Why is this?

[RageBeoulve]

How come every scientist i've ever heard of that studies space and is interested in life on other planets is such a retarded dumbshit? They ALL stress that for life to exist, the conditions have to be earthlike. WTF why? Who the fuck says a lifeform HAS to survive on fucking liquid water? Who the fuck says that a lifeform HAS to breathe oxygen?

Dude on another planet life could exist that breathes helium and ingests selenium to survive! Why not? Theres a whole bunch of materials life could be based off of. It doesn't have to be carbon. I reject your stupid ass theories you quack scientists. You don't know a goddamn thing and neither do I. At least I admit it.

Phew.  Got that out of my system. Discuss people. What do you think?

[punkdrew]

I remember the first time I ever heard that life didn't have to carbon-based. It was an episode of Star Trek: OTS called "The Devil in the Dark," about a creature that was silicon-based but could exist in an oxygen-nitrogen atmosphere for brief periods. One of the best episodes of the original series, IMO.
It doesn't surprise me that the search for life on other planets is primarily focused on Class M planets. We're not really geared to study life on planets that don't have an Earth-type atmosphere. But it's pretty likely that any ET's that come by would have a physiology based on something other than carbon.

[RageBeoulve]

Well. We wouldn't be able to go to such planets, but I am just as certain that I know life doesn't have to be carbon based as I am certain that I really don't know jack shit about the universe. I hear these scientists rattling off all these "things they know" and it sounds like a bunch of shit to me. At least i'm smart enough to know how ignorant I am.

I love that episode too man. 

[ProfessorFarnsworth]

Well considering that the ten most abundant elements in the universe are:

1. Hydrogen
2. Helium
3. Oxygen
4. Neon
5. Nitrogen
6. Carbon
7. Silicon
8. Magnesium
9. Iron
10. Sulfur

It kinds of makes sense to expect life to follow a specific potential of compositions based on the most abundant elements in the universe, especially carbon due to it's superior ability to form complex molecular structures and it's light mass; and water (H2O) due to it's ideal solvency ability, and is composed of the two most abundance elements that can chemically bond. But that's not to say there's no exotic life forms out there, as alternative biochemistry would exist. Although it's most likely that, overall life in the majority, would be composed by at least some of the ten most abundant elements in the universe (with Carbon or Silicon as the best key element) with additional trace elements; along with molecules based on abundant elements (like water, peroxide or ammonia). I should note that inert gases like Helium or Neon cannot form anything complex, as they cannot bond to any other elements to form molecular structures.

Scientists have considered alternatives, and there is an interesting article about alternative biochemistry on wiki, you might want to read it:

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

But I disagree with scientists regarding their earth-like only arguments. I hardly consider earth-like as the only possible way for life to form; as it's more about the chemical processes in the conditions than the actual conditions alone that would allow life. I mean life could form on planets with major pressure, temperature, climate, geological, composition and/or radiation differences to Earth, providing the chemical processes are ideal to sustain it.

[vodz]

  Nexus

There was an episode of Stargate SG-1 in which a sulfer-based alien race was, errr... sulferising an earth-like planet to make it suitable for their own life.

[TheoK]

Carbon is the first element that isn't a gas. No wonder if life is primarily based on carbon in whole universe.

[P7PSP]

Perhaps it makes sense to some scientists to start from a known working reference point. One thing Creation and Evolution have in common is auto genesis. Stanley Miller put all the ammonia, methane, hydrogen & water together and ran charges through it but no one has created life from scratch. So until life is found that is not carbon based there will be no other real frame of reference. And Si being underneath C could make them analogous to O and S, with H2O you have a life sustaining liquid but the heavier H2S is a heavier than air poison gas that will nail you quicker than an equivalent weight of Cyanide. And that about exhausts my ability to wing it on this subject.

[renaeden]

It may be that once the human race gets out there and actually explores, they will be open minded enough to consider other kinds of life. Until then, we have Star Trek and Stargate.

[P7PSP]

I like Babylon 5 myself. It had a good, reasonably consistent storyline even though it stayed with the old, tired, anthropomorphic alien types.

[renaeden]

I haven't seen Babylon 5. Something for future watching.

[P7PSP]

It's sequential so it really will work best to start at the beginning Reaeden.

[Peter]

Carbon is the first element that isn't a gas. No wonder if life is primarily based on carbon in whole universe.

Perhaps you're thinking of lithium?

[TheoK]

Carbon is the first element that isn't a gas. No wonder if life is primarily based on carbon in whole universe.

Perhaps you're thinking of lithium?

No I don't mean in the table of elements, I mean abundant in the universe.

[vodz]

Carbon is the first element that isn't a gas. No wonder if life is primarily based on carbon in whole universe.

Perhaps you're thinking of lithium?

No I don't mean in the table of elements, I mean abundant in the universe.

[Peter]

'Goldilocks planet' thinking was semi-excusable back in the 1970's when extremeophiles were largely unknown, but now that we have examples of bacteria living on spent nuclear fuel rods, bacteria that live thousands of meters deep in fractures in the bedrock and use radioactive decay in the surrounding rocks for an energy source, bacteria that live in scalding pools of acid, inside small rocks in Death Valley, floating in the clouds and entire ecosystems of complex animals that live around deep sea thermal vents and cold seeps, only the ignorant or stupid should insist that an Earth-like planet is necessary for life.  

There are plenty of places even within our own solar system which have the potential to support life; the most promising are various Jovian and Saturnine moons which have layers of liquid or slushy water or water-ammonia mix in their interiors, forming vast ice-covered oceans that could host life.  Mars has huge reservoirs of subterranean ice, which is likely to be liquid at certain depths and around volcanically active areas, and it has anomalous methane sources that exceed what's expected from geological activity and could be coming from bacterial metabolism.  Venus has a fairly pleasant climate and a tolerable chemical composition at high altitude, and Jupiter has a layer in which clouds of water vapour form and precipitate.