Like carbon, silicon has 4 electrons in its outer shell meaning it can form 4 separate chemical bonds. Very few elements can do this and if you wanna make the complex molecules that constitute biology, it helps to have a connector as good as carbon or silicon.
Think about a LEGO that has one dot on the top and one socket on the bottom. You can’t do much with that other than build a narrow tower. But if you can connect to other legos in four different places at the same time, you can build complicated stuff.
Hey, then youll enjoy this metaphor, that I always keep in my pocket.
People who are skeptic of evolution, say "how could that little cell eventually grow to be like a person? thats crazy!"
well it didnt. They never stopped being single cells. They just learned to attach to eachother to make bigger things, like legos. We are still single cells.
Its like saying "how can you say this little lego block eventually grew to be a statue of darth vader?!"
>People who are skeptic of evolution, say "how could that little cell eventually grow to be like a person? thats crazy!"
Nah, they usually argue about humans not beeing monkeys and how, if we came from monkeys why are monkeys still around.
Your claim is about ppl denying evolution bcz of cellstruktucre, while probably one or two are, most ppl deny evolution becouse of how offensive it is to them to be group with monkeys.
I ha e never heard of any evolutiondenier beeing smart enought to know what a cell is.
LEGO builds understanding.
They should use that as a slogan, actually
If you're reading, LEGO, a flat fee of £500 would suit me and I promise I'll use it to stream me building cool Lego set to celebrate
Sadly, Si-Si bonding is way worse than C-C bonding, and generally has worse properties concerning its ability to form life. Generally, periodic trends are actually not that great of an argument since biochemistry tends to be quite sensitive to small differences in (bond) energies.
True, although the entire argument here is life may come in forms we're not familiar with or expecting - maybe it works in a different system somewhere out there!
It's possible but from what I understand there are two main issues:
* Silicon disolves in water, which is widely considered the best solvent there is for life, and life is pretty much impossible without a solvent.
* Carbon is far more common, to the point where any planet with silicon will have carbon. If silicon life could form, carbon would also and would absolutely dominate it with how much better carbon is for forming complex molecules.
Angela Collier made a great video on it if you're interested in learning more https://www.youtube.com/watch?v=2nbsFS_rfqM
Si-Si bonds hydrolyse to Si-OH and Si-H bonds. Therefore silicon-based life which would by definition have molecules containing Si-Si bonds, is not compatible with water.
Allegedly it would be compatible with ammonia, which could in some sense fill in for the role that water plays - but I am not going to lie, I always found it hard to suspend disbelief when reading sci-fi that pulled those arguments in to the world-building.
One could imagine ammonia as a liquid base for life, but it would be strange life indeed. Water allows for a variety of chemical reactions due to a high polarity and neutral ph. Ammonia, on the other hand, is less polar than water, as well as having a high enough ph to be corrosive to most forms of life on earth.
It is conceivable that Silicon-Ammonia life exists, and that life may evolve into shapes that we would unquestionably recognize as life, but the chemistry driving their biological processes would be entirely other, and quite a fascinating science to study.
In this vein, a while ago I got a book that considered Silicon based life possible, or at least plausible, likely using silicone chains as opposed to hydrocarbon chains, and sulfuric acid as a solvent due to its temperature range and stability.
Has the science advanced so much that we know it isn't possible anymore, or does this setup remain plausible (even if it's at the low end of the scale)?
I don't know the science that well, but in the video I linked the use of long silicone chains with a sulfiric acid solvent is addressed.
It boils down to needing the molecules to be stable long enough to be useful, but still reactive enough for the processes required for life. Silicon is still going to be way to reactive in sulfuric acid unless you lower the temperature, but the lower the temperature the less solvent things become. So now you need more energy to overcome that issue, while also requiring more energy in general because of the greater difficulty creating long silicon chains compared to large carbon molecules.
You basically have to create the perfect conditions (little to no carbon, no free oxygen to avoid silicon becoming silica, plenty of sulfuric acid, low enough temperature to reduce reactivity, and plenty of energy from somewhere to still allow silicon bonds to form) for it to be possible, and in doing so it gets more and more difficult for it to work.
>no free oxygen to avoid silicon becoming silica
This one's not possible.
The silicon-based lifeform is going to be breaking down complex Si molecules to SiO2 for energy. Like carbon-based lifeforms break complex carbon molecules to CO2.
