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# In the 1980's, astronomer Bohdan Paczynski proposed a way of determini

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In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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Updated on: 03 Sep 2019, 07:53
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In the 1980's, astronomer Bohdan Paczynski proposed a way of determining whether the enormous dark halo constituting the outermost part of the Milky Way galaxy is composed of MACHO's (massive compact halo objects), which are astronomical objects too dim to be visible. Paczynski reasoned that if MACHO's make up this halo, a MACHO would occasionally drift in front of a star in the Large Magellanic Cloud, a bright galaxy near the Milky Way. The gravity of a MACHO that had so drifted, astronomers agree, would cause the star's light rays, which would otherwise diverge, to bend together so that, as observed from Earth, the star would temporarily appear to brighten, a process known as microlensing. Because many individual stars are of intrinsically variable brightness, some astronomers have contended that the brightening of intrinsically variable stars can be mistaken for microlensing. However, whereas the different colors of light emitted by an intrinsically variable star are affected differently when the star brightens, all of a star's colors are equally affected by microlensing. Thus, if a MACHO magnifies a star's red light tenfold, it will do the same to the star's blue light and yellow light. Moreover, it is highly unlikely that a star in the Large Magellanic Cloud will undergo microlensing more than once, because the chance that a second MACHO would pass in front of exactly the same star is minuscule.
1. The passage is primarily concerned with

A. outlining reasons why a particular theory is no longer credited by some astronomers
B. presenting data collected by a researcher in response to some astronomers' criticism of a particular line of reasoning
C. explaining why a researcher proposed a particular theory and illustrating how influential that theory has been
D. showing how a researcher's theory has been used to settle a dispute between the researcher and some astronomers
E. describing a line of reasoning put forth by a researcher and addressing a contention concerning that line of reasoning

2. According to the passage, Paczynski's theory presumes that if MACHO's constituted the Milky Way's dark halo, occasionally a MACHO would

A. drift so as to lie in a direct line between two stars in the outer Milky Way
B. affect the light rays of a star in the Large Magellanic Cloud with the result that the star would seem for a time to brighten
C. become obscured as a result of the microlensing of a star in the Large Magellanic Cloud
D. temporarily increase the apparent brightness of a star in the Large Magellanic Cloud by increasing the gravity of the star
E. magnify each color in the spectrum of a star in the Large Magellanic Cloud by a different amount

3. It can be inferred from the passage that which of the following would constitute the strongest evidence of the microlensing of a star in the Large Magellanic Cloud?

A. The brightness of such a star is observed to vary at irregular intervals.
B. The brightening of such a star is observed to be of shorter duration than the brightening of neighboring stars.
C. The red light of such a star is observed to be brighter than its yellow light and its blue light.
D. The red light, yellow light, and blue light of such a star are observed to be magnified temporarily by the same factor.
E. The red light of such a star is observed to have increased tenfold.

Originally posted by PiyushK on 12 Aug 2014, 04:46.
Last edited by SajjadAhmad on 03 Sep 2019, 07:53, edited 7 times in total.
Updated complete topic (36).
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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09 Aug 2015, 14:49
34
6
I watch "thursdays with Ron" and Ron says about interesting way of solving main idea questions in highly technic RC passages. He recommend to omit all text except key words that change flow of the passage.

Here is my try to do that on this passage:

1) Bohdan Paczynski proposed a way of determining .... [some new theory]
2) Paczynski reasoned that .... [support of theory]
3) Because ... some astronomers have contended that .... [because of something this theory was argue by others astronomers]
4) However .... [author of passage doesn't agree with astronomers]
5) Thus .... [theory is good because of previous word "however"]
6) Moreover .... [and here is one more reason why theory is good]

So we see that first two parts is about new theory, then some arguing and last half of passage support theory.

The passage is primarily concerned with
A. outlining reasons why a particular theory is no longer credited by some astronomers
this answer miss parts 4-6. Incorrect

B. presenting data collected by a researcher in response to some astronomers' criticism of a particular line of reasoning
theory was created before critisms

C. explaining why a researcher proposed a particular theory and illustrating how influential that theory has been
We have only fact of theory and not reasons why it was created. Incorrect

D. showing how a researcher's theory has been used to settle a dispute between the researcher and some astronomers
theory procreate a critism so it can't be used for settling of this dispute. Incorrect

E. describing a line of reasoning put forth by a researcher [1-2 parts]
and addressing a contention concerning that line of reasoning [3-6 parts]

