frisk@askja.UUCP (Fridrik Skulason) (07/30/87)
As everybody knows, all life - as we know it - is carbon based. Now, what
I would like to ask is:
Is non-carbon based life possible?
In other words - is it possible that life could evolve on a planet where no
carbon existed ?
Silicon-based creatures appear in quite a few SF stories, but is it really
possible to obtain the necessary complexity without carbon ?
I am not sure if this question can be answered at all, or if one first has
to answer the following question:
What is life?
which - maybe - is a philosophical question rather than a biological one.
--
Fridrik Skulason Univ. of Iceland, Computing Center
UUCP ...mcvax!hafro!askja!frisk BIX frisk
"This line intentionally left blank"chiaraviglio@husc4.HARVARD.EDU (lucius) (08/03/87)
In article <265@askja.UUCP> frisk@askja.UUCP (Fridrik Skulason) writes: >As everybody knows, all life - as we know it - is carbon based. Now, what >I would like to ask is: > > Is non-carbon based life possible? > >In other words - is it possible that life could evolve on a planet where no >carbon existed ? Actually, the first question is the more general one. A. G. Cairn-Smith's intellectual exercise (in the book listed in the summary field of this article) suggests very strongly that the answer is yes. He postulates that life on Earth actually began as inorganic crystalline life which evolved to use organic molecules. Gradually the organic molecules began to store information, and eventually the original crystal structure became superfluous and was discarded. His argument is that such thing as self-replicating RNA molecules are too complicated *and* require too much energy to make (so that they are too unstable) for them to be formed without pre-existing life, whereas this limitation does not apply to self-replicating crystals. Crystals are capable of preserving and replicating information under the appropiate conditions (which are not as stringent, and closer to the conditions thought to exist on the primordial Earth), and can catalyze reactions; both features are needed for chemical life. >Silicon-based creatures appear in quite a few SF stories, but is it really >possible to obtain the necessary complexity without carbon ? Most people talking of silicon life (including in SF) make the mistake of simply substituting silicon for carbon. This doesn't work very well, because polysilanes are much less stable than hydrocarbons, and therefore silicon analogs of many carbon compounds could not exist or would be too unstable to use as structural compounds of life. However, life based on polysilicates (an entirely different kind of molecule) might be possible. . . This is the kind of material (actually things like silicoaluminates and other such minerals) that A. G. Cairns-Smith suggests might have made up the first life. >I am not sure if this question can be answered at all, or if one first has >to answer the following question: > > What is life? I would answer this, but the fact that I can post this message even is probably a fluke, and I had better finish up before this bad ARPAnet connection flakes out and loses all of it. Maybe in a later message. -- Lucius Chiaraviglio lucius%tardis@harvard.harvard.edu seismo!tardis.harvard.edu!lucius
glg@sfsup.UUCP (G.Gleason) (08/05/87)
In article <265@askja.UUCP> frisk@askja.UUCP (Fridrik Skulason) writes: >As everybody knows, all life - as we know it - is carbon based. Now, what >I would like to ask is: > Is non-carbon based life possible? Is carbon based life possible? If we did not have our own earth as an example, this would be just a speculative. When you really think about it, life is composed of networks of inter-connected processes that somehow manage to keep reproducing themselves. Probably the hardest thing to explain about life is how it got started in the first place. Present life forms are probably too complex to have come into being in one step. Some explainations rely on simpler precursor that are replaced at a later stage of evolution, and others speculate that it did not start here, but that inter-stelar microbes of viruses seeded life on out planet. >I am not sure if this question can