Glass viscosity calculations debunk the myth of flow in medieval windows (2017)(ceramics.org)
ceramics.org
Glass viscosity calculations debunk the myth of flow in medieval windows (2017)
https://ceramics.org/ceramic-tech-today/glass-viscosity-calculations-definitively-debunk-the-myth-of-observable-flow-in-medieval-windows
161 コメント
I was taught in physical sciences that friction was proportional to weight and surface area. We were given blocks and a 'force meter' that was a bendy springy length of metal in a wooden calibrated frame.
So pull blocks on a surface with the meter to measure friction. Try different surface area, stack them for multiples of weight, plot on a graph.
Mine weren't coming out on a straight line. Other people noticed theres' weren't either, so they fudged their data points. I put down the honest ones. I got it 'wrong', they got it 'right'.
Of course that old myth was nonsense, my experimental method was correct, and I've felt the injustice for decades now!
Of course that old myth was nonsense, my experimental method was correct, and I've felt the injustice for decades now!
Our physics teacher were clearly happy when we got weird results and actually wrote down what we saw and wrote a comment on the difference between expect and observed results.
The problem is that it's obviously wrong with a simple experiment - just look at a few really old windows. I live about 1/4 mile from a church that was built 1300 years ago (https://en.wikipedia.org/wiki/St_Peter%27s_Church,_Monkwearm...). There's not much of the original glass left but where there is the thicker part is occasionally at the top of the pane because that's how it was originally mounted.
Teachers (and everyone else) will be wrong about things. That's OK. The problems happen when people don't bother to do any simple checks themselves, and just accept things as fact without doing any critical thinking or experimentation of their own.
Teachers (and everyone else) will be wrong about things. That's OK. The problems happen when people don't bother to do any simple checks themselves, and just accept things as fact without doing any critical thinking or experimentation of their own.
I would not disagree that your teachers failed you or vice-versa. But making grand pronouncements about people ("everyone else") and their problems as you see them ("without doing any critical thinking or experimentation of their own") and teachers too - and apparently based solely upon your personal experience
in school and your thoughts on one church that just happens to be physically nearby you - isn't gonna convince anyone. Your comment is ignorant and offensive to teachers.
I didn't suggest they're always wrong, or that all of them are wrong, or that some of them won't have done any checks on what they're teaching. I said that teachers will be wrong about things. That only means they're fallible and don't get things right all the time.
If any teacher, or literally anyone else, is offended by the suggestion that they're human and could be wrong sometimes then I think I'm OK with offending them. If you think you're perfect and will never be wrong then frankly you deserve to be offended as often as possible.
If any teacher, or literally anyone else, is offended by the suggestion that they're human and could be wrong sometimes then I think I'm OK with offending them. If you think you're perfect and will never be wrong then frankly you deserve to be offended as often as possible.
I’ve often said that it is not whether or not you offend someone; it’s whether or not someone is offended.
Offence is up to the receiver after all.
Offence is up to the receiver after all.
> Teachers (and everyone else) will be wrong about things. That's OK. The problems happen when people don't bother to do any simple checks themselves, and just accept things as fact without doing any critical thinking or experimentation of their own.
While not doing checks against teachers is a problem... there is a bigger problem of teachers who don't accept being wrong.
While not doing checks against teachers is a problem... there is a bigger problem of teachers who don't accept being wrong.
Most school teachers are full of it, but they don’t mean to. They are simply low level clerics in the church of truth. They recite a very lossy account of what they were ordained with at a likely low level institution. It’s not really their fault - people need jobs, the ministry needs repeaters, and the pay is bad.
Your teachers weren’t the disease - they were just a symptom.
Your teachers weren’t the disease - they were just a symptom.
If only teachers were as intelligent and wise as HN’s anonymous commenters.
No disagreement with your jab. It's easy to be right once, when you get to choose whether you participate. If you had to speak for hours a day, days a week, you'd certainly be wrong some good amount of the time.
This is a great analogy. The teachers in school are not there to teach you the most detailed model of the world, they are mostly there to make you exercise your model critiquing ability on some toy models that are simple to deal with. Your math teacher might draw a blank when you tell him he taught you an inconsistent notion of limits in calculus, and your physics teacher will certainly admit that there are holes in the high school version of gravity.
But the point wasn't to tell you the exact version of what we know, it was to make you think about how models work.
But the point wasn't to tell you the exact version of what we know, it was to make you think about how models work.
I mean, the HS teacher that told me this had a masters in Mech E. Or so he claimed, hmm...
He must not have been the top of his class if he had ended up a HS teacher.
Which is actually kinda sad. Pay and working conditions for teachers shouldn't be so that being a teacher is regarded as a failure.
Which is actually kinda sad. Pay and working conditions for teachers shouldn't be so that being a teacher is regarded as a failure.
You are the one regarding them as failures. I had a variety of teachers in school, some were very educated (PhDs), and simply found a calling in teaching. Not everything is about money, you shouldn’t look down on teachers.
I think the public perception of teachers varies a lot between societies. In breaking bad it was clear that Americans don't think much of a guy who ends up teaching chemistry. If you go to other countries it's very different, eg in Switzerland it seemed totally legit to aspire to teaching. Salary was 120k according to the kid who told me.
> according to the kid who told me
Come on, you can do better than this and actually invest the minute to type this into your search engine of choice and verify:
https://www.swissinfo.ch/eng/society/swiss-salaries-teachers...
So according to this, Swiss teachers make between CHF 95,590 and CHF 110,590 annually. Cost of living is also higher in Switzerland, so it's a bit less than "120k" would suggest, but still a solid salary. Refer to the link for details.
Come on, you can do better than this and actually invest the minute to type this into your search engine of choice and verify:
https://www.swissinfo.ch/eng/society/swiss-salaries-teachers...
So according to this, Swiss teachers make between CHF 95,590 and CHF 110,590 annually. Cost of living is also higher in Switzerland, so it's a bit less than "120k" would suggest, but still a solid salary. Refer to the link for details.
It's in the ballpark, and will certainly get to 120K once you have some seniority.
The point was more that a person thinking about what to do could admit to saying he wanted to be a teacher in Switzerland, whereas in the US it seems like making Walter White a teacher was the perfect way to say he'd somehow failed.
The point was more that a person thinking about what to do could admit to saying he wanted to be a teacher in Switzerland, whereas in the US it seems like making Walter White a teacher was the perfect way to say he'd somehow failed.