Correct

So with such technic we can solve main idea question even if completely didn't understand topic of the passage.
And this is at least one correct question per completely incomprehensible passage
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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12 Aug 2014, 19:39
2
for many short passages in og, gmatprep, the first question about the main idea is hard while the second or third question about a detail in the passage is easy. this passage is an example of this point.

for 2 and 3, the answer is B and D clearly.

for the first, which I feel hard, the answer is C.
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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Updated on: 27 Jul 2017, 08:05
1
Time taken 7:35 min. What shld be the expected timing for this Q?
Latest timing 11/07: 5:50 mins.
1. The passage is primarily concerned with
E. describing a line of reasoning put forth by a researcher and addressing a contention concerning that line of reasoning
" astronomer Bohdan Paczynski proposed a way of determining whether the enormous dark halo constituting the outermost part of the Milky Way galaxy is composed of MACHO's
blah blah
Because many individual stars are of intrinsically variable brightness, some astronomers have contended that
blah
blah
However, whereas the different colors of light emitted by an intrinsically variable
"

2. According to the passage, Paczynski's theory presumes that if MACHO's constituted the Milky Way's dark halo, occasionally a MACHO would
B. affect the light rays of a star in the Large Magellanic Cloud with the result that the star would seem for a time to brighten
>>Got this by elimination. Also the language seems to match the para. What I didn't understand is the meaning of "the star would seem for a time to brighten".

3. It can be inferred from the passage that which of the following would constitute the strongest evidence of the microlensing of a star in the Large Magellanic Cloud?
D. The red light, yellow light, and blue light of such a star are observed to be magnified temporarily by the same factor.
>>if a MACHO magnifies a star's red light tenfold, it will do the same to the star's blue light and yellow light.

Originally posted by JarvisR on 12 Aug 2014, 08:41.
Last edited by hazelnut on 27 Jul 2017, 08:05, edited 3 times in total.
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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15 Aug 2014, 22:21
1
2
Below is my reasoning to cancel D.
D)temporarily increase the apparent brightness of a star in the Large Magellanic Cloud by increasing the gravity of the star.
"The gravity of a MACHO that had so drifted, astronomers agree, would cause the star's light rays, which would otherwise diverge, to bend together so that, as observed from Earth, the star would temporarily appear to brighten, a process known as microlensing."

As per the argument, MACHO doesn't increase the gravity to achieve mentioned effect. It's the "drifted gravity " that does it.

Regards.
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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02 Mar 2015, 11:17
1
Thanks a lot . I support your strategy in fully comprehending the passage first then answering the questions. Sometimes if it is a scientific passage I prefer not to spend so much time understanding the passage fully but just to get a general understanding of what every paragraph speaks about.

quote="deepakpatter"]
saraafifiahmed wrote:
Hi, How long should a RC passage on the actual exam take ? Approximately . Thanks

Well that depends on the length of the passage
Normally for a long passage you should take max to max 5 mins reading so you get the data in your mind. After this the questions are piece of cake.
This is my strategy. Some people just vertical scan the passage in less than minute but i don't prefer that. My strategy works best for me.
Try if it helps.
Once you grasp the content believe me you'll find the answers to the questions so easily within seconds.
KEEP IN MIND..! Avoid reading again and again is the key to rc's. Take time but do it once.
Best if luck..!![/quote]
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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03 Mar 2015, 00:32
deepakpatter wrote:
got the 1st Q wrong.. can anybody please explain this Qstn and similar types

I think you mite b confused b/w C & E.
Isn't it..?

Same was with me.

1. The passage is primarily concerned with
A. outlining reasons why a particular theory is no longer credited by some astronomers
B. presenting data collected by a researcher in response to some astronomers' criticism of a particular line of reasoning
C. explaining why a researcher proposed a particular theory and illustrating how influential that theory has been
D. showing how a researcher's theory has been used to settle a dispute between the researcher and some astronomers
E. describing a line of reasoning put forth by a researcher and addressing a contention concerning that line of reasoning

Option C says WHY researcher proposed the theory... >> The passage no where states this, in fact just says he proposed.
Why he proposed..? We are not bothered..!!

It helped . (y)
thnx a lot
My speed. Is slow with. Rc's
Suggest me something. And am getting 050 percent. Of the answer s wrong
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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29 Aug 2016, 23:50
Took 5 mins 10 seconds , including 2 mins 10 seconds to read
-The author describes a theory put forth by an astronomer
- The author the points out certain astronomers' concerns regarding the theory
- The author then addresses those concerns

1.

