>>18505232That is incorrect. The Earth has never been out of the habitable zone. It's way past Mars.
The habitable zone is 0.38 to 10.0 astronomical units, Earth to the Sun is 1 AU. We're not in the center, but we're nowhere near the edge. Our orbit is slightly elliptical and moves from aphelion to perihelion within only 3M Miles. Earth would need to go another 822.6 million miles away from the sun to leave the zone.
It is true that Earth is not perfect for life (Antarctica exists) but we don't know what more perfect would look like. Being a little closer or farther both seem like it would be negative for us. Bigger and things would be too heavy, smaller and the core may not last as long. A better planet would need many different parameters which we try to define on other star systems. So far "Habitable zone" just refers to where water can be liquid based on a Star's temperature and what we know about our system. But it's not perfect, the habitable zone does not refer to human life. We would go extinct long before animals that survive near thermal vents.
JWST will help us understand more once it gets spectral analysis of extra solar planets but we don't have the info to better define it.