Admittedly, if the choice is being a "successful" chemist, and bringing into existence VX gas, TNT, Phosgene, Thalidomide, Teflon, various industrial chemical wastes that tend to end up creating Superfund sites, and being a chemistry teacher... I may be getting pretty lame as I get older, but I think the Teacher strictly speaking has the quantifiably lesser destructive footprint of the two outcomes. Then again, the argument there is likely one against mixing business majors, industrial chemists, and more lawyers than you can shake a stick at. So... Yeah. Take it with a grain of salt and call me in the morning.
My high school was in the US. I think good teachers anywhere are teachers because it is their calling. Breaking Bad is hardly the normative reference of how people should view teachers.
I can agree with that, but the fact that it's believable is the giveaway.
Could you make a movie where being a doctor makes the main character a failure in life? Such a movie would almost certainly have to be a comedy where the character is a failure in spite of being a doctor, not because.
Could you make a movie where being a doctor makes the main character a failure in life? Such a movie would almost certainly have to be a comedy where the character is a failure in spite of being a doctor, not because.
Is it regarded as a failure? Teachers in public schools work part time for 25 years and get a scaling pension they “negotiated” with the politicians their union dues elected. I’d call them fantastic winners. Grifters? Sure. But certainly not losers.
My parents, both with master’s degrees, worked at least eight hours every day teaching, grading assignments, and then preparing for the following day. I would guess about ten hours on average, seeing as I was mostly left alone as a child while my parents worked over the kitchen table. Yes, they don’t teach during the summer. Their pay reflects that. I won’t even touch on personal expenditures for supplies. Grifters?! My lord. Teachers are criminally underpaid, highly educated adults who shape society’s future while fighting its current failures. All while being inexplicably hated and ridiculed by students, parents, and I guess HN.
No need to take my word for it: https://www.cnn.com/2018/04/15/us/teacher-pay-myth-misconcep...
No need to take my word for it: https://www.cnn.com/2018/04/15/us/teacher-pay-myth-misconcep...
The article cites the BLS for other professions so why not take the BLS's word for teachers, too?
https://www.bls.gov/opub/mlr/2008/03/art4full.pdf
https://www.bls.gov/opub/mlr/2008/03/art4full.pdf
> ...shape society’s future while fighting its current failures. All while being inexplicably hated and ridiculed by students, parents, and I guess HN.
I’m not sure how to interpret this. Are you saying they indoctrinate kids? Do they exist to teach kids __how__ to think or __what__ to think?
Which current failures are they fighting?
As to my previous comment about “grifters”, I’ll admit that was too cynical and over the top. I don’t think individual teachers are. However, their unions are pretty close.
I’m not sure how to interpret this. Are you saying they indoctrinate kids? Do they exist to teach kids __how__ to think or __what__ to think?
Which current failures are they fighting?
As to my previous comment about “grifters”, I’ll admit that was too cynical and over the top. I don’t think individual teachers are. However, their unions are pretty close.
> Which current failures are they fighting?
Depending on the teacher and school, everything from kids coming to school hungry or without supplies to obesity to discipline problems to cheating to bullying/cyberbullying to child abuse to uninvolved parents to mental health problems to anxiety to drugs to deficiencies in the curriculum to achievement gaps between genders, classes and races to lack of good role models to gang culture.
That's not to say every teacher works to address all those things at once - at some schools they might not contend with any at all! But I've seen people call on the education system to do almost everything you'd otherwise expect parents to do.
Depending on the teacher and school, everything from kids coming to school hungry or without supplies to obesity to discipline problems to cheating to bullying/cyberbullying to child abuse to uninvolved parents to mental health problems to anxiety to drugs to deficiencies in the curriculum to achievement gaps between genders, classes and races to lack of good role models to gang culture.
That's not to say every teacher works to address all those things at once - at some schools they might not contend with any at all! But I've seen people call on the education system to do almost everything you'd otherwise expect parents to do.
So it's the system that is failing, not the teachers...
Public schools are a part of the system and the system has only continued to grow larger and larger over the last 75+ years. So what is the solution, to make the system even larger? More of the same failed therapeutic?
More and more "solutions" have been added to an outdated school system and has continued to show worse and worse results. This is quantitatively proven. Yet, we continue to tinker and politicize public schooling. To your point, we've decided to inject more and more social issues into schools, expanding scope of all things except effective learning.
And the teachers unions are a huge part of this. They support unaccountable teachers, pay for time and not for merit, and combined with the progressive wing of the country they are allied with countless special interests which are all too eager to continue to have their interests blended into the curriculum. Because no time to make a customer for life then when they're young.
So yes, the system is failing and the solution has continued to be "Add more system". We spend more and more every year and get worse and worse results. We should dissolve the public school system (government should not be in this business at all) and grant each student a sum of money that parents can use to place kids in private schools of their choice that suit their child's abilities and the parents aspirations.
This is a good breakdown on how some teachers are in fact a big part of the problem with educating kids:
https://fee.org/articles/the-failure-of-american-public-educ...
Public schools are a part of the system and the system has only continued to grow larger and larger over the last 75+ years. So what is the solution, to make the system even larger? More of the same failed therapeutic?
More and more "solutions" have been added to an outdated school system and has continued to show worse and worse results. This is quantitatively proven. Yet, we continue to tinker and politicize public schooling. To your point, we've decided to inject more and more social issues into schools, expanding scope of all things except effective learning.
And the teachers unions are a huge part of this. They support unaccountable teachers, pay for time and not for merit, and combined with the progressive wing of the country they are allied with countless special interests which are all too eager to continue to have their interests blended into the curriculum. Because no time to make a customer for life then when they're young.
So yes, the system is failing and the solution has continued to be "Add more system". We spend more and more every year and get worse and worse results. We should dissolve the public school system (government should not be in this business at all) and grant each student a sum of money that parents can use to place kids in private schools of their choice that suit their child's abilities and the parents aspirations.
This is a good breakdown on how some teachers are in fact a big part of the problem with educating kids:
https://fee.org/articles/the-failure-of-american-public-educ...
"part-time" is not something I would ever describe teaching as. All the teachers I've seen take huge amounts of work home with them, even on vacation. There may be a slight lull in the summer but it's filled with training, learning changes in the curriculum, etc. It's not uncommon for teachers to pay for classroom materials out of pocket because the schools are unable or unwilling to pay for them (this would be utterly ridiculous in many other industries). Teaching is something you go into because you enjoy it or it satisfies you on some level and you can put up with ridiculous workloads, not because it pays well.
