteristic "whomp!", the bottle mouth becoming the rim.
- kergonath 4y ago
- fourthark 4y ago> Even more surprising, though, is the onset of glass behaviour in certain computer algorithms. For instance, if an algorithm is designed to seek out progressively better solutions to a problem with a large number of variables it can become overwhelmed by complexity and grind to a halt before the optimal solution is found. By borrowing statistical methods designed for the fundamental study of glasses, however, such algorithms can be improved, and better solutions found. Are they talking specifically about simulated annealing here, or is this a more general observation?
- jefftk 4y agoPretty sure the former
- iaw 4y agoFor anyone curious I believe the statistical method referred to in the last segment is annealing[1] [1] https://en.wikipedia.org/wiki/Simulated_annealing https://en.wikipedia.org/wiki/Simulated_annealing
- ramraj07 4y agoI’d love it if someone can direct to an explanation accessible to a non physics college graduate that actually explains why glass (and other things like quartz and even water/air) are transparent, how exactly does light pass through them that also makes them that causes refraction and what exactly makes them reflect light as well.
- Gigachad 4y agoI have seen a few casual explanations of it and I still don’t really understand it.
- s0rce 4y agoThings are transparent that don't absorb, scatter or reflect the light. For stuff like quartz the band gap (energy above which photons get absorbed) is higher than the energy of visible light so the light just goes through and its transparent... Are you asking why certain materials don't absorb visible light?
- analog31 4y agoThe oscillating electric field of the light wave induces a sympathetic oscillation of the electric charges bound to atoms or molecular bonds in the material. The degree to which those charges can align themselves to the field is a characteristic of each material. Taking that polarizability into account in Maxwell's Equations yields a wave equation for electromagnetism, just like it does in a vacuum, but with a different propagation velocity, slower than the speed of light. In a vacuum, there's a corresponding polarizability of free space, related to the speed of light. In undergrad electrodynamics, prior to learning about relativity or quantum, we didn't try to explain it any further than that. It's transparent because the electrons stay attached to their atoms. If they could break free, then conduction would occur, and another solution of Maxwell's equations shows the wave being quenched. You could imagine conduction causing loss of energy via heating, like the way an electric stove works. If the electrons could absorb energy by making a quantum transition, some of energy could be released as heat rather than light. Refraction and reflections could be thought of as necessary consequences of continuity at an interface between materials of different composition. A number of things related to electric and magnetic field vectors have to remain the same at both sides of the boundary. This is akin to a conservation law, and requires introduction of a third wave at the boundary -- the reflected wave -- to make everything balance. Another way to look at refraction is via Huygen's Principle, where each point on a wave front is a source of a spherical wave front, and accounting for the different speeds in the two materials (e.g., air and glass) gives the law of refraction. And there's even yet another explanation which can be found by figuring out the path that the light takes, which results in a minimum for the time of travel. It's interesting that the law of refraction was worked out before electromagnetism was understood. I'm an industrial physicist, and this is hand-wavy, but I'm trying for an explanation that doesn't require equations.