It has been known for many decades that the appearance of sunspots is

Question

1990 10 SECTION A 17-23

It has been known for many decades that the appearance of sunspots is roughly periodic, with an average cycle of eleven years. Moreover, the incidence of solar flares and the flux of solar cosmic rays, ultraviolet radiation, and x-radiation all vary directly with the sunspot cycle. But after more than a century of investigation, the relation of these and other phenomena, known collectively as the solar-activity cycle, to terrestrial weather and climate remains unclear. For example, the sunspot cycle and the allied magnetic-polarity cycle have been linked to periodicities discerned in records of such variables as rainfall, temperature, and winds. Invariably, however, the relation is weak, and commonly of dubious statistical significance.

Effects of solar variability over longer terms have also been sought. The absence of recorded sunspot activity in the notes kept by European observers in the late seventeenth and early eighteenth centuries has led some scholars to postulate a brief cessation of sunspot activity at that time (a period called the Maunder minimum). The Maunder minimum has been linked to a span of unusual cold in Europe extending from the sixteenth to the early nineteenth centuries. The reality of the Maunder minimum has yet to be established, however, especially since the records that Chinese naked-eye observers of solar activity made at that time appear to contradict it. Scientists have also sought evidence of long-term solar periodicities by examining indirect climatological data, such as fossil records of the thickness of ancient tree rings. These studies, however, failed to link unequivocally terrestrial climate and the solar-activity cycle, or even to confirm the cycle’s past existence.

If consistent and reliable geological or archaeological evidence tracing the solar-activity cycle in the distant past could be found, it might also resolve an important issue in solar physics: how to model solar activity. Currently, there are two models of solar activity. The first supposes that the Sun’s internal motions (caused by rotation and convection) interact with its large-scale magnetic field to produce a dynamo, a device in which mechanical energy is converted into the energy of a magnetic field. In short, the Sun’s large-scale magnetic field is taken to be self-sustaining, so that the solar-activity cycle it drives would be maintained with little overall change for perhaps billions of years. The alternative explanation supposes that the Sun’s large-scale magnetic field is a remnant of the field the Sun acquired when it formed, and is not sustained against decay. In this model, the solar mechanism dependent on the Sun’s magnetic field runs down more quickly. Thus, the characteristics of the solar-activity cycle could be expected to change over a long period of time. Modern solar observations span too short a time to reveal whether present cyclical solar activity is a long-lived feature of the Sun, or merely a transient phenomenon.  
 1 
 1. The author focuses primarily on

(A) presenting two competing scientific theories concerning solar activity and evaluating geological evidence often cited to support them
(B) giving a brief overview of some recent scientific developments in solar physics and assessing their impact on future climatological research
(C) discussing the difficulties involved in linking terrestrial phenomena with solar activity and indicating how resolving that issue could have an impact on our understanding of solar physics
(D) pointing out the futility of a certain line of scientific inquiry into the terrestrial effects of solar activity and recommending its abandonment in favor of purely physics-oriented research
(E) outlining the specific reasons why a problem in solar physics has not yet been solved and faulting the overly theoretical approach of modern physicists

2 
 2. Which of the following statements about the two models of solar activity, as they are described in lines 37-55, is accurate?

(A) In both models cyclical solar activity is regarded as a long-lived feature of the Sun, persisting with little change over billions of years.
(B) In both models the solar-activity cycle is hypothesized as being dependent on the large-scale solar magnetic field.
(C) In one model the Sun’s magnetic field is thought to play a role in causing solar activity, whereas in the other model it is not.
(D) In one model solar activity is presumed to be unrelated to terrestrial phenomena, whereas in the other model solar activity is thought to have observable effects on the Earth.
(E) In one model cycles of solar activity with periodicities longer than a few decades are considered to be impossible, whereas in the other model such cycles are predicted.

3 
 3. According to the passage, late seventeenth and early eighteenth-century Chinese records are important for which of the following reasons?

