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Oops. Forgot to mention chlorophyll's absorption in the blue range. (To be honest, I just plain forgot it. We didn't spend nearly as much time on chlorophyll as on hemoglobin, and all the example calculations regarding the energy and efficiency of photosynthesis were done with the peak in the red.) (And looking back, I am embarrassed to have spelled chlorophyll wrong. That's what I get for posting first thing in the morning, while trying to type up notes on a different topic.)
If you want a look at the absorption spectra of chlorophyll and some other plant pigments, you can check out
As far as the reason for trees being green--well, as I said above, there are other pigments that absorb in other parts of the visible range. Why is chlorophyll the dominant one in most plants? I suspect it's complex. I'm sure there are several good stories hiding among the thoughts that follow from this discussion.
Actually, my next major project, once the current novel is done, involves plants, so I need to be thinking along these lines soon anyway. Thanks, everyone, for getting me started!
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Actually, while we're on the subject of light absorbtion there's an interesting story I heard about WWII. The science is valid, but I don't know if it actually happened.
After someone has cataract surgery they can see farther into the infrared spectrum that normal people. In the story I heard, (on Car-talk so there's no telling if it's based in fact.) there was an agent behind enemy lines who used an infrared lamp to signal a boat. The boat used an older soldier who'd had cataract surgery to get read the signals.
Even if it's not true, having aliens who see farther up and down the spectrum than we do could off some interesting possibilties.
[This message has been edited by MaryRobinette (edited May 27, 2004).]
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I also heard that Cartalk. (I get homesick every time I listen to that program!) I'll have to ask my grandmother-in-law if the world looks different; she just had cataract surgery last week.
Actually, in the novel I'm working on, I have aliens who see farther into the UV than humans. It's not a major aspect of the story, though it has offered a few interesting twists.
Look, of course the actual molocular structures that we call hemoglobin and chlorophyl are red and green, respectively (actually, there are several different types of each...more different types of hemoglobin than chlorophyl, though, for the simple reason that all chlorophyl comes from a single common ancestor).
But chlorophyl doesn't only derive energy from light at a specific wavelength. That's a misconception. And the red color of mammalian hemoglobin is a biochemical accident of the gross shape of the molecule, it doesn't come about because the hemoglobin contains iron any more (or less) than because of all the other elements it contains--it is the molecule as a whole that determines the color.
If you add iron to glass, it turns it green, not red (if you want red glass, you need to use gold rather than iron).
The visible color of a substance is usually an accident of it's molecular composition. There are quite a few exceptions, but neither hemoglobin nor chlorophyl are among them.
posted
As far as the color of hemoglobin--granted, the overall molecule plays a role in fine-tuning the precise color, but it is largely dependent on the iron. If you remove the heme group, the protein itself is pretty much colorless in its pure form. Most proteins are. The heme group exerts more influence on the color than the protein does, because it's complexed directly with the iron. (Anyone who's studied more than basic chemistry, you can think of heme binding to iron as a big organic coordination compound.)
Granted, in terms of the grand scheme of things, the color of hemoglobin is a biological accident. Unlike chlorophyll, its color doesn't play a role in its function. It is, however, a direct result of the same things that allow it to carry out its function.
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What about the appearance of your aliens...are they crystaline or rock-based or humanoid at all or evolved into a humanoid shape of the animal or plant that once dominated the planet and has since developed augmented senses of their non-evolved "cousins"?...is that a place to start for you Ms. Christine...or even an extinct species from our planet didn't actually become extinct on our planet, just taken to a different one to evolve?....( say like the dinosaurs or whatnot )...leave me a response and let me know what you think of these ideas....
[This message has been edited by Monolith (edited June 03, 2004).]
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Human blood is red in air because the Iron Oxidizes.(I know it's been said, I'm just reiterating.) Horeshoe Crabs have blue because their blood is Nitrogen Based. (It's good stuff, Vital for drug production.) Now If something were to have Copper based blood, it would be green. What if our alien had Uranium based blood, with all the glowiness and the radioactivity. That would be fun. Is Uranium really green like they show? And our governments will be taking them and Harvesting the stuff. And Iron is a rare comodity to them so they are attacking us. I can even see the title 'War of The Blood'
Monolith, I've seen many good stories about Dinosour aliens. Why don't we go for something else, like the Dodo bird? Intelligent Dodo birds coming to meet their cousins and finding that their cousins were destroyed but evil Rats. (and dogs but Rats are better enemies.
quote:And Iron is a rare comodity to them so they are attacking us
Have you ever read Triplanetary, by EE "Doc" Smith? That plot is used there. They have a wonderful weapon that just extracts all the iron from an object they point it at...
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So what we really need is someone with uranium whose willing to leave it out in the rain. Then I need to get one of those Iron-Sucker-thingies Then I could rule the world. (which world I'll never know.) Posts: 1895 | Registered: Mar 2004
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