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So, I just finished PT 44, and was doing great up until the fourth section. Then, I bombed it. I was embarrassed to be in the same room with myself...

I looked back over my mistakes and for the most part see what I did wrong, but I cannot for the life of me figure out question seventeen. Did anyone else have trouble with this one? Can anyone else explain the why the correct answer is "D"?

Sure. First lets break down the argument
Climatologists think they know why ice-ages started BEGINNING 800k years ago. Our orbit with the sun lines up with the ice ages, and they think cosmic dust is to blame because it blocks the sun by entering our atmosphere as we orbit through these clouds. However, there are a bunch of these dust clouds, and only the dense ones would likely cause an ice age.

Now, we are looking at a strengthen EXCEPT question. The two possibilities for a correct answer are 1) actually weakens the argument, or 2) does nothing to the argument, is outside the scope/irrelevant.

a) Because they specified that the ice ages started 800k years ago, us passing through clouds earlier then that would be problematic, so saying we did not pass through any dust clouds before the first ice age strengthens the hypothesis.

b) This accounts for the creation of the dust they believe is causing the ice-ages, and it coincides with the 800k timeline, this too lends support to the hypothesis.

c) This leaves the orbital stuff behind, but explains that even dust created by volcanoes on earth tends to drop the temperature, which supports the hypothesis that large dense orbital clouds could be the cause of the ice age.

d) "Large bits of cosmic rock" is outside of the scope as this wouldn't do anything, and the fact that the cosmic rock raises dust in itself doesn't strengthen the theory. If this answer choice read "raises dust on earth and causes cooling" similar to the volcano answer, we would have a problem; but it doesn't. Large rocks are irrelevant in themselves, and their causing a large amount of dust on earth doesn't come in to play because it the argument doesn't talk about earth dust...so without specifying the results of this earth dust, it doesn't strengthen the story at all.

e) This strengthens the argument substantially... They did a study and found hard evidence supporting the correlation between cosmic debris and the ice ages.

Yeah, I remember this one. Here we go.

PT 44, S4, Q17: StrenthenX

Core: When fluctuations occur, Earth moves through cosmic dust, and that dims the sun, that causes the ice ages.

Why?

(p1) Correlation between Earth's orbit fluctuations and ice ages

Point Conceded: Clouds of cosmic dust has to be really thick to achieve this effect

Ok, well there's a few ways the wrong answers could strenthen. I'm thinking that one will counter the point conceeded, and three will strengthen the alleged casual relationship. By definition, we know that the right answer will not strengthen the causal relation in the core.

A: Strengthens the background information by eliminating the possibility the cause happened but the effect did not happen. Eliminate

B: Strengthens (p1) and the background information by showing that when the causes happened, 800k years ago, the effect happened. Eliminate

C: Strengthens by showing that an increase in cosmic dust results in decreased temperature. Eliminate

D: This literally does absolutely nothing to the argument. The argument is talking about cosmic dust, which seems to be dust that leaves our atmosphere. This answer is talking about dust, that for all we know, leaves Earth's surface but does not go into the atmosphere.

E: Strengthens the correlation in the stimulus.

I was beat to the explanation.

Support Except. Oy.

Let's look at the stimulus.

The earth has had a regular cycle of ice ages, starting 800,000 years ago. And climatologists think they know why! The earth goes around the sun, at times causing some weird cosmic dust to be put into the atmosphere. It dims the sun and makes it colder. Got it. Oh-- and a little qualification-- for this to put us in an ice age, we need a dense cloud of dust.

The argument is possible, definitely not great. Let's see what supports the argument.

A) This definitely supports it! Establishes that the phenomenon started 800,000 years ago. Eliminate.

B) Another supporter. Something happened 800,000 years ago, causing this phenomenon to happen. Eliminate.

C) Hmm. While this doesn't talk about cosmic dust, it talks about volcanic dust having the same effect. It supports the argument because volcanic dust does the same thing, but it's a bit weird because it DOES establish an alternate cause. Still, we don't know how often or regular volcanoes occur. I think this should be eliminated, but I'll keep it just in case.

D) Cosmic ROCK periodically enters the atmosphere, causing dust from the surface to be raised. But we don't know what surface dust does to our temperature. Furthermore, the argument doesn't deal with cosmic rock--- rather it deals with cosmic DUST having the effect. Cosmic rock is irrelevant here, unless it also brings cosmic dust with it. This does not support the contention that cosmic dust causes ice ages. We know nothing about cosmic rock or its relation to the dust.

E) This is a definite supporter. We found the dust corresponding with the ice ages in the sediment! This would definitely help prove the scientists' argument.

So D is the outlier. C is the next best answer, but to me it can be eliminated because there it DOES establish what dust does-- and not strong enough to establish an alternate cause.

I came late to the party. Haha, you guys are awesome.

Thanks everyone. When I did the problem, I narrowed it down to either C or D. I honestly thought that neither of them helped the argument, but I can see now that C supports at least an aspect of it—that dust can cause cooling. D just does absolutely nothing.

This helps a lot. Much appreciated.