现在世界的总人口是多少？今年全世界生产了多少辆汽车？排放了多少二氧化碳气体？消费了多少石油？打了多少吨鱼？一连串的问题，都可以在Worldmeters找到数据，而且这些数据是实时更新的。包括的大类有世界人口、政府与经济、教育和媒体、环境、食品、水、能源、健康等8个大类，每个大类又由许多统计项目构成，具体请看下图。Worldmeters的数据来源都是非常可靠的，具体可以看这里。
Worldmeters-world statistics updated in real time.
如果把地球上的水和空气都打包的话，就是上图中的样子。左图是把所有的水都放到一个球里，这个球并不大，直径1390公里，体积约14亿立方公里。这包括了河湖海冰所有的水了。右图是把所有的空气放到一个球体里。直径1999公里，5140兆吨，半数的空气存在于 距地面5公里的大气层中。水和空气，其实就那么一点点。
（图片和资料来源：ADAM NIEMAN / SCIENCE PHOTO LIBRARY）
Global water and air volume
Conceptual computer artwork of the total volume of water on Earth (left) and of air in the Earth’s atmosphere (right) shown as spheres (blue and pink). The spheres show how finite water and air supplies are. The water sphere measures 1390 kilometres across and has a volume of 1.4 billion cubic kilometres. This includes all the water in the oceans, seas, ice caps, lakes and rivers as well as ground water, and that in the atmosphere. The air sphere measures 1999 kilometres across and weighs 5140 trillion tonnes. As the atmosphere extends from Earth it becomes less dense. Half of the air lies within the first 5 kilometres of the atmosphere.
(via sciencephoto.com)
