I'm on the more pessimistic side of this argument. Lots of very smart people have thought about this, and really the only element that is able to form complex molecules besides carbon is silicon, and there are good arguments as to why it's a much worse basis for life. And if you have carbon-based life forms, you will have water and CO2.
In any case, it is just way more likely than any other form and makes absolutely the most sense to look for this first.
Sure, you can always say that we don't know what we don't know, but the periodic table of elements is finite and complete, and we are pretty sure that chemistry doesn't change across the universe. I realize I'm fighting an uphill battle in my position, because it's hard to prove the non-existence of things, so you will always be able to say "whatever, maybe you didn't think of everything", and it's true, but I have a hard time seeing how life can be anything but carbon-based. If you have more insight besides what resembles a god of the gaps, I'd be very interested.
Yeah that make sense, but still very much earthlike biology perspective. I mean almost everyone here also believes in digital intelligence at some point.
Are there elements that are more stable under high pressure or heat? Or opposite?
> Yeah that make sense, but still very much earthlike biology perspective.
What does that mean? The parent’s point was that this isn’t just a matter of looking for what is already familiar, but a matter of through the lens of what affordances the elements have and therefore what, in principle, is likely or even possible, to the best of our physical/chemical knowledge.
There’s a rational middle ground between parochialism and anything goes.
Worth noting that even "digital" doesn't mean "not carbon". The current likely end-state of electronics is likely moving from silicon back to carbon due to abundance and durability.
People are working on diamond-based semiconductor devices, and organic-transistors are built experimentally all the time (nothing commercial but it's an area of active research).
An advanced bit of nanotechnology that could self-repair would likely consist of a computer chip which fabbed up replacement organic components for itself and could transport and replace them in-situ, even if it was still just a computer otherwise being digital - after all, that's how our cells do it.
Sillicon is actually significantly more common, so relative abundance isn't a good reason to use carbon. Carbon would be used because it performs better
Maybe in earth's crust, but on a galactic scale carbon is more common.
But they're both one of the most common elements either way, so I think other properties would be more important.
The way the GP comment describes carbon-based technological life made out of transistors doesn't sound like the metabolize carbon to CO2 or would require a lot of water, though, which are two important markers when searching for life.
I would argue abundance based on CO2 being a fairly common gas and "easily" processed. Silicon in silicate minerals is common, but it's much harder to crack out of them.
I'm up for it, but since you are the one who proposed we could have unimaginable forms of life, and I'm coming up short, I'm relying on you (or anyone who holds your position) here to be the creative one.
What's more likely is finding carbon-based life of opposite chirality from the left handed kind native to Earth. This would make life from each planet fundamentally incompatible with each other in numerous surprising ways.
Doesn't this depend on the STP of the alien environment? It seems plausible that planets that are a few hundred degrees warmer might benefit from silicon based life, no?
Kind of a tangent but I'm really interested in why statements like:
> if you have carbon-based life forms, you will have water and CO2.
..can lead to statements like:
> it is just way more likely than any other form
I totally agree on the observation, but what is fascinating to me is why a deductive statement can be considered to indicate likelihood in probability. It seems there is a bit of abductive reasoning going on behind the scenes which neither the deductive logic or inductive probability can really capture on their own.
I don't see that particular statement "leading" to the second statement. You quoted very selectively and didn't quote the part that is the reason why I believe carbon-based to be much more likely, i.e. the fact that silicon is such a bad candidate and that no other molecule allows complex chemistry. Maybe that helps with your fascination. Obviously I skipped all the actual arguments, but they are easy to find by the interested reader in standard literature.
In any case, it is just way more likely than any other form and makes absolutely the most sense to look for this first.
Sure, you can always say that we don't know what we don't know, but the periodic table of elements is finite and complete, and we are pretty sure that chemistry doesn't change across the universe. I realize I'm fighting an uphill battle in my position, because it's hard to prove the non-existence of things, so you will always be able to say "whatever, maybe you didn't think of everything", and it's true, but I have a hard time seeing how life can be anything but carbon-based. If you have more insight besides what resembles a god of the gaps, I'd be very interested.