OT: Extrasolar planets discovered directly

[Hunpecked]

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.

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.

but I think that to support life the building blocks don't need to posess similar properties as carbon.

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.)

For all we know, there might be iron-based life forms out there debating whether or not carbon-based life is possible.

See below.

Plants breathe carbon dioxide, yet are still considered Terran life.

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.

What are the similarities between, say, a stag deer and a clump of moss?

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.