I would like to know the name of the theory which states that the Earth is a living organism much like us human beings. And what it means in today's context. I suppose it's a fairly famous hypothesis.
The theory you asked about is known as the "Gaia Hypothesis".
The Gaia hypothesis has both scientific and philosophical components.
Gaia is theorized to be a living entity that is greater than the
sum of all the living and non-living aspects of the Earth. In
proposing this theory, James Lovelock sought to explain the
many complex natural mechanisms that the earth has for regulating
things such as climate and biological diversity. In this theory,
the whole Earth is a sentient "being" that regulates processes in
the natural environment by balancing various aspects of it against others.
Gaia makes modifications to itself as necessary in order to keep itself
"running smoothly" for as many of it's "aspects" as possible (be them specific
organisms such as humans or entire ecosystems such as the oceans).
Gaia does not have an "anthrocentric" (centered on humans)
perspective and we are only one small part of the overall entity
that Gaia is theorized to represent.
Because it is only a theory (and a rather controversial one at that) it's "meaning" in a modern scientific or social context must be judged on the basis that it provides a viewpoint, or a framework, for describing and understanding the Earth; it does not, however, provide absolute answers to questions we have about our planet.
Nevertheless, it is important for natural and social scientists to consider this theory when they conduct research and collect data that is intended to help us understand the Earth because it provides one possible explanation for "how things work". Additionally, it provides a very important perspective that is often missing in human intellectual endeavors: that we are not the center of form and function for the world in which we live. Rather, it reminds us that Earth will maintain some sort of balance as humans continue to modify it and this balance, while being satisfactory for most aspects of Gaia, may not be satisfactory for us. If humans are mindful of the present functioning of "Gaia" (or the whole Earth) and try to keep our modifications to a minimum, it stands to reason that Gaia (or something like it if it exists) will continue to help make Earth livable for us.
I would like to point out that while this theory seems "far out" to some (and certain aspects are difficult for me to believe), almost any Earth scientist, ecologist or other natural scientist will tell you that complex and delicate balances that keep the oceans and atmosphere and lakes and forests and other things "functioning properly" are so intricate and orderly that if it isn't a living being that controls it all, it certainly sometimes acts like one. Thus, whether Gaia is a sentient being or simply a device for explaining the very complex functioning of nature in a way humans can relate to, the theory of Gaia has a well-deserved place in modern scientific paradigms.
Ken Rubin, Professor
Department of Geology and Geophysics
University of Hawaii, Honolulu HI 96822