All life on our planet, ALL of it, from bacteria to elephants to trees to humans to platypuses, uses a very specific system. DNA has a very specific structure that allows it to replicate itself and synthesis proteins, and allow life to form. Furthermore all of these molecules are organised into cells.

This very specific chemistry of life is unlikely to arise on another planet, and even if it did, it is extremely unlikely that the life forms would evolve like life did on Earth. So chances are, these alien organisms, even if they existed, would probably be microorganisms and primitive multicellular organisms. Certainly they would be adapted to conditions that are very different from those on our planet.

On the other hand, maybe there is life that uses an entirely different system for biology that is too alien and bizarre for us to imagine.

I think I've seen 5 UFOs in a span of three months five years ago.  At first I thought "It's just some plane or something..." but planes are usually loud and you can hear them. What I saw was completely silent.  A friend of mine said, "Maybe it was one of those stealth jets used by the Military?"  I considered the thought, then I replied to him, "Yeah, but how many stealth jets fly at night with red, blue, and green lights? Not very 'stealthy' now is it?"  I still don't know what I saw...

Anyway, the Universe is large so there is a possibility that they do exist.

(16/06/2010 11:38 AM)andrewcc Wrote:  for all wee know our solar system could be the only place in the whole universe capable of having a planet which could support life......

Depending on how you look at it. From a human standpoint, many have placed forth sensible hypotheses about some of our solar system's planets, and even moons (like Europa
http://www.pbs.org/lifebeyondearth/alone/europa.html ), that might have some form of life, or might have, at one point, been inhabited by life (people still think about Mars' past). There's really no way to know. Not to mention, wee really don't know what makes something "hospitable", since wee make generalizations about the organisms being required to be within a "reasonable" distance of a star, so as to get enough sunshine, vegetation, blah blah blah, but again this is what would be necessary for it to be hospitable to humans and carbon-based lifeforms of Earth (further discussion in next paragraph)

(16/06/2010 05:44 PM)Digital-Archangel Wrote:  All life on our planet, ALL of it, from bacteria to elephants to trees to humans to platypuses, uses a very specific system. DNA has a very specific structure that allows it to replicate itself and synthesis proteins, and allow life to form. Furthermore all of these molecules are organised into cells.

This very specific chemistry of life is unlikely to arise on another planet, and even if it did, it is extremely unlikely that the life forms would evolve like life did on Earth. So chances are, these alien organisms, even if they existed, would probably be microorganisms and primitive multicellular organisms. Certainly they would be adapted to conditions that are very different from those on our planet.

On the other hand, maybe there is life that uses an entirely different system for biology that is too alien and bizarre for us to imagine.

That's assuming that the exact same spark that gave life on Earth would be the catalyst on other worlds. And by life, I assume you mean something that exhibits some sort of reaction to stimuli, and not just the basic "reproduces, has a cell wall, requires energy, etc" requirements from our 4th grade schoolbooks. Wee base all our thoughts, laws, and physics on what wee know from this world. If it is to be believed that all life evolved from one single cell, then that cell would dictate quite a bit of similarities between all life. The reason I say it makes more sense for there to have been one single cell that started it is because otherwise, multiple "bits" of life would have had to spring up at nearly the same time (comparatively) to allow for constant evolution throughout the world.  However, then, another another possibility arises. What if it was due to geographical interferences that allowed for certain primitive life to never come into contact with one another? Well, if that is the case, then what caused life to spring up at MULTIPLE times? Whatever the catalyst is, it would have had to occur multiple times. Doesn't the universe seek complexity? Or is chaos truly what is desired? If so, then more and more life forming constantly would be more logical. However, I still have trouble grasping the original first few steps.

As I've said before, the problem isn't whether there is a possibility of alien life, but more whether there is a god. If there is no god, then I'd say the chances of life REQUIRING DNA or any other human science fundamental is much reduced, since it is then all a matter of chance. Perhaps it is purely because of how wee adapted to our atmosphere that wee (and ironically machines) require electricity for our nervous systems to function. Who are wee to say that this EXACTLY is the only possible way? To make such a claim seems awfully closed minded, personally.


It also depends on how long the universe has existed... if it has been around "forever" (can't comprehend something like that, so idk), then the chances are that at some point or another there has been alien life, though I don't know if our existence is simultaneous with theirs or not.

Yes, they are out there somewhere.