The mid-thirteenth-century King’s Mirror contains extraordinarily accurate descriptions of sea mammals and other natural phenomena. The section dealing with the North Atlantic describes only three phenomena that assume an aspect of the marvelous: the hafgerdingar (sea fences) and the Norse merman, both sighted in the Greenland Sea, and the hafgufa, sighted in Icelandic seas. Scientists have long assumed that the Norse mermen were nothing more than manatees or dugongs; however, that theory ought surely to be reconsidered in light of new research findings indicating that hafgerdingar are a visual effect created by anomalous atmospheric refraction of light rays.

Light is refracted downward during a temperature inversion, a condition in which atmospheric temperature increases with elevation. During an inversion, irregularities in the atmospheric temperature profile, especially thermoclines (layers where the temperature gradient is steeper than in adjacent layers), create irregularities in light refraction. The resulting optical distortion may be so severe as to make ordinary objects unrecognizable, even at short distances. One excellent source for mermen images, for instance, may have been whales projecting their heads vertically out of the water (such activity, called “spy-hopping” is common among cetaceans). Our computer simulations suggest that, with changes in the temperature profile, a whale’s head can appear slender and vertically elongated to a degree three times its actual height above water. Since the horizontal dimension remains unchanged, the distorted image possesses a large height-to width ratio, a form associated with humans. The refractive distortion diminishes if the image can be viewed from above the thermocline, but to sail thirteenth-century vessels, Norse mariners worked from the deck, only a few meters above the sea. Subsequent use of higher-decked ships and of elevated lockouts would explain the infrequent sightings of mermen by Norse mariners in later centuries.

Apparently, the thermoclines that generate mermen images are most likely to be created when a warm air mass moves slowly over significantly cooler surface air, as in the last stages of a warm front, when the warm-cold interface has descended almost to the surface (some experimental verification of this hypothesis has already been provided by Wegener, who correlated mirages in the North Atlantic with the arrival of warm fronts). The typical conditions just before a major storm in the Greenland Sea, dead calm followed by a sudden rise in temperature, are ideally suited to the development of thermoclines. The amount of optical distortion depends directly on the temperature difference between the two air masses, which in turn determines the strength of the front and the severity of subsequent storms. The King’s Mirror quite correctly associated the appearance of Norse mermen with the advent of storms on the open sea. However, Norse mariners thought that the mermen brought on the storms. In fact, the opposite was true.

Paragraph 1

Paragraph 1 Analysis

(1)= The mid-thirteenth-century King’s Mirror contains extraordinarily accurate descriptions of sea mammals and other natural phenomena. The section dealing with the North Atlantic describes only three phenomena that assume an aspect of the marvelous: the hafgerdingar (sea fences) and the Norse merman, both sighted in the Greenland Sea, and the hafgufa, sighted in Icelandic seas.

(1) A very old Norse document contains accurate descriptions of many sea animals. Only a few of these animals are actually not real.

(2) Scientists have long assumed that the Norse mermen were nothing more than manatees or dugongs; however, that theory ought surely to be reconsidered in light of new research findings indicating that hafgerdingar are a visual effect created by anomalous atmospheric refraction of light rays.

(2) Scientists tend to think that sea mammals were mistaken for mermen but the truth is more complicated: mermen sightings were caused by optical illusions.

Paragraph 2

Paragraph 1 Analysis

(1) Light is refracted downward during a temperature inversion, a condition in which atmospheric temperature increases with elevation. During an inversion, irregularities in the atmospheric temperature profile, especially thermoclines (layers where the temperature gradient is steeper than in adjacent layers), create irregularities in light refraction. The resulting optical distortion may be so severe as to make ordinary objects unrecognizable, even at short distances.

(1) Don’t worry too much about the details here. The point is that these temperature and light conditions cause “ordinary objects” to appear “unrecognizable.” The author is setting up for an explanation of how mermen fit in.

(2)One excellent source for mermen images, for instance, may have been whales projecting their heads vertically out of the water. (such activity, called “spy-hopping” is common among cetaceans). Our computer simulations suggest that, with changes in the temperature profile, a whale’s head can appear slender and vertically elongated to a degree three times its actual height above water. Since the horizontal dimension remains unchanged, the distorted image possesses a large height-to width ratio, a form associated with humans.