> Teachers in public schools work part time
Typically full-time and usually year round, though some work seasonally for about 3/4 year (but still full-time), with commensurately reduced annual pay.
Typically full-time and usually year round, though some work seasonally for about 3/4 year (but still full-time), with commensurately reduced annual pay.
nemo44x(1)
It’s amazing a man would work for a masters degree and end up teaching mainly below average people at a public institution. What’s a masters degree worth?
Good lord this comment is condescending.
Some people are teachers because they want to be teachers, period. They find fulfillment in it.
That’s not even touching the unnecessary dig at public institutions.
Some people are teachers because they want to be teachers, period. They find fulfillment in it.
That’s not even touching the unnecessary dig at public institutions.
Did you go to public schools? I did. The student body is mainly uninterested, incapable, or irredeemable. Some great diamonds in the ruff to be sure. But certainly these people would excel regardless of a 1-off actual good teacher seeing as most of them are just mailing it in, like their student body.
Why go to the trouble of getting a masters to waste it like this?
FWIW I don’t believe teachers should need a bachelors. A 2-year trade school should suffice.
Why go to the trouble of getting a masters to waste it like this?
FWIW I don’t believe teachers should need a bachelors. A 2-year trade school should suffice.
I went to public schools. The majority of teachers worked hard and did well with what they had. And many of them had masters.
I sure am glad my fantastic public high school teachers didn't have your attitude. They sacrificed so much for so little, and I'll tell you what, they made a word of difference in at least one life: mine. From what I've learned of teachers, that's more than enough for them.
Shame.
Shame.
My (public) high school physics/chemistry teacher had two PHDs and is responsible for me getting interested in science in general.
He probably had more impact on the world than some CERN researchers spending their entire lives working on theoretical physics with 0 application in the real world whatsoever
Who should teach below average people ? Below average teachers with no education ?
He probably had more impact on the world than some CERN researchers spending their entire lives working on theoretical physics with 0 application in the real world whatsoever
Who should teach below average people ? Below average teachers with no education ?
[deleted]
That's the reason why I love the internet. Things are so easy to fact check now, at least compared to the way it was before.
Many people talk about the problem of "fake news". What they may not realize is that falsehood have always existed, but we now have unprecedented tools to debunk them.
When I was a kid, I learned loads and loads of bullshit, the glass thing was one of it. The problem was, how could I know it was wrong? Obviously, I didn't know enough about material science to figure it out by myself, and I didn't know any material scientist. Books were mostly useless for that purpose, searching for the answers would have taken days at best, and I didn't have that much time to debunk something that insignificant. Now just searching "glass thicker at the bottom" on the web yields exactly what I need.
In fact, I am quite sure, there is much less bullshit going on today, but it looks like there is more because that these are so much easier to figure out.
Many people talk about the problem of "fake news". What they may not realize is that falsehood have always existed, but we now have unprecedented tools to debunk them.
When I was a kid, I learned loads and loads of bullshit, the glass thing was one of it. The problem was, how could I know it was wrong? Obviously, I didn't know enough about material science to figure it out by myself, and I didn't know any material scientist. Books were mostly useless for that purpose, searching for the answers would have taken days at best, and I didn't have that much time to debunk something that insignificant. Now just searching "glass thicker at the bottom" on the web yields exactly what I need.
In fact, I am quite sure, there is much less bullshit going on today, but it looks like there is more because that these are so much easier to figure out.
> In fact, I am quite sure, there is much less bullshit going on today, but it looks like there is more because that these are so much easier to figure out.
You're "quite sure" but how would one fact check this?
Other possibilities:
- There are more new claims being made and circulated, even if the same proportion of them initially are false, the fraction that any given person can follow up on to validate or debunk decreases, and then the share of propagated claims which is false is higher.
- The share false "facts" is higher because the ability to disseminate information has been democratized, but us amateurs have a lesser commitment to fact-checking than press professionals a generation ago.
- The share of bullshit is greater today than when you were a kid because the internet makes it financially rewarding to churn out content regardless of accuracy.
You're "quite sure" but how would one fact check this?
Other possibilities:
- There are more new claims being made and circulated, even if the same proportion of them initially are false, the fraction that any given person can follow up on to validate or debunk decreases, and then the share of propagated claims which is false is higher.
- The share false "facts" is higher because the ability to disseminate information has been democratized, but us amateurs have a lesser commitment to fact-checking than press professionals a generation ago.
- The share of bullshit is greater today than when you were a kid because the internet makes it financially rewarding to churn out content regardless of accuracy.
I seem to remember research has found some windows were placed upside down so these would now support the story that glass flows up.
The article says the glass does actually have a viscosity, so maybe she was not quite that wrong - just about the magnitude.
I think glass has a viscosity, but other solids do not, but will creep.
I hope my understanding is correct - if not, can anyone help explain?
I think glass has a viscosity, but other solids do not, but will creep.
I hope my understanding is correct - if not, can anyone help explain?
I believe you are correct. I had to shorten the title, and removed “observable” because the word “medieval” already refers to the science class meme that the viscous flow is at human history timescale (as opposed to ~1 nm/10^7 years).
See also: the myth of taste buds with specific functions neatly layered on the tongue.
What other unsubstantiated claims did she make?
I'm not the original poster, but I was shocked by how many of the otherwise super smart friends I had in college were taught common falsehoods in high school. For example: the idea that your veins look blue through your skin because the deoxygenated blood in them is blue, and that it only turns red outside your body because it's exposed to oxygen.
Or how reentry heating is apparently caused mostly by friction. (Compression of air is the main cause in actuality)
Technically it's not "friction" because "friction" has to be between two solids. But arguably that's just being pedantic. The air gets in the way of the object moving through it and slows it down, but energy is conserved, as always, so the energy ends up as heat. Knowing that the correct term is "air resistance" rather than "friction" doesn't seem to provide any insight into what's happening, so I don't understand the obsession with correcting people online who call it "friction".
I've been told you can bring water to the boil with a food mixer and a bit of patience. That's not friction either. It's water getting in the way of and slowing down the blades.
I've been told you can bring water to the boil with a food mixer and a bit of patience. That's not friction either. It's water getting in the way of and slowing down the blades.
> so I don't understand the obsession with correcting people online who call it "friction".
It lets dumb people feel intelligent. The type of person that confuses trivia for insight.
It lets dumb people feel intelligent. The type of person that confuses trivia for insight.
No, actually friction is closer to the truth. It's air running into air at a shock, a process that generates entropy, just as friction does.