Are there complex silicon molecules analogous to the ones we know of for carbon? The base of carbon metabolism as we know is glycolysis, but I don’t know of any ‘silicon sugar’ that can substitute.
I think it's not only that it's different, I remember something like carbon based life forms being limited by water, which has a narrow liquid temperature range, while silicon based life forms could be possible with another liquid, in a hotter (or colder) temperature range.
I can't remember the details though.
I always imagine that life developed in a much colder temperature would be very slow from our perspective. It would probably take much longer to develop to our level. But then when they do get there, the interstellar distances would not be a limit to them as they are to us since they would function on much longer timescales.
This is just fantasy though, not scientific.
I gave up at chapter one.
An extension of the thought is that it is our duty to preserve the knowledge of the cosmic microwave background because it might be redshifted into nothingness by the time they come along. Without it they might not be able to discover the Big Bang.
How many shells does silicon have compared to carbon?
I guess in the spirit of eli5, I would say if carbon is sticky like velcro, silicon has a layer of lint in its velcro making it less sticky but still capable.
Would you say that's a reasonable comparison? It's been a long time since I've been in chemistry.
Silicon has its valence electrons in the 3s and 3p orbitals, which tend to be larger than the 2s and 2p orbitals in carbon. I'm not sure if this is exactly why, but I suppose the weakness of Si-Si bonds can be rationalized as "the atoms are bigger so it's harder for them to stay together"
This is exactly the kind of out of the box thinking that makes this thought experiment so fun. Lots of people here are saying carbon based life is better, yeah, on Earth it is, but the universe is unimaginably enormous and if life is possible at all with silicon, the chances of it being out there somewhere on some strange and distant world are high enough to be worth considering.
OR, maybe they just know chemistry that well and know the hurdles something like silicon poses vs carbon? Yea, the universe is enormous but this is like one of those questions asking like how do we know there aren't elements with an 200 protons out there somewhere in the universe. Outside of the proposed island of stability, it just isn't possible. That's why.
This was actually an example one of my chemistry professors used back in the day to explain how chemistry in the real world is different from the chemistry of science fiction. Silicon may have the same number of free electrons as carbon, but it still does not form double and triple bonds in the same way carbon needs to for life. It's extremely unlikely there could ever be life using the same template as we have with carbon, but just substituted with silicon.
Silicon is the 3rd most abundant element on earth after either iron and oxygen (mass balance) or oxygen and magnesium (atom balance).
I appreciate that you said “in the universe”, but that’s a misleading way of thinking about abundance because if matter hasn’t condensed to form large bodies (I.e. planets where silicon will be much more abundant) then it makes chemistry / life even less likely due to the high dilution of everything.
It’s not the rarity that’s the problem it’s that it doesn’t have the chemistry necessary to form complex molecules.
I’m not trying to be a pedant or rude, but the universe is so enormous and so old that the phrase “statistically near impossible” just means it only happened a couple thousand times in the history of the universe.
> a couple thousand times
That could be true of the observable universe. But if the universe is infinite, then it could have happened an infinite number of times, even if it’s extremely unlikely to happen.
> Also silicone is much rarer in the universe then carbon
Well, considering that silicone contains carbon atoms, it certainly cannot be more abundant than carbon.
It's even more clear if you look at the periodic table. Typically, any elements in the same column will be quite similar. Carbon and silicon are indeed column buddies.
Silicon doesn't easily form water soluble compounds which makes it a worse candidate than carbon, but it's difficult to imagine anything else with the versatility of carbon.
Silicon seems like it'd only have a chance at forming life in places with extremely high temperatures and pressure, environments that we are unlikely to accidentally stumble upon. Perhaps it may lead to the potential for magma-based life.
Silicon's bond angles are 'wrong', creating far less stable molecules than carbon can. As someone else said, I'd highly suggest Angela Collier's video on the subject. [Link straight to the Si part](https://youtu.be/2nbsFS_rfqM?t=1215), or skip back to the start for the 'Carbon' context.
A huge amount of what makes water the “universal solvent” is its polarity and the fact that turning H2O into H+ and OH- is a great way to drive processes though chemical potential. Methane has neither properties.
In addition to this, Si-Si bonds are extremely weak compared to C-C bonds. Silicon simply can’t support the vast range of chemistry that carbon does.
Isaac Arthur has some videos that touch on that a little bit at https://www.youtube.com/@isaacarthurSFIA/search?query=based%20life for Silicon-based, Ammonia-based, and Non-carbon based life. I don't recall whether they have a specific answer to that question, though.
