Re: OT: Extrasolar planets discovered directly
 

Strategia and Renegade make the point that "life" in our galaxy need not be of a sort familiar to us, i.e. carbon-based. This is certainly valid (within the limits of our knowledge), and makes irrelevant any probability calculations requiring Earth-like conditions. Of course it's only natural to look for more-or-less familiar life forms first: we already have one example of a carbon-based ecosystem, but exactly zero examples of any other type.

What forms could "unconventional" life take? I vaguely recall a juvenile science fiction novel which featured Mercurian creatures that resembled ball lightning. Arthur C. Clarke wrote a short story ("Out of the Sun" ???) in which an electromagnetic entity of some sort was ejected from the sun in a solar flare. Silicon seems to be a popular basis for sci fi life forms, probably because of its position just below carbon in the Periodic Table. If I recall correctly the "Horta" of Star Trek fame (episode "Devil in the Dark") was silicon-based.

Nevertheless, silicon is not carbon. As I recall from my prehistoric chemistry classes, silicon's 4 valence electrons are one electron shell "out" from carbon's, giving the elements roughly similar but far from identical chemical properties. For example, silicon does form polymer chains (as the bosoms of countless Hollywood starlets attest), but I've read (I'm no chemist) that these chains don't approach the length and complexity of carbon polymers (DNA, anyone?). Recall also that silicon dioxide is a solid at temperatures that vaporize carbon dioxide. Now some earth organisms (e.g. diatoms, sponges) take advantage of that and use silicon dioxide STRUCTURALLY, but on Earth at least evolution has favored carbon chemistry for life's vital functions, despite the greater abundance of silicon.

Incidentally, as a naive layman I wonder if a detailed study of the ways these creatures build their silica frameworks might suggest how a hypothetical silicon-based life form could "work".

A couple of places on the web with some tidbits about silicon:

http://en.wikipedia.org/wiki/Silicon_dioxide

http://www.webelements.com/index.html (click on the elements)

Re: OT: Extrasolar planets discovered directly
 

There are silicon-based lifeforms on the Earth right now... They are all monerans, nothing complex, but they are out there.

Re: OT: Extrasolar planets discovered directly
 

Interesting. I wasn't aware that any Monerans formed silicaceous structures. Protistans, yes. Any references on the web?

Re: OT: Extrasolar planets discovered directly
 

Dunno. It was in a scientific journal of some sort I read several years ago. A quick google turned up this mention to an upcoming book. No idea if this is a reputable site or not, but there it is:

http://www.gsreport.com/articles/art000035.html

Re: OT: Extrasolar planets discovered directly
 

Whoa... Using silicon in part of their metabolism does not make them 'silicon based' life. Don't monerans have ordinary DNA like every other form of life on earth? Something analagous to DNA but using silicon that forms the core of their entire suite of biochemical processes would be 'silicon based' life. I don't think there is any such thing known.

Re: OT: Extrasolar planets discovered directly
 

Hunpecked you make good points. The only problem with imagining the different forms that silicon based life (or, to be honest, life based on anything other than carbon) is that the imagination of humanity is actually limited to a certain extent to what we are already familiar with. We can not imagine what form a silicon based life form would take since we are not familiar to any great extent with silicon-based life-forms. We say life "would/could not exist" in certain situations, but do we really know?

Also, just because life on Earth favored the development of carbon-based life-forms does not mean that another planet, with similar metallic ratios would not favor another, totally different approach to forming life.

And all of this leaves out the idea of a supreme being (God). If, as some believe, the universe was created, then God could have created whatever forms of life based on whatever elements he wanted to. But I think that's all I'll bring religion into this thread, as we all know that religious discussions can quickly degenerate.

Re: OT: Extrasolar planets discovered directly
 

We would simply have to try to construct a silicon-based ecosystem, down to the molecular level.

It would simply take a while. http://forum.shrapnelgames.com/images/smilies/laugh.gif

Re: OT: Extrasolar planets discovered directly
 

We've already discovered organisms that live and breed in acid pools (something like that anyway)

So the theory that all life must be Earth life (ie. oxygen & water) has already been proved false
Oh and too the fact that planet life consumed Carbon Dioxide, means that a Carbon Dioxide planet could easily support some form of life

There is no doubt in my mind that life can exist out there, its just a case of whether sentient life has yet to develop out there that I wont make up my mind until its proven either way

Re: OT: Extrasolar planets discovered directly
 

Perhaps silicon beings don't have such complex and long polymer chains and therefore are simpler, but this does not mean that they cannot be alive. Perhaps their "DNA" length is as long as a human's, but simply cut up into much more small pieces - chromosomes, anyone?

And silicon isn't the only element in the periodic table next to carbon. I'm utterly terrible at chemistry (or science in general), but I think that to support life the building blocks don't need to posess similar properties as carbon. For all we know, there might be iron-based life forms out there debating whether or not carbon-based life is possible.

