Discussion
How truly unique is Earth in the grand scheme of the galaxy? I see many mentions of "Earth-like" planets meaning basically rocky (vice gaseous), with an atmosphere, within the "Goldilocks zone", and within a few multiples of Earth's size. But those definitions include Mars and Venus, and neither of those are really Earth-like.
How many planets have we found that seem to be actually like our Earth -- a place where humans could possibly live without having to wear life-support suits or to terraform? [Side question: How much gravity difference could humans survive long term?]
How unique is Earth with regard to having such a wide variety of climates? I mean, looking at the planets just in our Solar System, it looks like the old sci-fi trope of each being one climate or geological feature is a norm, and our varied planet geology is special.
