#13 - Astronomers have long thought that the irregularity

[Rosaline]

I was torn between B and D, could some please explain why B is wrong?

[Francis O'Rourke]

Hi Rosaline!

Answer choice (B) does certainly resolve the facts to some extent. If Neptune's orbit is much more irregular than we once thought it was, then we would have to look for something besides Pluto's influence to figure out why Neptune's orbit is what it is. This gives us a possible reason why scientists' earlier ideas were incorrect.

However, the stimulus already gives us an update of what was wrong with our earlier theories. Because of recent observations we now know that Pluto is much smaller than we once thought it was. This is the issue that we must address in this question.

Given that Pluto is much smaller than we once thought it was, how can we explain why Neptune's orbit is so odd? Pluto alone is inadequately small to cause Neptune to veer so far off course according to the stimulus. So, something else must be influencing Neptune to get it into this irregular orbit! This is where answer choice (D) comes in. Although we do not know what is setting Neptune off course, something else beside Pluto must be acting on Neptune.

In this way answer choice (B) is a bit odd. If we learned that Pluto is much smaller than we once thought, that may tell us that our observations of Neptune's irregularity was too large. That is, if Pluto is small, it will have a smaller influence on Neptune. Answer choice (B) seems to think that Pluto's decrease in size would increase the effect that it has on Neptune.

Let us know if this helps!

[lsatfighter]

For this question, I chose C. Is C wrong because it's provides too much specific information which isn't certain based upon the facts in the stimulus? Are the words "undiscovered planet" and "orbit beyond that of Pluto" the reasons why C is wrong? Can you please explain why D is a better answer than C?

[James Finch]

Hi LSAT Fighter,

Putting the correct answer choice immediately before or after the other most attractive wrong answer choice is a very common tactic, designed to confuse test takers under the timed conditions. This is especially true when the correct answer choice comes after the attractive incorrect one, as it tests how wedded one becomes to an answer choice before reading all of them.

Here, as a Most Strongly Supported question, a good Prephrase is crucial. And this question's stimulus yields up a fairly obvious one: there has to be something other than Pluto affecting Neptune's orbit. (C) certainly looks good at first glance, as it gives us another specific object (a planet), but also has a seemingly irrelevant second clause about where that planet would be located. (D) is much more general statement that doesn't zero in on a planet, but does end up fitting more closely with the scope of our Prephrase. How? There are two issues with (C): it tells us about a "planet" being another cause, when in fact it could be one or more of any celestial object(s), such as moons, stars, asteroids or planets. Secondly, a planet located beyond Pluto is less likely to have a noticeable affect on Neptune, as Pluto was (at the time) considered the farthest planet from the sun in our solar system. There are likely innumerable undiscovered planets in other solar systems and galaxies that would be further away from Neptune than Pluto, so the actual scope of what (C) is dealing with is so broad as to be meaningless to the stimulus. So whenever choosing between two answer choices, try to think through all the implications of both before settling on one.

Hope this clears things up!

[Jerrymakehabit]

I have one concern with (D). "is not the sole cause of" could imply that the gravitational pull of Pluto contributes to the Neptune. But the stimulus does not imply that gravitational pull of Pluto even contributes to the Neptune. Can someone please help?

Thanks
Jerry

[Dave Killoran]

I have one concern with (D). "is not the sole cause of" could imply that the gravitational pull of Pluto contributes to the Neptune. But the stimulus does not imply that gravitational pull of Pluto even contributes to the Neptune. Can someone please help?

Thanks
Jerry

Hi Jerry,

It's actually ok if Pluto exerts some pull, because the issue isn't whether it has any pull at all, but whether it exerts enough on its own to pull Neptune into an irregular orbit. As the stimulus says, "this planet is much too small to exert the amount of gravitational pull on Neptune that astronomers once thought it did," which means that by itself Pluto can't cause the irregularity. so, answer choice (D) is here is the best supported statement. Pluto by itself isn't causing the irregularity, but there's nothing stopping it from playing some role.

Does that help out?

[Jerrymakehabit]

I have one concern with (D). "is not the sole cause of" could imply that the gravitational pull of Pluto contributes to the Neptune. But the stimulus does not imply that gravitational pull of Pluto even contributes to the Neptune. Can someone please help?

Thanks
Jerry

Hi Jerry,

It's actually ok if Pluto exerts some pull, because the issue isn't whether it has any pull at all, but whether it exerts enough on its own to pull Neptune into an irregular orbit. As the stimulus says, "this planet is much too small to exert the amount of gravitational pull on Neptune that astronomers once thought it did," which means that by itself Pluto can't cause the irregularity. so, answer choice (D) is here is the best supported statement. Pluto by itself isn't causing the irregularity, but there's nothing stopping it from playing some role.

Does that help out?

Hi Dave,

Thank you for your explanation! I agree every single word in your explanations. "but there's nothing stopping it from playing some role" so it for sure has the possibility playing some roles. However, this is a Must Be True question. The answer should be 100% supported by the stimulus. Though it is not perfect answer, it is still the correct one because:
1. It is the most ideal one among of the answer choices.
2. The stimulus' conclusion is whether it exerts enough on its own to pull. Focus on enough.
Above is my understanding, can you please comment?

Thanks
Jerry

[Dave Killoran]

Hi Jerry,

Thanks for the reply! A few thoughts:

• First, this is a Most Strongly Supported variant within the Must Be True group, so they've allowed for possible variations of strength within the answer choices.
  
  Second, even with the above present, I don't see an issue with the strength of this answer. Here's why:
  
  • Premise: Astronomers' thought it was Pluto causing the orbit irregularity.
    Premise: Pluto is now found to be too small to cause such irregularity.
    
    Conclusion: Something other than Pluto has to be playing a role. Or, as worded in (D), Pluto isn't the only cause.

Does that help?

[Jerrymakehabit]

Hi Jerry,

Thanks for the reply! A few thoughts:

• First, this is a Most Strongly Supported variant within the Must Be True group, so they've allowed for possible variations of strength within the answer choices.
  
  Second, even with the above present, I don't see an issue with the strength of this answer. Here's why:
  
  • Premise: Astronomers' thought it was Pluto causing the orbit irregularity.
    Premise: Pluto is now found to be too small to cause such irregularity.
    
    Conclusion: Something other than Pluto has to be playing a role. Or, as worded in (D), Pluto isn't the only cause.

Does that help?

Hi Dave,

I almost forgot the Most Strongly Supported type On P123 in the LR Bible! I think the explanation of "allowed for possible variations" is more convincing. I do not think "Something other than Pluto has to be playing a role" is the same as "Pluto isn't the only cause". It is more accurate to say "Pluto isn't the only possible cause".

Thanks
Jerry

[Malila Robinson]

Hi Jerry,
Let's see if we can break this down a little more. The argument is setting us up to see that something other than Pluto definitely has to be exerting a gravitational pull because Pluto's mass isn't enough to do it alone. However, that doesn't mean that Pluto isn't causing some amount of gravitational pull. So, the statements you cited do seem to be conveying the same sort of idea.
Hope that helps!!
-Malila