What is the Rare Earth Hypothesis?
The Rare Earth hypothesis argues that the development of complex complex multicellular life on Earth required an extremely unlikely combination of astrophysical and geological events and circumstances. Some of the circumstances that had to be just right are: – the sun is in the galactic habitable zone – the Earth is in the sun’s habitable zone – the Earth is the right size – we have a large moon – the Earth has a magnetic field, plate tectonics, the right chemistry of the lithosphere, atmosphere, and oceans – the role of “evolutionary pumps” such as massive glaciation and rare bolide impacts (and whatever led to the still mysterious Cambrian explosion of animal phyla) In order for a small rocky planet to support complex life, the values of several variables must fall within narrow ranges. The universe is so vast that it could contain multiple Earth-like planets. But if such planets exist, they are likely to be separated from each other by many thousands of light years. The main opposin
The Rare Earth hypothesis claims that the Earth is rare, and that few planets can support complex life. The Rare Earth hypothesis stands in contrast to the principle of mediocrity, which assumes that the Earth must be a typical planet, as there should be nothing special about humanity or the Earth. Numerous arguments for the Rare Earth hypothesis have been put forward, to explain why the Earth is unique; some analyses suggest that the Earth is the only planet capable of supporting complex life in the Milky Way, or even the entire visible universe. Supporters of the Rare Earth hypothesis point out the long list of conditions needed to evolve complex life on Earth. Abiogenesis, the creation of life, requires a broth for organic chemicals to react in, which in turn requires large bodies of water. No planet other than Earth is known to have liquid water in significant quantities, and few planets have the right temperature for water to stay a liquid; if the planet is too hot, the water will
Gonzalez: The Rare Earth hypothesis simply proposes that Earth-like planets capable of supporting complex life are not as common as many astronomers have believed. Is it only astronomy that seems to be leading to the conclusion that Earth is rare? Gonzalez: No. The more inclusive discipline of astrobiology is tending that way. Astrobiology is really an interdisciplinary topic, which includes astrophysics, biochemistry, celestial dynamics, climatology, comparative planetology, life in extreme environments, among others. It is ironic that some astrobiologists would come to the position of our rarity, given that most in this field are motivated by the hope of one day finding intelligent life on another planet. About the only field that has produced evidence in the other direction is extremophile research. But, at the same time, we’ve learned that Mars, today, appears to be sterile, even though it probably got a helping of Earth’s microbes early on via meteorite transfer. Are you in comple
Gonzalez: The Rare Earth hypothesis simply proposes that Earth-like planets capable of supporting complex life are not as common as many astronomers have believed. Is it only astronomy that seems to be leading to the conclusion that Earth is rare? Gonzalez: No. The more inclusive discipline of astrobiology is tending that way. Astrobiology is really an interdisciplinary topic, which includes astrophysics, biochemistry, celestial dynamics, climatology, comparative planetology, life in extreme environments, among others. It is ironic that some astrobiologists would come to the position of our rarity, given that most in this field are motivated by the hope of one day finding intelligent life on another planet. About the only field that has produced evidence in the other direction is extremophile research. But, at the same time, we ve learned that Mars, today, appears to be sterile, even though it probably got a helping of Earth s microbes early on via meteorite transfer. Are you in comple