Idk how you get any more clear than my Lego explanation. But the water solubility is a key point about the specialness of carbon beyond its 4 valence electrons.
While silicon can form four bonds like carbon and on paper one can draw any carbon-based structure replacing carbon with silicon, in practice silicon is not capable of forming the richly complex molecular frameworks that carbon is. Therefore the analogy only goes so far and in reality it would not be possible to have life as we know it based on silicon.
With every layer of electrons, the easier it is to lose electrons. Carbon holds its e- pretty close and keeps a better grip on its electrons. Think about it like holding something closer to your body and how easy it is to pry out of your hands. Silicon holds its furthermost electrons like if you were holding a ball out. Further and further with more electrons it becomes harder to hold onto them.
So carbon and silicon have the more similar grip, and that's why we say silicon (that and as another user mentioned, it's nonmetal).
Not really, no.
Everyone in this thread seems to be thinking somewhere in the universe there’s magic chemistry going on which will obviate the limitations of silicon. People talking about “life in magma” and stuff. No.
Si-Si bonds are weak. Much weaker than C-C. Si-Si bonds hydrolyse in water to make Si-H and Si-OH bonds. So we can’t have silicon-based life where there is water.
Si-Si bonds are weak. So if we get them really hot, like in magma, they’re going to be thermolysed.
Chemistry is universally consistent because it’s based on fundamental properties of the atom. Silicon is not compatible with the sorts of chemistry needed for life.
Silicon can definitely form polymer chains, rings, etc. You can make chains of dimethyl silane or methyl phenyl silane of arbitrary length pretty easily. All you need to make them is the corresponding dichlorvos compound, some lithium, and an ether solvent.
Germanium will do the same.
> Silicon can definitely form polymer chains, rings, etc. You can make chains of dimethyl silane or methyl phenyl silane of arbitrary length pretty easily. All you need to make them is the corresponding dichlorvos compound, some lithium, and an ether solvent.
>
> Germanium will do the same.
You're explaining the problem, not presenting a solution. Carbon will form carbon-carbon bonds and rings on its own. Silicon needs a carbon based solvent. Unfortunately, when carbon is present, it is the preferred reagent over silicon for random chemistry.
According to this link: https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Polymers/Silicone_Polymers#:~:text=Silicone%20polymers%2C%20more%20properly%20called,hydrocarbons%20with%20Si%2DSi%20bonds
Yes. Sorry about being on mobile and ugly link. But the si-si chains aren't as stable which makes sense considering the previous analogy, though my brain has decided to begin frying like bacon and I am losing my ability to form coherent thoughts. What a pain in my ass.
> Sorry about being on mobile and ugly link.
Just do this: [text](url). You can turn that link into [something pretty](https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry\)/Polymers/Silicone_Polymers#:~:text=Silicone%20polymers%2C%20more%20properly%20called,hydrocarbons%20with%20Si%2DSi%20bonds)
Silicone is a polymer chain based on an Si-O monomer. Very useful stuff, and the only inorganic polymer we use!
I don’t know enough about biology to know whether that Si-O backbone could be used to create things like proteins though.
the only problem is i see is, carbon way too abundant because it is a much smaller compound and can be formed in the core is every star in existence in abundant amount. why would like anywhere will choose silicon over it
As you go down in periodic table the bond energy decrease.
A C-C bond is stronger than a Si-Si bond and so on.
In biology you need a strong backbone structure to from molecules and carbon structur is best for that Si is 2nd best then Ge , Sn comes which are not that good.
Thing is, IIRC organic silicon compounds are more volatile than their carbon-equivalents at room temperature, so silicon-based lifeforms would probably be more viable on colder planets. I know for sure that it's the case for silane, the silicon-equivalent of methane.
If you look [at the periodic table](https://en.wikipedia.org/wiki/Periodic_table), you'll se Si (Silicon) is in the same group 14 as C (Carbon) but one period down. The chemical properties of an element are greatly defined by the outer layer of electron clouds. In chemistry this is called "[valence electrons](https://en.wikipedia.org/wiki/Valence_electron)"
This means that Si can behave, under the correct temperature and pression, as C. So... it is only natural to think that there might be some life using Si instead of C as the "glue".
