PrepTest 126, Section 4, Question 23
Physics professor: Some scientists claim that superheated plasma(68 more words not shown)
The physics professor's conclusion follows(9 more words not shown)
- ASuperheated plasma in(14 more words not shown)
- BThe phenomena observed(13 more words not shown)
- CBall lightning can(8 more words not shown)
- DSuperheating of gaslike(7 more words not shown)
- EAll types of(6 more words not shown)
Reading the argument
The professor's observations rule out this explanation for the lightning the professor saw. Why should they rule it out for every instance of ball lightning?
We don't need to understand the physics of superheated plasma to follow the test. If that plasma caused the lightning, the passage says we'd see intense light and upward movement. Instead, the observed lightning was dim and moved horizontally. Given that rule, those observations don't fit the proposed cause.
But perhaps there are different kinds of cases. Imagine the professor saw mild, dim lightning produced by another cause, while some brighter, rising lightning elsewhere involved the plasma. That's a possibility, not a scientific claim. It shows the gap between “not in my observations” and “never.”
What we’re looking for
The question asks us to make the conclusion follow. I'd look for a rule that lets the observed cases settle all the cases—especially a statement that all types have the same cause. Then the professor couldn't have encountered a different causal story from the one applying elsewhere.
Working the answers
- A
Other kinds of lightning aren't the issue. The professor concludes that the plasma is never a factor in ball lightning. Whether it causes some different kind of lightning doesn't establish that universal claim about this kind.
- B
Another observer could confirm exactly what the professor saw, and we'd still have the same problem. Those particular cases didn't fit the plasma explanation. More witnesses to them don't establish that every other case has the same cause.
- C
This opens the possibility we want to close. If ball lightning can result from different factors, the professor could have observed cases with one cause while other cases involved plasma. C doesn't prove that plasma actually causes any cases, but it leaves room for the distinction that defeats the professor's generalization. We're trying to make the conclusion follow, so this goes in the wrong direction.
- D
We already have the premise that the proposed plasma explanation would produce bright light. Adding another statement about brightness doesn't connect the observed cases to every instance of ball lightning. The remaining gap is the scope of the conclusion, not what light we would expect from this proposed cause.
- ECorrect
If all types have the same cause, the observed cases can't be explained by one cause while other types have a different one. The observations rule out the specified plasma in these cases; the shared-cause rule carries that result across all types. That supplies the missing basis for “never.”
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