Gravity - IELTS Reading Sample With Explanation

The IELTS Reading section tests the candidate's understanding ability through a passage. This IELTS reading sample is an Academic reading topic. The passage contains the following question types from IELTS Reading Question Types:

1. Matching headings
2. Sentence completion
3. True False Not Given

There are plenty of reading topics found in IELTS reading practice papers for practice.

Topic: IELTS Reading Sample - Gravity

1. Without forces of gravitation, Earth and other planets would be unable to stay in their orbits around the Sun. the Moon would be unable to orbit the Earth, tidal waves would not occur and the rising of hot air or water convection would be impossible. Gravitation is a phenomenon which allows objects to attract other matter; the physics behind it have been explained in The Theory of Relativity and Newton’s Law of Universal Gravitation; though attempts to explain gravity hail back to ancient times. In the 4th Century B.C. the Greek philosopher Aristotle developed the hypothesis that all objects were drawn into their correct position by crystalline spheres and that a physical mass would fall towards the earth in direct proportion to its weight.
2. In the late 16th century Galileo deduced that while gravitation propels all objects to the ground at the same rate, air resistance resulted in heavier objects appearing to fall more quickly; his theories contradicting earlier belief systems put in place by Aristotle and others; so paving the way for formulation of the modern theories of today. Though the two terms are now used interchangeably in layman's use, strictly by scientific definition, there are distinct differences between ‘gravitation’ and ‘gravity’. The first relates to the influence exerted by different objects which allow them to attract other objects, whereas ‘gravity’ refers specifically to the force possessed by such objects which facilitates gravitation. Certain scientific theories hold that gravitation may be initiated by a combination of factors and not simply the existence of gravity alone; though doubts have been raised regarding some of these theories.
3. Gravity is directly proportional to mass; a smaller object possessing less gravity. To illustrate, the Moon is a quarter of the Earth’s size and possesses only 1/6 of its gravity. The mass of the Earth itself is not spread out proportionally, being flatter at the poles than the equator as a result of its rotation; gravity and gravitational pull in different locations throughout the world also vary. In the 1960s, as a result of research into the worldwide gravity fields, it was discovered that inexplicably areas around and including the Hudson Bay area of Canada appeared to possess significantly lower levels of gravity than other parts of the globe; the reasons for this dissimilarity have since been extensively investigated resulting in two explanations.
4. The original theory attributed this anomaly to activity which occurs 100-200 kilometres below the Earth’s surface within the layer known as the ‘mantle’. The mantle is composed of hot molten rock known as magma which flows under the earth’s surface causing convection currents. These convection currents can result in the lowering of the continental plates which make up the Earth’s surface, as a result when this occurs, the mass in that area and its gravity is also reduced. Research findings indicated that such activity had occurred in the Hudson Bay region.
5. More recently a second conjecture suggested that, in fact, lower levels of gravity in the area are a result of occurrences during the Ice Age. The Laurentide Sheet, which covered most of Canada and the northern tip of the USA until it melted 10,000 years ago, is thought to have been 3.2 kms thick in most parts and 3.7 kms thick over two areas of Hudson Bay. The sheer weight of the ice layer weighed down the surface of the earth below, leaving a deep indentation once it had melted, having caused the area around Hudson Bay to become thinner as the earth’s surface was pushed to the edges of the ice sheet.
6. Extensive investigation has since been carried out by the Harvard-Smithsonian Center for Astrophysics using data collected by satellites during the Gravity Recovery and Climate Experiment (GRACE) between 2002 and 2006. The satellites are placed 220kms apart and orbit 500kms above Earth. Being extremely sensitive to even minor differences in gravitational pull of the areas of earth they pass over, as the first satellite enters an area with decreased gravity it moves slightly away from the earth as the gravitational pull is reduced and also moves slightly further away from the sister satellite that follows, such activity allowing scientists to create maps of gravitational fields. The GRACE findings also allowed scientists to estimate the appearance of Hudson Bay over 10,000 years ago, prior to the great thaw. The areas possessing the lowest gravity today correlate with the areas covered in the thickest layers of ice at that time.
7. Researchers now believe that both theories regarding reduced gravity levels in the Hudson Bay region are accurate and that the area’s characteristics are a result of both magma activity and the impact of the Laurentide Sheet. It has been estimated that the former has resulted in 55-75% of gravity reduction and that pressure resulting from the latter accounts for 25-45%.
8. The effects of the Laurentide Sheet are reversible due to the earth layer’s capability to ‘rebound’ in response to removal of the weight which once restricted it. Returning to the original position, however, is an extremely slow process; it is estimated that the area around Hudson Bay will take a further 5,000 years to recover the altitude it once possessed prior to the Laurentide Sheet. The rebound activity in the area is also measurable through observation of sea levels; unlike the rest of the world, sea levels are not rising in the area as a result of melting ice caps, but are dropping as the land recovers its previous form

Research conducted into the Laurentide Sheet has significant implications on a global scale. The increased knowledge of how that particular area has changed over time and the long-term implications activity in the Ice Age had, pave the way to a better understanding of how current changes elsewhere will manifest themselves over the long term.