(2) “Spy-hopping,” “cetaceans?” – don’t worry! Again, look for the main ideas; don’t worry about jargon. It is there to complicate the reading, but never to stand in the way of the author’s point. Here the author is telling us that whales could have been mistaken for mermen due to temperature factors that made the whales’ shape appear to change.

(3) The refractive distortion diminishes if the image can be viewed from above the thermocline, but to sail thirteenth-century vessels, Norse mariners worked from the deck, only a few meters above the sea. Subsequent use of higher-decked ships and of elevated lockouts would explain the infrequent sightings of mermen by Norse mariners in later centuries.

(3) The object is more distorted the closer one is to it. The decks on Norse mariners’ ships were low, causing objects to be quite distorted in their appearance. As higher decked ships came along in later centuries, there were fewer and fewer mermen sightings. No coincidence there, says the author.

Paragraph 3

Paragraph 3 Analysis

(1)` Apparently, the thermoclines that generate mermen images are most likely to be created when a warm air mass moves slowly over significantly cooler surface air, as in the last stages of a warm front, when the warm-cold interface has descended almost to the surface (some experimental verification of this hypothesis has already been provided by Wegener, who correlated mirages in the North Atlantic with the arrival of warm fronts).

(1) Mermen images arise in weather conditions where warm air and cold air are very close together.

(2) The typical conditions just before a major storm in the Greenland Sea, dead calm followed by a sudden rise in temperature, are ideally suited to the development of thermoclines. The amount of optical distortion depends directly on the temperature difference between the two air masses, which in turn determines the strength of the front and the severity of subsequent storms.

(2) The Greenland Sea is the area where mermen were sighted by the Norse. The weather in the Greenland Sea is exactly the type that causes the warm air/cold air condition, and thus makes perfect sense as a spot for viewing optical illusions.

(3) The King’s Mirror quite correctly associated the appearance of Norse mermen with the advent of storms on the open sea. However, Norse mariners thought that the mermen brought on the storms. In fact, the opposite was true.

(3) The author brings back the document from the beginning of the passage to show that the Norse mariners, who wrote the document, understood that mermen sightings and storms coincided. However, their belief in these mythical creatures misled them to think that the mermen brought the storms. What really happened was that the weather conditions prior to a storm were the type that causes optical illusions. Thus, mermen sightings were the result of the weather, not the other way around.

1. What is the passage type?

Subject: Science
Action: Describe

2. What is each paragraph about?

P1: The Norse mermen phenomenon
P2: Optical illusions cause mermen sightings.
P3: Weather conditions create illusions.

3. What is the organization?

This is a general to specific passage, beginning with a phenomenon, then explaining its cause, and then explaining the cause of the phenomenon’s cause.

Original Theory: (Simple) Sea animals were mistaken for mermen

New Theory: (Complex) Optical illusion causes appearance of sea animals to be deformed

Explanation of Theory: Light refraction

Larger Causes: Weather Patterns

4. What is the big idea?
Mermen sightings happened because certain weather patterns influence light and temperature to create optical illusions in the sea.

5. What is the author’s purpose?
To show the scientific reasons behind mermen sightings.
Explanations:

Q1. Which of the following statements best expresses the central idea of the passage?

(A) Early Norse mariners were incorrect in attributing to mermen the power to bring on storms at sea.
(B) A Norse merman is actually a distorted visual image created by anomalous atmospheric refraction.
(C) The Norse merman is unlikely to be merely a manatee or a dugong.
(D) The thermoclines that generate mermen images are more common in the North Atlantic than elsewhere in the world.
(E) A whale projecting its head vertically out of the water is an excellent source for mermen images.

