Archive for October, 2010

The Great Filter

With no evidence of intelligent life other than ourselves, it appears that the process of starting with a star and ending with “advanced explosive lasting life” must be unlikely. This implies that at least one step in this process must be improbable. Hanson’s list, while incomplete, describes the following nine steps in an “evolutionary path” that results in the colonization of the observable universe:

1. The right star system (including organics & potentially habitable planets)
2. Reproductive molecules (e.g. RNA)
3. Simple (prokaryotic) single-cell life
4. Complex (archaeatic & eukaryotic) single-cell life
5. Sexual reproduction
6. Multi-cell life
7. Tool-using animals with big brains
8. Where we are now
9. Colonization explosion

According to the Great Filter hypothesis at least one of these steps – if the list were complete – must be improbable. If it’s not an early step (i.e. in our past), then the implication is that the improbable step lies in our future and our prospects of reaching step 9 (interstellar colonization) are still bleak. If the past steps are likely, then many civilizations would have developed to the current level of the human race. However, none appear to have made it to step 9, or the Milky Way would be full of colonies. So perhaps step 9 is the unlikely one, and the only thing that appears likely to keep us from step 9 is some sort of catastrophe. So by this argument, finding multicellular life on Mars (provided it evolved independently) would be bad news, since it would imply steps 2–6 are easy, and hence only 1, 7, 8 or 9 (or some unknown step) could be the big problem.

Although steps 1–7 have occurred on Earth any one of these may be unlikely. If the first seven steps are necessary preconditions to calculating the likelihood (using the local environment) then an anthropically biased observer can infer nothing about the general probabilities from its (pre-determined) surroundings.








尽管如此,经过时间以及概率的累积,新的星系内产生越来越多的星体,太阳系内部星体被干扰的可能性越来越来,直到不可避免。太阳系中的太阳也许能幸存,但最终,在10 x10的17次方年,已经死去的太阳及其他星体,将被附近的星体撕裂。整个太阳系,从任何角度来说,都将不复存在。

-Wikipedia The Free Encyclopedia