Re:What If We Haven’t Met Aliens yet Because They’ve Messed ...
by LorenPechtel on Saturday August 03, 2019 @08:33PM
(#20603696)
We have managed to at least ballpark numbers for many of the terms in the Drake equation.
Planets are common.
Given the speed with which life evolved on Earth it's also probably common.
That leaves four barriers:
1) Multi-cellular life. Looking at Earth that took billions of years--it's likely a hard barrier to cross.
2) Intelligence. It took hundreds of millions of years but there were a lot of steps, this doesn't seem like evidence that it's all that hard.
3) A term not in the Drake equation--effective lifespan of the biosphere. This is the main argument of the Rare Earths hypothesis. Most planets do not remain stable enough for intelligence for long enough for it to arise. Looking at our own world we can see that we have already used up 99% of that time, we barely eeked under the line. (We have only about 50 million years before solar warming can be countered by lowered CO2, after that we have several hundred million more habitable years but they won't be friendly to big, slow-evolving animals of the sort needed for intelligence.) This very well might be a substantial barrier.
4) Intelligence is destructive, species that can communicate do not remain in that state for long. Note, also, that a species that can communicate probably can in an eyeblink of galactic time do interstellar colonization. Even by slowboat they should spread across the galaxy in at most a few tens of millions of years. Also, once a species has reached this point it would be almost impossible to destroy--thus we can conclude no species in the history of the galaxy reached this point.
The product of these terms must be infinitesimal. Either we have been extremely lucky so far, or we are facing an almost insurmountable barrier to survival in the near future.
Planets are common.
Given the speed with which life evolved on Earth it's also probably common.
That leaves four barriers:
1) Multi-cellular life. Looking at Earth that took billions of years--it's likely a hard barrier to cross.
2) Intelligence. It took hundreds of millions of years but there were a lot of steps, this doesn't seem like evidence that it's all that hard.
3) A term not in the Drake equation--effective lifespan of the biosphere. This is the main argument of the Rare Earths hypothesis. Most planets do not remain stable enough for intelligence for long enough for it to arise. Looking at our own world we can see that we have already used up 99% of that time, we barely eeked under the line. (We have only about 50 million years before solar warming can be countered by lowered CO2, after that we have several hundred million more habitable years but they won't be friendly to big, slow-evolving animals of the sort needed for intelligence.) This very well might be a substantial barrier.
4) Intelligence is destructive, species that can communicate do not remain in that state for long. Note, also, that a species that can communicate probably can in an eyeblink of galactic time do interstellar colonization. Even by slowboat they should spread across the galaxy in at most a few tens of millions of years. Also, once a species has reached this point it would be almost impossible to destroy--thus we can conclude no species in the history of the galaxy reached this point.
The product of these terms must be infinitesimal. Either we have been extremely lucky so far, or we are facing an almost insurmountable barrier to survival in the near future.