Many people dream of traveling into outer space. However, spending too much time in space may cause health problems. That’s why astronauts shouldn’t spend more than six months on the International Space Station (ISS) at a time.
Muscle (肌肉) and bone loss(骨质损失). In a weightless environment, astronauts don’t need to use their muscles to support themselves. So their muscles start shrinking (萎缩). To keep their muscles strong, astronauts need to exercise for about two hours each day on the ISS.
Sleep disorder (紊乱). In space, the sun rises every 90 minutes. It is hard for astronauts to get used to this light-dark cycle (循环) when they sleep. Also, they need to sleep in a sleeping bag that is fixed to a wall. It is uncomfortable. Now astronauts have individual (单独的) sleeping pods (睡眠舱) that help shut out some of the light. Still, studies have found that most astronauts only sleep about six hours each night, even though they should have eight and a half hours.
Brain changes. Scientists have found that the position of the brain changes during spaceflight. This can influence how the brain deals with how we see, stay balanced (平衡) and move around. That’s why some astronauts can’t control their movement and balance after returning to Earth. Scientists have also found that astronauts may get used to this change after going on more spaceflights. But they still need to do more research.
【小题1】When astronauts don’t use their muscles in space, _______.| A．they should eat much meat | B．their muscles start shrinking |
| C．they need to exercise all day | D．they can’t support themselves |
| A．the weight | B．the temperature | C．the light | D．the air |
| A．his muscle shrinks | B．he can’t sleep well |
| C．he doesn’t have any research | D．the position of his brain changes |
A． | B． | C． | D． |