Compression is a process that is adiabatic, generating no entropy. And in an ideal gas the density increase across a shock reaches a finite limit even as the mach number goes to infinity.
Compression is a process that is adiabatic, generating no entropy. And in an ideal gas the density increase across a shock reaches a finite limit even as the mach number goes to infinity.
I can't make sense of your claim. Compression could be done adiabatically, or not, but that doesn't mean it's isothermal or somehow inherently adiabatic. In fact, for it to be isothermal would require the transport away of compression heat, which would be decidedly non-adiabatic.
The parent is correct.
The parent is correct.
I didn't say the compression was isothermal.
The parent is not correct. Compression occurs at a shock, but this is not heating due (solely) to adiabatic compression. This is clearly seen by considering the case where mach number goes to infinity: in that limit, the fraction of heating due to compression goes to zero (as the gas density remains below some finite limiting value.) What is causing heating is a dissipative process in the shock itself. This dissipative process is more akin to friction than it is to compression.
The parent is not correct. Compression occurs at a shock, but this is not heating due (solely) to adiabatic compression. This is clearly seen by considering the case where mach number goes to infinity: in that limit, the fraction of heating due to compression goes to zero (as the gas density remains below some finite limiting value.) What is causing heating is a dissipative process in the shock itself. This dissipative process is more akin to friction than it is to compression.
Parent just said "compression heating" which no one takes as a claim of isentropic compression. Shock-driven compression still qualifies as compression.
This has just defined shock heating as compression heating. But as I argued elsewhere, that makes no sense, since the compression at a shock is bounded by a finite maximum value regardless of the mach number.
This is very interesting, is there a textbook for this?
I haven't seen any of pfdietz' arguments in a book.
But ThenAsNow already recommended the excellent "Modern Compressible flow" by J.D. Anderson, and, in extension, I can recommend "Hypersonic and High-Temperature Gas Dynamics" by the same author.
But ThenAsNow already recommended the excellent "Modern Compressible flow" by J.D. Anderson, and, in extension, I can recommend "Hypersonic and High-Temperature Gas Dynamics" by the same author.
I am having trouble seeing how compression in a shock would be isentropic? Care to elaborate?
And why passing through a shock (compression) is akin to friction, but not to compression?
And why passing through a shock (compression) is akin to friction, but not to compression?
Because compression, as normally considered, does not generate entropy. It causes gas to become hotter because the temperature has to be higher for entropy to remain constant, as the volume is reduced. This is a reversible process. But shocks are inherently irreversible.
But as my last sentence said, as the mach number goes to infinity the density increase across the shock is finite. Therefore, compression cannot be the (primary) source of the heating; dissipation is.
But as my last sentence said, as the mach number goes to infinity the density increase across the shock is finite. Therefore, compression cannot be the (primary) source of the heating; dissipation is.
I have never seen compression to be considered inherently reversible, certainly not in the aerospace or hypersonics/reentry communities. I assume you come from a different background?
Care to explain your second argument? Even when the density reaches a limit, the change in pressure over the shock does not, so you can pump in energy arbitrarily (of course your gas would dissociate at some point). The total pressure loss can be complete if your initial Mach number is high enough.
Care to explain your second argument? Even when the density reaches a limit, the change in pressure over the shock does not, so you can pump in energy arbitrarily (of course your gas would dissociate at some point). The total pressure loss can be complete if your initial Mach number is high enough.
Let's look up a definition.
"Compression: decrease in volume of any object or substance resulting from applied stress."
Compression refers to a reduction in volume, not an increase in pressure. This is finite for gas crossing a shock, even as the mach number goes to infinity.
"Compression: decrease in volume of any object or substance resulting from applied stress."
Compression refers to a reduction in volume, not an increase in pressure. This is finite for gas crossing a shock, even as the mach number goes to infinity.
Exactly. There's no mention at all about the foundation of all your arguments, namely that compression be inherently isentropic. It simply is not. You can add it as an additional constraint, if you want to.
What I say is that even when dV approaches a constant, the pressure still rises, so the product also rises.
[edit: removed snark]
What I say is that even when dV approaches a constant, the pressure still rises, so the product also rises.
[edit: removed snark]
Requiring compression to be isentropic is just requiring "compression" to be a well-defined term with a specific quantitative result. Otherwise, it's a vague term that offers no quantitative prediction for how much heating it produces for a given change in density. That's not science.
Look, where does this idea come in that compression "as normally considered, does not generate entropy"? The inlet of a supersonic aircraft or a ramjets/scramjet performs non-isentropic (shock-based) compression. You're coming up with your own definition of compression that is inconsistent with gasdynamics practice.
Considering compression to be isentropic is just nailing down what compression means enough for its heating to be actually definable. Otherwise, the argument is just "if there's compression occurring, all the heating must be considered as being due to compression" which is just bullshit.
Compression due to a shock is not isentropic. Parent is incorrect. This is basic gasdynamics. An accessible reference: Modern Compressible flow, by Anderson.
I didn't say compression at a shock was isentropic. I was saying the claim that compression at the shock could not be the cause of (all) the heating, unless you simply define heating at a shock as being due to compression. Instead, I think you should separate out the heating there into two parts: one due to isentropic compression, and one due to injection of additional entropy by dissipation at the shock.
Yes you do, you keep repeating that 'proper' compression is isentropic. That's simply not the case, certainly not across a shock.
The second part of your argument is well defined and makes sense, and no-one argued that.
But explain to me again how this is now 'like friction'?
The second part of your argument is well defined and makes sense, and no-one argued that.
But explain to me again how this is now 'like friction'?
Requiring compression to be isentropic is just requiring "compression" to be a well-defined term with a specific quantitative result. Otherwise, it's a vague term that offers no quantitative prediction for how much heating it produces for a given change in density. That's not science.
Replying to myself since I guess there's a thread depth limit. Now what you are saying is making sense, your original post did not. Irreversibility (increase in entropy) across the shock does cause a significant temperature gain (and at re-entry speeds, nonequilibrium flow, radiation, etc.), but isentropic compression does as well. Still, the shock is a compression artifact, and while you can draw an analogy between the irreversibility within a shock and that in a friction process like in a viscous drag, the original poster's categorization of re-entry heating as compression heating is completely consistent with how practitioners in the gasdynamics community would categorize it.
(you have to wait a short time before you can reply to a message; it's not a depth limit)
Practitioners may say that, but it's sloppy and makes no sense when examined closely, as I've argued here. Compression (as the word is properly defined) is finite even as mach number and heating increase without limit.