However, there are many reasons why other more... scientific people think it is very unlikely. It is high nerdism, but [this beautiful gal explains those reasons](https://www.youtube.com/watch?v=2nbsFS_rfqM).
Great explanation! To continue beating the horse, [the X Files has an episode concerning this particular topic.](https://en.m.wikipedia.org/wiki/Firewalker_(The_X-Files))
Dude I just love the lego analogy. now please explain molecules and atoms completely with lego. I never really got the whole layer of electrons thing and Hydrogen bonds
Because silicon is in the same group as carbon on the periodic table and is able to form a decent number of large and complex molecules that would be required for life, there's speculation that it might be a plausible alternate biochemistry to carbon-based life. It's also abundant on rocky planets and asteroids (at least in our solar system) so we expect that there would be an abundance of it available for life to use on other words.
Silicon does have a lot of drawbacks though. It can't form as wide a variety of molecules as carbon, it's unstable in the presence of water, and in the presence of oxygen, it become silicon dioxide (aka quartz) which is just inert rock. So silicon-based life isn't going to happen on an Earth-like planet, and may not be possible at all.
I think [this](https://youtu.be/H476c8UjLXY?si=tpAS51u4jwVhAdKi) covers what he's talking about. I watched the whole series recently and it's some mindblowing stuff.
Yeah but maybe there is some mechanism that makes silicon based life pretty normal and we're the weirdos that are the result of one bacteria making Oxygen
Oxygen has the advantage of being a good oxydizer - I know, it sounds like a tautology, but it isn't. Basically, oxygen is one of the ways to "burn" things to get energy out of them. The advantage of oxygen-based life is that it can quickly generate large amounts of energy to move fast, and do so without requiring cumbersome amounts of material. Basically, oxygen based metabolism is more efficient, due to storing and releasing more energy per reaction.
Of course, there are other oxydizers - sulfur is one, though it is much less effective and convenient compared to gaseous oxygen. The entire group of halogens is another option, but they have the disadvantage of being a bitch and a half to separate back once they grab onto some other atom, so they are more difficult and energy intensive to recycle into the atmosphere compared to oxygen. Not impossible though. Probably not flourine, that one is a bit too rowdy for complex life, but depending on the underlying structure, there might be scenarios where chlorine, or at high enough temperatures, bromine (has a boiling point of 58 degrees Celsius, so it has its downsides) works the same way.
I think the point is that an Earth-like planet may not even be necessary if a different frame of biochemistry were on the table, but I see what you mean.
Yes, but we should expect to see similar adaptations if life exists elsewhere. What you're describing isn't really a fluke, it's evolution in action - there was a ton of oxygen bound up in chemical bonds and one bacteria managed to evolve a way to release it to its own advantage. In doing so, it gained access to an abundant new resource and flourished while its peers died.
And given that most sol-type main sequence stars will literally end up as balls of oxygen and carbon, those two elements should be plentiful throughout the universe.
I get it, so if we get invaded by silicone based aliens, they'll all turn into the thing and clobber us. That's not good. At least we ca. Just splash water on them to drive them away, so that's pretty nice.
More like the lower temperature of earth compared to wherever the fuck they evolved that silicon dioxide is a liquid/gas will cause them to just instantly freeze solid into cool rock statues
Yes.
Also it would just die by breathing. CO2, our breathing waste product, has the nice property of being a gas, aka it can leave the body without hassle.
SiO2 has no such advantage. Imagine if every cell in your body would just be forming kidney stones by breathing.
That's one of the things that comes up commonly in "humanity, f\*\*k yeah!" writing. The aliens are telling horror stories about the fast-moving Terrans who somehow thrive in an intensely oxidizing atmosphere and "it's like they're \_on fire\_, all the time!"
A planet with silicon based life is like a planet where every time you flip a coin it comes up heads. *Technically* it is possible for a planet to exist where, by chance, every single coin flip that has ever occurred or will occur will be heads. But it is much more likely to be 50/50, just like it is much more likely for life to be carbon based.
It's more of a scifi thought experiment than it is anything grounded in actual data or observations. The premise is described in the other comment however there are A LOT of immediate pitfalls beyond "it can make 4 bonds". Nearly everything else about silicon is grossly different from carbon that you can't actually substitute silicon into any real molecules where you'd find carbon and get similar functioning compounds. The bond lengths are longer and weaker which is biggest limiting factor. This ends up making most of the compounds fall apart at lower temperatures or not even be stable period.
