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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."
your just poo pooing other peoples assumptions while making your own in the same breath.
If you mod me down, I will become more powerful than you can imagine....
I agree. I sometimes wonder if there could even be upside-down life under us, at the interface of liquid vs solid rock. What would such life forms think the universe was like? Too bad there's no such evidence in lava-rock :-)
Beer is proof that God loves us, and wants us to be happy.
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
It would be silly to exclude conditions not similar to Earth alltogether, but it is definitely reasonable to focus on conditions that are similar. Other conditions could qualify but that's pure speculation, for the conditions we live in we actually have a proof of concept. I'll take the refined "it works here, so why not elsewhere" over "anything could work" any day.
Your idea of looking for non-natural patterns is interesting but note that it would very much limit search results to life so intelligent that like ourselves we would consider it above natural. You wouldn't find any microbes on Europe because in our frame of reference they too would be very natural.
Looking for liquid water isn't just human arrogance. Water is an effective and stable polar solvent, and there aren't many chemical processes as widely applicable as hydrolysis. In addition, the presence of liquid water indicates temperatures cool enough to allow organic molecules to stay stable, but warm enough to undergo the reactions necessary for life. These things are true throughout the universe, not just here.
ResidntGeek
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.
That idea comes from the time before we started realising that the nutty Gia concept (of the earth as a living entity) was actually a hypothesis with more than a little proof to back it up. I'd go so far as to say it's a theory.
Thing is, no matter how far down we drill, we still find life, and no matter how cold or hot or dangerous (to us) an environ we find, there is always life there.
It's taken a long time for this realisation to permeate through the wider scientific community, and it's a long way from becoming accepted fact for the general public.
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.
Given how many planets exist in our galaxy that are already inconceivably far away, including this new wet planet just 20 light years away (or 4 billion years travel time away at current technology levels that are capable of carrying people), you're right, inter galactic travel is something we shouldn't waste time thinking about.
Even if we did manage to find a way to do it, we could do little more then explore the minutest fraction of another galaxy. It would be pointless for all but a minority of pioneers willing to take the risk.
The problem with travel methods that let you go huge distances (wormholes, whatever, jolly fast stuff anyhow) is that they miss all the stuff between you and your destination. That is not the way true exploration works, likely we'd miss lots of interesting things.
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
Your argument, put another way, reads: since plants use chlorophyll and that specific molecule requires energy levels corresponding to red & blue light, things are required to be like they are. This is almost tautologic. The more interesting question would be, why something like chlorophyll evolved to power plants, instead of reactions with a potentially higher gain
605413? Yes, it's a prime.
The problem boils down to carbon. Of all the elements on the periodic table, there is one (1) which acts like carbon. Other molecules like nitrogen and silicon can form long chains and rings like carbon, but they don't like it. Carbon _loves_ forming itself into complicated molecules that cooperate to reproduce. There might be some non-carbon-based form of life out there, but it's very unlikely, and even if it does exist wouldn't easily evolve to macroscopic scales. It's just so unlikely there's no point looking for it.
Once you accept that life is carbon-based, the rest follows. All we know about organic chemistry, and the temperatures and conditions it requires for optimum function, apply everywhere. Heat that breaks down carbon chains and makes life unlivable in the lab makes life unlivable on a planet orbiting too close to its sun, too. Water, which is pretty much the ultimate solvent here, allowing acid-base chemistry to exist, hydrolysis and dehydration synthesis to take place, protein microdomains to move diffusively.... it all happens on other planets too. While we shouldn't look for pretty blue centaurs with eye stalks or humans with funny ears, carbon-based life is a pretty good bet fi we're looking for anything.
ResidntGeek
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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
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
I believe that it is inevitable that computers/robots will gain intelligence. If I am right, then there will be a non-carbon based intelligent life form on this planet. So perhaps we should be looking for steel, aluminum, and silicon instead of water and carbon.
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:
. view&FriendID=187945&blogMonth=9&blogDay=24&blogYe ar=2006
http://blog.myspace.com/index.cfm?fuseaction=blog
And here, all this time, we thought it was all about Rayleigh scattering.
/. moderators trumps all!
I guess the collective wisdom of