LSAT Question Stem

Each of the following, if true, would lend support to the climatologists' hypothesis EXCEPT: 

Logical Reasoning Question Type

This is a Strengthen question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

The passage presents an argument by climatologists about the cause of Earth's ice ages. They believe that fluctuations in Earth's orbit coincide with ice-age cycles and hypothesize that during these fluctuations, Earth passes through cosmic dust clouds, which enter the atmosphere and dim the Sun, causing an ice age. However, they acknowledge that the cosmic dust clouds would need to be particularly dense to have this effect. The structure of the argument is as follows:

Premise: Earth has undergone a regular sequence of ice ages beginning around 800,000 years ago.

Premise: Calculations show that Earth's orbit has fluctuations that coincide with the ice-age cycles.

Premise: Cosmic dust clouds are common, but they would need to be particularly dense to cause an ice age.

Conclusion: The fluctuations in Earth's orbit cause it to pass through dense cosmic dust clouds, which result in ice ages.

To make this concept more accessible, imagine a car driving through a foggy area. The car represents Earth, and the fog represents cosmic dust clouds. The thicker the fog, the more difficult it is for the car to navigate and maintain its speed, just like the dense cosmic dust clouds affecting Earth's temperature.

An "Evaluate" question for this argument would be: "Are there any other factors that could cause the ice-age cycles, besides the dense cosmic dust clouds?"

The question type for this problem is Strengthen Except, which means we need to find the answer choice that does not support the climatologists' hypothesis.

a) This answer choice supports the hypothesis by stating that Earth did not pass through cosmic dust clouds before the first ice age, implying that the appearance of dust clouds coincided with the beginning of ice ages. This is not the correct answer.

b) This answer choice strengthens the hypothesis by providing a possible source of dense cosmic dust clouds that could have caused the ice ages. This is not the correct answer.

c) This answer choice strengthens the hypothesis by showing that dust in Earth's atmosphere can cause temperature drops, making it more plausible that cosmic dust clouds could cause ice ages. This is not the correct answer.

d) This answer choice does not support the hypothesis, as it talks about cosmic rock entering Earth's atmosphere and raising dust from Earth's surface, not cosmic dust clouds entering the atmosphere. This is the correct answer.

e) This answer choice strengthens the hypothesis by providing evidence that cosmic debris is present in sediment layers corresponding to ice ages, suggesting a connection between cosmic dust clouds and ice ages. This is not the correct answer.