Earth as a Living Planet

I recently wrote a note on the number of possible habitable planets. You can read it [here]. Here I want to emphasize the Relevant Science aspect of this fact. An introductory study of Astronomy teaches us how unique the Earth is.

Four conditions are important for life:

1. Surface liquid water
2. Atmospheric oxygen
3. Plate tectonics
4. Climate stability

It is not accidental, that oxygen in the atmosphere is produced by life, and it is necessary to have life as we know it. This is a feedback mechanism. At some point in the beginning of life on Earth, the atmosphere was made of a compound with carbon. CO₂. Carbon dioxide does not help mammals to move on the surface. These organisms need energy, oxygen provides this energy, and it is produced by plants, which do not move.

As James Lovelock postulated many years ago,  Earth seems to be alive. He called it Gaia.