Q1 Ex Type: Main Idea
(B) The last sentence of the first paragraph illustrates that scientists have long assumed that the Norse mermen were nothing more than manatees or dugongs; however, that theory ought surely to be reconsidered in light of new research findings indicating that hafgerdingar are a visual effect created by anomalous atmospheric refraction of light rays. This sentence gives us the central idea of the passage. Correctly answering this question requires an understanding of the passage’s main purpose: to explain the scientific basis for mermen sightings. The other answer choices are details from the passage, not its main idea.
Q2. The author is impressed by the King’s Mirror because of its:

(A) universality
(B) comprehensiveness
(C) ingenuity
(D) faithfulness to reality
(E) sound reasoning

Q2 Ex Type: Detail of the passage
(D) The author mentions in the first line of the passage that the mid-thirteenth-century King’s Mirror contains “extraordinarily accurate descriptions of sea mammals and other natural phenomena.” Thus the descriptions are quite accurate and we can say that the author is impressed by how faithful the King’s Mirror is to reality.

Q3. According to the passage, the thermoclines that generate mermen images are most likely to be present when two air masses in close proximity differ significantly in:

(A) elevation.
(B) density.
(C) temperature.
(D) rate of movement.
(E) moisture content.

Q3 Ex Type: Detail of the passage
(C) In the last paragraph of the passage, the author says “The amount of optical distortion depends directly on the temperature difference between the two air masses, which in turn determines the strength of the front and the severity of subsequent storms.” The answer is evident from the context of the sentence.

Q4. According to the passage, an object sighted at sea will appear most distorted by a thermocline when the:

(A) distance from the object to the observer is short.
(B) vertical dimension of the object is large.
(C) surface of the water near the observer is smooth.
(D) elevation of the observer above the water level is low.
(E) frontal system that created the thermocline is strong.

Q4 Ex Type: Inference
(D) The author tells us that Norse sailors spotted the legendary “merman” more frequently than sailors who sailed in subsequent high-decked ships with elevated lookouts. Therefore, an object sighted at sea will appear more distorted by a thermocline when the elevation of the observer above water level is low. This question requires inference based on the actual text.

Q5. According to the author, Norse mariners made which of the following errors?

(A) They worked their ships only from the deck.
(B) They converted to higher-decked ships in later centuries.
(C) They did not record their sightings of mermen in later centuries.
(D) They mistook one sea mammal for another.
(E) They mistook an effect of storm conditions for a cause of storms.

Q5 Ex Type: Detail of the passage
(E) The answer to this question is in the last two sentences of this passage, “The King’s Mirror quite correctly associated the appearance of Norse mermen with the advent of storms on the open sea. However, Norse mariners thought that the mermen brought on the storms. In fact, the opposite was true.” The answer is evident from the context.

Q6. Which of the following phrases could best be substituted for the word “reconsidered” in the last sentence of the first paragraph, without changing the meaning of the passage as a whole?

(A) evaluated objectively
(B) verified experimentally
(C) questioned seriously
(D) compared with other theories
(E) reasserted more emphatically

Q6 Ex Type: Definition of a term or phrase
(C) To “reconsider” is to take another look in a more thorough manner. The author tells us about an old theory that states that manatees or dugongs were mistaken for mermen. However, the author posits that a new, more complex theory is correct. Therefore, the old theory should be “reconsidered” or “questioned seriously.” This question does not require further knowledge of the passage. The sentence the word belongs in provides enough context. However, you must be able to understand the meaning of the sentence fully, so that you may substitute a word correctly without changing the sentence’s meaning.

Q7. According to the passage, the likelihood of optical distortion is increased in the presence of which of the following atmospheric conditions?
I. a temperature inversion
II. a warm front
III. dead calm followed by a sudden rise in temperature

(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III

Q7 Ex Type: Detail of the passage
(E) In the second sentence of the second paragraph, the author says that “during an inversion, irregularities in the atmospheric temperature profile, especially thermoclines (layers where the temperature gradient is steeper than in adjacent layers), create irregularities in light refraction.” This answers I.
Also, in the first part of the last paragraph the author says that the “thermoclines that generate mermen images are most likely to be created when a warm air mass moves slowly over significantly cooler surface air, as in the last stages of a warm front, when the warm-cold interface has descended almost to the surface.” This answers II and III.
To answer this question, you must be able to understand detailed scientific text from the passage and be able to recognize, from a list, all the laws governing light refraction.

Q8. Which of the following would most strengthen the author’s assertions concerning the cause of mermen images?

