Re: Light and sound waves

So what is the glass transition temperature? The "flow" of glass is well known. Glass tubing leaned into a corner for years will develop a permanent bend. That still doesn't mean that it won't hold an edge long enough to be useful in a microtome.

I suggested that you look it up. It is obvious that you will not take my word for any of this.

Those glass rods do not bend. And if glass flowed, glass knives would not keep their edge. Glass knives hundreds of years old have been discovered with their edge. You are saying that a glass rod will sag, and a hundred year old glass knife will keep its edge?

--
Michael Press

Why should I 'take your word" on this? I'd rather have YOUR answer and THEN look it up to see if you are telling the truth!

They don't? Are you calling me a liar? I've personally SEEN those 'bent" rods. I take it you consider this a "semantic" problem rather than a scientific one? What word shall we use instead of "bend"? "kink" perhaps?

Glass rods DO sag! Of course a knife edge is a slightly different problem. 1. because the rods are sagging (flowing) under the action of a constant force (gravity). 2. The ground edge of a glass knife isn't under a long-acting constant force to "round" except the surface tension of the liquid which is much less of a force.(hence will take much much longer to act.) 3. There is also the question of crystals formed in the glass. If the knife edge has crystals in it then it's much more like a ceramic than a glass and clearly won't sag. I, of course, don't have exact information on the exact composition of the "100 year old knife edges" of which you speak. To really test the "knife edge" theory you'd probably have to say press a diamond edge into to blade edge for years and then see if you got a dent. My guess is you would.

Anybody can look up the meaning of glass transition temperature and determine the truth. You already know what I am saying. Do you feel lucky?

[...]

--
Michael Press

It isn't true that glass is a liquid. That was an old, old chestnut that some idiot came up with by looking at the stained glass in cathedrals--the pieces are generally thicker at the bottom, so he leapt to the conclusion that the glass had flowed over several hundred years.

Of course, a moment's thought would demonstrate that all the old lenses in the world would have stopped working properly long ago if that were true...it would be an easily measurable effect even over a few days. Turned out, of course, that the artisans always installed the pieces with the fat side down, but the urban myth remains.

Glass has a stress relaxation rate far below that of steel, for instance. If you want to make something really stable for a long time, make it out of fine-annealed fused silica.

IIRC it's just the statistics of the thermal fluctuations. In 1-D and

2-D the uncertainty in the distance between atom 1 and atom N diverges as N-> infinity, but in 3-D there's another power of X in the denominator of the integrand and the integral converges.

Cheers,

Phil Hobbs

well, isn't this supposed quality of glass, teh basis for "liquids in the mantle," in spite of the seismic readings?

thus: and, it was written by an ex- Baptist preacher, with the "under God" redundancy later added by an act of Congress, it is said.

thus: that is to say, there is a proof, that any planar section of a quadric surface is a conic, possibly degenerate.... lots of good trigonometry is associated with this, usually done in homogenous (3D) coordination.

thus: yes, but Newton was not -- a scientist!... _The Bible Code_ was a simple hoax using gematria.

thus: amuzing follow-on in today's paper, the Church refuzed to apologize for not trashing C.Darwin. anyway, it was really intended to be social darwinism, from the malthusians & physiocrats (or oligarchy). (well, that is secondary, from the Larouchiax; their research is fully supported by research in Europe from sources.)

g d

thus: so, you learned a weeks-worth of geometry, or you'd already had a couple of weeks-worth of it as a headstart?... what was the TIP programme of A Week in Geometry? after my first year of "euclidean" geometry, sans demonstrations, in junior high, I've been on my own -- as the only actualy student of Bucky Fuller, after he died (I say .-)

--USA out of Darfur Cruizade!

--ROTC, your summer vacation in the Sahara Desert ( S u d a n ) ; presage the Draft for your middleschool class of '12 -- brought to you by Allstate (tm) and Oxford U. Press!

Thanks for the information Phil, there goes another urban myth. George

Just a minute there Phil. The "sagging" glass in old windows is a myth for sure, but the "sagging" of glass tubes and rods in not! And your assertion that it isn't true that glass is a liquid is just your opinion. One can easily find other opinions.

Example from the net:

"Conclusion"

"There is no clear answer to the question "Is glass solid or liquid?". In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid. The difference is semantic. In terms of its material properties we can do little better. There is no clear definition of the distinction between solids and highly viscous liquids. All such phases or states of matter are idealisations of real material properties".

My personal favorite is "another state of matter which is neither liquid nor solid" but that is ALSO just my opinion.

I really don't know why "proof by assertion" seems to be such a popular way to try to win arguments on the internet, but it is. This is a major problem with science and especially physics today: People just make assertions and try to carry the argument with force of personality and credentials instead of scholarship and data.

Cheers

he said, glass has adifferent stress relaxation rate than stell e.g.; so, what does that mean & is it not true?

thus: this is probably not really any longer a visible dystinction, inasmuch as as inductive & deductive proofs are 1-to-1; the proof is 5/2 pages long!

thus: not really; Galileo was a protege of Sarpi. well, only larouchiax seem to know this part of history -- sorry. so, perhaps, "pawn of the 'reformation'" is more aptly said; what do you call THE enlightenment?

thus: I have tried to congfigure the theory from scratch, and have gotten most of the basic techniques from moments of excessive freetime

-- I don't know if I've gotten all of them, becase I haven't looked at any sites/books on it.... one can easily see, for instance, that most newspapers use a program

-- see, the symmetry, most have? -- to generate sudokus with presumably unique solutions; guessing without a pencil & eraser is counter- productive!