2. "The gravity of a MACHO that had so drifted, astronomers agree, would cause the star's light rays, which would otherwise diverge, to bend together so that, as observed from Earth, the star would temporarily appear to brighten"

3.
"all of a star's colors are equally affected by microlensing. Thus, if a MACHO magnifies a star's red light tenfold, it will do the same to the star's blue light and yellow light."
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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19 Jan 2017, 20:57
In the 1980's, astronomer Bohdan Paczynski proposed a way of determining whether the enormous dark halo constituting the outermost part of the Milky Way galaxy is composed of MACHO's (massive compact halo objects), which are astronomical objects too dim to be visible. Paczynski reasoned that if MACHO's make up this halo, a MACHO would occasionally drift in front of a star in the Large Magellanic Cloud, a bright galaxy near the Milky Way. The gravity of a MACHO that had so drifted, astronomers agree, would cause the star's light rays, which would otherwise diverge, to bend together so that, as observed from Earth, the star would temporarily appear to brighten, a process known as microlensing. Because many individual stars are of intrinsically variable brightness, some astronomers have contended that the brightening of intrinsically variable stars can be mistaken for microlensing. However, whereas the different colors of light emitted by an intrinsically variable star are affected differently when the star brightens, all of a star's colors are equally affected by microlensing. Thus, if a MACHO magnifies a star's red light tenfold, it will do the same to the star's blue light and yellow light. Moreover, it is highly unlikely that a star in the Large Magellanic Cloud will undergo microlensing more than once, because the chance that a second MACHO would pass in front of exactly the same star is minuscule.

2. According to the passage, Paczynski's theory presumes that if MACHO's constituted the Milky Way's dark halo, occasionally a MACHO would
A. drift so as to lie in a direct line between two stars in the outer Milky Way
B. affect the light rays of a star in the Large Magellanic Cloud with the result that the star would seem for a time to brighten
C. become obscured as a result of the microlensing of a star in the Large Magellanic Cloud
D. temporarily increase the apparent brightness of a star in the Large Magellanic Cloud by increasing the gravity of the star
E. magnify each color in the spectrum of a star in the Large Magellanic Cloud by a different amount

Hi sayantanc2k / Experts,

Can somebody explain In Question 2, why not option A is correct? In the passage it says "Paczynski reasoned that if MACHO's make up this halo, a MACHO would occasionally drift in front of a star in the Large Magellanic Cloud, a bright galaxy near the Milky Way."
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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31 Jan 2017, 08:00
NandishSS wrote:
In the 1980's, astronomer Bohdan Paczynski proposed a way of determining whether the enormous dark halo constituting the outermost part of the Milky Way galaxy is composed of MACHO's (massive compact halo objects), which are astronomical objects too dim to be visible. Paczynski reasoned that if MACHO's make up this halo, a MACHO would occasionally drift in front of a star in the Large Magellanic Cloud, a bright galaxy near the Milky Way. The gravity of a MACHO that had so drifted, astronomers agree, would cause the star's light rays, which would otherwise diverge, to bend together so that, as observed from Earth, the star would temporarily appear to brighten, a process known as microlensing. Because many individual stars are of intrinsically variable brightness, some astronomers have contended that the brightening of intrinsically variable stars can be mistaken for microlensing. However, whereas the different colors of light emitted by an intrinsically variable star are affected differently when the star brightens, all of a star's colors are equally affected by microlensing. Thus, if a MACHO magnifies a star's red light tenfold, it will do the same to the star's blue light and yellow light. Moreover, it is highly unlikely that a star in the Large Magellanic Cloud will undergo microlensing more than once, because the chance that a second MACHO would pass in front of exactly the same star is minuscule.

2. According to the passage, Paczynski's theory presumes that if MACHO's constituted the Milky Way's dark halo, occasionally a MACHO would
A. drift so as to lie in a direct line between two stars in the outer Milky Way
B. affect the light rays of a star in the Large Magellanic Cloud with the result that the star would seem for a time to brighten
C. become obscured as a result of the microlensing of a star in the Large Magellanic Cloud
D. temporarily increase the apparent brightness of a star in the Large Magellanic Cloud by increasing the gravity of the star
E. magnify each color in the spectrum of a star in the Large Magellanic Cloud by a different amount

Hi sayantanc2k / Experts,

Can somebody explain In Question 2, why not option A is correct? In the passage it says "Paczynski reasoned that if MACHO's make up this halo, a MACHO would occasionally drift in front of a star in the Large Magellanic Cloud, a bright galaxy near the Milky Way."

