Jklint wrote: ↑December 15th, 2018, 6:42 pm
Greta wrote: ↑December 15th, 2018, 5:14 pm
Given that the number of stars and galaxies capable of hosting habitable planets is wildly overestimated, it is still possible that we are the first or the only. That would not make life on Earth a miracle, just unique or rare.
On that we disagree. How wildly overestimated habitable planets may be it's only that, an estimation. How many galaxies have we examined beyond our own? Do we really have any idea of how many there are with the potential to host intelligent life?
It wouldn't say much for the universe either if we were the only intelligent or even the most intelligent within it. For me, such a scenario amounts to the ultimate absurdity equivalent to Earth having hosted only one human. If we are here, assuming "here" is where we think it is and not manufactured in some computer as a "virtual reality", the possibility of such a singularity owning all the galaxies out there, even if we'll never get to claim direct ownership, is a complete non-sequitur. In a manifold as incomprehensibly huge and complex as the universe wherever there's one there's invariably more than one. If not true then our existence simply defaults to an accident never meant to exist in the first place. It requires a god to cradle life on one rock among the trillions that exist in the universe.
If the laws or processes which created us are indigenous to the universe overall and not merely centered on one place in it called Earth the possibility of there being only one of anything is zero.
Yes, if humanity is the peak of the universe's intelligence then it belongs in the dunce corner of the multiverse (maybe).
Still, there's much overestimation, akin to looking at the Earth and wondering why there's no human settlements at the bottom of the ocean (most of the Earth is inhospitable to complex life). The inner and outer parts of galaxies are most unlikely to host multicellular life due to either excess radiation and activity or a lack of heavy elements respectively. Further, the spiral arms themselves are thought to be highly energetic and possibly hazardous. That leaves the spurs of the arms and the spaces between them. Further, galactic superclusters also probably have habitable zones and otherwise (it would not surprise if galaxies near The Great Attractor, for instance, were sterile).
This update (also in a TED talk) on the Drake equation seems credible, if a dull conclusion:
https://www.universetoday.com/139467/ne ... -universe/
Still, the universe is about 13.8b years old and the Stelliferous Era should last for another trillion years. The cosmos is still in its infancy - in a juvenile form, so to speak. Thus it's all just (interesting) guesswork at this stage. Our apparent isolation may stem from being in a relatively young an active galaxy too. It has been postulated that intelligent life may well be much more rare in a spiral than in ancient elliptical galaxies, where there's very little star formation and is thus a much more stable and less fiercely irradiated environment.