be answered at all, or if one first has >to answer the following question: > What is life? >which - maybe - is a philosophical question rather than a biological one. It probably is, but of course to some people it is a matter of definition, rather than a question to answer. Food for thought: If somehow artifitial intellegence developes into a reality rather than a limited game we play with computers, and a group of intellegent robots are isolated either by extinction of carbon-based life, or simply physical separation. Imagine what a tricky problem it would be for these robots to speculate about their origins. Even if they came accross carbon-based life again, I don't think they would ever believe they evolved from that, much less that such creatures actually designed and assembled their ancestors. Gerry Gleason
jiml@alberta.UUCP (Jim Laycock) (08/05/87)
In article <1767@sfsup.UUCP> glg@/guest4/glgUUCP (xmpj20000-G.Gleason) writes: |Food for thought: If somehow artifitial intellegence developes into a |reality rather than a limited game we play with computers, and a group |of intellegent robots are isolated either by extinction of carbon-based |life, or simply physical separation. Imagine what a tricky problem it |would be for these robots to speculate about their origins. Even if |they came accross carbon-based life again, I don't think they would |ever believe they evolved from that, much less that such creatures |actually designed and assembled their ancestors. |Gerry Gleason Precisely this issue is addressed in James P. Hogan's _Code of the Life Maker_ -- a fantastic book -- Jim Laycock Philosophy grad, University of Alberta alberta!Jim_Laycock@UQV-MTS OR decvax!bellcore!ulysses!mhuxr!mhuxn!ihnp4!alberta!cavell!jiml
cgl@beta.UUCP (C G Langton) (08/06/87)
I am organizing a workshop on Artificial Life that will address this
question, as well as other related questions. The workshop will be held
at the Center for Nonlinear Studies of the Los Alamos National Laboratory
during the week of Sept. 21-25, 1987. Among the confirmed attendees are:
Richard Dawkins, A.G. Cairns-Smith (mentioned by Lucius previously),
Valentino Braitenberg, Aristed Lindenmayer, Richard Laing, Hans Moravec,
James G. Miller, John Holland, ...There will also be many computer and
other demos of "living" artifacts, and an artificial "4H-Show" with a
$100 prize for the most life-like software, hardware, or wetware system.
Social and ethical issues will be explored, as well as alternative media
for embedding the processes of life, applications of the mechanisms of
adaptation and evolution, contributions toward a general theory of
life - abstracted from the particular details of any particular physical
implementation, the role of modelling in theoretical biology, and so
forth.
For more information, see a previous posting in this news group, in
news.announce.conferences, or call, write, or email a request to me:
Chris Langton cgl@lanl.gov
Center for Nonlinear Stuidies
Los Alamos National Laboratory 505-667-1444
Los Alamos, New Mexico USA
87545
krista@ihlpa.ATT.COM (K.J.Anderson) (08/06/87)
In article <265@askja.UUCP>, frisk@askja.UUCP (Fridrik Skulason) writes: > As everybody knows, all life - as we know it - is carbon based. Now, what > I would like to ask is: > > Is non-carbon based life possible? Unfortunately, I cannot remember any details, but there were some articles out maybe 2 or 3 years ago about some evidence that "life" was evolving in some ocean trough. It was based on sulfer. I wish I could remember more. Anyone else? -- ihnp4!ihlpa!krista
mccarthy@uiucuxe.cso.uiuc.edu (08/06/87)
Written 12:19 pm Aug 3, 1987 by chiaraviglio@husc4.HARVARD.EDU >In article <265@askja.UUCP> frisk@askja.UUCP (Fridrik Skulason) writes: >> What is life? Life (or rather, biology) is anything that isn't astronomical, geographical, or meteorological. Or so says Carl Sagan. _____ _____ The Mental Midget Member, ECIS - S division {ihnp4, seismo, cmcl2, pur-ee} !uiucdcs!uiucuxe!mccarthy mccarthy%uiucuxe@a.cs.uiuc.edu "OTISburg??!?" -L. Luthor
jru@etn-rad.UUCP (John Unekis) (08/06/87)