Practitioners may say that, but it's sloppy and makes no sense when examined closely, as I've argued here. Compression (as the word is properly defined) is finite even as mach number and heating increase without limit.
The basis of the disagreement hinges on your original claim that "compression is a process that is adiabatic, generating no entropy" which doesn't have any valid basis. Nothing about even the definition of compression that you provided above implies that compression is or isn't by definition isentropic (also, adiabatic and isentropic are not the same thing). Are you trying to argue that flow passing through a shock is not compressed by passing through the shock?
I'm also struggling to understand your point about the hypersonic density ratio limit. You keep repeating it but how specifically does it support your argument?
I'm also struggling to understand your point about the hypersonic density ratio limit. You keep repeating it but how specifically does it support your argument?
Of course it has a valid basis. The alternative is to say that in any process that reduces the volume of the material, all the heating is due to compression (even though the amount of heating can vary widely in different processes with the same reduction in volume.)
The logical error you are committing is saying "if a process includes compression, then the heating is due to compression".
The logical error you are committing is saying "if a process includes compression, then the heating is due to compression".
The semantic error you're making is redefining the general term compression as the more specific "isentropic compression". The process by which the compression takes place is not prescribed just by the term "compression" as you did originally. Just saying "compression" specifies nothing about the process by which it happens. Compression can take place (theoretically) through an isentropic process, or a non-isentropic process, with work being done on the fluid (increasing its total enthalpy) or not.
I get your point that the shock contributes to the heating through irreversibility, and agree that has a significant impact on the sensed temperature. If we want to tie your point back to the original post, one could say that "compression and shockwaves" are the cause of re-entry heating to ensure you are explicitly capturing the effect of the shock.
Whether you consider the shock heating to merit explicit mention or whether you see it as a detail associated with the specific means of compression is largely a matter of perspective & practice.
The gasdynamic basis of shock formation is derived by considering what happens when pressure fields are no longer able to smoothly vary as the speed of a body exceeds the speed at which pressure disturbances can be communicated upstream, namely the speed of sound. The pressure jump across the shock is elemental to its derivation. Practitioners commonly view the shock as the means by which compression takes place and pressure fields reconciled. As I noted above, just saying "compression" doesn't imply "isentropic" and so the entropy-generating processes associated with a shock performing compression are viewed, for example, as thermodynamically similar to viscous heating of the fluid in a gas turbine compressor.
I get your point that the shock contributes to the heating through irreversibility, and agree that has a significant impact on the sensed temperature. If we want to tie your point back to the original post, one could say that "compression and shockwaves" are the cause of re-entry heating to ensure you are explicitly capturing the effect of the shock.
Whether you consider the shock heating to merit explicit mention or whether you see it as a detail associated with the specific means of compression is largely a matter of perspective & practice.
The gasdynamic basis of shock formation is derived by considering what happens when pressure fields are no longer able to smoothly vary as the speed of a body exceeds the speed at which pressure disturbances can be communicated upstream, namely the speed of sound. The pressure jump across the shock is elemental to its derivation. Practitioners commonly view the shock as the means by which compression takes place and pressure fields reconciled. As I noted above, just saying "compression" doesn't imply "isentropic" and so the entropy-generating processes associated with a shock performing compression are viewed, for example, as thermodynamically similar to viscous heating of the fluid in a gas turbine compressor.
Or the whole taste bud taste map of the tongue.
One of my favourites is the myth that Iodine doesn't melt: https://www.youtube.com/watch?v=dPIaEWd8zf4
I think a lot of them have only been solidly disproven in the last ~15 years, and it takes some time for that science update to propagate through the world.
...especially in a time before Internet access was common.
Or how wings work.
For anyone thats interested in what the parent is talking about: http://www3.eng.cam.ac.uk/outreach/Project-resources/Wind-tu...
I've had people get like legit upset at me when i correct this.
I've had people get like legit upset at me when i correct this.
My god, thank you. I remember as a kid this explanation "the top has to move fast to meet the bottom stream at the trailing edge" always confused the hell out of me. Why do the top and bottom have to meet? How would they know? Even as a 10 year old it confused me no-one could answer this.
Especially for hydrofoils. Makes no sense
That's the now famous Bernouilli vs Newton debate.
Personally, I am in camp Newton. Not that Bernouilli doesn't work, they both give the same results in the end, and they are both a simplification of the "truth" which is the Navier-Stokes equations.
The reason I like the Newton explanation better is that if you start with the Bernouilli principle, it is much easier to come up with the wrong idea. The Newton is straightforward: push air down, plane goes up. A bit shallower but at least, the basic idea is hard to get wrong.
Personally, I am in camp Newton. Not that Bernouilli doesn't work, they both give the same results in the end, and they are both a simplification of the "truth" which is the Navier-Stokes equations.
The reason I like the Newton explanation better is that if you start with the Bernouilli principle, it is much easier to come up with the wrong idea. The Newton is straightforward: push air down, plane goes up. A bit shallower but at least, the basic idea is hard to get wrong.
It's reasonable to phrase the working of a wing either in terms of momentum or in terms of a different in pressure between the top and bottom. What's incorrect is when trying to explain the action through bernouilli it's often asserted that the air above the wing must take the same time to transit the wing as the air on the bottom. Not only is this completely unjustified to assume when trying to solve the problem, it's also false in practice: in general air above and below will not pass the wing in the same time, even though the air over the top is travelling faster.
Not the OP, but a fourth grade substitute teacher made the claim that we always saw the same side of the moon because it didn't rotate. I don't know what got to me the most: that she didn't understand, that my attempt to explain it didn't go over, or that the other kids in the class didn't get it either. In any case, I've been working on improving my explanations ever since.
What's your explanation now? I think people just get tripped up thinking about rotation of an object in circular motion and just ascribe one motion for the other.
For example, if you imagine a newly reunited couple and they hug each other while simultaneously spinning, this is exactly what the moon and Earth are doing. I think most people would also say that the outside person isn't rotating. However, they would also say that the inner person is obviously spinning.
Describing in words is often not the best way to impart explanations of physics, but the easiest way to show this concept for me is to imagine both people separately and consider a half turn. The inner person, rotates 180 degrees, simple rotation. What does the outside person have to do to get to the right position? They have to walk around the inner person to the other side and then rotate 180 degrees to see their partner again.
For example, if you imagine a newly reunited couple and they hug each other while simultaneously spinning, this is exactly what the moon and Earth are doing. I think most people would also say that the outside person isn't rotating. However, they would also say that the inner person is obviously spinning.
