Reading Comprehension

PT143 · S2 · P4 · Q23 The Myth of Liquid Glass

A free, expert breakdown of this official LSAT Reading Comprehension question.

Save & drill this skill — build targeted practice sets from questions like this one
Video walkthroughs — watch every question solved step by step
81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

To glass researchers it seems somewhat strange that many people throughout the world share the persistent belief that window glass flows slowly downward like a very viscous liquid.

Topic

The myth that old window glass flows downward over time, and the science debunking it.

Framework

Challenge Position

Main Point

The commonly held belief that window glass flows downward over time (causing old windows to be thicker at the bottom) is a myth; scientific calculations and historical glassmaking techniques explain the thickness differences instead. (The main point is most directly addressed at the beginning of paragraph 2 and fully explained in the last paragraph.)

P1: Introduction to the Glass Flow Myth

A lot of people (even in science books) mistakenly believe that window glass is a super slow-moving liquid and gradually flows downward, explaining the thicker bottoms in old windows. This myth likely started because glass's atoms are not arranged like in crystals, but the structure alone doesn't mean glass is liquid—it's solid at room temperature, just with a unique atomic arrangement.

P2: Scientific Debunking

A recent study shows that, although glass *can* flow under gravity, it would take longer than the age of the universe for old windows to change thickness from flow. So, that's not the reason old windows are thicker at the bottom!

P3: Why Flow Still Isn’t the Answer

Even the easiest-flowing glass (like germanium oxide glass) would still take trillions of years to change shape noticeably, and medieval glass—even with impurities—wouldn't flow in just a few centuries. The science is clear: for glass to flow, it actually needs to be heated to at least 350°C.

23.

Which one of the following best summarizes the author's view of the results of Zanotto's study?

Correct
They provide some important quantitative
Why this is right
We can match this up with the last sentence of the 3rd, in which the author says that Zanotto's study dramatically demonstrates what many scientists had reasoned earlier. That sentence doesn't mention quantitative data, but can we support the notion that Zanotto provides important quantitative data? Sure. The end of the 2nd and beginning of the 3rd paragraphs discuss Zanotto's study and both of those sentences talk about his calculations. He calculated the time needed for viscous flow to change the thickness of different types of glass by a noticeable amount (many trillions of years at a minimum).
Skill tested: Author Opinion · how this choice captures the passage's function is the move to repeat next time.
62% picked this
They have stimulated important new
Out of Scope: stimulated new research
Nothing in the 2nd or 3rd paragraphs talks about new research being stimulated by Zanotto.
16% picked this
They offer a highly plausible
Out of Scope: backstory of myth
This is saying that Zanotto's study tells us the story of how people came to mistakenly believe that glass flows downward. But there's no support for that. From what we're told, all Zanotto's study does it provide calculations that show that people's belief that glass flows downward is false. He debunks their belief; he doesn't explain the origin story of their belief.
13% picked this
They provide a conceptual basis
Out of Scope: reconciling views
There's nothing in the 2nd and 3rd paragraphs that's talking about reconciling scientific views. Is there anything in the passage about two scientific views that were previously thought to be incompatible (i.e. contradicting each other)?
3% picked this
They suggest that neither of
Out of Scope: two hypotheses
The puzzling phenomenon was "why is the glass in old houses ripply? why do stained glass windows in medieval cathedrals get thicker at the bottom?" There is only one hypothesis being considered at this point in the passage: glass flows downward over time, since its atoms are not in a fixed crystal structure. Zanotto's study definitely suggests that "glass flows downward" is not an adequate explanation for the puzzling phenomenon (we could say even that it's an incredibly wrongheaded explanation). But there isn't any second hypothesis that his research is undermining.
6% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill

LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free