(A) accurate measurement of the average temperature gradient in a thermocline
(B) empirical verification of computer simulations made by the author
(C) explanation by historians of the reasons behind the design changes made in Norse ships after the thirteenth century
(D) discovery of records showing frequent sightings of mermen by Norse mariners after the thirteenth century
(E) discovery of errors in the correlations developed by Wegener

Q8 Ex Type: Support for a premise
(B) The author’s assertions concerning the cause of mermen images can be strengthened by presenting real evidence (empirical verifications) to back up the passage’s claims about computer simulation studies. The author says “Our computer simulations suggest that, with changes in the temperature profile, a whale’s head can appear slender and vertically elongated to a degree three times its actual height above water…” Going into more detail about these simulations or providing actual data would make the author’s argument more convincing. This question not only requires the use of inference based on text, but also the ability to understand how each answer choice may affect the credibility of the information contained in the passage.

Q9. The passage implies that the hafgerdingar are most likely to be seen as a result of which of the following?

(A) irregularities in the atmospheric temperature profile
(B) movement of a cool air mass over significantly warmer surface air
(C) upward refraction of light rays through the atmosphere
(D) a period of several consecutive warm days on the Greenland Sea
(E) a change in atmospheric temperature profile after a storm at sea

Q9 Ex Type: Detail of the passage
(A) In the last line of the first paragraph, the author says that, “indicating that hafgerdingar are a visual effect created by anomalous atmospheric refraction of light rays.” “Irregularities in the atmospheric temperature profile” is the best summary of this idea. The rest of the answer choices are either results of the irregularities in the atmospheric temperature profile or other details from the passage that do not answer the question.

Q1. Which of the following statements best expresses the central idea of the passage?

(A) Early Norse mariners were incorrect in attributing to mermen the power to bring on storms at sea.
(B) A Norse merman is actually a distorted visual image created by anomalous atmospheric refraction.
(C) The Norse merman is unlikely to be merely a manatee or a dugong.
(D) The thermoclines that generate mermen images are more common in the North Atlantic than elsewhere in the world.
(E) A whale projecting its head vertically out of the water is an excellent source for mermen images.

Q1 Ex Type: Main Idea
(B) The last sentence of the first paragraph illustrates that scientists have long assumed that the Norse mermen were nothing more than manatees or dugongs; however, that theory ought surely to be reconsidered in light of new research findings indicating that hafgerdingar are a visual effect created by anomalous atmospheric refraction of light rays. This sentence gives us the central idea of the passage. Correctly answering this question requires an understanding of the passage’s main purpose: to explain the scientific basis for mermen sightings. The other answer choices are details from the passage, not its main idea.

Q2. The author is impressed by the King’s Mirror because of its:

(A) universality
(B) comprehensiveness
(C) ingenuity
(D) faithfulness to reality
(E) sound reasoning

Q2 Ex Type: Detail of the passage
(D) The author mentions in the first line of the passage that the mid-thirteenth-century King’s Mirror contains “extraordinarily accurate descriptions of sea mammals and other natural phenomena.” Thus the descriptions are quite accurate and we can say that the author is impressed by how faithful the King’s Mirror is to reality.

Q3. According to the passage, the thermoclines that generate mermen images are most likely to be present when two air masses in close proximity differ significantly in:

(A) elevation.
(B) density.
(C) temperature.
(D) rate of movement.
(E) moisture content.

Q3 Ex Type: Detail of the passage
(C) In the last paragraph of the passage, the author says “The amount of optical distortion depends directly on the temperature difference between the two air masses, which in turn determines the strength of the front and the severity of subsequent storms.” The answer is evident from the context of the sentence.

Q4. According to the passage, an object sighted at sea will appear most distorted by a thermocline when the:

(A) distance from the object to the observer is short.
(B) vertical dimension of the object is large.
(C) surface of the water near the observer is smooth.
(D) elevation of the observer above the water level is low.
(E) frontal system that created the thermocline is strong.

Q4 Ex Type: Inference
(D) The author tells us that Norse sailors spotted the legendary “merman” more frequently than sailors who sailed in subsequent high-decked ships with elevated lookouts. Therefore, an object sighted at sea will appear more distorted by a thermocline when the elevation of the observer above water level is low. This question requires inference based on the actual text.

