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Do You Believe In Aliens?

There was a paper published in the journal Science that suggested there are indeed ars arsenic-based life forms in the sense that they built their DNA using arsenic. I remember reading that paper and thinking wow.

That story turned out to have some faulty conclusions in it, though the organisms showed a remarkable ability to work with arsenic compounds selectively. Not to mention organoarsenic compounds are known and used by life.

http://www.nature.com/news/arsenic-life-bacterium-prefers-phosphorus-after-all-1.11520

Just want to point that out because the lake mono study has some controversy behind it. It has lead to some really interesting science though.

As for silicon-based life (if I can speculate a bit) what I've seen about silicon chemistry is it is remarkably rich, more so than carbon based chemistry under conditions we associate with life (aqueous environments and room temperature). Of course carbon based chemistry has been studied a lot more, so maybe that is merely the impression one gets. The chemistry of silicates in aqueous environments is basically a wide open frontier in science because of the polymerization and complicate polyanion structures that form. I studied this stuff in the literature for a time because I worked with silicon etching reactions. I didn't get very far because the chemistry is so complicated and there are so many types of players in solution that you can't really tease out any workable hypothesis. The people that study this stuff talk in generalities and statistics, not refined chemical pathways like organic chemists. Basically, you can't even give a concise answer to the question: "what is the etching byproduct of crystalline silicon in aqueous alkaline solution"

so if aqueous, silicon-based life were feasible, I'm inclined to say it would require even more selectivity and control than carbon-based life. Silicon-based chemistry certainly seems rich enough to satisfy the complexity required for life. The fundamental building blocks of this life might gain an advantage as far as the versatility of its components (ex like an enzyme that catalyzes multiple chemical reactions). Complexity would have to be higher.

Edit:B_D beat me to it
 
Yes, it's definitely unique in its versatility as a building block for all kinds of chemical structures. If we look at the 2nd period, then lithium and and beryllium are useless (as building blocks) metals, nitrogen and oxygen can't form stable skeletons* due to their repulsive electron pairs. Boron can form compounds similar to hydrocarbons (called boranes), but due to its one empty orbital, it's quite reactive as a Lewis acid, which in general precludes the existence of such stable compounds containing any reactive Lewis bases (such as oxygen or nitrogen containing groups).

Silicon is the next candidate. It has the same regular number of bonds as carbon, and is able to form quite stable Si-Si skeletons, but due to its extra electron shell, its radius is too big to form sufficiently stable double bonds, its hydrogen compounds are very reactive, and it also has empty electron shells, making it pretty reactive towards Lewis bases. Besides, it reacts with oxygen to form the very stable and tough material quartz - which is a continuous network of the atoms, unlike the volatile separate molecules that CO2 forms - which means that oxidizing silicon-based chemical fuel (analogously to carbon) would produce quartz crystals within the cells or whatever the organism has; not ideal!

Phosphorus I haven't thought about much, and right now I can't think of major problems with it being a building block, but it's quite late and I'm probably missing something; in any case, I've never heard of it being suggested as a possibility. Sulfur has, again, too many electron pairs to easily form stable continuous structures with itself and other elements. The rest of the elements have even bigger radii, which makes for some unsuitable properties, but this post has already turned out to be way too long and probably extremely boring.

*there are some compounds containing only nitrogen or high atom percentage of it, but on the whole continuous nitrogen-nitrogen skeletons are not stable.

E: I'm off to bed right now, but maybe levels you can expand on what aspects of silicon chemistry are suitable for life? I actually haven't really heard much about aqueous silicate possibilities.
 
Not boring for the other chemistry nerds, and there are a few of us on BL.

Indeed there are other elements like silicon which are 'close'. Which is of course where the idea that aliens might be silicon based in popular culture comes from.

I'm certainly not saying that I believe it to be impossible for there to be life based on a different element. I don't know one way or the other. All I was suggesting in my initial post is that because of its unique suitability. Most, and 'possibly' all life is probably carbon based. I'm certainly not willing to go so far as to say that non-carbon based life is impossible. And especially not for simple life. I don't know for sure one way or the other. All I was saying is that I suspect aliens are more like us than many suggest. And one of those ways in which they are likely like us is that they are likely mostly or exclusively carbon based too.
 
I was careful to take no position on the feasibility of silicon-based life. Just don't think it is fair for people to dismiss it either based on the current state of our understanding, which is still pretty primitive. Silica easily forms polymers, is rich with polymorphism, chemical versatility, and a long library of known interactions with other chemical species like metals and organic compounds. I am unaware of any arguements that conclusively rule silicon out. I've limited my discussion to aqueous silicates because those are the ones I studied and those are the ones that have interesting life-like chemical properties under familiar temperatures and environments.

The polymers formed are pretty fragile, so that's a problem, but that depends in a way on the level of control required and the ability to regulate the environment or stabilize the polymers with other types of chemistry. My conclusion is that if silicon based life were feasible it would require more complexity and some new paradigms then we are used to when considering life. Right now it is mearly an exercise in imagination.
 