And if carbon-based life does exist, why does it have to be Earthlike carbon life? Diamonds are carbon, why couldn't there be diamond-like beings out there? Carbon-based yet totally different from Terran life. And even if it looks like Terran life, what criteria are there save for oxygen-breathing, water-needing creatures? Plants breathe carbon dioxide, yet are still considered Terran life. And if we compare Terran life forms, are they so alike? What are the similarities between, say, a stag deer and a clump of moss? An elephant and an oak tree? A Bengal tiger and an amoeba?

Re: OT: Extrasolar planets discovered directly
 

Typical, my email server has just gone down, meaning if its not back up and I do get in, the email will bounce, and I will most likely loose my spot

Why do computers have to stop working when you want them the most

Re: OT: Extrasolar planets discovered directly
 

HUH what are you talking about? This is a discussion about extrasolar life forms.....

oh but if your e-mail server is giving you problems you can open a Hotmail account temporarily and change your email adress in your profile to that adress until your original email account is back. That is, if you're talking about your account here..... otherwise, you could also open the hotmail account anyway and forward all the mails you want to keep, contacts etc. there.

Re: OT: Extrasolar planets discovered directly
 

I believe he's talking about a beta test spot, if he gets one. The email notification would bounce.

Re: OT: Extrasolar planets discovered directly
 

Fyron,

Thanks for the link. I thought your post was about silica structures secreted by certain prokaryote cells, but I see that the link actually refers to Dr. Tom Gold's (so far unconfirmed) speculations on the existence of true silicon-based organisms on Earth. Dr. Gold's book was indeed published in 1999; I found a review here:

http://www.findarticles.com/p/articl...80/ai_56022636

Unfortunately, none of the reviews I read mentions any discussion of silicon-based life. The focus of the book is Dr. Gold's theory of a deep underground biosphere supported by an abundance of hydrocarbons (oil and gas) left over from the formation of the Earth (i.e. of non-biological origin). Of relevance to our forum discussion is his suggestion to look for extraterrestrial life BELOW the surface of such bodies as the moon, Mars, and Saturn's moon Titan.

Re: OT: Extrasolar planets discovered directly
 

Well, even the creatures that exist under (for us) extreme conditions on Earth are still based on carbon, water, nucleic acids, etc. In other words, they're variations on a theme, but not a new theme.

As long as even a little corner of the universe remains unexplored, the existence of alien life/sentience can't be disproven. So despite the skepticism of some, an enthusiast for ET's can only be proven right, never wrong. http://forum.shrapnelgames.com/images/smilies/wink.gif

Re: OT: Extrasolar planets discovered directly
 

I recall a line from Carl Sagan's "Cosmos" series on PBS many years ago: "We are a way for the universe to know itself." Since we (and possibly other intelligent species) are part of the universe, then in a sense the universe itself is alive and sentient.

Or maybe just alive... http://forum.shrapnelgames.com/image...es/biggrin.gif

Re: OT: Extrasolar planets discovered directly
 

Yea, it posted into the wrong bloody thread, forum plays up for me sometimes

Re: OT: Extrasolar planets discovered directly
 

Well, "simpler" is a complex concept when it comes to alien life. If silicon-based life is unable to mimic carbon's complicated polymers, the required chemical "workarounds" might be extraordinarily complex. As a layman I can't even begin to think about the chemical gymnastics required...I think I'm getting a headache. http://forum.shrapnelgames.com/images/smilies/Sick.gif

Which would render useless just about all of our current knowledge of life. To imagine non-carbon life we'd have to start from first principles, e.g. what chemical structures could/would our chosen element(s) form to reproduce, react to stimuli, evolve...? (My head hurts more.)

See below.

Green plants also consume oxygen, just like we do, though they're net oxygen producers. BTW, one gets a real sense of our place in the universe by remembering that we survive only by breathing plant excrement. http://forum.shrapnelgames.com/images/smilies/eek.gif

Strangely enough, I understand that the genetic differences are smaller than one might think. Note also that they're similar enough chemically that they both survive in the same overall environment (a North American woodland, say) and the deer can even eat the moss.

Returning to iron and silicon as building blocks of alien life, I'm actually kicking myself here for overlooking popular scifi "silicon-based" lifeforms that actually seem quite plausible: mechanoids (droids, robots, automata...). So far our own efforts in the areas of AI and self-directing automata are fairly primitive, but we're far enough along to envision far more sophisticated forms worthy of the adjective "alive". Although it's hard to imagine how mechanical "life" could develop on its own, we already know of one carbon-based lifeform that may some day give rise to such "iron-based" life. http://forum.shrapnelgames.com/image...es/biggrin.gif