Talk:Crystal
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I don't care if YOU, PERSONALLY, think they read like a cut-and-paste job, they aren't. --corvus13
I thought so too, and you should care. Our goal here is to create a good encyclopedia, not to coddle your sensitivities. If an article by anyone looks copyrighted, it's everyone's responsibility here to say so, and it's the author's responsibility to clear it up. It's not about personalities--it's about content. You've cleared up that this stuff is written by you, and that's good. So the copyright issue is settled; no problem. Now there's the issue of exactly what culture this "folklore" is from. That needs to be spelled out here too. We're not singling you out for criticism here--everyone criticizes everyone else here, from PhD's to dropouts. That's the process, and it works pretty well. --LDC
Amorphous solids can be considered liquids that flow but very slowly
Isn't this an urban legend? see [1] (http://www.ualberta.ca/~bderksen/antique.html)
Yes and no. The stories about the old glass windows being thicker at the bottom than at the top are probably either not true or are misinterpreted (if you have a sheet of glass that's thicker on one end, you'd install it with the thick end down, wouldn't you?)
But here's the thing...any solid, amorphous or crystalline, that is kept under a sustained stress, is going to flow "very slowly". The reason for this is that any material has an equlibrium vacancy concentration, and vacancy diffusion under an applied stress will cause creep. In fact, this is true even at absolute zero, because of the zero-point energy. Sure, it might take trillions of years, but the equations predict it.
There are two fundamental differences between a liquid and a solid. One is that the constituents of a liquid have a rotational mode of motion. The other is the enthalpy change when a liquid solidifies. I know you don't get the enthalpy release in a glass transition. Any statistical mechanics guys out there know of any evidence that a glass has rotational modes? --MaterialsScientist
- This has nothing to do with how the glass is installed in the window. Rather, it has to do with window glass that has been in situ for a long time (I'm not talking on the order of fifty years, either; more on the order of the six- and seven-hundred-year-old glass one finds in old British castles and churches; but definitely not the "trillions of years" referred to above). The glass is slightly thicker at the bottom in such windows, indicating a (very slow) flow downwards. Also, some glass bottles of Roman era have been found which have been squashed rather than broken. Glass is simply an extremely slow-flowing fluid.
- Here at the University of Queensland, there is a physics experiment that has been taking place for some 80 years, involving a container of pitch. This so-called pitch drop experiment demonstrates this phenomenon of "liquid solids"; the container of pitch has a small hole in the bottom of it which allows the pitch to drip through it. In the 80 years the experiment has been running, I believe the pitch has dripped just seven times.thefamouseccles 01:40 13 Jan 2004 (UTC)
Not sure about the description of liquid crystals -- can anyone verify ? I was under the impression that a liquid crystal was a material which undergoes an ordering transition upon the application of an electrical field -- i.e. switches between crystal and amorphous easily with a external stimulus. -- Olof