Questions 1-6

There are 9 paragraphs (A-I) in the reading passage.

Write the correct heading (from the heading list given below) for the paragraphs B, C, E, F, G and H.

Write the correct answers i-x in boxes 1-6 in your answer sheet.

List of Headings

1. Return to previous form
2. Substantiating a Hypothesis
3. Historic theories
4. General rule of gravity and an exception
5. The initial explanation
6. How proximity to the poles affected Hudson Bay
7. Scientific definition and contemporary views
8. Relevance to our future
9. An alternative view point
10. Consolidating theories

(Guide: The candidates are required to read the given passage very carefully to answer the questions marked 1-6. Each passage can only have one option out of i-x headings as the correct answer.)

1. Paragraph B
2. Paragraph C
3. Paragraph E
4. Paragraph F
5. Paragraph G
6. Paragraph H

Question 1

Answer: (vii) - Scientific definition and contemporary views.

Supporting sentence: Line 4 tells how the new theory developed by Galileo based on the earlier belief system about Gravity and its force by Aristotle ; and in lines 6-8 the scientific definitions are written hence making the heading appropriate for this paragraph.

Keyword: Gravity,gravitation.

Keyword location: Paragraph B, line 6

Explanation: Lines appropriately explain the new and the earlier beliefs in the paragraph ‘his theories contradicting earlier belief systems put in place by Aristotle and others’, also in the last few lines of the paragraph, ‘gravitation relates to the influence exerted by different objects which allow them to attract other objects, whereas gravity refers specifically to the force possessed by such objects which facilitates gravitation,’ gives us the scientific definition of these two terms.

Also, check:

Question 2

Answer: (iv) - General rule of gravity and an exception

Supporting sentence: the paragraph explains about the rule of gravity related to its direct proportionality with mass. Also there is mention of the exception of Hudson Bay.

Keyword: Proportionality, mass, poles, equator, Hudson Bay.

Keyword location: In paragraph C, line 1, lines 6-8

Explanation: In line 1 ‘ Gravity is directly proportional to mass, smaller objects possess less gravity’, in line 7 ‘...Hudson Bay of Canada appeared to possess significantly lower levels of gravity than other parts of the globe…’

Question 3

Answer: (ix) - An alternative view point

Supporting sentence: The paragraph itself suggested in the first line ‘... second conjecture suggested that…’ which makes the title appropriate for this paragraph.

Keyword: Hudson Bay, Laurentide sheet, ice layer, ice sheet.

Keyword location: paragraph E, lines 2, 4, and 6

Explanation: this paragraph mentions and discusses the other theory related to the Hudson Bay low gravity reason. It provides the reason for low gravity at Hudson Bay being the molten rocks (mentioned in the previous paragraph), this Laurentide sheet being melted is the alternative reason.

Question 4.

Answer: (ii) - Substantiating a Hypothesis

Supporting sentence: Howard-Smithsonian Centre for Astrophysics carried out the experiment GRACE (Gravity Recovery and Climate Experiment) between 2002 and 2006 that helped the scientists draw a map of the changing gravity on different surfaces of the earth, hence proving (substantiating) the hypothesis about the Hudson Bay low gravity is due to the thick ice sheet layers at that time.

Keyword: GRACE, gravity, satellite, Hudson Bay

Keyword location: Paragraph F, line 3, line 8

Explanation: The GRACE findings allowed the scientists to understand and establish the hypothesis about Hudson Bay, “the areas possessing the lowest gravity today correlate with the areas covered in the thickest layers of ice at that time”

Question 5

Answer: (x) - Consolidating theories

Supporting sentence: The first theory about the Magma melting and causing gravity reduction in the area around Hudson Bay mentioned in paragraph D, and, the alternative theory of Laurentide Ice sheet for gravity reduction as mentioned in paragraph E. Both the theories were taken to be accurate. Further stating in paragh G, that magma melting is responsible for 55-75% of gravity reduction and Laurentide sheet 25-45%.

Keyword: Magma activity, Laurentide sheet, gravity reduction.

Keyword location: Paragraph G, lines 2-4

Explanation: In this paragh, the two theories of magma melting and Laurentide ice sheet are both accepted to be reasons for the gravity reduction at the Hudson Bay region, “...the area’s characteristics are a result of both magma activity and the impact of Laurentide sheet.”

Question 6

Answer: (i) - Return to previous form

Supporting sentence: This paragraph mentioned about the possibilities of the Hudson Bay area to recover and the time span that it would take, also mentioning how slow this process would be. “...will take a further 5000 years to recover the altitude it once possessed prior to the Laurentide Sheet ''. Hence, the title being appropriate for this paragraph.

Keyword: Laurentide sheet, rebound process, sea levels.

Keyword location: Paragraph H, lines 1, 2 and 6

Explanation: “The effects of the Laurentide Sheet are reversible due to the earth layer’s capability to ‘rebound’...”, the paragraph mentions that the process is possible and it can get back to the position and structure that it once had. “The rebound activity is also measurable through observation of sea levels…”, the recording of the slow process will be the proof of the natural rebound.

