The Copernican Principle and Rare Earth
The rare earth hypothesis states that life, like our own, is a very rare occurrence throughout the universe. Scientists believe it is about 4.5 billion years since the earth was formed. However, it has been 500 million years since complex life started existing on the earth. It is still unclear about the chain of events that led to the surfacing of complex life on face of the earth. The hypothesis also argues that complex life emergence needs some fortuitous circumstances. These circumstances are placed under several headings; a circumstellar and galactic habitable zone. They can also be placed under other headings like the availability of large satellite and gas giant guardian. A long period of stable climate is one of the circumstances that scientists consider necessary for the existence of complex life. The hypothesis also suggests that the existence of life on earth required an incredible blend of geological events and astrophysical circumstances. It also implies that most parts of the known universe are not able to support complex life. The parts of the universe that do not sustain complex life are known as ‘dead zones’. On the contrary, those parts of the galaxy that can be able to sustain complex life are called galactic habitable zones (Ward 34).
The Copernican revolution, which is also known as the principle of mediocrity contradicts initial beliefs that the earth is the central point of the universe. In his writings, Nicolas Copernicus proposes a heliocentric system as opposed to the adversely known geocentric system at those times. Heliocentric means that the sun is at the centre of the universe. The planets rotate the sun, which is fixed on the one position in this system. He implied that all planets keep the same annual movement apart from the sun (Ward 45).
The Copernican principle or the mediocrity principle contradicts the rare earth theorem in that the Copernican principle suggests that the earth is a typical planet, while the earth hypothesis assumes that there is nothing special about the earth and humanity. In support of the uniqueness of the earth, several arguments are laid down. Some analysts suggest that complex life can only be supported by the earth and not anywhere else in the planet (Scharf 7). Those in favor of rare complex hypothesis put across several conditions needed to sustain complex life on earth. Life creation requires a combination of organic chemicals for reaction to occur; in addition, this requires large water bodies. Only planet earth has been proved to have significant quantities of liquid water. Temperatures vary across planets. In planets with very high temperatures, the water will boil into vapor form whereas for that planet with very low temperature, the water freezes (Scharf 7).
The rare earth theorem can be seen as less scientific in the fact that it assumes that life is rare in the universe and can only be found on earth. This assumption cannot be supported scientifically. Other planets found in the universe may support life. In a case where extraterrestrial life is discovered, our lives would change forever. Seeing life in a different planet would shock, terrify or excite us. There has been no proof that there are no lives in other planets although the conditions for life to exist are rare in these other planets. Other planet and the moon may have the potential to hold life. However, the latter would have to be at some ultimate distance from the parent star. The ideal distance at which it has to be is called habitable zone. If this condition exists, life can be supported. As these zones have not been deemed non-existent, the rare earth can be said to be less scientific compared to the Copernican principle (Ward 22).
Scharf, Caleb A. The Copernicus Complex: Our Cosmic Significance in a Universe of Planets and Probabilities. , 2014.
Ward, Peter D, and Donald Brownlee. Rare Earth: Why Complex Life Is Uncommon in the Universe. New York: Copernicus, 2004.