On Earth，gravity is the force that keeps your feet on the ground and your sandwich on your plate.But there's no gravity in space.To keep food from floating away，astronauts on the Space Shuttle attach the packets to a special tray.The tray can be fixed to a wall or to the astronaut's lap.To prepare their food，astronauts use liquid forms of salt and pepper.The liquid sticks to the food better.Regular salt and pepper would float away，maybe up an astronaut's nose.Achoo!

　　Liquids float right out of cups and glasses，though.So astronauts drink everything from a small bag with a straw(饮料吸管) that can be closed.Astronauts say that most space foods taste pretty good.Some，such as apples and pudding are the same as the foods you eat on Earth.

　　Astronauts eat tortillas(玉米粉圆饼) instead of bread because they make fewer crumbs(碎屑)．Floating crumbs could get stuck in equipment or an astronaut's eye.

　　Your body uses food in space the same way it does on Earth.Your body must get rid of waste in space too.

　　During take off and landing，astronauts can't leave their seats to go to the bathroom.They wear diapers(尿布) under their spacesuits instead.

　　The Space Shuttle has a bathroom the size of a small closet.The toilet has bars that keep astronauts from floating away.

　　A strong flow of air is used instead of water to flush waste down the toilet.Back on Earth it's flushed away－or sometimes studied by scientists.　

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