Questions 7-11

Do the following statements agree with the information given in the reading passage?

Write your answers in the boxes given from 7-11 on your answer sheets. Marks,

True - If the statement agrees with the information
False - if the statement contradicts the information
Not given - if there is no information on this

(Guide: Candidates must read the passage carefully before answering the questions from 7-11. The answer will be either of the three options - true/False/Not given. Each question can only have one answer from the options)

Question 7

Differentiation between gravity and gravitational pull is generally only made by academics in the field.

Answer: True

Supporting sentence: “ the two terms are now used interchangeably in layman's use, strictly by scientific definition there are distinct differences between ‘gravitation’ and ‘gravity’.” This sentence in the passage given proves the above statement as true.

Keyword: Gravity, gravitation, force, theories

Keyword location: Paragraph B, lines 4-10

Explanation: As precisely mentioned, the two terms might seem to be similar or even one when used in layman’s language, but only when it comes to scientifically differentiating the two, they are different.

Question 8

Gravity levels in areas around the equator are significantly higher than around the poles.

Answer: Not Given

Question 9

It was first believed that lower gravity levels in Hudson Bay could be attributed to its location between the poles and the equator.

Answer: False

Supporting sentence: the Hudson Bay gravity reduction is due to the magma activity and the Laurentide Sheet. These two theories were also taken as accurate and accepted as the reasons for the gravity reduction in the Hudson Bay area.

Keyword: Hudson Bay, Molten magma, Laurentide Sheet.

Keyword location: Paragraph G, lines 1-3

Explanation: In paragraph G, “both theories regarding reduced gravity levels in the Hudson Bay region...are a result of both magma activity and the impact of the Laurentide Sheet”

Hence, the statement given is False. The location of the Hudson Bay between the Poles and the Equator was never the reason.

Question 10

Molten rock activity within the magma layer has had less of an impact on gravity levels in the Hudson Bay area than the Laurentide sheet.

Answer: False

Supporting sentence: The magma layer has had more impact on the gravity levels in the Hudson Bay area than the Laurentide Sheet.

Keyword: Magma, Laurentide sheet.

Keyword location: Paragraph G, lines 1-4

Explanation: In paragraph G, “it has been estimate that the former has resulted in 55-75% of gravity reduction and that pressure resulting from the latter accounts for 25-45% “

The former being the Magma activity and latter the Laurentide sheet. Hence, the statement of the question is False.

Question 11

The GRACE project’s main focus was areas of Canada and North America once thought to be covered by Laurentide Sheet.

Answer: Not Given

Questions 12-15

Complete the sentences using the words given in the box below.

Write the correct answer A-J in your answer sheet in boxes 12-15.

Question 12

The impact of ___________ on objects falling to the ground was not considered by Aristotle.

Answer: J - Air Resistance

Supporting sentence: Galileo figured that as the objects are propelled to the ground at the same time due to gravity, the air resistance resulting in heavier objects appearing to be falling more quickly.

Keyword: Aristotle, Galileo, gravity, air resistance.

Keyword location: Paragraph B, lines 2-4

Explanation: “...his theories contradicting the earlier belief systems put in place by Aristotle…”, the gravitational pull was considered by Aristotle but not the later theory of air resistance was discovered by Galelio.

Question 13

Investigations of ___________ first led to the discovery of the unusual levels in Hudson Bay.

Answer: E - Gravity fields

Supporting sentence: In 1960, it was discovered after a worldwide gravity field research, that the area around Hudson Bay in Canada had significantly lower levels of gravity.

Keyword: Hudson Bay, gravity, research

Keyword location: Paragraph C, lines 5-7

Explanation: “...Hudson Bay of Canada appeared to possess significantly lower levels of gravity, than other parts of the globe”

It was concluded after worldwide gravity field research.

Question 14

The earth’s surface has been observed to sink as a direct result of ___________

Answer: I - Convection currents

Supporting sentence: “These convection currents can result in the lowering of the continental plates which make up the earth’s surface, as a result when this occurs, the mass in that area, and its gravity is also reduced”, this statement supports the above question.

Keyword: convection currents, earth’s surface,

Keyword location: Paragraph D, lines 4-6

Explanation: In paragraph D, it is explained that the layer of the earth’s surface called the mantle, consists of hot molten rocks called magma which flow under the earth's surface causing convection currents.

Question 15

The largest proportion of the Laurentide Ice sheet was ____________ in depth.

Answer: 3.2 Kms

Supporting sentence: “ the laurentide ice sheet which covered most of Canada and the northern tip of the USA until it melted 10,000 years ago, is thought to have been 3.2 kms thick in most parts and 3.7 Kms thick over two areas of Hudson Bay.”

Keyword: Laurentide sheet, Canada, USA, Hudson Bay

Keyword location: Paragraph E, lines 2-4

Explanation: In this paragraph, the above statement is written completing it. The largest Laurentide ice sheet was 3.2 kms thick.