GRE RC Select Many Sample Questions
NASA is more than halfway through a search for asteroids and comets that come within striking distance of Earth—called “near Earth objects,” or NEOs—and are wider than a kilometer. Experts calculate that the chance of an object that size hitting Earth in the next century is only one in several thousand, but the result would be global havoc. After astronomers spot an asteroid in their telescopes, they use radar tracking to get a more precise picture of where it’s headed, how fast it’s moving, and whether its orbit around the Sun will intersect with Earth’s orbit. Of the 600-plus large NEOs tracked thus far, only 1950DA poses any threat at all. But at this stage of the search, there are an estimated 400 potential global killers left to find, not to mention over a million hard-to-spot smaller asteroids capable of regional destruction. Making the tallying work trickier are a few long-period comets, which only swing by every few hundred years and aremuch more difficult to track.
The asteroid interception and diversion experts have been focusing on the use of solar collectors, which could concentrate sunlight on an asteroid, vaporizing enough material to gradually nudge the rock off course. It would take years for sunlight to redirect an asteroid, so advance notice is absolutely critical. Given ample time, an effective defense strategy might require that a probe be launched to study the structure of the incoming body. Not all asteroids are the solid objects familiar from museum meteorite displays. Some are porous, others are collections of rubble loosely held together by gravity. Exploding a nuclear bomb nearby might nudge a dense asteroid off track, but it could break a brittle one into pieces, effectively multiplying the threat by creating smaller but still lethal rocks. One approach uses so-called kinetic kill vehicles—numerous small spacecraft placed in an asteroid’s path. Hit by hit, they slow it down enough that Earth will pass through the projected collision point before the asteroid does. Also possible is a dock-and-push approach, in which a spacecraft parks on the asteroid’s surface, fires its thrusters, and alters the trajectory. Still, none of this will work without advance notice. Currently, NASA expects to find only about 90 percent of the NEOs large enough to cause global catastrophes. The remaining 10 percent are too dark for today’s telescopes, or too difficult to distinguish from the many asteroids that orbit harmlessly in the solar system’s main asteroid belt between Mars and Jupiter.
Consider each of the choices separately and select all that apply.
1. An impending catastrophe that can be caused by an asteroid can be averted by
- A. detonating a nuclear weapon on the path of the asteroid
- B. placing obstacles in the path of the asteroid
- C. concentrating solar energy on the asteroid’s surface
- D. waiting and watching as it will take years to divert an asteroid from its path
- E. getting forewarned
The correct answers are B, C and E
It has been clearly brought out that detonating a nuclear bomb near an asteroid will be successful in diverting it from its path only if the asteroid is dense. The threat from the asteroid will be multiplied if it is brittle. A is ambiguous in the sense that it does not specify the type of asteroid being referred to. Therefore, A is incorrect. D is clearly incorrect as simply waiting and watching will not be able to avoid the impending catastrophe in any way whatsoever. All the remaining answer options have been brought out as effective means for diverting an asteroid from its path of collision with Earth. Therefore, B, C andE are the correct answers.
2. According to the author, it is safe to say that Earth does not face any threat from
- A. “numerous small spacecraft placed in an asteroid’s path”
- B. “hard-to-spot smaller asteroids”
- C. “a dense asteroid”
- D. “asteroids that orbit harmlessly in the solar system’s main asteroid belt between Mars and Jupiter”
- E. “long-period comets”
The correct answers are A and D.
It is obvious that A is correct as the small spacecraft have been placed in the path of the asteroid to divert the asteroid from its path. These spacecraft definitely do not pose a threat to Earth and hence, A is correct. The author uses “hard-to-spot smaller asteroids” to refer to asteroids that are capable of regional destruction and are still left to be found. They are a potential threat to Earth although on a smaller scale. Therefore, B is incorrect. A dense asteroid may not pose a threat to Earth if it is nudged off its course by a nuclear explosion. Therefore, in the context in which it has been used by the author, C is incorrect. It has been clearly brought out that the asteroids in the main asteroid belt of the solar system as indicated by D do not pose any threat to Earth and hence, D is correct. The author makes a reference to ‘long-period comets’ to emphasise that there are some comets that are difficult to track and to ascertain if they are a threat to Earth. There is no indication of the fact that such comets are definitely a threat to earth. At the same time, there is no assurance that these comets are harmless. In view of the ambiguity involved, E is incorrect. Therefore, A and D are the correct answers.
