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Technical Passage_______Veritas

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conquistador Master | Next Rank: 500 Posts
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Technical Passage_______Veritas

Post Thu Sep 10, 2015 2:56 am
While popular science tends to favor extra galactic astronomical research that emphasizes current challenges to physics, such as the existence of dark matter, dark energy, and Cosmic inflation, significant research continues to take place in the field of planetary astronomy on the formation of our own solar system. In early attempts to explain this phenomenon, astronomers believed in the encounter, or “rogue star,” hypothesis, which suggests that matter was tidally stripped away from our sun as a larger star passed within a gravitationally significant distance some billions of years ago. The encounter hypothesis postulates that after being stripped away, the matter cooled as it spun farther from the sun, and formed planets with their own centers of gravity. This hypothesis conveniently accounts for the fact that all planets in the solar system revolve in the same direction around the sun; it is also consistent with the denser planets remaining closer to the sun, and the more gaseous planets traveling further away.

The encounter hypothesis explained the phenomenon sufficiently enough that it allowed scientists to focus on more immediately rewarding topics in physics and astronomy for most of the first half of the 20th century. Closer investigation, however, found several significant problems with the encounter hypothesis, most notably that the hot gas pulled from the sun would not condense to form dense planets, but rather would expand in the absence of a central, gravitational force. Furthermore, the statistical unlikelihood of a star passing in the (astronomically speaking) short time of the sun’s existence required scientists to abandon the encounter hypothesis in search of a new explanation. Soon after, astronomers formed a second theory, the nebular hypothesis, which submits that the solar system began as a large cloud of gas containing the matter that would form the sun and its orbiting planets. The nebular hypothesis suggests that when the cloud reached a critical mass, it collapsed under its own gravity. The resulting angular momentum would have morphed the nebula into a protoplanetary disc, with a dense center that generated intense heat and pressure, and a cooler, thinner mass
that revolved around it. The central mass would have continued to build in density and heat, forming the sun, while the centrifugal force around the disc’s edge kept smaller masses from being pulled in to the sun; those masses, upon cooling, would break off to become planets held in orbit by the competing gravitational force of the sun and centrifugal force of their orbital inertia.

The nebular hypothesis, however well it explained the sun’s formation, remained problematic in its ability to account for the formation of several planets with differing physical and chemical properties. Encouraged by their advance toward a provable hypothesis for the solar system, scientists have recently come to adopt a third
hypothesis, the protoplanet hypothesis. This currently accepted theory holds that the gaseous cloud that would form the solar system was composed of particles so cold that even the heat of the forming sun could not significantly impact the temperature of the outer reaches of the cloud. Gas in the inner region, within what scientists refer to as the frost line, was quickly either burned or dispersed, leaving a small amount of metallic matter, such as nickel and iron, to form the inner planets. Such matter would need to have an extremely high melting point to avoid becoming liquefied, ensuring that Mercury, Venus, Earth, and Mars would remain small and dense. Outside the frost line, however, gas was kept cool enough to remain in solid, icy states. Over time, planets such as Jupiter and Saturn would amass large quantities of frozen gas, enough to grow to hundreds of times the size of the Earth.

3) Which of the following discoveries, if true, would best support the protoplanet hypothesis that the temperature difference is responsible for the different sizes of planets on either side of the frost line?
(A) The core of Saturn and the core of Mercury are found to be 98% composed of the same materials.
(B) The cores of Saturn and Jupiter are found to each contain at least five chemical elements not found in the other.
(C) The core of the Earth and the core of Mars are found to be comprised of the same mix of chemical elements.
(D) A nearby star is found to be orbited by six planets, and the size of each is inversely proportional to its distance from the star.
(E) The Earth’s moon is found to have a vastly different composition from that of the moons of Jupiter.
OA:C

Can someone explain why option B is wrong for 3rd question.
I filtered the options to B and C but selected B thinking that both Jupiter and Saturn must have some extra chemical elements and that is the reason that author mentioned that
Quote:
Over time, planets such as Jupiter and Saturn would amass large quantities of frozen gas, enough to grow to hundreds of times the size of the Earth.

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Marty Murray Legendary Member
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Post Thu Sep 10, 2015 12:26 pm
Quote:
Can someone explain why option B is wrong for 3rd question.
I filtered the options to B and C but selected B thinking that both Jupiter and Saturn must have some extra chemical elements and that is the reason that author mentioned that

Quote:
Over time, planets such as Jupiter and Saturn would amass large quantities of frozen gas, enough to grow to hundreds of times the size of the Earth.
Yes, Jupiter and Saturn could well have some elements that the inner planets, such as Earth, do not have, but B says that Jupiter and Saturn each contain "chemical elements not found in the other."

The protoplanet hypothesis involves the idea that the inner planets are different from the outer planets. Choice B is not relevant to the hypothesis because it discusses the outer planets' being different not from the inner planets, but from each other.

