Some GMATclubbers ask me how I' improved my RC skills and how to apply the technique that I described in my debrief
. Vishy007 asked me to show how to use the technique for one of the passage in OG11th (page 384). I think it maybe useful for others. So the passage with my "thoughts":
[Keep in mind question: structure, purpose and tone
After evidence was obtained in the 1920's that the universe is expanding, it became reasonable to ask: will the universe continue to expand indefinitely, or is there enough mass in it for the mutual attraction of its constituents to bring this expansion to a halt? [Aha, universe is expanding and we do not know whether it expand infinitely or switch to compression. Aha, or empty space or big-bada-bum
] It can be calculated that the critical density of matter needed to break the expansion and "close" the universe is equivalent to three hydrogen atoms per cubic meter. [critical point: 3 H atoms per 1m^3
] But the density of the observable universe-luminous matter [we see less
] in the form of galaxies-comes to only a fraction of this. If the expansion of the universe is to stop, there must be enough invisible matter in the universe to exceed the luminous matter in density by a factor of roughly 70. [Wow! 70! …invisible/visible.
[What is the paragraph about? Our universe is expanding, there is critical mass density that needed to reverse that. Mass is visible and invisible. Invisible mass is not enough to collapse the universe. Hm…it is interesting, what a situation is in reality?
] [Author tone: neutral
] [purpose of paragraph: introduction to the problem, raising a question about expansion/compression, invisible mass will determine our answer
Our contribution [aha! author contribute!
] to the search for this "missing matter" has been to study the rotational velocity of galaxies at various distances from their center of rotation. [Oh, what does it mean? … Aha, it is like velocity of wind at various distances from center of tornado…I saw one small tornado in my life, and it was incredible…
] It has been known for some time that outside the bright nucleus [galaxy has nucleus
] of a typical spiral galaxy luminosity falls off rapidly with distance from the center [of course! the further from tornado, the less velocity of wind
]. If luminosity were a true indicator of mass, most of the mass would be concentrated toward the center. [Be careful! Velocity determine mass distribution!
] Outside the nucleus the rotational velocity would decrease geometrically with distance from the center, in conformity with Kepler's law. [Aha, if there is no invisible mass, we have Kepler’s law. Interesting, what did the author find?
] Instead [Aha! I caught this “instead’
] we have found that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly. [Velocity does not decrease!
] This unexpected result [Aha! “unexpected” – athour’s attitude!!! I caught it
] indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass. [Of course, there is invisible mass. But what about expansion/compression? Hey, author, does not forget about that!!!
[What is the paragraph about? Author finding that there is invisible mass. Author studied distribution of velocity in galaxy
] [Author tone: I’ve caught ‘unxpected’ attitude to results!!!
] [purpose of paragraph: show author results that there is invisible mass but we still do not know answer to the main expansion/compression question.
Our findings [Again finding
] suggest that as much as 90 percent of the mass of the universe is not radiating at any wavelength with enough intensity to be detected on the Earth. [90% of mass is invisible in our universe… factor 70… it seems not enough… and… author studied galaxy but conclude about whole universe….it looks like generalization….but what is author’s answer?
] Such dark matter could be in the form of extremely dim stars of low mass [small and dim stars..why small? because we perhaps can detect large dim stars
], of large planets like Jupiter, or of black holes, either small or massive [because black hole is a hole It is invisible
]. [invisible mass could be a few types….could be…the author suppose these types….read again to understand and memorize these types…attitude towards types of invisible mass
] While it has not yet been determined whether this mass is sufficient to "close" the universe, [So, author still does not answer… odd author…
] some physicists [some physics… who are they? Does author belong to them? I do not know...
] consider it significant that estimates are converging on the critical value. [Wow, so somebody, maybe author also, maybe not, thinks that total mass is near critical value
[What is the paragraph about? Author has found that invisible mass is 90% of total mass. Author proposes some types of invisible mass. Question is open. But some physics believes that we are near critical point
] [Author tone: hypothetical towards types of invisible mass and neutral to conclusion about expansion/compression question
] [purpose of paragraph: finishing description his/her results (90% invisible mass), hypothesis about types of invisible matter, statement that question is still open and some say that mass is near critical level. it sounds like conclusion….
[Structure of the passage: 1st: introduction that expansion/compression means how much does invisible mass exist. 2nd: author results that invisible mass exists. 3rd: question still open but some believe that we are near critical point
[Primary purpose: introduce problem, own finding and provide open conclusion
[Tone: unexpected results, hypothetical types of invisible matter and neutral
[Important ideas: rotational velocity: constant instead of geometrical decrease. Invisible matter.
Now, You can go to OG11th RC questions 111-116 and try to answer. I hope you will answer fast and without return to the passage.
Please, post your results: is it work for you?
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