Jess, I was just continuing the discussion, not criticizing your points :) if asked seriously, I would answer the same way as you, but for the sake of discussion, I'm willing to entertain other ideas as well.
 
@Jess

I have no knowledge whatsoever of physics - nor pretend nor intend to, too, by the way - but I am not in any way buying that we are at a point in time where we can affirm with any certainty how aliens should or should not be, or anything else of this calibre. Thinking that we do, in fact looks to me exactly like those prophets of the apocalypse, who thought that it was *their* pont in time that was the chosen one. Why particularly *now* it is that we are grown up enough to say how things happen in the farest corners of the universe? Yeah, we do know a lot, but do we know *that* much?

How many times haven't people been completely certain that something was or was not possible only to be proven wrong later? That's basically the whole history of science, one prejudice broken after the other. It reminds ne of the attitude that b_d mentioned - or rather what I interpreted - in the "What is science to you?" thread; as if science dictated reality, and not the other way around. You grab domeone with this type of attitude from a time of the past and tell them about this crazy things that we have that are computers, or those microcannons that fire nanobullets that recently came out (that shit is insane), or about that monkey that moved an arm on the other side of the globe with his mind and they'll tell you it's impossible!

I guess my point is: other people in the past have been as sure about what could and what could not be, and they were wrong. Why aren't we subject to be wrong?

Finally, I think you're directing your post at the types you referred to in that "aliens exist only in four dimensions" thing. I am not in their side either. But not because they don't know anything about science, rather because as you have remarked their arguments tend to be incoherent or just plain nonsense. Personally I'd favour a sound argument from someone with no *knowledge* than an incoherent one citing all sorts of studies or coming from a Nobel laureate...

BTW, life right here on Earth is rather diverse. There are carbon based lifeforms that although are all about guanine cytosine and stuff are quite different from us humans. Meanwhile it is my impression that most people view aliens as humanoid. I was criticising that when I made my post [which you might not have seen, but it was of the "how can we know what aliens look like?" genre] but I ramble..
 
Great post. I would like to add that science as it's structured is not to provide absolutes but only to follow what we think is the evidence and make a guess at reality based on that knowing that we are on a long journey and we don't have it all down. That's what a real scientist does. Unfortunately due to human frailties it's hard to not let our personal aspirations infect and distort it. If we could get that bullshit and ego out of it we'd be so much further along it would truly amaze us.

Personally I think there is some evidence that aliens have been on earth in the past. I don't know about now. There's not really great evidence that I have seen.
 
I think it is more likely that there are aliens in the universe than not. Obviously you can't know for sure until you see them, but the universe is so big that there has to be other lifes.
 
My girlfriend and I both saw 3 UFO's. I've always believed in aliens even before this experience. We were laying in the grass staring at the stars completely sober and 3 triangle shaped aircrafts zoomed by. It was pretty amazing we both assumed aliens and talked about extraterrestrial life for the rest of the night. The way I see it, the universe is far too big to not have other life forms in it.
 
@psychedstoner cool. The triangular pattern of flight seems to be a common theme in sightings and videos on YouTube. People often see these things flying in formations of three. In this case you say the craft was actually close enough that you could ascertain it was triangular in shape? Also heard about triangular-shaped craft sightings reported. Where they flying in a consistent formation across the sky? Were the flight trajectories pretty consistent or did they move in an unusual trajectory (I.e. stop and go, zig-zag, etc)? Were they moving unusually fast across the sky? Anyways, all things to pay attention to and if you can remember the details there are sighting databases out there you might consider recording it. Definitely helps people to check their sightings against other peoples sightings if they are reported. If you live in a densely enough populated area chances are good someone else saw it and reported it.

I myself haven't seen anything entirely unusual in the sky that I would qualify as a sighting. I'd like to honestly. I look up at the sky often enough. A few months ago I saw a long streak of cloud in the sky in the shape of musical bars with notes like the kind in sheet music. It was fading by the time I saw it but I got pretty excited. Was one of the stranger things I'd seen. Looked it up online and found out that there are these cloud printing aircraft that now have the capacity to write fairly complicated things with high resolution in the sky like music bars (weather permitting). What I saw was still up and coming technology wise from the things I read. I experienced annoyance tbh. Guess the sky is a great untapped frontier in advertising.
 
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It's hard for me believe that in this huge infinite universe that we are the only life. To believe we are the only life in this super massive space, knowing now that basically every star we can see has planets orbiting it seems somewhat small minded.
 
I don't so much "believe in" aliens as much as I understand that it's exceptionally unlikely, even inconceivable, for us to be the only intelligent life form out here. According to the new, updated Drake's Equation, with correct figures, the chances of us being the only intelligent life form in the universe is at least 1 in 10 billion-trillion. The chances of us being the only intelligent life form just in our galaxy is 1 in 60 billion. According to statistics, it's more likely that I'll be struck by lightning, get a hole-in-one in golf, AND win the lotto jackpot, all in one single day, than it is for humans to be the only intelligent life form in the universe, and I don't even play golf.
 
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