Q25 - In our solar system

[alinanny]

Why is E wrong?
If the scientist or the author is using the 9:1 ratio to compare other solar systems to ours wouldn't that be the flaw in his argument?
I can see how there can be 9 planets in each solar system and all of them have the ability to sustain life which makes B a better choice becuae the author assumes that the other solar systems are similar in numbers and conditions, etc.
I would just like a better explanation to get rid of E happily.

[theaether]

The argument is not assuming that every other planetary system is going to require having 9 planets. You could have 1 system with 4 planets, and another system with 5 planets, and still have one planet in one of those systems being likely to support life. The ratio still holds.

If I state that there is 1 criminal in a city of 300, and I make the conclusion that given the many cities out there, there must be many criminals based on this 300:1 ratio, must I assume that most other cities are exactly size 300? No, I don't. We can have NYC with 10 million people, and a boatload of criminals, or we could have some small town of 500 with 1 or 2 criminals, etc.

However, I am assuming, as (B) states, that the other cities are similar in condition to my city of 300. What if every other city is a perfect little utopia, and my 300:1 ratio would never hold there? Then my conclusion that there must be a lot of criminals is false.

[bbirdwell]

Nice!

That's a good explanation. Using the ratio 1:9 does not mean that every planetary system has only 9. Nor, as (E) states, does it mean that "most" of them have 9 planets.

The author's just saying that we have 1:9 here, and there's a zillion systems out there, and 1:9 times a zillion is a lot.

[lhermary]

Why is C wrong?

[timmydoeslsat]

Why is C wrong?

It is because the author does not need this assumption.

Even if the conditions necessary for life are not well understood, this author is using the facts that 1:9 in this system have life + so many other systems out there ---> Concludes that there must be an extremely large number of planets fit to sustain life.

This answer choice is not addressing the links this author is using to reach his conclusion.

Premises---------------------------------------Conclusion

1:9 Ratio has life in solar system ----------------Therefore, #
------------------------------------------------ of planets fit
Large number of planetary systems--------------- to sustain life
-------------------------------------------------is extrem. big

[bbirdwell]

Exactly. We don't necessarily need to "understand them well" to simply be able to identify them.

Negating this choice does nothing to affect the logic of the argument itself: "We have NO IDEA how the conditions for life work." So what? This argument is based on math, not understanding life.

[WaltGrace1983]

To go off of that, I find that these "X is well understood" answer choices very sketchy. We are talking about sheer observation here. We observe that 1/9 planets in our solar system is fit to sustain life. We may not know how this is. Yet this doesn't matter!

[ohthatpatrick]

Here's a complete explanation for posterity:

Flaw (Necessary Assumption)

Prem 1
1 out of 9 planets in our solar system can sustain life

Prem 2
There are TONS of planetary systems in the universe

Conc
There must be tons of planets fit to sustain life

The question stem says "argument is questionable", which tells us it's a Flaw question. But whenever an answer choice on Flaw questions begins with "takes for granted" or "presumes without providing justification", the answer choice is just offering us a Necessary Assumption.

So since this question is really asking, "Which of these answer choices does the author presume without providing justification?", it's really a Necessary Assumption question.

I bring that up because on Necessary Assumption questions, it's super helpful to be wary of extreme language. (You should have the same "red flag" when you're doing Flaw and an answer choice begins with 'takes for granted' or 'presumes').

(A) This is an extreme idea. ALL Earthlike planets will have life? Notice that the argument is only about "fit to sustain life", not about actually having life develop.

(B) This is something the author was assuming, insofar as the author wants to use OUR solar system's 1:9 ratio and apply it to other planetary systems. If we negate this answer, "our solar system is NOT similar to many others", it weakens the argument by making it inappropriate for the author to apply something he knows about OUR solar system to OTHER planetary systems.

(C) "Well understood" is a loaded phrase that is almost universally wrong on Necessary Assumption. When you negate "well understood", you get "NOT well understood", but that still leaves room for "pretty well understood", which is gonna be enough to make an argument. Plus, the author's argument has nothing to do with naming/explaining/understanding the conditions for life. As the previous poster mentioned, the author is merely observing that Earth is capable of sustaining life and applying a mathematical ratio to unknown planetary systems.

(D) This does not sound a lot like the author. The author's argument is based off thinking that other planetary systems would have our same ratio of life sustaining planets ... that life would be possible elsewhere for similar reasons / in similar proportions to how it's possible in our solar system. This answer is WEAKENING the analogy between our solar system and other planetary systems, so the author wouldn't be assuming something that weakens his central analogy.

(E) "Most" is a loaded term that is wrong 98% of the time you see it in Necessary Assumption. The author WAS indeed applying the 1:9 ratio to other planetary systems, but a ratio is a simplified fraction, not a raw number. Applying a ratio to other planetary systems would mean that if a system had 18 planets, than 2 of them would be life sustaining. If a system had 27 planets, than 3 of them would be life sustaining. The author only assumed the RATIO would be similar elsewhere, not that the ACTUAL NUMBER of planets would be the same.