My feeling is the number of galaxies and stars out there is so large, that life elsewhere in the universe seems inevitable.
It feels that way. But... there are impediments, at least for us. A lot has to go right.
Then again, when you have trillions on trillions of possible tries, it seems inevitable, especially for the lowest forms of life.
If you are into cosmology, I recommend the series on Science Channel called "How the Universe Works."
This topic comes up frequently. In this season's episodes, they covered more than the "habitable zone." For example, a few other things that allow us to be here:
- Our funky large moon, we are a double planet
- Our tides (courtesy moon)
- Iron core (protect us against cosmic rays, keep our atmosphere)
- Specific sequence of planet formation (likely two waves from two different supernovas, second wave provided the water)
- Chaotic reassembly
- Extinction events, bad for the time, good for later times (mammals!)
- And on and on
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