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

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. Which of the following would make the most appropriate title for this passage?

A. Going Boldly Where No One Has Gone Before: The Promise and Peril of Interstellar Space Travel
B. The Day the Earth Stood Still: Why Interstellar Space Travel Is Essential to Human Survival
C. The Wrath of Larson: Egbert Larson’s Quest to Build an Interstellar Spacecraft
D. Busted Flat in Beta Regulus: The Crushing Challenges of Interstellar Space Travel
E. Say It Isn’t So, Mr. Einstein: Egbert Larson’s Challenge to the Theory of Relativity


2. Based on the tone and content of the passage, it is most likely which of the following?

A. A book review in a journal intended for astrophysics professionals
B. A movie review in an entertainment industry publication
C. A book review in a science magazine aimed at a general audience
D. A book review in a newspaper
E. A transcript of a talk given at a science fiction convention dedicated to “The poetry of space”


3. The passage implies that all except which of the following could be threats to human health during extended interstellar voyages?

A. Meteor impact
B. Radiation poisoning
C. Accelerating too fast
D. Starvation
E. Old age


4. According to the passage, which of the following will present the most difficult challenge for humans attempting interstellar space travel?

A. Achieving velocities near the speed of light
B. Withstanding the acceleration necessary for traversing interstellar distances
C. Maintaining clean air and water on a journey that could last centuries
D. Accommodating the effects of relativistic time dilation
E. Enabling the humans on board to survive during the journey


5. 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


6. 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


7. 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