ABSTRACT
It is assumed that the Earth is 4.6 billion years old and that life evolved about 4 billion years ago. Since then, the Earth repeatedly experienced climate warming and cooling. This is known to have arisen through a complex process involving multiple factors including changes in gases in the atmosphere caused by major volcanic activity and photosynthesis, asteroid collisions, changes in the inclination of the Earth’s axis of rotation, the eccentricity of its orbit, and its precession. On a geological time scale, the global environment has experienced carbon cycling, in the process of which carbon fixation has occurred.
