Hacker News Reader

Comment by blkhawk | Hacker News Reader

If you assume that physics works the same on other planets then carbon-based life is simply the most likely simply from the chemistry we know about. Speculation about say Si based life isn't new but nobody has come up with how that type of organic chemistry might plausibly work.

View on HN

There's an entire Wikipedia article on alternative biochemistries [1].

Quoting that page, with regards to Si: However, silicon has several drawbacks as an alternative to carbon. Silicon, unlike carbon, lacks the ability to form chemical bonds with diverse types of atoms as is necessary for the chemical versatility required for metabolism. Elements creating organic functional groups with carbon include hydrogen, oxygen, nitrogen, phosphorus, sulfur, and metals such as iron, magnesium, and zinc. Silicon, on the other hand, interacts with very few other types of atoms [...]

[1] https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...

I’d really hope that physics work the same on other planets. If that were not the case, we’d have a fundamental problem with our understanding of the universe.

That would actually be really exciting. In trying to resolve where we had gone wrong, we'd learn even more about how the universe works. Our current theories still have holes (no pun intended)

but then, do chemists really know how carbon based life works really? if it weren't for the living examples, wouldn't it be just as hard to work out how proteins form and so on?

It isn’t about knowing how carbon life works but understanding basic chemistry which we do.

Carbon is the atomic floozy it will hook up with a lot of other elements and can form relatively strong bonds, and it can have upto 4 bonds per carbon atom nominally.

This makes carbon the star of its little own chemistry show.

Silicon is similar to carbon in this regard which is why it is in the same column in the periodic table however it bonds with fewer elements and it’s chem requires more energy and is often less stable.

This is what the grandparent question always skips over.

"Why not alternatives to organic life?"

Underestimates the fact that, as near as we can tell, building life from organic molecules is easier (and substantially so).

Given that life seems to be a relatively rare event sequence, and that organic life is the easiest form we've been able to figure out from chemistry (ne physics)... betting on another kind is a long shot.

Granted, maybe we've missed something obvious. Maybe our understanding is critically flawed. But from everything we know right now, one can't just handwave and say "Well, many kinds of life are possible."

Indeed, currently there is no replacement for organic chemistry for life because it seems that we can't find another combination that would be as flexible and stable as carbon.

Silicon can replace carbon in a few scenarios but it isn't likely enough for any plausible mechanism that would support life to be based on silicon alone.

This is why likely all life is carbon based, some of the other elements like phosphors vs arsenic have more wiggle room but there is simply no "glue" other than carbon and this is simply due to physics not lack of imagination or knowledge.

Has there been any thought given to the possibility of life at the subatomic level?

Yes not possible not enough complexity or stability for that matter and the energy levels required are well explosive the smaller you go the more energy is needed since you essentially go form gravity (macro) to electroweak (molecular and atomic) to the strong nuclear force (subatomic) and there is a pretty big increase in magnitude of the forces that govern interactions between each phase.

Heck even within the unified electroweak force there is a huge range e.g. burning coal releases he energy in the stored covalent carbon bonds which are tied by electromagnetism part of the electroweak force but if you start breaking protons a part from neutrons which is the weak force you get a nuclear bomb.

Life needs bonds that are cheap to create, cheap to break and ones that don’t explode once you do break them.

To bolster your other response: in college chemistry classes are split into two kinds: “organic chemistry”, and “everything else”. But he term “organic” in this context means “compounds with carbon atoms”. There are so many ways that carbon bonds to other atoms, and in such complex configurations that there are classes reserved for this single element. And as undergrads will tell you, these are the hard classes!

Organic chemistry isn't required. I can easily come up with one mechanism: What if AI is a common development for advanced organic life forms, after which those organic life forms die out, but silicon or otherwise non organic life forms continue on and move out to other planets?

We have SETI for that, and Mars isn't a likely place for advanced technological life to be hiding out on.

Perhaps a bit arrogant to presume that something is unlikely to exist simply because we haven't yet conceived of it.

Look at the complexity of life on earth alone. There's plenty that neither you nor I will ever even imagine.

Reply on news.ycombinator.com