I agree that it be highly unlikely, but could these life forms exist even if very very rare?
I agree that it be highly unlikely, but could these life forms exist even if very very rare?
Maybe what would be helpful is a run down of what other chemicals MIGHT be the basis for life. Silicon is often cited in science fiction, but silicon doesn't react with other chemicals nearly as readily as carbon. Silicon based life would happen on much larger timescales than our own version, if it could happen at all.
I've also read about electromagnetic-based life forms, that would be awesome
Shockingly attractive I'd say.Originally Posted by Platinum Rhymer
So very true
Perhaps you could have "pure energy" life forms of that sort, but they couldn't be "self contained" in the way humans are AFAIK...
What do you mean? like gaseous types of beings?
Yes, possible but in an extended-carbon way.
I'd speculate that all life would begin as carbon based. But what happens after a technologically advanced life form (such as man) evolves? Will 'we' be carbon based in a hundred thousand...million...10 million years? Or will we alter ourselves into a lifeform impervious to reasonable destruction from the environment around us?
What if we sent manmade non-carbon baced lifeforms out into the nearby star systems in our part of the galaxy? Would they also spread in the following billion years?
Actually, I'm very interested in the replies from people with greater expertise than I have; this is an area of interest for me, but a strictly amateur one. However, here's some of what I've managed to glean from my reading:Originally Posted by Platinum Rhymer
Chemically based life requires a bunch of chemical reactions. (Life not based on chemicals is going much farther into the speculative realm--more on that later.) To get the right sort of chemical reactions, you're going to need an element that does form chemical bonds--no argon-based life, in other words--and can form a fair number of them at once. However, it also needs to be somewhat fickle, if you will, and be able to change what it's "attached" to without something pumping a great deal of energy into the system.
Oh, and you also need hydrogen, said the article I got this from; it does some bonding stuff you'll probably need. Fortunately, there seems to be a bit of it strewn around the universe.
Anyhow, carbon has both of the characteristics needed; it can form several different bonds at once, and it will change what it's attached to. Silicon used to be considered as a likely life-chemical. The Horta in original Star Trek was supposed to be based on it--you know, the thing in "Devil in the Dark," which looks like an animate throw-rug after a pizza party gone hideously wrong. (It is also, in my opinion, the coolest of their non-humanoid life-forms; too often, they just resorted to mucking with lens flare and declaring an Energy Being. This was doubtless because of budget, but it still got old.) The problem with silicon, as I understand it, is that it generally bonds with other silicon to form crystals. And then it just sits there.
Doing nothing interesting.
However long you stare at it.
This is plainly not the behavior you want out of a life chemical. Now, I have heard that some scientists have talked about silicon and other elements in chains, at high temperatures--fluorine, I think it was?--being more exciting than silicon here on Earth. This raises a valid, if obvious, point: elements act differently at different temperatures. One of the arguments against life on Titan, as I recall, was that it was simply too cold to have the happenin' chemical stew that (probably) led to the development of life on Earth.
Which of course leads to the fascinating question of what speed alien life would happen at. Cue Robert Forward.
Speaking of Forward, I was going to spout off a little about life not based on chemistry, and I think I'd better do that now, before I reveal any more of my ignorance about chemistry. In my ever-so-humble opinion, Star Trek was a bit misguided in having so many life forms based on "pure" energy. Pure energy tends not to be organized. It's energetic, see. 8) It doesn't stay where it was put. If you try to make a life-form out of light, for instance, you find that all of your material is inevitably zipping off at the speed of you-know-what, and is [/i]physically incapable of going any slower without getting a major gravity field involved.
Which would come from matter. In this universe, matter is in charge of organization and energy is in charge of change, and you need both to make a life form. Now, I think you could imagine, and even make an argument for, a life form that has far more energy and far less matter than we do. You'd need an "exotic" environment, I think, but there are plenty of those out there. How about a star? Or, to go completely in the other direction, how about Sedna, where it has to be cold enough for superconductivity in everyday materials, so a little bit of electricity could get you a loooong way?
There are also exotic forms of matter in this universe; the reason I used Robert Forward as a segue above is because he once wrote about life on the surface of a neutron star. The protagonists of the story (his humans were really mainly there to look at them) were made of the dense extra-crushed materials of a neutron star; they were extremely tiny and lived their life at the speed of physics, rather than chemical reactions. I haven't the expertise to evaluate whether or not this was possible, and my feeling is that no-one on Earth can really say whether or not it's probable. There are many, many environments that humanity has minimal knowledge of. There are environments that we may always have minimal knowledge of, such as near a black hole.
Yet again, we're faced with a very limited sample size. Carbon forms the basis of the only life we know. Speculation about other suitable elements--well, until we see them in action, it's speculation. Me, I tend to bet on the universe being both weirder and cooler than I can imagine, but again, that's just a hunch on my part.
It certainly seems possible that any aliens we meet could be partly, or wholly artificial; the original species might be dead, or very distant, or confined to an Earth-like planet by the inhospitable nature of space.
A couple of my aliens;
This alien phylum is part carbon-based, part silicon-based, and seems to have been developed as an artificial terraforming swarm;
these creatures are semisolid crystalline silicon creatures.
