摘要
Conditions in space are very different from those on Earth.There is no air to breath.The temperature can be freezing cold or boiling hot.Without the protection of Earth's atmosphere,the Sun's rays are very dangerous.Spacecraft like the shuttle(航天飞机)and the ISS(International Space Station国际空间站) are built to make humans as comfortable as possible in space.They have their own supply of air.They have temperature controls.They have hulls (外壳)and windows that block the Sun's dangerous rays.
