#15 - Astronomer: In most cases in which a planet has been

[jrc3813]

I have a question concerning how you came to the conclusion that the author doesn't think that a close encounter with a planet always causes a circular orbit. Although he doesn't explicitly say so, one of the central assumptions in LSAT, although not real world, causal relationships I thought was that a cause always leads to the effect. I don't think the world "probably" rules this out. I interpreted it to mean that the author doesn't have enough evidence to conclusively prove this relationship so its only a probability. But it seems fair to assume that the author believes that if the causal relationship exists (that close encounters lead to circular orbits) then a close encounter will always cause a circular orbit. Of course he's not saying that all circular orbits are caused by close encounters, so there are other possible causes. Any help would be appreciated.

[James Finch]

Hi JRC,

The issue here isn't whether the author believes that close encounters with planets always lead to oval orbits (he/she clearly does), but whether that is the only possible cause of oval orbits. One of the ways to strengthen a causal conclusion is to add information making it more likely to be the sole cause of the given effect. Here it's easy to think of possible alternate causes; the scope of the argument in this question only deals with close encounters with planets, but there are many other celestial bodies (stars, comets, asteroids, moons, etc.) that could conceivably force oval orbits as well.

Because the conclusion here is so heavily qualified (some, probably) it it doesn't take much to strengthen it, and correlating any of the planets in oval orbits with nearby planets will serve that purpose, making (C) correct.

Hope this clears things up!

[harvoolio]

I am trying to categorize correct answers within the framework taught in the Logical Reasoning Course. There we learn 5 ways to strengthen an argument (paraphrased): eliminate alternate cause, show cause together with effect, show no cause and no effect, eliminate reverse cause and data good. Would this be a 6th reason or is this an extension (or subset) of the 5th reason that the data is good because the analogy is good or is my understanding of the ways to strengthen an argument incorrect?

Thanks.

[Daniel Stern]

No, this correct answer C would be the 2nd of the ways that you listed to strengthen causal reasoning arguments by showing the cause -- other planets in orbit around that star -- together with the effect -- planets orbiting the star in oval orbits.

After all, if there are no other planets there with whom the oval-orbit planets could have had a "close encounter," then the author's hypothesis that it is these close encounters with other planets that cause the oval orbits would not be supported.

I hope that helps.
Best,
Dan

[harvoolio]

Thanks Daniel.

[sneeze]

hi! so i was just working on this question, and I think i'm almost at full understanding, but there's something i'm still stuck on.

So I originally crossed out C because I thought that it sounded like a necessary assumption rather than a strengthen. [While taking the test, i had a moment of remembering someone say "don't confuse NA with Strengthen" but what i forgot was that I'm pretty sure the idea is actually that necessary assumptions can strengthen, but not all strengthens are necessary assumptions. Is that a fair way to look at it?] [I also thought that a weakness in C was that it didn't mention that, in most cases where planets were found orbiting a distant star, those orbits were ovular. I guess that was incorrect?]

I realize now that if that was my logic, that actually should have led me to C as the right answer. Additionally, now that I've read these other explanations, it makes sense to me that the

But what I actually ended ended up picking was E :/
The reason why was, combined with my [incorrect] NA/S logic as per above, it was attractive that E seemed to be getting rid of an alternate cause, the alternate cause being that there was nothing other/larger than a planet that could have caused the orbit to become ovular. Now that i've read the explanation, I see that causal reasoning is not the weakness here (bc just showing one instance of removing an alt cause is not enough, since the causal reasoning in the stimulus is already so qualified), but instead it is the analogy itself.

But what I'm confused on is that it still seems like E is not completely wrong? Like did I just totally read E incorrectly? I didn't read the "other" as saying that nothing at all existed in that distant star's system that could have affected the orbit (thereby weakening the argument). I read it as saying that there were no other objects larger than a planet that could have been the thing affecting the orbit.


Sorry for the long post. It's so hard to put crazy logic like this into words lol

[Christen Hammock]

Hey Sneeze!

Your understanding of the relationship between strengthen and necessary assumptions is right—explicitly stating that a necessary assumption is true strengthens the conclusion!

This question is really about picking the best answer choice. You're right that (E) is a very attractive choice, but it can't compete with (C)! There is a causal element to this conclusion. The author argues that close encounters with other planets caused oval orbits. Answer Choice (C) answers the obvious question that this conclusion requires us to ask: are there other planets that could cause an oval orbit? Answer Choice (E) doesn't answer this question, and it doesn't conclusively rule out an alternative cause—just makes it less likely. Without Answer Choice (C), Answer Choice (E) could strengthen the conclusion just a little bit, but it can't compete with (C).

[sneeze]

Thanks Christen! That makes a lot of sense, especially the point where you said that E simply makes an alternate cause less likely, rather than conclusively ruling it out. It would have been a fine answer had there not been something as good as C, which helps us more conclusively rule out other issues with the analogy.

Thanks for your time!

[Taraneh]

Hi,

So I read through all the posts here, and I understand the reasoning behind answer C. However, as I read through the question, answer choice A seems very plausible to me. The author states that planets orbiting our sun have an approximately circular orbit whereas comets orbiting our sun have an oval orbit because of their close encounter with planets orbiting our solar system. Since a planet is a larger object than a comet, then it would help explain this observed phenomenon. Could you please explain to me why my reasoning is flawed or not applicable to this particular question? Is it because it doesn't strengthen the conclusion about planets orbiting other planets? Thanks!

[Rachael Wilkenfeld]

Hi Taraneh,

It seems like you are reading something into the argument that isn't there---there's no statement that the oval orbit planets are smaller than the close encounter planet. Answer choice (A) isn't something that would help our argument that planets can change the orbits of other planets. Answer choice (A) answers the question of which planet would be most impacted by a close encounter, but that isn't the question at hand. For this argument, we only want to show that one planet can change the orbit of another. That's what answer choice (C) does by showing that in those solar systems with an oval orbit planet, there was at least one other planet in that solar system that could have had a close encounter.

Hope that helps!