In article <1767@sfsup.UUCP> glg@/guest4/glgUUCP (xmpj20000-G.Gleason) writes: >In article <265@askja.UUCP> frisk@askja.UUCP (Fridrik Skulason) writes: > >> Is non-carbon based life possible? > ....(Carbon based life)... >did not start here, but that inter-stelar microbes of viruses seeded >life on our planet. There is a polpular misconception about viruses, namely that they are the simplest and probably first form of life. Viruses are nothing but genetic material wrapped in protien. They cannot assimilate nutrients, and they cannot reproduce alone. A virus replicates itself by injecting its DNA sequence into a host cell and tricking the host cell to copy it. When enough copies accumulate, the cell ruptures, spewing out new clones to find other victim cells. To seed a planet with a virus would be like seeding it with nothing but sperm - a completely wasted effort. One school of thought says that all viruses originated as accidentally fatal genetic sequences which escaped from their mother cells. > >Food for thought: If somehow artifitial intellegence developes into a >reality rather than a limited game we play with computers, and a group ... >they came accross carbon-based life again, I don't think they would >ever believe they evolved from that, much less that such creatures >actually designed and assembled their ancestors. This sort of speculation makes great science fiction (read - "Code of the Lifemaker"). For my part, someone would have to convince me that intelligent life exists on Earth now first. ihnp4!wlbr!etn-rad!jru
eugene@aurora.UUCP (Eugene miya) (08/07/87)
Hum, always an interesting question. (Cleaning my news groups, so I don't
read this, I'll ask Greg, one of the exobiology types, what he thinks.)
Please consider answering the following:
1) What is life (biological sense)?
2) How do you test for it? (Were 3 tests on Viking enough [out of 100s]?)
3) It's not just carbon, it's carbon-water, what solvent would silicon use?
Water is pretty amazing stuff.
4) Does Si-based life reduce O2?
This latter question is directed because Titan has a very heavy Methane
atmosphere and we were postulating CH4 oceans, snows (on "land"), and clouds.
Solid CH4 does not float in liquid CH4. NH3 might be another candidate.
From the Rock of Ages Home for Retired Hackers:
--eugene miya
NASA Ames Research Center
eugene@ames-aurora.ARPA
"You trust the `reply' command with all those different mailers out there?"
{hplabs,hao,nike,ihnp4,decwrl,allegra,tektronix,menlo70}!ames!aurora!eugenelewando@phri.UUCP (Mark Lewandoski) (08/11/87)
In article <265@askja.UUCP>, frisk@askja.UUCP (Fridrik Skulason) writes: > I am not sure if this question can be answered at all, or if one first has > to answer the following question: > > What is life? > Life is a fountain.
glg@sfsup.UUCP (G.Gleason) (08/13/87)
In article <241@etn-rad.UUCP> jru@etn-rad.UUCP (0000-John Unekis) writes: >In article <1767@sfsup.UUCP> glg@/guest4/glgUUCP (xmpj20000-G.Gleason) writes: >>In article <265@askja.UUCP> frisk@askja.UUCP (Fridrik Skulason) writes: >> >>> Is non-carbon based life possible? >> ....(Carbon based life)... >>did not start here, but that inter-stelar microbes of viruses seeded >>life on our planet. > > There is a polpular misconception about viruses, namely that they are > the simplest and probably first form of life. Viruses are nothing > but genetic material wrapped in protien. They cannot assimilate > nutrients, and they cannot reproduce alone. A virus replicates itself > by injecting its DNA sequence into a host cell and tricking the host > cell to copy it. I only used the term "viruses" as an example of a small package of life bearing material, I understand your objection. I can also imagine mechanisms that would allow a virus like unit to "infect" our planet. In a primitive earth environment, conditions in the biosphere as a whole might be able to support infection by a particular virus. This would not be a virus capable of infecting any organism on earth today. In any case, this is just speculation, and what I was trying to point out is that a single "seed" from outside might be able to "crystalize" life on the whole planet. A difficult theory to test since all the evidence may have been wiped out already. Gerry Gleason