Another example of a technogaian practice is an artificial closed ecological system used to test if and how people could live and work in a closed biosphere, while carrying out scientific experiments. It is in some cases used to explore the possible use of closed biospheres in space colonization, and also allows the study and manipulation of a biosphere without harming Earth's. The most advanced technogaian proposal is the "terraforming" of a planet, moon, or other body by deliberately modifying its atmosphere, temperature, or ecology to be similar to those of Earth in order to make it habitable by humans.