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# Forget hostile aliens. According to a forthcoming book by noted astrop

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Forget hostile aliens. According to a forthcoming book by noted astrop  [#permalink]

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22 May 2018, 11:30
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New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Passage # 26, Date : 13-FEB-2019
This post is a part of New Project RC Butler 2019. Click here for Details

Forget hostile aliens. According to a forthcoming book by noted astrophysicist Egbert Larson, the intrepid humans who first attempt interstellar space travel will face far more daunting challenges before they ever meet the Little Green Men. Larson begins with the problem of relativistic time dilation. If you travel all the way to Alpha Centauri, you’d like to come back and tell your friends about it, right? It’s not too likely to happen, though. If Mr. Einstein was right about relativity—and we’re not going to say he wasn’t—then time slows down when you approach the speed of light. A person traveling at any velocity near the speed of light will age only days for every week, month, or even year that passes on earth. Relativity does not present a problem for interstellar space travel, per se, but it does mean that interstellar civilizations or even just interstellar communications will require a mind-boggling amount of calendar juggling.

Did we mention that you’d have to travel at near the speed of light? That’s because the distance between stars is so vast that even if you could travel at the speed of light— which, Larson reminds us, you can’t—it would take more than four years to reach our closest star neighbors, Alpha Proxima and Alpha Centauri, and decades or centuries to reach the other stars in our “immediate neighborhood.” And if you tried to accelerate directly to the speed of light like they do in the movies, you’d be instantly splattered on the back of your theoretical spacecraft. Achieving anything close to light speed will require sustained acceleration at a level that human bodies can withstand—say, a crushing two gravities—for over a year. Better hope somebody brings some chips.

Speaking of chips, food is going to be a problem. Since it is economically, if not physically, impossible to accelerate 200 years’ worth of food to nearly the speed of light, and since you’re not likely to find any grocery stores along the way, someone will have to figure out how to make food in space. Keeping a crew alive on the way turns out to be the trickiest part of all. Once you’ve got the nearly impossible physics of space travel worked out, you still have to figure out the chemistry and biology of keeping your air and water clean and keeping your crew fed and safe from radiation and infection, and—did we mention the 200 years?—you’ll probably need several generations of crew members to complete the trip. Ever been on a bus for more than 24 hours? It’s not a pretty picture.

We applaud Larson for his insightful writing and his scrupulous attention to scientific detail. For those of you seeking a cold, hard look at the reality of interstellar space travel, this is a stellar read. But be warned: Larson doesn’t let you down gently. For those of you sincerely hoping to beam up with Scotty—and you know who you are—you might want to give this one a pass.

1. According to the information given in the passage, if two 20-year-old twins lived on earth, and one of them left on a journey for Alpha Centauri at very close to the speed of light, then managed to survive the journey and return to earth having aged 40 years during the journey, what could she expect to find upon her return to earth?

A. Her great-grandmother
B. Her twin at the age of 20
C. Her twin at the age of 40
D. Her twin at the age of 60
E. Her twin’s great-grandchildren

2. Which of the following inventions, if it could be perfected and manufactured at a viable cost, would address the most challenges to human interstellar space travel, as presented in the passage?

A. A ram-scoop drive that can accelerate a spacecraft of any size to four-fifths of the speed of light within 24 hours
B. A cold-sleep capsule that essentially halts the passage of time for human inhabitants while protecting them from all physical harm
C. A sustainable biosphere that reliably generates healthy food and automatically cleans air and water
D. A neutrino-based communications system that permits instantaneous communication across any distance without any relativistic time dilation
E. An impervious force field that protects the ship and its inhabitants from radiation, meteor strikes, or hostile alien attacks

3. The author of the passage most likely mentions “Little Green Men” in the first paragraph for what purpose?

A. To poke fun at the ignorance of most science fiction readers
B. To introduce a daunting challenge that will have to be addressed before human interstellar space travel can become possible
C. To draw a comparison between the attempts of humans to voyage in space and the more successful attempts of other civilizations
D. To draw an amusing distinction between a supposed danger of space travel, as presented in the popular media, and the actual challenges posed by interstellar space travel, as perceived by scientists
E. To suggest that the concept of human interstellar space travel is as much of a myth as the “Little Green Men” that appear in science fiction movies and television programs

Source: McGraw-Hill's GMAT 2013
Difficulty Level: 700

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01 Jun 2018, 22:48
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Can you give OE for question 2.
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Forget hostile aliens. According to a forthcoming book by noted astrop  [#permalink]

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03 Jun 2018, 05:11
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Princ wrote:
Can you give OE for question 2.

Official Explanation

2. Which of the following inventions, if it could be perfected and manufactured at a viable cost, would address the most challenges to human interstellar space travel, as presented in the passage?

Explanation

B addresses all the survival issues handled by C, and in addition its protection “from all physical harm” addresses the radiation mentioned in E and the acceleration problems that are inherent in A. B also protects against the daunting passage of time necessary for interstellar space travel. Based on the information in the third paragraph, the invention in A would not be usable without some other protective invention because humans could not withstand that rate of acceleration. D would be an astounding invention on its own, but it does not address as many of the challenges mentioned in the passage as B. B is the best answer. Why hasn’t someone invented this thing yet?

Hope it Helps
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Re: Forget hostile aliens. According to a forthcoming book by noted astrop  [#permalink]

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15 Feb 2019, 12:43
This is a really good passage! I liked it!! For me, it's a 700!!
It's perfect!!! Thank you for posting it
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Re: Forget hostile aliens. According to a forthcoming book by noted astrop  [#permalink]

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24 Mar 2019, 00:11
The author of the passage most likely mentions “Little Green Men” in the first paragraph for what purpose?
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24 Mar 2019, 06:01
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diljeetsingh wrote:
The author of the passage most likely mentions “Little Green Men” in the first paragraph for what purpose?

Official Explanation

3. The author of the passage most likely mentions “Little Green Men” in the first paragraph for what purpose?

Explanation

The passage states: “Forget hostile aliens. According to a forthcoming book by noted astrophysicist Egbert Larson, the intrepid humans who first attempt interstellar space travel will face far more daunting challenges before they ever meet the Little Green Men.” While the passage is light in tone, it does not suggest that the aliens are necessarily a “myth,” as in E, or that those who believe in them are ignorant, as in A. On the other hand, it does not say that they exist or that humans are likely to contact them, which rules out C. The point of the introduction is that there are more daunting immediate problems than the theoretical risk of alien attacks, so B is out. D captures the essence of the introduction.

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Re: Forget hostile aliens. According to a forthcoming book by noted astrop   [#permalink] 24 Mar 2019, 06:01
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