This could also be a description of our own future "ancestors" in space.Originally Posted by eburacum45
Ancestors? Do you mean descendants?Originally Posted by Chip
Yes, you're right. I guess in the future they'd call us their ancestors. :-kOriginally Posted by um3k
I'm going to have to go with if you can't kill and eat it, it's not a life form.
I agree with Izunya, we dont know enough to rule it out...anyways what Izunya said about silicon and crystals, could it be possible for a crystally life-form walking around in some weird planet?
And what would an electromagnetic-based life-form look like?
For some form of life, there needs to be the ability to form large consistant chain molecules. Only carbon does this readily. Silicon does to some extent, buit not enough to form protein like molecules. While I'm not going to say that it is impossible, it is highly unlikely that life forms would have any other basic chemistry other then organic. They might not be oxygen breathers or have iron based blood however, in fact some life on Earth has copper based blood, so if life where to be elsewhere it's likely that they might have something similar.
From a purely chemical point of view, if life exists elesewhere it is likely to be very close to what we already know, though there could be differences such as the handness of the proteins and such, but otherwise.....
AFAIK, Carbon forms the maximum number of compounds of any element. And most of the more complex compounds are carbon based. So, I think it most likely that life will usually have a carbon based structure.
Of course, there could be things like Silicone, which is a Carbon + Silicon polymer, but that's not very likely, I guess...
Purely energy and other such beings, I don't know, really...
But how about beings that exist in a specific medium? Something like AIs in a large computer network? Some sort of a natural computer that formed (what an amazing accident that would be!) and AIs (basically patterns) that formed within it...
There is an excellent short story called "Wang's Carpets" that explores this very possibility. Quite interesting.
Magnetic structures ARE self-contained, and no limit on their complexity is known. Perhaps a self-organizing (i.e. alive) magnetic structure is possible.Originally Posted by Gullible Jones
We already know of lifeforms made (partially) of that!Originally Posted by shash
I tend to agree with PhantomWolf and shash above.
About existing "in a specific medium" - that's interesting. (In a broad sense we do in terms of existing in a medium of oxygen-nitrogen gasses.) But existing as part of what we would conceive of as a naturally evolved computer may not be too far-fetched. Considering the complexity of life forms and their adaptability on Earth, it seems that a seemingly complex computer environment could perhaps come about chemically and eventually evolve to accommodate a natural "software" so that programs analogous to DNA would "run" within the alien environment and even "launch" biological processes. There are some Sci-Fi stories written about biological computer-like creatures and/or living Internet-like communications systems, but I don't remember the authors.
Also along the lines of other life forms "likely to be very close to what we already know," This may be true but even within those parameters, E.T. life could be very very alien from us in behavior and appearance, even if evolved within a similar environment.
Is it possible (silicon-based creatures) on a planet that has everything it needs to make it happen?
Since we have no idea what those conditions might be, if they exist, my answer would have to be an unqualified, "Um . . ." 8)Originally Posted by Platinum Rhymer
Izunya gives a good description of the silicon-based lifeform problem, but as a chemist I would like to stick in my oar
You can build silicon analogues of long-chain carbon molecules, but these require bridging oxygen atoms between the silicon ones. It's not quite the same as a purely carbon chain, but it works.
The problem this leads to is that the silicon equivalent of carbohydrates spontaneously combust in oxygen. So silicon analogues of carbon-based life cannot exist in an oxygen atmosphere.
So we're not likely to inhabit the same planets and end up mining the "Tomb of the Ages" (I think it was called ).
BTW I remeber reading a short story about lifeforms in the coronasphere of our sun, made possible by the conducting nature of the plasma within the magnetic field constraints creating the analogue of neural pathways.
PR, Iīm reproducing here part of the contents of our PM exchange.
Arthur Clarke once proposed the existence of a "crystaline" creature. I think (a cautious expression) that if the ideal conditions were given, such a creature could exist. It would be a "neural" life form, not depending on solvents, nor organic compounds. It wouldnīt need metabolism nor reproduction. It would feed directly into the solar radiation.
Electromagnetism from the local sun would be somehow modulated in the planet-wide crystal, turning thinking possible, just as it happens, in a certain sense, in our computers. It could even transmit its "brain" activity, since it would be made of pure electromagnetism.
(unfortunately, I donīt have any evidence of this, case someone gets angry about my "opinion")
Now that sounds like Terry Pratchett's Bank of Sirius (see Dark Side of the Sun), a planetary sentience created by the numerous fractures in silicate rocks causing many semi-conductior junctions.
So these "creatures" are plausible then
How about, say, Sulfur as a basis for life? It seems to be relatively reactive and fairly common in the universe.
Well sulfur dioxide's boiling point is -10C, which means it would be more than capable of being used in place of CO2. C-O bonds have dissociation energy of about 85.5 and S-O bonds have dissociation energy of about 87 IIRC. So the energy needed for sulfur photosynthesis could be just as possible (unless I'm missing something out of course). Also if I'm not mistaken sulfur is more reactive than carbon.Originally Posted by Avatar28