The above diagram is an over_simplification of the spatial relationship between the cosmic and the terrestrial environments. It represents the local neighbourhood of the cosmos in relation to the terrestrial realms which life has inhabited for the last 4 billion years. It shows the definition of the terrestrial environment to be the earth/moon binary eco-system. It shows that this terrestrial nature is part of a greater nature which, to a first approximation, may be taken to be the local representative of the huge abundance of those natural cosmic entities which every child knows to be the stars.
Additionally, we observe in the diagram, that although the terrestrial environment appears to be a subset of the cosmic environment, it is also infused with the nature of the cosmos: that of sunshine - starshine. The impregnation of sunshine into the terrestrial realms has generated the myriad phenomena of life. Born, it is told, in the primeval oceans of a young half-billion year old planet and its tidal moon, the first stirrings of microbiological Gaian life appeared.
The terrestrial atmosphere, it is said, was then (some 4 billion years ago) very much like both the Martian and Venusian atmospheres are now ... about 96% carbon dioxide. The very first living things - single celled organisms known today (yes - they still exist) as prokaryotes - were single celled organisms without a cell nucleus, and largely functioned as living photosynthetic systems - taking in the carbon dioxide and giving out oxygen. These primal living organisms took just 2 billion years, by the processes of photosynthesis, to convert the earth's atmosphere to its present levels of life-bearing oxygen, and set the stage for the furtherance of life in the evolution of multi-cellular and aerobic organisms.
Thus, by systematic prevalence over vast geological time spans, we may clearly