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届高考英语一轮复习考点真题演练：Section 12 阅读理解之时闻报道类（含解析）】相关文章：

★ 2017届高考英语二轮复习课时训练：20（含解析）

★ 2017高考四川省广安市英语阅读理解一轮系列训练：26（含解析）

★ （安徽专用）2014届高考英语一轮复习方案 作业手册（15）模块5 《Unit 15 Learning》（含解析） 北师大版必修1

★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (23)

★ 2017届高考英语二轮复习大题冲关秘籍语法填空：命题分析（含解析）

★ 2017高考四川省广安市英语阅读理解一轮系列训练：16（含解析）

★ 2017高考四川省广安市英语阅读理解一轮系列训练：30（含解析）

★ 2017年高考英语二轮复习精品资料：专题14 阅读理解（押题专练）（原卷版）

★ 2017届高考英语二轮复习课时训练：17（含解析）

★ 2014高考英语（新人教版）一轮基础训练（11）A、B卷（附答案或解析）