LSAT 157 – Section 2 – Question 07

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PT157 S2 Q07
+LR
Most strongly supported +MSS
Fill in the blank +Fill
A
6%
149
B
8%
147
C
9%
149
D
76%
160
E
2%
146
135
144
154
+Medium 143.482 +SubsectionEasier

The mu mesons generated by cosmic rays just outside Earth’s atmosphere travel to Earth at speeds approaching the speed of light. Mu mesons generated in the laboratory, however, are nearly at rest. Mu mesons generated in the laboratory typically decay in much less time than it takes for a mu meson to travel from just outside Earth’s atmosphere to our detection apparatus on Earth. If mu mesons traveling through the atmosphere at speeds approaching the speed of light typically decay as fast as they do in the laboratory, then we should detect only about one one-hundredth of the number we actually do detect. Apparently, mu mesons moving at speeds near the speed of light _______.

Summary
Let’s learn about mu mesons! These mesons originate just outside Earth’s atmosphere, and shoot to Earth nearly at light speed. There are also some lab-generated mesons, which are at rest, but decay faster than the time it takes for an atmospheric meson to travel to Earth. If atmospheric mesons decayed that fast, we would expect to only pick up about 1/100th as many as we do using equipment on Earth (because they would almost all decay during the journey).

Strongly Supported Conclusions
Based on the actual number of mu mesons detected, we can infer that mesons moving near light speed decay more slowly than mesons generated in the lab at rest.

A
take longer to reach Earth than was supposed
This is anti-supported. The stimulus makes us think that mu mesons might actually decay very fast, so if they took longer to reach Earth, we would be seeing fewer than expected. Instead, we’re seeing more.
B
are quite difficult to detect with available equipment
This is not supported. The stimulus never mentions any difficulty with detecting mesons. Quite the opposite, we’re actually detecting many more than we would expect based on how fast they decay in the lab!
C
are much less numerous than previously thought
This is anti-supported. The stimulus never questions the number of mu mesons, and even talks about how we’re actually seeing way more mesons than lab results would suggest. If anything, there might be more of them, not fewer.
D
decay more slowly than mu mesons almost at rest
This is strongly supported. The stimulus says that we detect way too many mesons based on how fast they decay when at rest, but never questions the original number of mesons. This leaves us the explanation that fast-moving mesons just don’t decay that fast.
E
are probably not generated by cosmic rays
This is anti-supported. The stimulus states as a fact that mu mesons in the atmosphere are generated by cosmic rays, and never contradicts that or gives us a reason to think otherwise.

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