Q5. According to the author, Norse mariners made which of the following errors?

(A) They worked their ships only from the deck.
(B) They converted to higher-decked ships in later centuries.
(C) They did not record their sightings of mermen in later centuries.
(D) They mistook one sea mammal for another.
(E) They mistook an effect of storm conditions for a cause of storms.

Q5 Ex Type: Detail of the passage
(E) The answer to this question is in the last two sentences of this passage, “The King’s Mirror quite correctly associated the appearance of Norse mermen with the advent of storms on the open sea. However, Norse mariners thought that the mermen brought on the storms. In fact, the opposite was true.” The answer is evident from the context.

Q6. Which of the following phrases could best be substituted for the word “reconsidered” in the last sentence of the first paragraph, without changing the meaning of the passage as a whole?

(A) evaluated objectively
(B) verified experimentally
(C) questioned seriously
(D) compared with other theories
(E) reasserted more emphatically

Q6 Ex Type: Definition of a term or phrase
(C) To “reconsider” is to take another look in a more thorough manner. The author tells us about an old theory that states that manatees or dugongs were mistaken for mermen. However, the author posits that a new, more complex theory is correct. Therefore, the old theory should be “reconsidered” or “questioned seriously.” This question does not require further knowledge of the passage. The sentence the word belongs in provides enough context. However, you must be able to understand the meaning of the sentence fully, so that you may substitute a word correctly without changing the sentence’s meaning.

Q7. According to the passage, the likelihood of optical distortion is increased in the presence of which of the following atmospheric conditions?
I. a temperature inversion
II. a warm front
III. dead calm followed by a sudden rise in temperature

(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III

Q7 Ex Type: Detail of the passage
(E) In the second sentence of the second paragraph, the author says that “during an inversion, irregularities in the atmospheric temperature profile, especially thermoclines (layers where the temperature gradient is steeper than in adjacent layers), create irregularities in light refraction.” This answers I.
Also, in the first part of the last paragraph the author says that the “thermoclines that generate mermen images are most likely to be created when a warm air mass moves slowly over significantly cooler surface air, as in the last stages of a warm front, when the warm-cold interface has descended almost to the surface.” This answers II and III.
To answer this question, you must be able to understand detailed scientific text from the passage and be able to recognize, from a list, all the laws governing light refraction.

Q8. Which of the following would most strengthen the author’s assertions concerning the cause of mermen images?

(A) accurate measurement of the average temperature gradient in a thermocline
(B) empirical verification of computer simulations made by the author
(C) explanation by historians of the reasons behind the design changes made in Norse ships after the thirteenth century
(D) discovery of records showing frequent sightings of mermen by Norse mariners after the thirteenth century
(E) discovery of errors in the correlations developed by Wegener

Q8 Ex Type: Support for a premise
(B) The author’s assertions concerning the cause of mermen images can be strengthened by presenting real evidence (empirical verifications) to back up the passage’s claims about computer simulation studies. The author says “Our computer simulations suggest that, with changes in the temperature profile, a whale’s head can appear slender and vertically elongated to a degree three times its actual height above water…” Going into more detail about these simulations or providing actual data would make the author’s argument more convincing. This question not only requires the use of inference based on text, but also the ability to understand how each answer choice may affect the credibility of the information contained in the passage.

Q9. The passage implies that the hafgerdingar are most likely to be seen as a result of which of the following?

(A) irregularities in the atmospheric temperature profile
(B) movement of a cool air mass over significantly warmer surface air
(C) upward refraction of light rays through the atmosphere
(D) a period of several consecutive warm days on the Greenland Sea
(E) a change in atmospheric temperature profile after a storm at sea

Q9 Ex Type: Detail of the passage
(A) In the last line of the first paragraph, the author says that, “indicating that hafgerdingar are a visual effect created by anomalous atmospheric refraction of light rays.” “Irregularities in the atmospheric temperature profile” is the best summary of this idea. The rest of the answer choices are either results of the irregularities in the atmospheric temperature profile or other details from the passage that do not answer the question.