(A) They suggest that the data on which the Maunder minimum was predicated were incorrect.
(B) They suggest that the Maunder minimum cannot be related to climate.
(C) They suggest that the Maunder minimum might be valid only for Europe.
(D) They establish the existence of a span of unusually cold weather worldwide at the time of the Maunder minimum.
(E) They establish that solar activity at the time of the Maunder minimum did not significantly vary from its present pattern.

4 
 4. The author implies which of the following about currently available geological and archaeological evidence concerning the solar-activity cycle?

(A) It best supports the model of solar activity described in lines 37-45.
(B) It best supports the model of solar activity described in lines 45-52.
(C) It is insufficient to confirm either model of solar activity described in the third paragraph.
(D) It contradicts both models of solar activity as they are presented in the third paragraph.
(E) It disproves the theory that terrestrial weather and solar activity are linked in some way.

5 
 5. It can be inferred from the passage that the argument in favor of the model described in lines 37-45 would be strengthened if which of the following were found to be true?
 
(A) Episodes of intense volcanic eruptions in the distant past occurred in cycles having very long periodicities.
(B) At the present time the global level of thunderstorm activity increases and decreases in cycles with periodicities of approximately 11 years.
(C) In the distant past cyclical climatic changes had periodicities of longer than 200 years.
(D) In the last century the length of the sunspot cycle has been known to vary by as much as 2 years from its average periodicity of 11 years.
(E) Hundreds of millions of years ago, solar-activity cycles displayed the same periodicities as do present-day solar-activity cycles.

6 
 6. It can be inferred from the passage that Chinese observations of the Sun during the late seventeenth and early eighteenth centuries
 
(A) are ambiguous because most sunspots cannot be seen with the naked eye
(B) probably were made under the same weather conditions as those made in Europe
(C) are more reliable than European observations made during this period
(D) record some sunspot activity during this period
(E) have been employed by scientists seeking to argue that a change in solar activity occurred during this period

7 
 7. It can be inferred from the passage that studies attempting to use tree-ring thickness to locate possible links between solar periodicity and terrestrial climate are based on which of the following assumptions?
 
(A) The solar-activity cycle existed in its present form during the time period in which the tree rings grew.
(B) The biological mechanisms causing tree growth are unaffected by short-term weather patterns.
(C) Average tree-ring thickness varies from species to species.
(D) Tree-ring thicknesses reflect changes in terrestrial climate.
(E) Both terrestrial climate and the solar-activity cycle randomly affect tree-ring thickness.

CrackverbalGMAT · Accepted Answer

1. The author focuses primarily on

A brief reading of the passage informs us that the author has spent a large part of the passage talking about the various differences and gaps in measuring solar activity over history, and how the lack of such measurements is making it difficult to predict the future behavior of the sun. A hint of the main idea is also presented in the conclusion of the passage, which states, "Thus, the characteristics of the solar-activity cycle could be expected to change over a long period of time. Modern solar observations span too short a time to reveal whether present cyclical solar activity is a long-lived feature of the Sun, or merely a transient phenomenon."

(A) presenting two competing scientific theories concerning solar activity and evaluating geological evidence often cited to support them  While this is mentioned in the last paragraph, the rest of the passage makes no mention of this. Hence, this cannot be the "primary focus" of the passage. Eliminate.

(B) giving a brief overview of some recent scientific developments in solar physics and assessing their impact on future climatological research  The passage does talk about some developments in solar physics, such as the Maunder minimum. But the specific impact of this on future research is missing. In fact, the author suggests we have too little data presently to have any meaningful impact. Eliminate. 
 
(C) discussing the difficulties involved in linking terrestrial phenomena with solar activity and indicating how resolving that issue could have an impact on our understanding of solar physics  Correct. Consistent with our thinking above.

(D) pointing out the futility of a certain line of scientific inquiry into the terrestrial effects of solar activity and recommending its abandonment in favor of purely physics-oriented research  The passage does talk about shortcomings in the available information, but does not specifically critique any particular line of inquiry. Also, there is no recommendation to abandoning any line of inquiry. Eliminate.