3. It has been emphasised that advance notice is critical because
- A. an asteroid will take a long time to cross Earth’s orbit
- B. a strategy for averting a collision with Earth will take time for being tested and implemented
- C. strategies for deflecting an asteroid from its path will be a slow process
- D. numerous asteroids are yet to be found
- E. some NEOs swing close to Earth every few hundred years
The correct answers are B and C
It has been brought out that advance notice is critical because time will be required to work out a strategy to divert an asteroid from its path of collision with earth. Such a strategy will have to be tested first and the shortcomings of the strategy will have to be worked out before it is finally implemented. Moreover, a strategy like usage of sunlight for deflection of an asteroid will be a slow process so advance notice will be crucial for its success. In view of the above, it is evident that B and C are correct. Options A, D and E are clearly incorrect as they are not related to the importance of advance notice with reference to an impending collision with Earth. Therefore, B andC are the correct answers.
4. Which of the following conclusions based on the contents of the passage are justified?
- A. There is no danger of an asteroid colliding with the Earth in the next 100 years
- B. An asteroid’s collision with Earth cannot be avoided if it is not destroyed
- C. Exploding a nuclear bomb near an asteroid is the most effective method for avoiding its collision with earth
- D. Asteroids differ in their constitution
- E. All asteroids do not cross the Earth’s orbit
The correct answers are D and E.
It has been brought out in the beginning of the passage that there is a chance that a NEO will hit the Earth in the next century. Therefore this possibility cannot be entirely ruled out and hence, A is incorrect. The author has highlighted ways and means for slowing down an asteroid to avoid its collision with Earth. Therefore, B is incorrect. C is clearly incorrect as it has been clearly brought out that the threat to Earth in this strategy will be multiplied if the asteroid is brittle. The author has clearly emphasised on the different types of asteroids and therefore, D is correct. E is also correct as it has been explained that astronomers need to verify whether the orbit of the asteroid will intersect that of Earth around the Sun and this implies that all asteroids do not cross the Earth’s orbit. Therefore, D and E are the correct answers.
5. The sentence, “Exploding a nuclear bomb nearby might nudge a dense asteroid off track, but it could break a brittle one into pieces, effectively multiplying the threat by creating smaller but still lethalrocks” implies that
- A. It could be catastrophic for earth if a nuclear explosion is triggered near an asteroid
- B. A nuclear explosion near an asteroid will divert it from its track
- C. The nuclear explosion being discussed is for diverting an asteroid which is on its path of collision with Earth
- D. The technique discussed cannot be compared with the one explained in the succeeding sentence for achieving the required effect
- E. There are no chances that the technique explained may fail to achieve the desired results
The correct answers are A, B and C.
The author gives a brief introduction to the effects of triggering a nuclear blast near an asteroid. It is clearly mentioned that the consequences would be disastrous if the asteroid breaks into small fragments. The succeeding sentences clearly indicate that the asteroids being discussed are the ones that are on a path that is likely to cross that of the Earth. This implies that the conclusions mentioned at A, B and C can be implied from the given sentence and hence, all of them are correct. The technique mentioned in the given sentence and that in the succeeding sentence both aim for avoiding a direct contact of the asteroid with Earth. Since, the desired result for both the techniques is the same; they both can be compared to identify the one that would be better. Therefore, the conclusion at D is not justified and hence, D is incorrect. The nuclear explosion is being triggered with the aim of deflecting the asteroid from its path. If it breaks into fragments, this aim will not be achieved. Therefore, E is an incorrect answer option. Hence, A, B and C are the correct answers.
GRE RC Select Many Sample Questions