#25 - Must Be True, Purpose

[Administrator]

Complete Question Explanation
(See the complete passage discussion here: lsat/viewtopic.php?t=14311)

The correct answer choice is (A)

This Specific Reference/Purpose question asks us to identify what the author means by “the relevant
evidence” in line 62. Such questions almost always require a more thorough understanding of the
context in which the quoted reference appears, and their answers should generally be prephrased:
The “relevant evidence” refers primarily to the results of experiments that corroborated the existence
of nuclear fission without being recognized as such at that time (i.e. “lacking mainly the right
conceptual link,” lines 63-64).

Answer choice (A): This is the correct answer choice. The evidence relevant to the discovery of
nuclear fission was gathered between 1934, when Fermi first bombarded uranium with neutrons,
and 1939, when Meitner provided the crucial theoretical connection (lines 7-11). This evidence had
been ignored because scientists lacked the theoretical connections necessary to appreciate its full
significance.

Answer choice (B): Although the results of Meitner’s experiments were relevant to the discovery of
nuclear fission, they cannot be described as “lacking the right conceptual link.” Rather, they were
instrumental in establishing that link.

Answer choice (C): As with answer choice (B), the evidence obtained by Hahn was not only
“relevant” to the realization that atoms were being split, but it also paved the way for this realization.
The author’s phrase, by contrast, refers to the kind of evidence scientists obtained without
recognizing what they were witnessing (“lacking mainly the right conceptual link”).

Answer choice (D): As with answer choices (B) and (C), the evidence described here—though
technically “relevant”—does not match the intended meaning of the phrase in line 62. The phrase
more appropriately refers to the results of experiments that corroborated the existence of nuclear
fission without being recognized as such, i.e. results “lacking mainly the right conceptual link” (lines
63-64). Hahn’s results, by contrast, helped Meitner recognize that atoms were being split.

Answer choice (E): The fact that the radioactive products of neutron bombardment of uranium
went unidentified for so long hindered Fermi’s understanding of nuclear fission, but was not itself
evidence relevant to the discovery of nuclear fission. It was the radioactive products themselves that
would have been the relevant evidence, not Fermi’s failure to identify them as such.

[Henry Z]

I wonder if (B) and (C) can be eliminated because they are included in (A), as Hahn's experiment was between 1934 and 1939. I just felt the explanations given above are ambiguous, as Hahn did lack the conceptual link when he had the results, and when Meitner made the link, the results had indeed been present for some time.

[Robert Carroll]

Henry Z,

Ultimately, the "relevant evidence" was around for a long time before the conceptual link was provided. Thus, it should be relatively "old" evidence that was around for a while, which is why the time frame of answer choice (A), going back farther than the others, is to its credit.

Robert Carroll

[DaveWave24]

After reviewing this I still see D as the correct answer. When I read this question I assumed that old scientific evidence would refer to something that has been around for more than a few years, which is why I eliminated answer A. The neutron bombardment experiments feel like a relatively recent thing. Answer choice D is knowledge that we could believe has been available for a long time. The passage states that Hahn "noted that together the number of protons and neutrons in the nuclei of barium and technetium, the accompanying product of the experiment, added up to the number of such particles that compose a uranium nucleus." This does not imply that Hahn was the one who discovered barium, technetium, or the number of protons and neutrons in each. It is possible that Hahn was the first one to realize the connection between those numbers with the numbers present in uranium, but that does not mean that the evidence of the connection wasn't present before Hahn. We know that Hahn was aware of the numbers and relayed it to Meitner, but it is absolutely consistent with the text to believe that the knowledge of the number of protons and neutrons had been around for a long time.

When I first read the last sentence of the text I didn't think it was referring to any specific piece of data, but rather the collection of all scientific knowledge available. There was data to suggest that it should be possible to break atoms apart, and there was the data I discussed about the number of protons and neutrons, as well as the experiments referred to in answer choice A. To me it feels arbitrary to identify answer A as the relevant evidence. The passage reads as though answer choice D is the thing that triggers Meitner's realization. The phrase "been present for some time" seems to point away from answer choice A because it is restricted to a recent time frame, while the level of scientific knowledge expected of the LSAT test taker leaves open the possibility that the knowledge referenced in answer choice D has been around for a long time. Just knowing the numbers present in barium and technetium vs realizing that the fact that they match up with uranium and that this could suggest the splitting of nuclei is occurring feels like the kind of conceptual link that we're looking for.