843: Misconceptions

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"Grandpa, what was it like in the Before time?" "It was hell. People went around saying glass was a slow-flowing liquid. You folks these days don't know how good you have it."
Title text: "Grandpa, what was it like in the Before time?" "It was hell. People went around saying glass was a slow-flowing liquid. You folks these days don't know how good you have it."

[edit] Explanation

The Wikipedia article List of common misconceptions gives a list of commonly-repeated anecdotes that are widely believed to be true, but actually are not. Miss Lenhart, or the school board has made the reading of this article a curriculum requirement to stem the repetition of these incorrect anecdotes.

The title text refers to a specific one of these false stories: That glass, while seeming solid, is actually an extremely viscous liquid and will flow over time, as is seen on older buildings where the window panes are thicker at the bottom. In reality, older manufacturing processes did not produce glass panes with as uniform thickness as modern processes, and people tended to install the uneven panes with the thicker side at the bottom for stability. Glass simply does not flow at room temperature; it's more viscous than solid lead by a factor of over a billion.

[edit] Transcript

[Miss Lenhart is standing in front of a board, holding a laptop computer and elocuting.]
Miss Lenhart: Okay, middle school students, it's the first Tuesday in February.
Miss Lenhart: This means that by law and custom, we must spend the morning reading through the Wikipedia article List of Common Misconceptions, so you can spend the rest of your lives being a little less wrong.
Miss Lenhart: The guests at every party you'll ever attend thank us in advance.
I wish I lived in this universe.
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Note: The xkcd forums contain a great discussion of this comic.

When I took Calculus-based Physics in college (2003), my professor taught us that glass was an "extremely viscous fluid." When was glass reclassified as an amorphous solid?
Smperron (talk) Your professor was simply incorrect. Glass never was, and has never been, an "extremely viscous fluid". Molten glass is a "molecular liquid" where the viscosity depends on temperature. 22:14, 13 December 2012 (UTC)
"Extremely viscous fluid" is just another way to describe an amorphous solid (as opposed to the crystallic solid). There is no sharp cut-off between these states. Just at some point it starts feeling solid enough, so it gets called a solid. See the Pitch Drop Experiment [1] for an example (though glass is obviously harder than pitch). 19:21, 16 January 2014 (UTC)

I had a chemistry professor in 2011 tell me that glass flowed, even citing old buildings with thicker glass on the bottom. I tried to argue against it, but I was interrupting a lecture. I discussed it with some students later, though. 00:49, 1 February 2014 (UTC)
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