PT62.S2.Q20 - earlier estimates of the distances

Sarah889Sarah889 Alum Member
edited February 2017 in Logical Reasoning 877 karma

Hi All,

Any help with this question would be appreciated. This is a resolve the discrepancy question (arguably a strengthen or PSA).

I'm going to present the stimulus below, accompanied by my train of thought, so someone can point out to me where I am erring in my approach to the stimulus. I am definitely misinterpreting/overthinking something.

P1: Earlier estimates of the distances of certain stars from Earth indicate that these stars are about 1 billion years older than the universe, which is impossible.

P2: My estimates of the distances indicate that these starts are much farther away than previously thought.

Okay so, at this point the discrepancy is introducing itself. Early estimates indicate that the stars are too old, yet the astronomer is now asserting that they are farther/not too old. What changed between early estimates and the astronomer's estimate? My natural assumption is that the farther the star is, the less bright it is. It seems as though the astronomer is about to call that assumption out.

P3: The farther away the stars are, the greater their intrinsic brightness must be, given their appearance to us on Earth.

Okay so this must have been the change. The early estimates probably weren't educated with this new fact, so they were off in their distance estimates.

C: So the new estimates of these stars' distances from Earth help resolve the earlier conflict between the ages of these stars and the age of the universe.

Okay so the stimulus draws a correlation between brightness and distance, and then infers from that that the age discrepancy is therefore resolved. In order for this to be the case, we need an answer choice that creates a correlation between age and distance.

I was able to select C because it was the only answer choice that directly had to do with the stars' age, but I am confused because C draws a correlation between brightness and age. We don't need that correlation...we need a correlation between age and distance. I have learned from much LR practice that if there is an established correlation between A and B, as well as a correlation between B and C, that does not necessarily entail a correlation between A and C. Likewise, we have a correlation between brightness and distance, C gives us a correlation between brightness and age, so how then can we infer the needed correlation between distance and age?

Thanks in advance.
https://7sage.com/lsat_explanations/lsat-62-section-2-question-20/

Comments

  • GrecoRomanGrecoRoman Alum Member
    edited February 2017 140 karma

    It seems pseudo sufficient assumption to me and I think it can be mapped like this:
    stars are farther > farther stars are brighter

    therefore, stars are younger

    So the gap you need to fill in the argument is: if brighter then younger, as answer C says. Not sure if this is the correct way, but it's how I came up with C as the right choice.

  • JustDoItJustDoIt Alum Member ⭐
    3112 karma

    I know this gets really sciencey but think about this in terms of your knowledge about the universe.

    Current estimates about the distances stars are away from us reveal they are 1 billion years older than the universe itself. But they are even further away than we thought, according to this person's estimates. This is really weird because this would seem as though the stars are even older than 1 billion years. This is the discrepancy! How is this even possible? Well, the astronomer says, the farther they are away, the brighter they are. Stop. What does this have to do with anything? It is a completely irrelevant. Therefore, we resolved the discrepancy. I mean did they though? It honestly seems as though they are missing a premise. That is why this is kind of a SA/PSA/Resolve. They didn't resolve anything.

    Now let's get back to that seemingly irrelevant statement. Don't think of it as a correlation. It is a link; we have one idea and we are missing the other. We have to link up the idea of intrinsic brightness to something. It really just comes out of nowhere. (This is good by the way because the idea of intrinsic brightness gives us something to work with.) What do we have to link it up to? The only thing that we can link it up to is age in order to answer this question. Age is the main issue at hand it would seem as though the further the star, the older it is. Even if we don't bring our knowledge of the universe in, we can't just assume the age either way. The discrepancy is not resolved unless we can link this idea of intrinsic brightness up to age. Which direction of age though, older or younger? It has to be younger because if it is older, that just confounds the situation further.

    So linking brightness to younger age resolves our initial presupposition that greater distance = older age. Greater distance = greater brightness (this is explicitly stated) = younger age (this is what we need).

    Hope this helps!

  • Sarah889Sarah889 Alum Member
    edited February 2017 877 karma

    @"work all week" and @JustDoIt

    Thank you both! @JustDoIt , I completely understand what you are saying now. I posted this question on Manhattan Prep and someone (ohthatpatrick) had responded with a very enlightening perspective on this question. It is similar to yours. I've pasted it below for anyone who might struggle with this question in the future:

    Written by ohthatpatrick from the Manhattan Prep LSAT forum:

    Admin note: Removed. Please do not copy text from other sites, instead link to them. This will avoid copyright issues.

  • JustDoItJustDoIt Alum Member ⭐
    3112 karma

    Glad to help! Manhattan is a great source for questions, since most of them have already been answered by someone who works there already. I use their RC explanations frequently when I get stumped.

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