Describing in words is often not the best way to impart explanations of physics, but the easiest way to show this concept for me is to imagine both people separately and consider a half turn. The inner person, rotates 180 degrees, simple rotation. What does the outside person have to do to get to the right position? They have to walk around the inner person to the other side and then rotate 180 degrees to see their partner again.
And your beef is that it does rotate, at a rate of one rotation per revolution?
Sounds kind of pedantic to me, and confusing (certainly to kids).
Sounds kind of pedantic to me, and confusing (certainly to kids).
I'll grant that I was a pedantic fourth grader. And I'll grant that the other kids didn't care. Still, seems to me that the teacher could at least skip the topic if it's confusing.
The fact that we live our lives in a non-intertial reference frame is pretty mind blowing to everyone, I suppose.
Doesn’t seem like a small point to me.
Doesn’t seem like a small point to me.
Almost everything we think (including me) is probably trash. We just need to accept we are mostly idiotic. Unless we put the time in to understand something that _maybe_ is somewhat understood by people that have put their lives into it.
Truth is (heh) we are all mainly full of shit. We think we know more than we do. We confuse truth for BS constantly. We spend countless breaths debating unfalsifiable opinions as if they’re true - like we really know something. We are all mainly dumb at most things.
Truth is (heh) we are all mainly full of shit. We think we know more than we do. We confuse truth for BS constantly. We spend countless breaths debating unfalsifiable opinions as if they’re true - like we really know something. We are all mainly dumb at most things.
> Almost everything we think (including me) is probably trash. We just need to accept we are mostly idiotic.
I do not like this attitude. Everything is false, because the truth exists only in ideal condition of math. But it doesn't mean that we are all idiotic and know nothing worthy knowing. The trick is to understand the relation between knowledge and the reality, to feel this relation in your guts. It helps to know a lot of falsehoods, and to be smart, even wise and knowledgeable.
> We are all mainly dumb at most things.
I could agree with this, because to really know something one needs to spent all his life researching the topic. And even the life full of the dedicated research might be not enough.
But as I see, to be dumb is not so about having no knowledge, as about having no idea of limits of one's knowledge.
I do not like this attitude. Everything is false, because the truth exists only in ideal condition of math. But it doesn't mean that we are all idiotic and know nothing worthy knowing. The trick is to understand the relation between knowledge and the reality, to feel this relation in your guts. It helps to know a lot of falsehoods, and to be smart, even wise and knowledgeable.
> We are all mainly dumb at most things.
I could agree with this, because to really know something one needs to spent all his life researching the topic. And even the life full of the dedicated research might be not enough.
But as I see, to be dumb is not so about having no knowledge, as about having no idea of limits of one's knowledge.
No - truth doesn’t only exist in an ideal condition of math. I mean, yes maybe literally in some ways, maybe. But not really. Math doesn’t prove the sky is blue on a sunny day.
My main point is that of falsifiability. You don’t need math to make a falsifiable argument. However, much of our discourse can’t even meet this basic qualification.
My main point is that of falsifiability. You don’t need math to make a falsifiable argument. However, much of our discourse can’t even meet this basic qualification.
> Math doesn’t prove the sky is blue on a sunny day.
Yeah, it doesn't. So it is not a truth, but a belief. It is pretty strong belief, so strong that it almost indistinguishable from the truth. But nevertheless it is just a belief.
> My main point is that of falsifiability. You don’t need math to make a falsifiable argument. However, much of our discourse can’t even meet this basic qualification.
Even falsifiability is a too rigid property for some discourses. My main point is that attempts to find a silver bullet to shoot "bad beliefs" are no-go. Knowledge couldn't be bad or good, true or false. It is the way knowledge applied could be good or bad.
For example, even "the sky is blue on a sunny day" could be misapplied. Take the sky of a Moon or a Mars for example, which are not blue in a sunny day. Or let us imagine atmosphere of Earth with a lot of dust after collision of Earth and an asteroid: on such Earth sky could be orange, or gray or of some other color. I mean that even "true" statements have limits of their truthiness.
As an opposite example, a "false" statement could be applied in a "good" way. Earth is flat? Oh, yes, it is convenient to think so when dealing with a relatively small area of the Earth surface. Or when communicating with people, who believe that Earth is flat. You need only to remember the limits of this belief, to not misapply it accidentally.
In math the situation a little different. Math statements also could go wrong when assumptions change (the sum of angles of a triangle could be not equal to PI, if triangle drawn not on a plane but on some other surface), but mathematicians make sure to strictly state all the assumptions as axioms and definitions. It is possible in ideal conditions, but not possible in real ones.
Yeah, it doesn't. So it is not a truth, but a belief. It is pretty strong belief, so strong that it almost indistinguishable from the truth. But nevertheless it is just a belief.
> My main point is that of falsifiability. You don’t need math to make a falsifiable argument. However, much of our discourse can’t even meet this basic qualification.
Even falsifiability is a too rigid property for some discourses. My main point is that attempts to find a silver bullet to shoot "bad beliefs" are no-go. Knowledge couldn't be bad or good, true or false. It is the way knowledge applied could be good or bad.
For example, even "the sky is blue on a sunny day" could be misapplied. Take the sky of a Moon or a Mars for example, which are not blue in a sunny day. Or let us imagine atmosphere of Earth with a lot of dust after collision of Earth and an asteroid: on such Earth sky could be orange, or gray or of some other color. I mean that even "true" statements have limits of their truthiness.
As an opposite example, a "false" statement could be applied in a "good" way. Earth is flat? Oh, yes, it is convenient to think so when dealing with a relatively small area of the Earth surface. Or when communicating with people, who believe that Earth is flat. You need only to remember the limits of this belief, to not misapply it accidentally.
In math the situation a little different. Math statements also could go wrong when assumptions change (the sum of angles of a triangle could be not equal to PI, if triangle drawn not on a plane but on some other surface), but mathematicians make sure to strictly state all the assumptions as axioms and definitions. It is possible in ideal conditions, but not possible in real ones.
That traits of human physiology are heritable binaries.
https://udel.edu/~mcdonald/mythintro.html
https://udel.edu/~mcdonald/mythintro.html
I think there's only so much time children can spend on learning all their subjects, so they learn Mendelian genetics, Darwin's evolution, Rutherford's atomic model because they're easy to understand, and close enough approximations for everyday life for non-specialists.
Sure, but some of those things they used to teach us about aren't heritable traits at all. The article recommends studying examples that fit Mendel's model.
