PT 36.S3.Q26 - four universal forces

Nancy123

http://7sage.com/lsat_explanations/lsat-36-section-3-question-26/
Could anyone be kind enough to explain why is the correct answer choice "B". I fail to grasp this question! Here's is how I understand it-

Premise: Fifth force explains the occurrence of less gravitational force being exerted than has be predicted by established theories.
Conclusion: Fifth universal force of mutual repulsion between matter explain the above phenomena.

We are supposed to strengthen this argument but how does B strengthen it?

Thank you!

retaker2014

Hey Nancy, I hope I can help.

But to preface, I think you may have gotten tied up with the stimulus and what the author's point was. Luckily the question stem summarises the argument for us by directly asking us to choose an answer choice that strengthens the argument that the fifth force exists.

This is how I understand the stimulus:

Premise/Context: Before 1986, scientists thought there were only four forces.

Premise: Experiments then (around 1986) started showing that that a fifth force possibly existed.

Premise: The existence of the of this fifth force would explain why previously made experiments turned out the way they did. 'Way' being - different from what the established theories had predicted.

I couldn't find a conclusion written in the stimulus. But what the author is saying/ trying to convince us of, is that the fifth force probably exists. And this is the whole point of this stimulus.

By identifying what the author is trying to argue/convince us of, our job gets so much easier. Because its a most strengthens question, in evaluating each answer choice, ask yourself - is this evidence (answer choice) that best at convincing me of the argument i? (the fifth force exists)

(A) is wrong because 'before the 1970s' is an irrelevant point of comparison, to 'before 1986', because after telling us that there was no sophisticated equipment before the 1970s, we have no idea how that equipment would factor into detecting or understanding the fifth force.

(C) is wrong because this is weakening the argument. It does this by bringing up the opinions of scientists that say the fifth force is just an aspect of gravity. The 'alleged' should raise signals that the fifth force isn't taking seriously here, and the stimulus is all about convincing us that the fifth force does exist.

(D) is wrong because this also weakens the argument. By saying that poor testing sites affected scientists' understanding of gravity, why should we believe that the fifth force indeed exists? The fifth force after all, was supposed to explain why previous predictions were off. If its just the testing site, then understanding that only four forces exist, could be enough.

(E) is wrong because it is irrelevant and out of scope. Other exciting things were happening in theoretical physics at the time the fifth universal force was being postulated? So what? It could have been done by different people working on different ideas.

(B) is the correct answer, but it is a bit convoluted to read at the end of a section! If you flip the double negatives, it reads: '[All] previous scientific results are [compatible] with the notion of a fifth force'. If believing in the fifth force not only explains one small error in prediction but works for all previous experiments, then I'm definitely convinced it exists. And the author's argument is therefore strengthened.


I hope this helps.

Nancy123

And this absolutely helps!!! I couldn't translate the double negatives in answer choice B properly and didn't see how it strengthens!

Thank you so much for the explanation