I think the Drake equation isn’t really the way to estimate the probably of intelligent life—there is just too much we don’t know to use the inside view. Take one thing like the Moon and we just don’t know how important it was to have intelligent life on Earth (it definitely played a significant role, stabilizing the Earth orbit, and helping the sea ⇒ land transition with tidal forces) nor how rare such big satellites are.
To me the only way to look at it is to use the outside view, and do a reasoning like :
Look at us, and, like you said and realize it took us 5 billions of years to exist, which is actually half of the lifespan of Earth. We don’t know if we were exceptionally fast or exceptionally slow, but it gives an order of magnitude of the time it takes for intelligent life to appear on a planet with good conditions.
Realize that it would be exceptional coincidence if another intelligent life would appear within 0.1% of the time it took us—so if there is intelligent life somewhere else, it’s likely to be 5 millions of years in advance, or 5 millions of years late from us. 5 millions of years late means they are still apes.
Look around us, and see no trace of alien life—no Von Neumann probe visiting our system, no Dyson spheres or ringworlds around. And yet, if they were 5 millions of years in advance, we would very likely see such things.
So either there is a “great filter” and most of them didn’t make it to space, or just, well, intelligent life is rare, because it takes in average 20 billions of years to appear even if conditions are good, and we were lucky to be fast enough to exist before the Sun became a red giant. Which that there will be occasional intelligent life in the universe, but so far apart that we didn’t see them yet. If our nearest neighbor exists since 0.3 billion of years, but is 0.5 billions of light year from us, well, we’ll sill need a long time before communicating with them.
I think the Drake equation isn’t really the way to estimate the probably of intelligent life—there is just too much we don’t know to use the inside view. Take one thing like the Moon and we just don’t know how important it was to have intelligent life on Earth (it definitely played a significant role, stabilizing the Earth orbit, and helping the sea ⇒ land transition with tidal forces) nor how rare such big satellites are.
To me the only way to look at it is to use the outside view, and do a reasoning like :
Look at us, and, like you said and realize it took us 5 billions of years to exist, which is actually half of the lifespan of Earth. We don’t know if we were exceptionally fast or exceptionally slow, but it gives an order of magnitude of the time it takes for intelligent life to appear on a planet with good conditions.
Realize that it would be exceptional coincidence if another intelligent life would appear within 0.1% of the time it took us—so if there is intelligent life somewhere else, it’s likely to be 5 millions of years in advance, or 5 millions of years late from us. 5 millions of years late means they are still apes.
Look around us, and see no trace of alien life—no Von Neumann probe visiting our system, no Dyson spheres or ringworlds around. And yet, if they were 5 millions of years in advance, we would very likely see such things.
So either there is a “great filter” and most of them didn’t make it to space, or just, well, intelligent life is rare, because it takes in average 20 billions of years to appear even if conditions are good, and we were lucky to be fast enough to exist before the Sun became a red giant. Which that there will be occasional intelligent life in the universe, but so far apart that we didn’t see them yet. If our nearest neighbor exists since 0.3 billion of years, but is 0.5 billions of light year from us, well, we’ll sill need a long time before communicating with them.