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When the Earth Was Purple
Ollabelle writes "It's always been a bit of a mystery why plants absorb red and blue light, reflecting green, when the sun emits the peak energy of the visible spectrum in the green. A new theory offers one possible answer: that the first chlorophyll-utilizing microbes evolved to exploit the red-and-blue light that older green-absorbing microbes didn't use, eventually out-competing them through greater efficiency and the rise of oxygen."
The article mentions that when looking for life elsewhere in the universe, "We should make sure we don't lock into ideas that are entirely centered on what we see on Earth", suggesting basically that we don't just look for green plants, but accept that plants on other planets could be any color.
Duh.
I can't understand people who think that to find life on other planets we have to look for conditions similar to Earth. All of the hubbub over liquid water seems so silly to me. We have *no idea* what life on other planets might be like. I think that the only thing to look for is patterns which we don't believe could occur in nature, suggesting that the anti-entropy force of life might be present.
Anyway, I'm kind of a skeptic already, I don't think that looking for life outside our galaxy is particularly interesting or useful anyway, considering that the nearest life would be millions of years away by interstellar travel. Even if it's out there, we'll never meet it or communicate with it.
Green is the new purple, completly off topic but a scary resemblance.
I don't buy into it because (a) these people aren't rational and (b) taking away their religion could make them worse - they could easily be converted into Stalinists or extreme nationalists. But I am sure that this, as well as the desire to get budget for exploration, is one of the factors in the search for life on Mars, and in SETI.
Finally, looking for water is not irrelevant. Any practical life form is going to need a solvent and carrier for the various chemicals it needs to get from place to place internally. Water is unique because its strong hydrogen bonding gives it a wide liquid temperature range. Other small molecules which are good solvents also tend to have very low boiling points, meaning that the range of reactions that can take place in them is much more limited. Water has very unusual properties, in fact, that make it more probable that life would evolve on a planet with lots of liquid water than, say, one covered in methane or liquid carbon dioxide.
Pining for the fjords
Specific wavelengths of light are required to kick the electrons in specific molecules into the required energy level... i.e. Plants are green because red & blue light is required for a successful sequence of highly specific chemical reactions.
It has nothing to do with total levels of energy absorbed from the sun, but the energy produced by the chemical reaction which is triggered by photons. Or, plants are powered by chemicals, not by heat.
Deleted
The original form of photosynthesis resulted in a different metabolic pathway which used red or blue light and evolution took care of the rest
There were some conditions on the Earth at that time which meant that only red and blue light was available at the intensities required.
There are many possibilities why this might be so, including the nature of the media in which the first synthesising bacteria lived. I suspect the explanation when it is eventually found will be very interesting. However, it is by no means obvious that there is not a much simpler photosynthetic pathway using a single photon absorbtion, and it did not evolve simply because the conditions at the time - the predominant biochemistry of the bacteria and the wavelengths of light falling on them - were not suitable.
Pining for the fjords
This is proof that the artist formerly known as the artist formerly known as Prince has been here on earth since the dawn of time!
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Plants originated on a planet where the sun was a different colour (http://news.bbc.co.uk/2/hi/science/nature/6589157 .stm) and the hairdressers and telephone cleaners who colonized earth brought them here...
Excuse me, but please get off my Pennisetum Clandestinum, eh!
And all that was purple eventually died out...
Reaffirms my faith that there's still hope for childrens' TV.
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
All the plants were split into two camps, Green! and Purple! They fought until there was only one kind left.
"Waste not one watt!" - CZ
Nope. Other shows have tried weird looking aliens. Adults seem to treat them like kids' shows, and lose interest. The thing is... most sci-fi isn't about science or aliens at all; they're just re-tellings of old human stories; those alien stories are just modern versions of ghost/demon/knight stories from millenia ago, that humans find appealing.
The problem is just that most of us simply CAN'T imagine life from other worlds.
No, it doesn't!
- Solar irradiance at sealevel
- Absorption-spectrum
Solar irradiance at sealevel 'peaks' at 470nm which is exactly where chlorophyl-B absorption peaks. In fact the 'peaking', when put into context, is somewhat vague, since throughout the whole visible spectrum from 400nm - 700nm you have well over 50% of the real watts that you get at the peak 470nm, so an adaptation to a particular wavelenght within it gives at most only a conservative if not marginal advantage.
www.tribalnetworks.org - helping tribal people around the world to own their own means of high-tech communications
It's pretty obvious once you know the argument. It's due to light-scattering. There's so much energy in the sky all day that it doesn't matter what color you absorb, there's plenty at any visible wavelength. But during sunset and sunrise there's predominantly red light in the sky, and a green plant would be more efficient at absorbing red light (they're complementary colors) than if the plant were another color. This blog entry goes into it:
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http://blog.myspace.com/index.cfm?fuseaction=blog
keep your crack pipe topped up and it will continue to make perfect sense.
What if Tetris was invented by Nazis?
They're filming these on a studio lot. There are tons of idle cowboy, nazi, ancient greek, etc. costumes and sets available. It's an obvious cost-saving move. Not to mention it taxes the writer's brain a lot less to rip off these plotlines.
That's part of why I loved Star Trek. Where else could you see all the different genre prope in the same series?
Man, you really need that seminar!
Red and green aren't complementary colors in the light spectrum, they're both primary colors.
Red and green aren't complementary colors *period*. The Red-Yellow-Blue spectrum still taught to children and art students is simply incorrect, and the mixing of different ratios of "complementary" colors to get black is just a hack atop a poorly designed system. (And I say this as someone with an art degree, so don't think I'm bashing on art students here).
The additive primaries ("in the light spectrum" as you said) are red, green, and blue.
The subtractive primaries (as useful in inks and other pigments) are cyan, magenta, and yellow. This is what they ought to use in art classes.
The additive secondaries are the subtractive primaries, and vice versa; the two spectra are complementary. (As an additive primary is light of a frequency which stimulates only one of the cone types in the human eye, and a subtractive primary is something which absorbs only one such frequency range and reflects the rest).
Thus, the complement of red is not green, but cyan, which is a sort of blue-green. Interestingly enough, some of the earliest and most prevalent photosynthetic life forms were the blue-green algae, also known as cyanobacteria.
-Forrest Cameranesi, Geek of all Trades
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