PT4.S4.Q2 - If we are to expand the exploration of our solar system...

randoname123randoname123 Member
edited May 2021 in Logical Reasoning 10 karma

Hey I'm back again with a dumb observation about one of these questions that I think is frustrating.

In this case we're talking about the fuel requirements for a space ship going to Mars (or its moon, Phobos).

The question premise states that the mission is manned, which, if you assume that all manned flights mandate return trips, leads you to the correct answer, E. This is not explicitly stated - it's a required assumption to arrive at this answer choice.

Now lets talk about answer choice D - the SHORTEST distance between Mars and is less than half the distance between Earth and Mars. There is one thing I can logically infer from this choice:

1) There is a non-zero distance between Phobos and Mars, and covering that distance would require fuel.

Now it's possible that the moon has a stationary orbit and is always further away from Earth than Mars, however, if I assume that orbits Mars, then it necessarily will reach a point where it is closer to Earth than Mars is. Or perhaps it does have a stationary orbit, and it is always closer to the Earth than Mars. Doesn't matter. All other considerations being equal, this would mean that reaching Phobos at it's closest point could possibly be closer than Mars at it's closest point.

This inference assumes nothing outside of what is stated in the question - it's an inference based on the fact that there is a non-zero difference between the distance of Earth-Mars and the distance from Earth-Phobos.

The correct answer requires an assumption - that the manned expedition requires a return trip. If we don't make this assumption, this answer resolves the discrepancy in no way.

I realize that answer choice D does not provide objectively solid resolution to the discrepancy in the passage. In fact, the language seems to indicate that it does NOT resolve the discrepancy because it explicitly states that the distance between Phobos and Mars is less than half the distance between Earth and Mars, but the trip to Mars requires twice as much fuel than the trip to Phobos.

My argument is this: We don't know what other considerations affect fuel consumption. We don't know if the manned mission is coming back to Earth. What I do know, is that I can logically infer that a greater distance traveled will lead to greater fuel consumption. The only way this is possible is if answer choice D is true - that there is a non-zero distance between Phobos and Mars.

It seems unlikely that this question would appear on a modern LSAT - it's possible that one-way manned missions to Mars were simply outside of the realm of possibility when this question was written. Today that is not true. In fact, it is very possible that the first manned mission to Mars is one-way, but who knows - it's irrelevant in the context of the LSAT which is what makes this question so infuriating. At the end of the day, I'm not concerned with whether or not I get this question right, but rather whether my reasoning is sound. Overall, my argument is that this is just a bad question, with unsound answer choices - I wouldn't actually argue that they should change the correct answer to D as that would seem to be an unfair question due to the sheer weakness of the inference in resolving the discrepancy in the stimulus.

I guess my question is would this question exist on an LSAT written today, and could this objection get it thrown out? I don't think E can be considered a correct answer unless they were to both eliminate choice D and replace it with an answer choice that in no way speaks to the distance between Phobos and Mars. Maybe I've been doing to much LR practice and I'm just losing my mind.

Admin note: edited title; please use the format of "PT#.S#.Q# - [brief description]"

Comments

  • canihazJDcanihazJD Alum Member Sage ⭐
    edited May 2021 8491 karma

    I don't think E can be considered a correct answer unless they were to both eliminate choice D and replace it with an answer choice that in no way speaks to the distance between Phobos and Mars.

    The strongest answer is applied in isolation from the rest – "Which one of the following..." So you're not adding D's premise to the stimulus then comparing the effect of the other answers.

    But even if you were...

    If D were true (which it is by an enormous amount... 5000 something miles vs 200ish million miles) E still does the most to resolve the fuel requirement differential. It doesn't have to explain it... per the stem it just has to do the most to explain it out of all the answer choices given. That allows for assumptions and unknowns... and weak answers.

    The question is fine, and by all means email LSAC about it... they defend all released official content, and will respond to you very thoroughly. Makes for good material. I actually think it'd be sweet to have an army of people contesting questions until we have an official LSAC explanation for every released question.

  • premxsptppremxsptp Free Trial Member
    edited May 2021 14 karma

    Hey.
    You are correct in saying that (E) requires the presumption of a return trip, but the reason I considered E to be more cogent and explanatory than D is for the following reason:
    You rightly stated that it is possible that Phobos has a stationary orbit. If this were the case, two possibilities arise.

    i)Phobos is closer to Earth than Mars.
    ii) Phobos is farther from Earth than Mars.

    If it does not however, we encounter more problems:
    While it is true that if Phobos orbits around Mars, it must reach a point wherein it is closer to Earth than to Mars, this requires the additional presumption that we would launch in accordance with synchrony with this orbit.(ie that we would launch the flight when Phobos is closer to the Earth than Mars.)

    Additionally, even we were to presume this, could this fuel be less than half of what would be required to go to Mars? This would require us to know the size of the orbit and how far away from Mars does Phobos orbit. It is unlikely that fuel expenditure would be less than half even in a practical scenario.

    For the reasons above, I found (E) to be a much safer bet as it accounts for the amount of fuel used that matches the stimulus at hand. (To put it simply, it requires only one assumption, that there is a return trip.)
    And considering the fact that it is a manned expedition, I do not think that this assumption is unreasonable.

    Looking forward to hearing from you!
    Prem.

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