Hi,
This question is actually a 'Specific' type of RC question that requires paraphrase of something directly from the passage ( no assumption) .The statment in option A can not be justified by passage. In passage line related to this mentioned is 'Paczynski reasoned that if MACHO's make up this halo, a MACHO would occasionally drift in front of a star in the Large Magellanic Cloud, a bright galaxy near the Milky Way' . If you read carefully , nowhere star's position is mentioned to be in a line between two stars. We have to find a answer which can be inferred from the passage .
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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10 Oct 2019, 01:18
in question 1, answer choice b and e are close. choice b is wrong because of "data". there is no data here. choice e is problematic .not researcher but astronomer propose. this can be a mistake from gmac

reading gmat passage dose not require new words. in other words, if you get toefl 80 ibt, you have enough vocabulary for reading passage gmat.

gmat reading require you to read complex sentences with complex ideas. practice this skill. vocabulary is not hard but sentences are long and complex. the ideas in the sentences are hard to understand.
at first, we practice reading text with easy ideas, and realizing grammar things. latter, we practice reading the text and realizing grammar and understanding hard ideas in the text. the second level is gmat level. no problem of new words is here. dont try to learn new words.

for advanced learners, the difficulty is not limited vocabulary but the world of ideas. we need to be good at reading and realizing grammar in the easy text before to be good at reading and realizing complex ideas in hard text.
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Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini  [#permalink]

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02 Mar 2020, 20:02
Process map:
if MACHO exist, the star will brighten (microlensing).
variable brightness or ml?
can identify difference - 1) ml equally affect all colors while the variable feature doesn't 2) frequency of ml is low - implying variable brightness feature occurs more often

1. The passage is primarily concerned with

A. outlining reasons why a particular theory is no longer credited by some astronomers the theory is argued by astronomers but isn't "no longer credited"
B. presenting data collected by a researcher in response to some astronomers' criticism of a particular line of reasoning
C. explaining why a researcher proposed a particular theory and illustrating how influential that theory has been it didn't explain why and didn't illustrate the importance neither. In order to comment on how influence it is, author will need to evaluate its application, but in this passage he/she didn't
D. showing how a researcher's theory has been used to settle a dispute between the researcher and some astronomers the theory is not used to settle a disputer - rather that theory is distributed, and then astronomers have some doubts which are clarified afterwards
E. describing a line of reasoning put forth by a researcher and addressing a contention concerning that line of reasoning correct answer, the passage begins with a reasoning, cite astronomer's doubt and then provide reason to address their concern

2. According to the passage, Paczynski's theory presumes that if MACHO's constituted the Milky Way's dark halo, occasionally a MACHO would

A. drift so as to lie in a direct line between two stars in the outer Milky Way "lie in direct line" is not mentioned
B. affect the light rays of a star in the Large Magellanic Cloud with the result that the star would seem for a time to brighten this coincides with "temporarily appear to brighten" and "cause the star's light rays to bend together..."
C. become obscured as a result of the microlensing of a star in the Large Magellanic Cloud "obscured" is the opposite description of what occurred in the passage
D. temporarily increase the apparent brightness of a star in the Large Magellanic Cloud by increasing the gravity of the star mix-up answer - the first half looks right while the 2nd is wrong, gravity change of the star is not mentioned
E. magnify each color in the spectrum of a star in the Large Magellanic Cloud by a different amount opposite to what the passage described - all colors are affects equally

3. It can be inferred from the passage that which of the following would constitute the strongest evidence of the microlensing of a star in the Large Magellanic Cloud?

A. The brightness of such a star is observed to vary at irregular intervals. "irregular intervals" is wrong - microlensing barely occurs for the 2nd time given "the chance that a second MACHO would pass in front of exactly the same star is minuscule"
B. The brightening of such a star is observed to be of shorter duration than the brightening of neighboring stars. the frequency comparison is not mentioned, all we know is the brightening is temporary
C. The red light of such a star is observed to be brighter than its yellow light and its blue light. all colors are affected equally, so this cannot be right
D. The red light, yellow light, and blue light of such a star are observed to be magnified temporarily by the same factor. correct answer
E. The red light of such a star is observed to have increased tenfold. mix-up answer, "tenfold" is mentioned" but the necessary condition for microlensing - which should be all colors being enhanced equally
Re: In the 1980's, astronomer Bohdan Paczynski proposed a way of determini   [#permalink] 02 Mar 2020, 20:02