Why are there no restaurants on the moon? Great food. No atmosphere. The atmosphere is the layer of gases that surrounds a planet or other massive body. Although our atmosphere extends for tens of miles, almost ninety-nine percent of it is within eighteen miles of the earth's surface.
Our own atmosphere is mostly nitrogen, with about twenty-percent being the oxygen we breathe. But, a planet doesn't start out having an atmosphere like ours. Much of the carbon dioxide that envelops earth, for example, was originally embedded inside rocks, and later released by heat from the sun. About a billion years ago, simple green plants started generating oxygen, which soon became a major part of our atmosphere as well.
为何会月球上没有餐厅？很棒的食物。没有大气层。大气层是环绕星球或其他巨大天体的大气层。虽然我们的大气层延伸几十里，几乎99％的大气都在地球表面18英里范围内。我们自己的大气层主要成分是氮，约20％的成为我们呼吸的氧气。但是，一个星球最初时的大气层和我们的大气层并不一样。很多二氧化碳笼罩大地，比如，原本储存在岩石内的二氧化碳，经过太阳的加热而被释放出来。大约10亿年前，简单的绿色植物开始产生氧气，氧气很快成为了我们的大气层主要部分。