Spaceship earth example
Our planet Earth can be compared to a spaceship because, like the spaceship, it is a self-contained vessel orbiting the sun. It is also a nearly closed system where little gets in or out. The only significant input into our "spaceship" is the energy from the sun in the form of light and heat and the only thing that leaves our atmosphere (other than radio and TV waves and a real spaceship, of course) is the heat that is reflected or radiated from the surface of our planet.Spaceship Earth is composed of all the ingredients to support human life. In a never-ending loop, humans take food, water, air and raw materials from the environment to sustain their lives and produce products like houses and clothing and cars. Some of the resources we need to live2are renewable in that they can be regenerated. Examples of renewable resources are oxygen from plants, fresh water through the hydrological cycle, food crops, and timber. Resources that are considered non-renewable are such things as oil, natural gas, and coal.Unfortunately, human life in our spaceship also creates wastes in the form of sewage, air pollution, water pollution, radiation, and unwanted chemical and solid waste. In the past, we depended on Mother Nature to cleanse herself of these unwanted contaminates. Today, as the human population rapidly increases and our thirst for more and more products grows steadily, we depend on technology and environmental controls to help keep our spaceship clean and healthful.