LSAT 146 | Section 2 | Logical Reasoning: Q18

QUESTION TEXT: The consensus among astronomers, based upon observations…

QUESTION TYPE: Role in Argument

CONCLUSION: It’s possible that some pulsars are filled with quarks and not neutrons.

REASONING: It’s possible that some pulsars have a core of positively charged quarks. This attracts a layer of negatively charged particles on top, and this allows a final layer of neutrons on top.

This interior would be consistent with the observed properties that pulsars are 10 km diameter spinning balls with neutrons visible on the outside.

ANALYSIS: Often, on role in argument questions, you can skim for structural words and figure out the role without even understanding the argument. For fun, I tried that here.

Nope. This is a hard, dense argument and you actually have to understand it to answer the question. Looks like LSAC is upping the difficulty of this question type.

Basically, this argument lays out two possibilities:

1. Consensus view: Pulsars are spinning balls of neutrons, 10 km in diameter, as heavy as the sun.
2. Alternate possibility: Pulsars are actually filled with quarks. These attract negatively charged particles on top, and neutrons are the crust. [Mass isn’t specified]

Here’s a simple diagram of possibility two. Imagine the brackets ( ) divide layers:

(Neutrons(neg parts(quarks)neg parts)neutrons)

Quarks are in the middle, negative particles surround the quarks, and neutrons are on the outside. So, why are both possibilities consistent with the evidence? Because we can only see the outside of pulsars! We can’t see what’s inside.

The key phrase is “their observed properties are also consistent”. This is a fancy way to say “What we can see on the outside is consistent with”. The LSAT loves using complicated language!

The fact we’re trying to explain is that “quark cores have a positive charge”. The role of that is to say that this positive charge attracts a negative layer, which allows neutrons to be on top. (Presumably, neutrons can’t be directly on top of positive quarks)

You don’t need to know how neutrons and quarks works to answer the argument, but you do need to know the relationship of one thing to another. So if I say “Quozzles attract boozles which allow kandars to sit comfortably”, then all you need to be able to figure out is that boozles are what allow kandars to sit comfortably. You don’t need to know the meaning of the words or the reason for this relationship.

___________

1. CORRECT. See the end of the analysis above. The quark filled core attracts negatively charged particles, and the argument says this layer of particles would allow neutrons to form the outer layer of pulsars.
2. The opposite of this answer is true. The fact that quarks have a positive charge is part of the reason for the claim that some pulsars have a positive charge.
3. This might have been right if it had said “it helps explain why astronomers might not realize that some pulsars have a core of quarks”. But, that’s not what the answer said, and there’s no evidence in the argument that some pulsars are difficult to recognize. The dispute is only about what’s inside pulsars, it’s not about what’s visible on the outside.
4. The sentence in question is not a new finding! Stating that quarks would have a positive charge is basic physics (for an astronomer). It only becomes a challenge to received wisdom when you combine this fact about quarks with other facts, leading to the deduction that it would be possible to have a pulsar filled with such a quark core.
    
   So, the overall argument challenges the consensus, but the particular piece of evidence quoted in the question stem doesn’t challenge anything on its own.
5. This answer was never challenged in the argument. The author didn’t say quarks had a different mass from neutrons. They only said quarks have a different charge. It’s possible that a quark filled pulsar would weigh the same as a neutron filled one.

Quick Jump PT Section Que