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Post Thu Sep 10, 2015 1:16 pm
Marty Murray wrote:
Quote:
Can someone explain why option B is wrong for 3rd question.
I filtered the options to B and C but selected B thinking that both Jupiter and Saturn must have some extra chemical elements and that is the reason that author mentioned that

Quote:
Over time, planets such as Jupiter and Saturn would amass large quantities of frozen gas, enough to grow to hundreds of times the size of the Earth.
Yes, Jupiter and Saturn could well have some elements that the inner planets, such as Earth, do not have, but B says that Jupiter and Saturn each contain "chemical elements not found in the other."

The protoplanet hypothesis involves the idea that the inner planets are different from the outer planets. Choice B is not relevant to the hypothesis because it discusses the outer planets' being different not from the inner planets, but from each other.
Thanks Marty!
Surprisingly I missed the each part in the option and did not observe it until u mentioned it. Embarassed

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Post Thu Sep 10, 2015 4:51 pm
Haaaaaaaa

Seeing details is SO key for getting right answers to RC questions, and to GMAT questions in general.

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mindful Senior | Next Rank: 100 Posts Default Avatar
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Post Fri Sep 11, 2015 4:16 am
Great question. Took me full four minutes to read the question. (Is this normal? Probably not!)

I see what the answer is. But it also only refers to one kind of planet, the inner planets. It does not really explicitly make a distinction from the outer planets. Do we just go by inference or assume an implication that if the inner planets have something in common, then the likelihood of their being different from outer planets is higher?

Second, Marty's explanation about the inner and outer was spot on! It really helped me see the distinction, solidly (No pun intended.) However, I didn't understand how missing the word 'each' in the option alters the meaning of the sentence, as MM suggested. Can someone explain? (Incidentally, I too had chosen Option B when I first read the question.) Wink

Cheers!

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Post Fri Sep 11, 2015 6:55 am
mindful wrote:
Great question. Took me full four minutes to read the question. (Is this normal? Probably not!)

I see what the answer is. But it also only refers to one kind of planet, the inner planets. It does not really explicitly make a distinction from the outer planets. Do we just go by inference or assume an implication that if the inner planets have something in common, then the likelihood of their being different from outer planets is higher?
The OA is actually weak here. I guess that it tends to confirm that each of the inner planets was formed in the same way, but really it does not confirm much. Maybe the only reason to choose the OA is that it is better than the other answers.

Funny, originally I stuck to talking about the issues with answer B, because I didn't want to fight the battle of dealing with the weak OA.

Quote:
Second, Marty's explanation about the inner and outer was spot on! It really helped me see the distinction, solidly (No pun intended.) However, I didn't understand how missing the word 'each' in the option alters the meaning of the sentence, as MM suggested. Can someone explain? (Incidentally, I too had chosen Option B when I first read the question.) Wink
Regarding the word each, I think Meera is just using that word to illustrate that she missed that they are different from each other.

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Post Fri Sep 11, 2015 7:51 am
Ha. Thank you for the clarification. Much appreciated. Smile

Funnily, I read each but my brain understood it as both, and other I thought refers to the other set of planets (i.e. Earth, Mars) (not even mentioned in the option). Haha.

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Post Fri Sep 11, 2015 8:17 pm
mindful wrote:
Funnily, I read each but my brain understood it as both, and other I thought refers to the other set of planets (i.e. Earth, Mars) (not even mentioned in the option). Haha.
Haha. Maybe you need to be more...uh...mindful!

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shashank_10 Newbie | Next Rank: 10 Posts
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Post Mon Oct 02, 2017 12:44 am
Hey,

Can someone point out how they eliminated option E?

I feel option E compares moons of planets on both sides of the Frost line. I think this option explains the theory in a better way than option C as option C just talks about on one side of the Frost line.

I being an engineer know astrophysics concepts well and i am afraid, I may have gotten too much into the technical aspect i.e. Is planet's moon a jargon and not common knowledge and thus out of scope? Let me know if that is the case!

Thanks in advance for the help!

Cheers,
Shashank

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Post Tue Oct 03, 2017 9:42 am
Hey shashank,

This is a great example of how knowing too much about a subject can actually hurt you on the exam.

On the GMAT, we want to stay within the context of the passage as much as possible. When we see answer choice E, our first move should be scanning the passage for the word "moon", which we won't find anywhere.

Now, with an astrophysics background, it seems reasonable that if this theory holds true, moons would be formed in much the same way the planets were formed. However, the passage never tells us that - it never tells us anything about moons at all! Therefore, we should eliminate E for being, at best, an assumption and, at worst, unrelated to the passage.

A good rule of thumb is that if a critical concept from the answer choice does not show up in the passage or the question itself, the answer isn't going to have enough support to be correct.

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