(E) outlining the specific reasons why a problem in solar physics has not yet been solved and faulting the overly theoretical approach of modern physicists  While the passage does talk about the reasons why it has not yet been revealed "whether present cyclical solar activity is a long-lived feature of the Sun, or merely a transient phenomenon", it does not fault anybody for their approach. Eliminate.

2. Which of the following statements about the two models of solar activity, as they are described in lines 37-55, is accurate?

The following is stated about the two models:
i) The first supposes that the Sun’s internal motions (caused by rotation and convection) interact with its large-scale magnetic field to produce a dynamo, a device in which mechanical energy is converted into the energy of a magnetic field. In short, the Sun’s large-scale magnetic field is taken to be self-sustaining, so that the solar-activity cycle it drives would be maintained with little overall change for perhaps billions of years.
ii) The alternative explanation supposes that the Sun’s large-scale magnetic field is a remnant of the field the Sun acquired when it formed, and is not sustained against decay. In this model, the solar mechanism dependent on the Sun’s magnetic field runs down more quickly.

(A) In both models cyclical solar activity is regarded as a long-lived feature of the Sun, persisting with little change over billions of years.  Inconsistent with (ii). Eliminate.

(B) In both models the solar-activity cycle is hypothesized as being dependent on the large-scale solar magnetic field.  Correct. Consistent with (i) and (ii).

(C) In one model the Sun’s magnetic field is thought to play a role in causing solar activity, whereas in the other model it is not.  The magnetic field plays a role in both models - it is the hypothesized longevity of such field that varies between them. Eliminate.

(D) In one model solar activity is presumed to be unrelated to terrestrial phenomena, whereas in the other model solar activity is thought to have observable effects on the Earth.  Both models have the solar activity impacting terrestrial phenomena on earth. Eliminate.

(E) In one model cycles of solar activity with periodicities longer than a few decades are considered to be impossible, whereas in the other model such cycles are predicted.  There is nothing mentioned about the periodicities of the two models. Eliminate.

3. According to the passage, late seventeenth and early eighteenth-century Chinese records are important for which of the following reasons?

The passage states the following on this topic:

"The absence of recorded sunspot activity in the notes kept by European observers in the late seventeenth and early eighteenth centuries has led some scholars to postulate a brief cessation of sunspot activity at that time (a period called the Maunder minimum). The Maunder minimum has been linked to a span of unusual cold in Europe extending from the sixteenth to the early nineteenth centuries. The reality of the Maunder minimum has yet to be established, however, especially since the records that Chinese naked-eye observers of solar activity made at that time appear to contradict it."

(A) They suggest that the data on which the Maunder minimum was predicated were incorrect.  Correct. Consistent with above (since Maunder minimum is based on absence of recorded sunspot activity in Europe, which is contradicted by the Chinese observations.

(B) They suggest that the Maunder minimum cannot be related to climate.  Not consistent with above. Eliminate.

(C) They suggest that the Maunder minimum might be valid only for Europe.  Not consistent with above. Eliminate.

(D) They establish the existence of a span of unusually cold weather worldwide at the time of the Maunder minimum.  Not consistent with above. Eliminate.

(E) They establish that solar activity at the time of the Maunder minimum did not significantly vary from its present pattern.  Not consistent with above. Eliminate.

4. The author implies which of the following about currently available geological and archaeological evidence concerning the solar-activity cycle?

The author states the following about current available data: "Modern solar observations span too short a time to reveal whether present cyclical solar activity is a long-lived feature of the Sun, or merely a transient phenomenon."

(A) It best supports the model of solar activity described in lines 37-45.  This refers to model (i) as described in Q2. Not consistent with above. Eliminate.

(B) It best supports the model of solar activity described in lines 45-52.  This refers to model (ii) as described in Q2. Not consistent with above. Eliminate.

(C) It is insufficient to confirm either model of solar activity described in the third paragraph.  Correct. Consistent with above

(D) It contradicts both models of solar activity as they are presented in the third paragraph.  Not consistent with above. Eliminate.

