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.

【2016届高考英语考前必做黄金易错点：专题14 阅读理解（专题）（原卷版）】相关文章：

★ 常熟市2014高考英阅读理解语一轮（暑假）训练题（11）及答案

★ 2016届高考英语考前必做黄金易错点：专题14 阅读理解（易错练兵）（原卷版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题03 辩论对比话题指导（学生版）

★ 【课堂新坐标】2017届高考英语（通用版）二轮复习短文改错专题训练：训练4 短文改错（Ⅳ）（含解析）

★ 2017届高考英语二轮复习大题冲关秘籍阅读理解七选五：名校模拟（含解析）

★ 重庆市2014高考英语阅读理解一轮（精品）训练题（1）附答案

★ 2017届高考英语二轮复习大题冲关秘籍短文改错：体验真题（含解析）

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

★ 浙江省湖州市2014高考英语阅读理解一轮（暑假）精炼（3）含答案

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题12 人物类话题指导（学生版）