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Earth has sustained life for millions of years, yet the other planets in our solar system are incapable of doing so. This is primarily the result of the unique position Earth occupies in the solar system, as it is not too close or too far away from the sun to upset the delicate temperature requirements of life. Our position is in what astronomers call the habitable zone, the place where life exists. Yet, if Earth’s orbit around the sun were thrown off by just a few degrees, all life on Earth may be in danger. Such an event could happen if a passing massive gravitation field influenced Earth’s orbit. Astronomers have experimented extensively with such possibilities and have reached a surprising conclusion: Earth could sustain life if its orbit were changed in minor ways, but only with great dislocation of life.
Astronomers define the habitable zone as the region 75 to 140 million miles from a star with the intensity of our sun. Venus and Mars are outside this zone, the former too close to the sun and the latter too far away. Earth’s orbit is a near perfect circle, almost always 93 million miles from the sun. The average temperature of the Earth is 58˚F with average highs of 107˚F and lows of -81˚F. The axis is tilted so that Earth has various seasons at the northern and southern regions with the equatorial regions having similar weather year round.
The great fear is that a passing black hole will influence Earth’s orbit. Black holes are areas of massive gravitational energy that devour all things they pass, including stars. Astronomers have created computer modeling that allows them to run different orbits for Earth and examined the influences they would have on temperature and climate. As a control element, the computer model maintains Earth’s orbital period of 365 days. Minor variations in the orbit would keep Earth inside the habitable zone all year while a great shift would have Earth passing closer to the sun than Mercury on one end and being beyond the orbit of Mars on the other. Such large changes would dramatically change our climate.
The amazing revelation the astronomers discovered was that with orbit changes in the mid-range, life was still possible, but with significant changes in human places of habitation. Water, which one-fourth of Earth’s surface is composed of, has a tremendous capacity to retain heat. As Earth came extremely close to the sun, the water would pick up massive amounts of heat, which would be used to maintain livable temperature as Earth moved out to the colder regions near Mars. With an orbit passing near Venus but not beyond Mars, temperatures would average 73˚F, very livable. However, there would great changes for the inhabitants of different parts of the globe. People at the Equator would suffer temperatures above 140˚F at times, and great rivers and lakes would evaporate. The polar ice caps would melt, and the coastlines would change, drowning our coastal cities. Northern Canada and Russia would become prime real estate, even during the period when Earth’s orbit was near Mars, as the heat absorbed by the oceans would maintain a livable temperature and forestall the return of the ice caps to a great degree.
A At the other extreme, with Earth inside Mercury’s orbit and outside Mars’s, the temperatures would make life impossible in much of the world, especially the equatorial regions. B In a scenario where Earth was closest to the sun in March and April and farthest away in October and November, the temperatures in Africa, India, South America, and Australia would reach almost 200˚F, near the boiling point, in March. C These areas would cool down by October, but it is highly unlikely that people would form permanent living centers there, as the great heat would return come March. D The bottom line is that Earth will remain livable if our orbit changes mainly because of our great resources of heat-absorbing water. However, this is only because we would still pass close to the sun at one point. If Earth had an orbit permanently outside the habitable zone, either too close or far away from the sun, most life would surely perish.
dislocation: adisplacement; disruption
the bottom line: the most important thing; the essential point
11. The word delicate in the passage is closest in meaning to
A subtle
B fragile
C considerate
D graceful
12. According to paragraph 2, which of the following is true about the habitable zone?
A It can vary in size depending on the intensity of the star a planet orbits.
B It is the area of the solar system outside the orbits of Venus and Mars.
C It is where any type of planet can sustain life for a significant amount of time.
D It fluctuates in size if there is a gravitational pull nearby to affect it.
13. According to paragraph 2, all of the following factors influence climate on Earth EXCEPT:
A Earth’s nearly symmetrical orbit around the sun
B the angle of Earth’s axis as it rotates
C Earth’s position between two other planets
D Earth’s average distance from the sun
14. According to paragraph 3, the astronomers kept Earth’s orbital period the same in their experiments in order to
A judge which months on the planet would be hot and which ones cold
B maintain a familiar element as a reference point for their assessment
C prove that the orbital period would not alter with a change in orbits
D demonstrate that a change in orbits would cause a change in seasons
15. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect answer choices change the meaning in important ways or leave out essential information.
A It was surprising for the astronomers to discover that with orbit shifts in the mid-range, Earth could still sustain life with no significant changes.
B Not surprisingly, the astronomers found out that with mild orbit changes, life was still possible on Earth, but human beings would go extinct.
C Surprisingly, the astronomers learned that with mid-range orbit changes, people could not live in the same places though Earth could still sustain life.
D If Earth’s orbit changed in the mid-range, people could not live in the same places on Earth, which surprised the astronomers.
16. According to paragraph 4, all of the following factors concerning water would be the result of a shift in orbit near Venus EXCEPT:
A the subsequent melting of the polar ice caps
B the loss of a large amount of heat from the oceans
C rising coastal water levels throughout the planet
D the loss of many lakes and rivers in various regions
17. It can be inferred from paragraphs 4 and 5 that after a mild shift in Earth’s orbit, most humans would
A live in the planet’s northern regions
B live on water near the coastal areas
C remain living wherever they are now
D move to the interiors of the continents
18. According to paragraph 5, people would be unlikely to maintain permanent habitats in the equatorial regions in an orbit inside Mercury because of
A the extremes in temperatures during the different seasons
B the great amounts of water that would be lost in the summertime
C the extreme heat in summer that would kill any creatures there
D the constant migrations that people living there would make
19. Look at the four squares [■] that indicate where the following sentence could be added to the passage.
One of the big questions, which had no concrete answer, was in which months Earth would be closest to and farthest from the sun.
Where would the sentence best fit?
Click on a square [■] to add the sentence to the passage.
20. Directions: Complete the table below to summarize the information about Earth’s orbit as discussed in the passage. Match the appropriate statements to the correct orbits of the Earth when it is inside Mercury or near Venus. This question is worth 3 points .
Drag your answer choices to the spaces where they belong.
To remove an answer choice, click on it. To review the passage, click on View Text.
Inside Mercury
Select 3
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·
·
Near Venus
Select 2
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A Earth’s orbit would sometimes be beyond Mars.
B All the life on Earth would die.
C Life would be difficult but not impossible during the hot seasons near the Equator.
D Earth’s temperature would rise up to 73˚F on average.
E Life anywhere near the equatorial regions would be impossible to sustain.
F The planet’s polar ice caps would remain intact.
G People would be forced permanently to change location.