(E) It disproves the theory that terrestrial weather and solar activity are linked in some way.  Not consistent with above. Eliminate.

5. It can be inferred from the passage that the argument in favor of the model described in lines 37-45 would be strengthened if which of the following were found to be true?

The question refers to model (i) as described in Q2, which states that the solar activity cycle "would be maintained with little overall change for perhaps billions of years". Hence, we are looking for some evidence that the solar activity cycle on earth has remained unchanged for such a period of time.

(A) Episodes of intense volcanic eruptions in the distant past occurred in cycles having very long periodicities.  Nothing in the passage talks about volcanic eruptions being linked to solar activity. Also, there is nothing in this option about the present day. Eliminate.

(B) At the present time the global level of thunderstorm activity increases and decreases in cycles with periodicities of approximately 11 years.  There is nothing in this option about the distant past. Eliminate.

(C) In the distant past cyclical climatic changes had periodicities of longer than 200 years.  Since current sunspot activity has a periodicity of 11 years, this shows  a change  in the cycle and hence is inconsistent with model (i). Eliminate.

(D) In the last century the length of the sunspot cycle has been known to vary by as much as 2 years from its average periodicity of 11 years.  The timeframe being considered is too short to support model (i). Eliminate.

(E) Hundreds of millions of years ago, solar-activity cycles displayed the same periodicities as do present-day solar-activity cycles.  Correct. Consistent with the requirement described above.

6. It can be inferred from the passage that Chinese observations of the Sun during the late seventeenth and early eighteenth centuries

The passage states that Chinese observations of the sun in this period contradict European observations, which did not record any sunspot activity. Hence, Chinese observations must have recorded sunspot activity.

(A) are ambiguous because most sunspots cannot be seen with the naked eye  The passage does not say that sunspots cannot be seen with the naked eye. Eliminate.

(B) probably were made under the same weather conditions as those made in Europe  Nothing in the passage compares weather conditions of Europe and China during the period. Eliminate.

(C) are more reliable than European observations made during this period  The passage does not compare the reliability of the two observations. Eliminate.

(D) record some sunspot activity during this period  Correct. Consistent with the thinking above.

(E) have been employed by scientists seeking to argue that a change in solar activity occurred during this period  No such reference in the passage. Eliminate.

7. It can be inferred from the passage that studies attempting to use tree-ring thickness to locate possible links between solar periodicity and terrestrial climate are based on which of the following assumptions?

Explanation

On this topic, the passage states: "Scientists have also sought evidence of long-term solar periodicities by examining indirect climatological data, such as fossil records of the thickness of ancient tree rings."

(A) The solar-activity cycle existed in its present form during the time period in which the tree rings grew.  The passage does not mention the conclusions drawn from such study. Eliminate.

(B) The biological mechanisms causing tree growth are unaffected by short-term weather patterns.  Since tree rings are being studied to gauge climate data, it is reasonable to assume that weather patters do affect tree growth. Eliminate.

(C) Average tree-ring thickness varies from species to species.  Nothing in the passage about thickness of various species of trees. Eliminate.

(D) Tree-ring thicknesses reflect changes in terrestrial climate.  Correct. Consistent with above thinking.

(E) Both terrestrial climate and the solar-activity cycle randomly affect tree-ring thickness.  The passage states that the studies have proved inconclusive. Eliminate.

Hope this helps.

shameekv1989 · Answer

3. According to the passage, late seventeenth and early eighteenth-century Chinese records are important for which of the following reasons?

(A) They suggest that the data on which the Maunder minimum was predicated were incorrect.
(B) They suggest that the Maunder minimum cannot be related to climate.
(C) They suggest that the Maunder minimum might be valid only for Europe.
(D) They establish the existence of a span of unusually cold weather worldwide at the time of the Maunder minimum.
(E) They establish that solar activity at the time of the Maunder minimum did not significantly vary from its present pattern.

Can we discuss about this question? Isn't "incorrect" incorrect to say?

