[TML] Waterworld Ecology

[Jerry W Barrington]

On 10/4/07 10:06 AM, "Garry Ward" wrote:

> On Thu, Oct 04, 2007 at 08:24AM, "Timothy Little" wrote:
>> On Thu, Oct 04, 2007 at 06:35:27AM -0400, Garry Ward wrote:
>>> Clouds would only block certain wavelengths of light; the version of
>>> photosynthesis on this world might use other wavelengths of light
>>> that pass through the clouds. In fact, to the locals, the 'clouds'
>>> that humans talk about might not even be visible.
>> 
>> That is a good point, but there is a good reason why we see in the
>> wavelengths of light that we do: firstly, because it is energetic
>> enough to efficiently be absorbed in causing chemical changes.
>> Secondly, because the Sun puts out far more of it than in other
>> wavelengths.  Other temperatures of star will peak at different
>> wavelengths, but still within the visible spectrum.
>> 
> True.
> 
> There is also the problem that a heavy cloud cover will trap infared and
> raise the air temp something ugly, far beyond tropical. Which is going to
> mean that for a cloud enshrouded planet to be less than a blast furnace, the
> amount of incomming infrared is going to have to be low to slow the heating
> effect (or at least better balance the in and out infrared rates).
> 
> Which probably means that we're talking about a planet around a red star
> rather than a yellow which will, clouds or not, have an affect on the
> ability of local life to use photosynthesis.
> 
> But photosynthesis isn't the only game in town, as we are beginning to learn
> with some of the 'extremophiles' we're finding here on earth.

The Sun (Sol) peaks in the middle of the visible spectrum, with a
temperature of about 5778K.  Any cooler star will peak at redder
frequencies, with a lot more IR.  Below something like 4000K, IR will
dominate.  Likewise hotter stars will peak bluer, with more UV.  Higher than
about 10000K, UV will dominate.

One big issue of course, is what bands the atmosphere passes or blocks.  But
one would expect the natives to evolve both vision and photosynthesis best
adapted to the local light, as it reaches the surface.

And it's not just incoming IR that gets trapped.  A lot of the more
energetic photons get absorbed then re-emitted as IR.  And this greenhouse
effect can make a world habitable if it's further out from it's star.  :)