[LMB] Chlorophyll

Markus Baur baur at chello.at
Sat Dec 25 17:38:07 GMT 2021

otoh mars has a redish atmosphere


with bluish sunsets




Am 25.12.2021 um 18:30 schrieb Fred:
> we know that the blue in our sky comes from a specific (very tiny) particle
> size causing scattering of a narrow band of wavelengths of blue light (
> https://en.wikipedia.org/wiki/Diffuse_sky_radiation). Therefore I would
> expect that other worlds with an atmosphere of similar thickness would
> exhibit the same phenomenon. I can't imagine pink or orange or whatever
> being a natural sky color (failure of imagination??)
> I saw a video a few years ago of a MIT prof demonstrating this in the
> lecture hall by dimming the lights then blowing cigarette smoke into a
> chamber illuminated by a specific "color" of light. without the smoke it
> was white, with the smoke it was sky-blue.
> therefore I have a shortage of patience when an author (contemporary, not
> ancient, from before we knew about this phenomenon) posits a non-blue sky.
> Fred
> On Sat, Dec 25, 2021 at 12:19 PM Karen Hunt <huntkc at gmail.com> wrote:
>> On Sat, Dec 25, 2021 at 12:05 PM WILLIAM A WENRICH <wawenri at msn.com>
>> wrote:
>>> So are there chemicals/elements as or more common than magnesium that
>>> could be used?
>> On earth, not really. Elsewhere? We don't know enough. Best reference I can
>> give you:
>> https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements
>>>> The plants on Barrayar (on topic for once) are red and brown instead of
>>>> green (Ekaterin remarked that a green Barrayan plant would be very
>> sick.)
>>>> because the plants use a different chemical. This appears to be a
>> common
>>> SF
>>>> trope but do we know of any other chemicals that would work?
>>>> Also the sky on other planets is written to be just about any color.
>> Pink
>>>> or butterscotch on Mars?
>>> Sergyar's sky is apparently turquoise. Not sure what makes the greenish
>>> additions to the blue that comes from having an ozone layer.
>>> Some plants here on earth run to the reds - some just in fall, others
>> also
>>> in spring and other times (thinking of Japanese maples). These plants
>> have
>>> chlorophyll in the leaves, but also have lots of carotenoids.
>>> Now blood is red primarily because the hemoglobin includes a central
>> iron,
>>> and chlorophyll has a central magnesium (I think that gives it the color,
>>> but I'm not a chemist). One could picture a planet that built its
>>> energy-collecting storage around a different element than magnesium and
>>> thus having a different base color, but again, I am NOT a chemist and I
>>> don't know how well the game works with other metals.
>>> ------ imagining a system where the plants picked arsenic to put at the
>>> core of their not-chlorophyll: definitely they'd be poisonous to earth
>>> critters. On the other hand, I don't think arsenic is ever likely to be
>> as
>>> common as magnesium, so evolutionary attempts to use it would fail
>> against
>>> other critters using magnesium. ------
>>> --
>> --
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