Life on Kepler-62-e and Kepler-62-f

Originally posted by Soothfast
Okay. Biological evolution is wishful thinking. Got it.

Good for you.

Originally posted by Soothfast
Okay. Biological evolution is wishful thinking. Got it.

I have no idea where you came up with that. What I said was wishful thinking is the Gaia hypothesis.

Originally posted by Soothfast
You sure about that?

Water vapor may have greenhouse attributes, but if it forms clouds in the upper atmosphere it reflects sunlight and has a cooling effect. Of course clouds are basically bodies of condensed water vapor, and that's the difference.

The greenhouse properties of water are well known, the net effect of clouds less so. Although clouds reflect, they reflect in all directions thus trapping heat already here rather than allowing it to radiate back to space. Venus is the most reflective (highest albedo) planet in the solar system due to total cloud cover and yet it is still very hot!

Originally posted by twhitehead
Whether accepted as having happened or not, it remains more or less a valid possibility ie if earth gets enough ice cover, it turns into a runaway process resulting in a global freeze.

You don't really need total ice cover in any case. Ice bergs within a few degrees of the equator is quite extreme enough I'd think even if there is open water between the bergs.

Originally posted by Soothfast
Now now -- not so fast. It depends on the type of cloud.

http://science.nasa.gov/science-news/science-at-nasa/2002/22apr_ceres/

Thick clouds comprised of liquid water droplets -- which are the kind that I have in mind -- apparently cool the planet. Thin, high clouds comprised of ice crystals do trap heat.

The net effect of clouds is poorly known simply because we don't have 100% cloud cover of one sort on this planet. Even where there is a good covering of thick water droplet clouds there may well be other types of cloud above that. This is one reason climate models provide such variable results, we don't actually know how to code for clouds.

Originally posted by Kepler
Venus is the most reflective (highest albedo) planet in the solar system due to total cloud cover and yet it is still very hot!

So how does that work? Does this mean it radiates less on its night side? Or is the "highest albedo" thing 'total reflection' rather than 'total radiation' during day time? ie the heat radiation is ignored.

Originally posted by twhitehead
So how does that work? Does this mean it radiates less on its night side? Or is the "highest albedo" thing 'total reflection' rather than 'total radiation' during day time? ie the heat radiation is ignored.

Huge greenhouse effect. The atmosphere is dense and has a very high carbon dioxide content. Albedo measures how much light the thing reflects, which is why it seems so bright to us. However, the albedo is not 100% so some of that solar radiation gets through and is then trapped within the atmosphere leading to a surface temperature sufficient to melt lead.

Originally posted by Kepler
Huge greenhouse effect. The atmosphere is dense and has a very high carbon dioxide content. Albedo measures how much light the thing reflects, which is why it seems so bright to us. However, the albedo is not 100% so some of that solar radiation gets through and is then trapped within the atmosphere leading to a surface temperature sufficient to melt lead.

So earth has a lower albedo, but is actually brighter over the whole magnetic spectrum?

Originally posted by twhitehead
So earth has a lower albedo, but is actually brighter over the whole magnetic spectrum?

No, Venus is the brightest planet in the solar system. Albedo measures the proportion of solar radiation that is reflected back to space so a lower albedo would result in less brightness. Earth's albedo ranges between 30% and 40% according to cloud cover etc whereas Venus' is relatively constant at about 65%. Venus is also closer to the sun so is reflecting 65% of more incident radiation.

Originally posted by twhitehead
I have no idea where you came up with that. What I said was wishful thinking is the Gaia hypothesis.

Okay, well, it is just a hypothesis, but there certainly could be something to it. If a species can evolve in reaction to its environment to maximize its chance of survival, there could be subtle mechanisms whereby the biosphere as a whole evolves along lines that enhance collective survival. Not much can be influenced: the atmosphere, ocean salinity, and a few other factors, but it's not an implausible notion. It may be difficult to test, however.

So I guess I do buy into the Gaia hypothesis somewhat. When I said early on that I didn't I was referring mainly to the hippie-dippy idea that the Earth as a whole is a "living organism" -- which is popularly regarded as an integral component of the hypothesis but was never actually advanced by James Lovelock that I'm aware of.

Originally posted by Kepler
The greenhouse properties of water are well known, the net effect of clouds less so. Although clouds reflect, they reflect in all directions thus trapping heat already here rather than allowing it to radiate back to space. Venus is the most reflective (highest albedo) planet in the solar system due to total cloud cover and yet it is still very hot!

The sun is maybe twice as intense at Venus than at Earth, and its clouds have a different chemical composition.

As you say there is currently too little known about clouds, and so as far as we know it may be possible for the Earth to have a different cloud composition so as to offset a solar radiation increase of 10 percent a billion years from now.

If civilization is still around a billion years hence, I could envision a network of millions of reflective screens being put into orbit to reflect some of the incident radiation before it can enter the atmosphere.

Originally posted by Soothfast
If a species can evolve in reaction to its environment to maximize its chance of survival, there could be subtle mechanisms whereby the biosphere as a whole evolves along lines that enhance collective survival. Not much can be influenced: the atmosphere, ocean salinity, and a few other factors, but it's not an implausible notion.

There is a very big difference between something being a 'plausible notion' and suggesting that it is the case. There is nothing wrong with proposing it as a hypothesis and testing it. But until you have one shred of evidence, or at least a reasonable suggestion as to a mechanism that would cause it, then it remains wishful thinking.
We know of many instances of life forms modifying their local environment beneficially, and of life forms living in symbiosis, so the concept that life forms may on the small scale evolve in such a way as to benefit each other via environmental modification is not that far fetched, but I think on a global scale the equations are quite different. I think there would be a tendency to adapt to the environment rather than modify it, of if there was modification it might be a continuously drifting one, rather than a tendency towards stability. And there would always be winners and losers. In evolution there is always a delicate balance between selfish behaviour and societal behaviour.

Originally posted by Soothfast
The sun is maybe twice as intense at Venus than at Earth, and its clouds have a different chemical composition.

As you say there is currently too little known about clouds, and so as far as we know it may be possible for the Earth to have a different cloud composition so as to offset a solar radiation increase of 10 percent a billion years from now.
...[text shortened]... ing put into orbit to reflect some of the incident radiation before it can enter the atmosphere.

Provided we don't end up with Venusian sulphuric acid droplet clouds I suspect we'll be OK if survive that long.

Originally posted by twhitehead
There is a very big difference between something being a 'plausible notion' and suggesting that it is the case. There is nothing wrong with proposing it as a hypothesis and testing it. But until you have one shred of evidence, or at least a reasonable suggestion as to a mechanism that would cause it, then it remains wishful thinking.
We know of many inst ...[text shortened]... evolution there is always a delicate balance between selfish behaviour and societal behaviour.

I might be indulging in "wishful thinking" if I planned on being around a billion years from now and was worried about getting a sun burn.

Originally posted by twhitehead
There is a very big difference between something being a 'plausible notion' and suggesting that it is the case. There is nothing wrong with proposing it as a hypothesis and testing it. But until you have one shred of evidence, or at least a reasonable suggestion as to a mechanism that would cause it, then it remains wishful thinking.
We know of many inst ...[text shortened]... evolution there is always a delicate balance between selfish behaviour and societal behaviour.

I see evilution as wishful thinking on the part of atheists.