Replies

I'm reminded of the book, "Rare Earth", which argues that simple unicellular life is very likely quite common throughout the universe, but complex life...not so much.

True, but when you look at the sheer scale of planets in the known universe that can possibly harbor life of any kind, the number of those likely to have intelligent life is still mind boggling.

Some scientists, armed with recent findings of extrasolar planetary systems, have plugged that data into the famous Drake Equation and have concluded that there could be as many as 12,000 planets harboring intelligent life in our galaxy alone.

I fully expect for planetary explorations in our own solar system to turn up some forms of microbial life in the next few decades. Europa is an excellent candidate for that.

I'm skeptical...if even a small fraction of those had technology comparable to ours (or significantly higher) I think we would have detected their radio emissions by now.

I fully expect for planetary explorations in our own solar system to turn up some forms of microbial life in the next few decades. Europa is an excellent candidate for that.

And not just Europa! There's increasing evidence that subsurface oceans of liquid water are downright common in our solar system, even in bodies as small as Ceres and Enceladus!

Not going to argue the numbers since the numbers are unimaginable but I will point out that galaxies are very violent places particularly close to the galactic center. And some galaxies (elliptical) are more violent then others (spiral). In general you can rule out complex intelligent life (CIL) forming near the center of just about any galaxy it is just to violent a place.

Also the chances of CIL are unlikely at the edge of just about any galaxy due to a lack of violent activity. It seems to take a few generations of big stars (nearby super novas) to create the materials needed for life. To close to the galactic center is to violent, to far from the galactic center is not violent enough. So we can reasonably eliminate most of the billions of trillions of stars in the know universe. Perhaps only 15% or so are in the right place to possible candidates for CIL.

Still a considerable number of stars. But not all stars are the same. Quite a few of the 15% or so would not be stable enough long enough to permit CIL. Consider this; The Earth has been in the Suns Goldilocks zone for 4 billion years and will remain there for another few hundred million years. Call it 4.5 billion. How many Stars are that stable that long? Only Sun sized or smaller stars. Of course the Goldilocks zone is smaller for smaller stars so the chance of an Earth like (rocky) planet forming there is also less likely.

My point here is not to argue the numbers, they are overwhelming. But also overwhelming is the incredible luck it takes to get the right conditions at the right time for complex intelligent life. It almost makes one think that life here on Earth was planned. Lol, crazy talk!