On the station,the ordinary becomes strange.The exercise bike for the American astronauts has no handlebars.It also has no seat.With no gravity,it’s just as easy to pedal violently.You can watch a movie while you pedal by floating a microcomputer anywhere you want.But station residents have to be careful about staying in one place too long.Without gravity to help circulate air,the carbon dioxide you exhale(呼气)has a tendency to form an invisible(隐形的)cloud around your head.You can end up with what astronauts call a carbon-dioxide headache.

　　Leroy Chiao,54,an American retired astronaut after four flights,describes what happens even before you float out of your seat.“Your inner ear thinks you’re falling.Meanwhile your eyes are telling you you’re standing straight.That can be annoying—that’s why some people feel sick.”Within a couple of days—truly terrible days for some—astronauts’ brains learn to ignore the panicky signals from the inner ear,and space sickness disappears.

　　Space travel can be so delightful but at the same time invisibly dangerous.For instance,astronauts lose bone mass.That’s why exercise is considered so vital that National Aeronautics and Space Administration(NASA)puts it right on the workday schedule.The focus on fitness is as much about science and the future as it is about keeping any individual astronaut healthy.NASA is worried about two things:recovery time once astronauts return home,and more importantly,how to maintain strength and fitness for the two and a half years or more that it would take to make a round-trip to Mars.

【2017届《名师A计划》高考英语新人教版一轮复习配套练习：必修5 Unit 3《Life in the future》（含解析）】相关文章：

★ 【北京专用】2014届高考英语一轮复习方案课时作业：选修7 Unit 3 Under the sea

★ 贵州省贵阳市2014高考英语（新人教版）一轮阅读训练（20）附答案

★ 2014年牛津译林版高中英语总复习（第1轮）同步练习 M5《Unit 3　Science and nature》

★ 2017高考四川省广安市英语阅读理解一轮系列训练：2（含解析）

★ 【北师大版】2014届高考英语一轮复习指导课时作业：Unit 7 B卷 Word版含解析

★ 【北师大版】2014届高考英语一轮复习指导课时作业：Unit 5 A卷 Word版含解析

★ 【北京专用】2014届高考英语一轮复习方案课时作业：必修5 Unit 5 First aid

★ （安徽专用）2014届高考英语一轮复习方案 作业手册（22）模块8 《Unit 22 Environmental Protection》（含解析） 北师大版必修1

★ 【三维设计】2017版（江苏专用）二轮复习练习：必修1 Unit 1《School life》课时跟踪检测A卷（含解析）

★ 【课堂新坐标】2017届高考英语（通用版）二轮复习书面表达专题训练：Ⅱ卷强化增分练 训练2（含解析）