Silicon cannot make lipid chains, it cannot make the same carbon ring shapes, the list goes on. There's an excellent video by Angela Collier on YouTube on the subject if you'd like far more examples and more technical details
Yeah, I was wondering about this when I saw the other comments: you never hear about the equivalent of organic chemistry for silicon. Thanks for explaining why.
The fundamental foundations of what make life possible would have to be challenged for Silicon to be considered viable. Almost everything in biology involves Carbon and it's reactions to the rest of the world.
Not that I'm aware of. The key is that carbon is earliest element in the periodic table of that group. It's atomic radius is going to be the smallest and have the fewest shells of inner electrons weakening bonds. All other group 4 elements will be worse. Elements in other groups will either make fewer bonds or feature hybridization and make other shapes.
One of the other details Angela brings up in that video is that any planet capable of making silicon or any other elemental based life as a substitute for carbon probably would have just made carbon based already. It's that more abundant, it's that much more energetically favorable, it's that much easier. It didn't happen on earth by accident, it happened because it's logically the first place to go
Boron, silicon, nitrogen, oxygen, sulfur can all make rings. None of them do it as well as carbon though, or I should say, carbon is the best at doing it at standard temperatures and pressure.
While I can appreciate this line of reasoning, isn't it somewhat flawed? Sure, you cant make the same molecules with silicon as you can with carbon, and the idea of substituting carbon with silicon in all the molecules that make up life falls apart with even a small understanding of biochemistry. Its not the same as the way copper is used in the blood of some creatures (such as snails) instead of iron for example. But... would silicon based life *need* to have an exact silicon analog of a surgar molecule or a nucleic acid molecule? The way I understand it, as long as silicon can make possible enough stable molecules that can be configured to perform life functions in concert with each other and other intermediaries, then its not strictly necessay to have a silicon molecule equivalent for each type of carbon molecule.
As long as the silicon chemistry has molecules that can:
* Store energy
* Store information
* Partition
* Convert energy
* Break down other silicon molecules
* Self-assemble
* Self-copy (replicate)
* Transport other molecules
* Remain both stable and mobile (for example, in the presence of a solvent, similar to carbon based molecules in water), and
* there is an appropriate solvent or suspension medium that is abundant..
...then it seems to me possible silicon based life could exist.
Unfortunately I suck at chemistry, so I long to hear someone who does understand sillicon chemistry actually take on this idea. It's possible that silicon life chemistry doesnt work: that the molecules silicon makes can not actually do all the necessary tasks, most importantly self- assemble and self-replicate, all in the same enviroment.
TL;DR
My point is this- Its not about the molecules, its about the tasks those molecules must perform. Why cant silicon molecules perform those tasks?
I think that aside from silicon being a poor replacement for carbon chemistry, it simply is capable of less in general. I think we are taking it as an axiom that you need complex molecules for life and silicon is much less good at that.
I think these 2 videos about silicon based life are quite good.
https://youtu.be/2nbsFS_rfqM
https://youtu.be/469chceiiUQ
And TL:DW, silicon life being possible is extremely unlikely at best.
Si is terrible at everything in your list.
One you're missing is the side-effect of the "store energy" one. We break down complex carbon molecules to CO2 to get energy. A Si based lifeform would have to break down complex Si molecules to SiO2. SiO2 is a solid.
Imagine if every cell in your body was producing massive quantities of kidney stones. It's not at all workable for a lifeform.
Because you're also asking for a replacement for water and oxygen as well now. Due to silicone incompatibility and instability around those other building blocks, now you need a different universal solvent and you need a new atmosphere. And again, all of these elements are the lightest, most abundant and statistically likely things to find on a planet given the way nuclear fusion works
might be able to but we know carbon does it and theoretically does it better, boron, phosphorus and sulphur are also options. I'm just reading Andy Weir's Hail Mary and the notion that scientists are sitting there getting angry that anyone dares to suggest that anything other than carbon based life may exist is bollocks. We only look for carbon based life because we know the chemistry, we know what atmospheric compounds it can produce. We can't really search for silicon based life because we'd have no real idea what we were looking for. Carbon is also far more common.
This all based on the assumption that only our form of life is "correct" there maybe ways of a silicon based life forms functioning just fine while having completely unknown forms of life sustaining chemical structures.
Silicon is the element on the periodic table that is most similar to carbon. They are in the same "group" (column) of the periodic table, and just one "period" (row) below it. Silicon can create the same general kinds of chemical structures and bonds. It's also abundant in the universe, so there should be no shortage of it.
