Glass viscosity calculations debunk the myth of flow in medieval windows (2017)

Post by ThenAsNow » Fri, Oct 30, 2020, 3:19 AM UTC

pfdietz wrote: post #72

ThenAsNow wrote: post #62

Earlier quoted context omitted.

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.

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 dissipativ…

Post by abeppu » Fri, Oct 30, 2020, 3:21 AM UTC

GuB-42 wrote: post #68

nikisweeting wrote: post #2

Finally! I always knew my 7th grade science teacher was full of shit on that one, she was so adamant about some things that turned out to be wrong. 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 m…

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 wa…

Post by nemo44x » Fri, Oct 30, 2020, 3:24 AM UTC

dragonwriter wrote: post #79

nemo44x wrote: post #74

Earlier quoted context omitted.

You are simply full of it. Public school teachers are booked for around 180 days of teaching + admin work. I read my tax bill. This is like 36-38 (38 being generous) weeks of work per year. It’s 3 months off.

> You are simply full of it Except your calculations support exactly what I said. > It’s 3 months off. Yes, it's typically 3 months off if they don't work summer session in a traditional schedule. Which most who are able to (there are reduced available positions) do. Hence, the full-time but, for some, 3/4-year seasonal full-time that I stated.

Post by dragonwriter » Fri, Oct 30, 2020, 3:43 AM UTC

nemo44x wrote: post #85

dragonwriter wrote: post #79

Earlier quoted context omitted.

> You are simply full of it Except your calculations support exactly what I said. > It’s 3 months off. Yes, it's typically 3 months off if they don't work summer session in a traditional schedule. Which most who are able to (there are reduced available positions) do. Hence, the full-time but, for some, 3/4-year seasonal full-time that I stated.

They get paid for that extra time if they choose to work it. Otherwise a teacher works 30 hours a week when normalized to a 48 hour work year. This is part-time work. But they get golden health care, pension, and early retirement. Good for them. This is why teachers aren’t suckers as the OP suggested. They’re in on a great scam. Good for them. The sucker working retail could only dream.

Post by ThenAsNow » Fri, Oct 30, 2020, 3:51 AM UTC

pfdietz wrote: post #82

ThenAsNow wrote: post #77

Earlier quoted context omitted.

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…

(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.