"You won't always have a calculator in your pocket." - Every math teacher before 2005
To be fair it was usually small, inconsequential things, not major parts of the curriculum.
The only major one I remember is that water is conductive by itself. And that "C++ is the best programming language" (hah).
The only major one I remember is that water is conductive by itself. And that "C++ is the best programming language" (hah).
> To be fair it was usually small, inconsequential things
I’ve always wondered about this bit:
“One nation, under God, with liberty and justice for all”
I’ve always wondered about this bit:
“One nation, under God, with liberty and justice for all”
The "under God" was added after the fact: https://en.wikipedia.org/wiki/Pledge_of_Allegiance#Addition_...
The liberty and justice parts are questionable too.
I'm sure you could make the argument using some definition of best. Perhaps best in it's impact via software created in it rather than the language itself. Although then I think C would win over C++ because of Linux.
I'm imagining a slightly tongue in cheek 'best' alongside an implication of subjectivity. But given this was a highschool teacher I wouldn't be surprised if it was instead a multi choice test question with a single "correct" answer? Which of course would be ridiculous.
I'm imagining a slightly tongue in cheek 'best' alongside an implication of subjectivity. But given this was a highschool teacher I wouldn't be surprised if it was instead a multi choice test question with a single "correct" answer? Which of course would be ridiculous.
"make the argument using some definition of best"
I won't take the bait to dive into that discussion! ;)
Luckily she never tested us on it, I think she was understandably biased from working in C++ in an earlier job.
I won't take the bait to dive into that discussion! ;)
Luckily she never tested us on it, I think she was understandably biased from working in C++ in an earlier job.
Last one is correct, actually.
> The only major one I remember is that water is conductive by itself.
Most people don't know that pure water is an insulator.
However, in a practical sense that's ok since it's unlikely any pool of water is pure.
So for safety reasons involving electricity, one has to assume that any pool of water can conduct electricity.
Most people don't know that pure water is an insulator.
However, in a practical sense that's ok since it's unlikely any pool of water is pure.
So for safety reasons involving electricity, one has to assume that any pool of water can conduct electricity.
My uncle works for a water treatment company. Medical manufacturers often come to him saying his equipment is off because they open the test port ran the pure water into a clean glass and it tested below specs. He then has to explain that in the 30 seconds between opening the valve and the test the water absorbed enough impurities to fail the spec. The input water was fine.
Another interesting anecdote about water treatment facilities is the situation in Asia.
For example, Jakarta has a water treatment facility, but every tourist gets stomach illness there. The reason is that industrial facilities siphon off the treated water, and by the time homes and hotels get any, it's untreated.
To give you an idea how bad it is, tourists generally don't drink tap water, but they still get ill from the washed dishes, or not closing their mouth in the shower.
(Bali can always find money for road construction (they built two impressive underpasses in the last 6 years), but never enough for a power generation plant, so has continual brownouts.)
For example, Jakarta has a water treatment facility, but every tourist gets stomach illness there. The reason is that industrial facilities siphon off the treated water, and by the time homes and hotels get any, it's untreated.
To give you an idea how bad it is, tourists generally don't drink tap water, but they still get ill from the washed dishes, or not closing their mouth in the shower.
(Bali can always find money for road construction (they built two impressive underpasses in the last 6 years), but never enough for a power generation plant, so has continual brownouts.)
How does that work? If the water is being used by the industrial facilities then the water pressure/flow rate would drop.
Unless the facilities are adding dirty water to the pipe to push pressure back up after they remove it? But even then, unless they routed the pipe from the water treatment facility to the industry first, only the areas downstream from the industry would be affected.
More likely is that the water is not being adequately treated and/or that the infrastructure is not built/maintained and the pipes are leaky.
My guess would be that the treatment is to minimum spec and that there are leaky pipes which allow for contamination. It is hard to maintain pumped water pressure if there are brownouts.
Unless the facilities are adding dirty water to the pipe to push pressure back up after they remove it? But even then, unless they routed the pipe from the water treatment facility to the industry first, only the areas downstream from the industry would be affected.
More likely is that the water is not being adequately treated and/or that the infrastructure is not built/maintained and the pipes are leaky.
My guess would be that the treatment is to minimum spec and that there are leaky pipes which allow for contamination. It is hard to maintain pumped water pressure if there are brownouts.
I would guess that they have a treatment system that isn't big enough, and they pump in unfiltered water to make up the difference when the treatment plant cannot keep up.
Even in the US I know of cities that have had boil orders because the treatment plant couldn't keep up and they pumped in untreated water. The cases I know of the unfiltered water made it in via weather events (the treatment plant is on the river and it flooded. Also a case where the power went out on a big surge and so they hardwired the pumps to the well bypassing treatment until the treatment controller boards could be replaced.)
Even in the US I know of cities that have had boil orders because the treatment plant couldn't keep up and they pumped in untreated water. The cases I know of the unfiltered water made it in via weather events (the treatment plant is on the river and it flooded. Also a case where the power went out on a big surge and so they hardwired the pumps to the well bypassing treatment until the treatment controller boards could be replaced.)
Centrifugal force is a common one: https://xkcd.com/123/
I had an electronics professor who in 2012 was adamant that in five years smartphones would be using x-ray transceivers to communicate with cell towers.
I think your professor read about millimeter wave and misunderstood. I've had others confuse the two in conversation as well.
Confusing millimeters and nanometers? How? Visible light sits between the two, they're not even close.
>Confusing millimeters and nanometers? How? Visible light sits between the two, they're not even close.
Compared to kilometers and parsecs, they're extremely close...
Compared to kilometers and parsecs, they're extremely close...
Well, i once confused packaging and ordered ~100 kg of toiler paper
You could have made a fortune selling your stock in the covid era
Go brag on the prepper forums.
Lots of grade school teachers are full of shit.
I had one that claimed that a pentagon had 1 line of symmetry because "the top is bigger than the bottom".
I had one that claimed that a pentagon had 1 line of symmetry because "the top is bigger than the bottom".
Allow me to be dumb for a second--isn't that the case? I mean, if you label the vertices/edges then yes a regular pentagon has five distinct lines of symmetry, but typically people talk about lines of symmetry in a context where vertices are unlabeled, no?
There are 2n symmetries for an n-sided polygon. In this case five rotations and five reflections.
https://math.stackexchange.com/questions/490054/symmetries-o...
I agree, but I think in most cases where grade schoolers are made to draw mirror symmetries on work sheets that all symmetries are included, even if they are simply the same symmetry but rotated.
