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Originally Posted by CraigS
Interesting discussion … I'll be frank in saying that I'm not sure about it all myself ..
I mean, the Earth will get eaten up by the Sun (or collision with Andromeda, etc), so we have to find ways of leaving the place, eventually. So, we have to fund that exercise. Otherwise, following the "do nothing/don't spend" path logically results in us never escaping !
However, when you look at the unbelievable diversity of environments within our own Solar System planets/moons, it seems to me that the chances of finding another "goldilocks zone" are very slight. (Ie: extrapolating from our own earth-bound perspective, that is).
This then, is counter to the cosmological principal. So, how can one make the quantum leap from our own Solar System observations/empircial evidence to the guiding Cosmological Principle without a little 'faith' ?
Now there's a real question for a Cosmologist/Astro Physicist!! 
Cheers |
Habitable zones are a feature of all stars, no matter how large they are. The most pressing factor which dominates above all other is just how long that zone remains habitable for and how wide it is. Smaller stars may have very long lifetimes, but there HZ's are smaller than larger stars. So, there's less chance of planets being in them, given all factors. Larger stars have wide HZ's, but they don't last as long. Also, so these zones migrate over time, as stars increases in luminosity as they age. Our own star's HZ is getting larger and further out as it ages....in about 1 billion years, this place will be uninhabitable as the Sun by then will be about 10% brighter than now. We are in the process of migrating out of the HZ of the Sun, due to it shifting outwards.The Earth will lose its water because of this. But even before then, the increasing luminosity will make living here much more difficult. For instance, in about 500 million years, C3 plants (those that photosynthesise 3 carbons to produce energy) will be becoming extinct, as the increasing luminosity of the Sun robs the atmosphere of CO2 (due to increasing oxydation) and the partial pressure drops below sustainable levels for these plants. C4 plants will last another 200-400 million years, but not much longer. After that, when the surface temp reaches an average of 50 degrees and there's no plants left, oxydation will begin to runaway and rob the atmosphere of the gas. With our oceans becoming water vapour, the temp will heat up (GH effect), more oxydation will occur, the water will breakup due to increasing temp and higher UV, but the CO2 in the rocks will by now be getting cooked out. Eventually, the Earth will end up like Venus is now...in about 2-2.5 billion years.
There will be goldilocks zones no matter where we go and they will be as common as the stars themselves, so there's an almost 100% certainty of finding one. Just what's there and what's happening is another question altogether.