Logical ReasoningDifficulty: Medium

PT134 S3 Q13 Explanation

Astronomers have found new

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsParadox

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Stimulus

Astronomers have found new evidence that the number of galaxies in the universe is not 10 billion, as previously believed, but 50 billion. This discovery will have an important effect on theories about how galaxies are formed. But even though astronomers now believe of the universe's total mass remain virtually unchanged.

What this question is testing

Paradox

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
13.

Which one of the following, if true, does most to explain why the estimates

Answer choices

  1. Correct78% picked this

    The mass of galaxies is thought to make up only a tiny percentage of the

    Why this is right

    This is another way to increase the mass contained within galaxies and yet not have it significantly increase the estimate of the mass of the universe. Simply put, multiplying the number of galaxies would have little impact on the mass of the universe if galaxies were a relatively small percentage of the total mass of the universe.

    Skill tested: Paradox · how this choice captures the argument's function is the move to repeat next time.

  2. Too Weak3% picked this

    The overwhelming majority of galaxies are so far from Earth that their mass can be

    That the estimates are rough approximations does not explain why multiplying the number of galaxies by a factor of five did not significantly increase the estimate of the mass of the universe.

  3. Half Scope3% picked this

    The number of galaxies that astronomers believe exist tends to grow as the instruments used to detect

    This may explain why the estimate of the number of galaxies increased, but it does not explain why the estimate of the mass of the universe did not also significantly increase.

  4. Reversal11% picked this

    Theories about how galaxies are formed are rarely affected by estimates of the

    This reverses the causal relationship. It should be that estimates of the universe’s total mass are rarely affected by theories about how galaxies are formed. Even this, however, does not explain why it is not affected.

  5. Applies to Both5% picked this

    There is no consensus among astronomers on the proper procedures for estimating the

    This would apply both before the estimated number of galaxies was increased and after, so it cannot explain the difference.

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