In spite of an argument "the top is bigger than the bottom", it seems to me that he/she meant that there is no horizontal line of symmetry, so there is only vertical one.
A regular pentagon has 5 lines of symmetry. One from the center of each edge to the point on the other side.
Wikipedia - List of Common Misconceptions
https://en.wikipedia.org/wiki/List_of_common_misconceptions
https://en.wikipedia.org/wiki/List_of_common_misconceptions
Yeah, I learned this "fact" in school as well. Later I found a simple refutation: If a church window pane would deform by a measurable amount in 1000 years (say 0.5mm), then a 100-year old telescope or camera lens would be totally useless, and yet they seem to function all right.
To add some detail: a common minimum quality criterion for optical surfaces is λ/4 (divergence from an ideal surface), where λ is the wavelength used. For visible light this gives about 100 nm (though large professional telescopes are "figured" to more like λ/20). Any alleged glass creep visible in window panes over a few hundred years would quickly ruin any astronomical mirror (which definitely does not happen).
I mean... the obvious answer to that is that we don't use the same techniques to manufacture a telescope or camera lens that we used to manufacture church windows. In fact we don't use glass for large telescopes specifically because they'll deform under their own weight.
I'm not saying that original fact is correct, I'm just saying I don't think what you're saying disproves the idea that that glass could deform over time.
I'm not saying that original fact is correct, I'm just saying I don't think what you're saying disproves the idea that that glass could deform over time.
That's incorrect. We do use glass for large mirrors and it works just fine ([1], [2.1], [2.2]). Do not confuse these two effects:
1. Viscous liquid-like creep (does not occur).
2. Elastic deformation (sagging) under gravity - this of course takes place, and is compensated for by multipoint support and, in larger professional telescopes, "active optics" (actuactors that counter the deformation depending on mirror's orientation; not to be confused with "adaptive optics", which deform a mirror with high frequency to counteract atmospheric image distortion).
[1] https://en.wikipedia.org/wiki/Hale_Telescope
[2.1] https://en.wikipedia.org/wiki/Large_Binocular_Telescope
[2.2] https://www.newswise.com/articles/steward-observatory-mirror...
1. Viscous liquid-like creep (does not occur).
2. Elastic deformation (sagging) under gravity - this of course takes place, and is compensated for by multipoint support and, in larger professional telescopes, "active optics" (actuactors that counter the deformation depending on mirror's orientation; not to be confused with "adaptive optics", which deform a mirror with high frequency to counteract atmospheric image distortion).
[1] https://en.wikipedia.org/wiki/Hale_Telescope
[2.1] https://en.wikipedia.org/wiki/Large_Binocular_Telescope
[2.2] https://www.newswise.com/articles/steward-observatory-mirror...
I wonder if the craftsmen also knew that the windows were a little wedge shaped from manufacture and put the thick bit at the bottom. That's what I'd do at least, makes sense structurally.
Then later, random people made guesses as to the 'flow' of glass because all the windows are thick on the bottom...
If anyone can confirm this theory, you and I will feel eternally smug. Best of luck!
Then later, random people made guesses as to the 'flow' of glass because all the windows are thick on the bottom...
If anyone can confirm this theory, you and I will feel eternally smug. Best of luck!
but tarmac does flow at an observable rate, although only observable over the course of years
The related example that I always remember is: https://en.m.wikipedia.org/wiki/Pitch_drop_experiment
Especially if you live somewhere where the sun heats it over 50ºC! Then you get huge ruts from the trucks and potholes...
[deleted]
While this was specifically about glass from the middle ages, is there certain window glass more recently that does flow measurably? The soda lime glass referenced?
Or when you see waves in window glass in 1930s buildings, is that too from the original imperfections in the glass fabrication itself?
Or when you see waves in window glass in 1930s buildings, is that too from the original imperfections in the glass fabrication itself?
>Their measurements reveal that medieval glass has a much lower viscosity than expected at room temperature—16 orders of magnitude less than previous estimates
It's pretty rare to read an article in which the degree of previous error is sixteen orders of magnitude.
It's pretty rare to read an article in which the degree of previous error is sixteen orders of magnitude.
The way viscosity is measured doesn't follow naive expectation though.
Water at 0C has over six times the viscosity of water at 100C, yet to the untrained human they seen to flow about the same. Olive oil is 100 times more viscous that water. Yoghurt about 10000 times more viscous than water.
Water at 0C has over six times the viscosity of water at 100C, yet to the untrained human they seen to flow about the same. Olive oil is 100 times more viscous that water. Yoghurt about 10000 times more viscous than water.
Fair, but keep in mind that it's orders of magnitude we're taking about.
How does this viscosity compare to gold or silver? Those also have brownian motion under the force of gravity.
I bet it’s higher than 1 nm / billion years.
I bet it’s higher than 1 nm / billion years.
Well, glass is still a liquid, which was the most counter intuitive claim to me, whether or not the flow is humanly perceptible. In fact it is even more counter intuitive now, since glass is an even more solid liquid.
It makes more sense (to me at least) to think of glass as an amorphous solid and expand the concept of “states of matter.” It doesn’t have a repeating crystalline structure.
I think expand the concept of states of matter is key. It really helps make sense of a lot more things when you move beyond just solid, liquid, and gas (and plasma). A good example are liquid crystals, in LCDs yes but also cell membranes. What state of matter is the cell membrane? It makes more sense to create a new phase to categorize it. The lipid molecules are arranged in a certain orientation to each other (crystalline) but are also free to shuffle past each other (liquid). This is not just academic. Your body uses cholesterol to modify the fluidity vs. crystalinity of your cell membranes so they don’t “freeze) (stiffen too much) in the winter or melt in the summer.
I think expand the concept of states of matter is key. It really helps make sense of a lot more things when you move beyond just solid, liquid, and gas (and plasma). A good example are liquid crystals, in LCDs yes but also cell membranes. What state of matter is the cell membrane? It makes more sense to create a new phase to categorize it. The lipid molecules are arranged in a certain orientation to each other (crystalline) but are also free to shuffle past each other (liquid). This is not just academic. Your body uses cholesterol to modify the fluidity vs. crystalinity of your cell membranes so they don’t “freeze) (stiffen too much) in the winter or melt in the summer.
This one was maybe more excusable because it was common to teach at the time. Maybe it ended up making us better students in the end because we learned to fact-check our teachers, and not to be adamant about things we only think are true (though I'm still guilty of that myself sometimes)...