Q26 - Before 1986 physicists believed they

[netkorea06]

Can anyone explain why the answer is B for me? Thanks.

[ManhattanPrepLSAT1]

The great thing about the LSAT is that they are consistent, if nothing else!

Let's look at this argument from an abstract perspective. There is an observed phenomenon (the gravitational force actually exerted is less than that predicted by theory). The conclusion of the argument is an explanation for why the observed phenomenon occurred (the existence of a fifth universal force that exhibits mutual repulsion).

This is a really common construct. Let's put into other words.

Say a poll shows that 80% of shoppers prefer Brand X when they purchase tomato sauce. It might be concluded from this that Brand X tastes better than any other brand of tomato sauce. That would be one possible explanation of the observed findings. Of course, it also could be that people prefer Brand X because of it's ridiculously low price!

Offering competing alternative explanations for an observed phenomenon is a regular approach to undermining an argument that fails to consider an alternative explanation.

When strengthening an argument, think of yourself as playing defense. You want to protect the argument from something that may undermine it. So, in the above hypothetical argument one could strengthen it by saying that Brand X has a very high price, thus taking away something that could potentially weaken the argument.

Let's do the same thing in this argument. If traditional theory contradicted the existence of a fifth universal force, then removing that concern would strengthen the argument. Thus, (B) is correct. This may not be an answer choice you could prephrase, but it is one that you should see as protecting the argument from a potential weakness.

(A) is irrelevant. We don't care why it took them so long to discover the difference between predicted and gravitational forces.
(B) is correct for the reasons above.
(C) undermines the argument by suggesting that the phenomenon is an aspect of gravity rather than some new universal force.
(D) undermines the argument by suggesting that there might not actually be any discrepancy between predicted and actual gravity that needs explanation.
(E) undermines the argument by saying, "hey look, there could be other things that explain the difference between predicted and actual gravitational forces."

Let me know if you need further help working through this one!

[Mab6q]

The reason I saw A as being a good answer is that it gives an explanation for why the original physicists did not add the fifth force, because they did not have the equipment. As such, if they had the equipment, they would have seen the smaller measurements of gravitational attraction and would have had 5 forces.

[WaltGrace1983]

The reason I saw A as being a good answer is that it gives an explanation for why the original physicists did not add the fifth force, because they did not have the equipment. As such, if they had the equipment, they would have seen the smaller measurements of gravitational attraction and would have had 5 forces.

But remember that people thought that there were four universal forces until at least 1986. (A) only talks about what was available before the 1970s. At the very least, there would still be 7 years (1980-1986) in which they would have the equipment to discover the fifth universal force.