"The reality has yet to be established" doesn't mean to say the data  were incorrect . The author hasn't dismissed it completely.

SajjadAhmad  : Could you please provide OE or your thoughts on this question

bM22 · Answer

Hi  shameekv1989 ,

Let me try this one.

Consider the lines: "The reality of the Maunder minimum has yet to be established, however, especially since the   records that Chinese naked-eye observers of solar activity made at that time appear to contradict it. ".

True that "The reality has yet to be established" doesn't mean that the data is incorrect, but what author further mentions is that the reality of data is yet to be established because the records by Chinese observers of that time seem to be contradicting it, which is exactly why eighteenth-century Chinese records are important.

Hope This Helps.
Thanks.

shameekv1989 · Answer

bm2201  :- Thanks for the reply.

Maunder minimum is based on European notes. Chinese records seem to be contradicting these notes. Does this contradiction make European notes incorrect? Yes, it does make Chinese records important but important for a reason that the fact can not be concretely stated whether correct or incorrect.

What are your thoughts?

Ed1000 · Answer

When answering these questions is there a way to see the associated line numbers of the passages.? For example, question 5 refers to lines 37-45. Do you need to physically count down to 37 or is there a function to see line numbers? Thanks.

bM22 · Answer

Hi  shameekv1989 ,

The author mentions that the reality of Maunder Minimum cannot be established yet,  because of the Chinese records , now that would be mean that the records hold some truth. True that the concreteness of the Chinese records cannot be established, yet we can't rule out the possibility that they might actually be correct, which is exactly what's mentioned in the passage, otherwise why would they be even considered while establishing the reality of Maunder Minimum.

Thanks.

Pradeep099 · Answer

For Question number 7
I was confused between D and E ; more because it is an assumption question.
I feel like E is wrong because of the word " randomly".

The explanation given prior doesn't justify the reason to cancel E " The passage states that the studies have proved inconclusive." because it is an assumption that is made prior to a conclusion.... And the assumption made by the scientist is more like " the solar activity that affects the meteorology has a consistent or at least " not random" effect of tree thickness.

Am I correct or am misunderstanding it .. Any help would be appreciated

Akhil5495 · Answer

Can anyone please explain number 7 again?

Sajjad1994 · Answer

Explanation

7. It can be inferred from the passage that studies attempting to use tree-ring thickness to locate possible links between solar periodicity and terrestrial climate are based on which of the following assumptions?

Explanation

Explanation

First, the passage discusses how scientists have attempted to find evidence of long-term solar periodicities by examining indirect climatological data, such as fossil records of the thickness of ancient tree rings. These studies aim to establish a connection between solar activity cycles and changes in terrestrial climate.

A.  The passage does not explicitly state that the solar-activity cycle existed in its present form during the time period in which the tree rings grew. In fact, it discusses the uncertainty surrounding the solar-activity cycle's past existence. Therefore, this assumption cannot be inferred from the passage.

B.  If the biological mechanisms causing tree growth are unaffected by short-term weather patterns, then changes in tree-ring thickness could potentially reflect longer-term climate patterns, including those possibly influenced by solar activity cycles. However, the passage does not directly confirm or deny this assumption.

C.  While it's true that average tree-ring thickness varies from species to species, the passage does not specifically discuss this variation or its relevance to the studies mentioned. Therefore, this assumption cannot be inferred from the passage.

D.   This assumption is central to the studies mentioned in the passage. The studies seek to establish a link between tree-ring thickness and changes in terrestrial climate. If tree-ring thicknesses reflect changes in terrestrial climate, then variations in tree-ring thickness could potentially indicate periods of different climatic conditions, which may be influenced by solar activity cycles.

E.  This assumption suggests that tree-ring thickness could be influenced randomly by both terrestrial climate and the solar-activity cycle. However, the studies mentioned in the passage aim to find correlations between tree-ring thickness and solar activity cycles, suggesting a systematic rather than random relationship.

Answer: D

It has been known for many decades that the appearance of sunspots is

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It has been known for many decades that the appearance of sunspots is

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