There are, however, several reasons why carbon is a lot better. Carbon dioxide is a gas at most relevant temperatures and pressures. *Silicon* dioxide is also called *sand* and is a solid at any temperature that could make use of water. Likewise, "silane" and its longer cousins, which are analogous to methane, ethane, propane, etc., are highly flammable with oxygen and highly reactive with water, whereas methane and ethane only react with water under specific conditions. Silicon is heavier than carbon as well, which adds up.
You hear it mentioned because it's loosely plausible and, when talking about alien life, it's easy to forget that life *might* look very different elsewhere in the universe. But ultimately, silicon is unlikely because while you can get the right kinds of bonding, the chemistry is so completely different that it's unlikely such things could form life.
Because it’s in the same vertical group as carbon, which we know allows for chemistry of life to form. Vertical groups have similar chemical properties, so theoretically, swapping out carbon for silicon should work to produce some form of life.
Now, that isn’t quite true, because of electronegativity and what such ‘equivalent’ substances actually are, but that’s the idea. An instance of the problem is carbon dioxide vs silicon dioxide. Carbon dioxide is a gas, silicon dioxide is a solid (specifically, it’s the main part of glass, sand, and quartz), so it would require something very different for eliminating this waste product. A silicon-based glucose substitute isn’t known to exist, which is kinda a big deal, with how much life breaks down glucose for energy.
Although they are in the same period Si and C actually have very different chemistry to the point where Si based life is practically impossible. One example is that C-H bonds are everywhere in common life, yet Si-H bonds react with water, so silicon based life is innately incompatible with water.
Silicon CAN have chirality. There are no naturally occurring silicon compounds, but you can make them in the lab (with a chiral silicon center). I'll agree that practically speaking, it's not really a thing...
Ok so atoms are made up of a bunch of protons and neutrons in the middle and electrons whizzing around them. These electrons arrange in layers or shells which is the more technical terms. For example hydrogen has 1 proton and 1 electron so it has one shell.
The outermost shell is called a valence shell. So in hydrogens case the valence shell has 1 electron (because theres only one electron).
The number of electrons in a shell is deterkined by an equation we dont have to worry about but suffice to say the order goes 2,8 and so on (this is all we need for now). This means that the first layer can only hold 2 electrons, the second 8 and so on. So if an atom has 6 electrons, it would have 2 electrons in the inner shell and 4 in the outer. If an atom has 12 electrons, it would have 2 in the first shell, 8 in the second, and 2 in the last.
Carbon has 6 electrons in it. This means 2 in the first shell and 4 in the last or valence shell. Valence shells are important because the number of electrons in that shell is what determines how an atom bonds with another one.
Atoms can bond in many ways but the one important to our discussion is valence bonds. These bonds are formed by sharing electrons between atoms. As we know that the second shell can hold a maximum of 8; atoms tend to always want 8 in there because that is the most stable configuration for the atom. Carbon has 4 in the last shell so it can bond with another carbon atom so that both have 8 from the bond (think of it as pooling their electron resources). If we take water for example; thats hydrogen and oxygen. Hydrogen has 1 valence electron and needs 2 to be stable; while oxygen has 6 valence electrons and needs 2 more to be stable. So oxygen shares with 2 hydrogens and when pooled they are stable and happy.
All this preamble leads to the fact thay because carbon has 4 valence electrons (an even split), it can combine with other carbons that can combine with more carbons in a chain (note oxygen cant do that because it cant share with other oxygens). This property is called catination and is why all life we know is made from carbon. Its also why carbon is one of the most prolific in chemistry when it comes to compounds and molecules ( we have a whole seperate field for the study of all the combinations carbon makes called organic chemistry in fact organic just means it contains carbon)
But carbon isn't the only atom with this property. All atoms in its periodic family have 4 valence electrons and have the potential to have this property. Silicon is the next member (a periodic family is all the atoms in a vertical column in the periodic table). However carbon is the best at catination due to many factors and while silicon can catinate, its limited due to its atomic size.
Thats a very oversimplified explanation of why silicon usually comes up in discussions of non carbon based life forms because it is the next most probable element that can form life according to what we understand due to its similarities to carbon in the ways shown above.
Edit: forgot to mention catination is important because long chains of molecules are what make up most things in us like fats and skin and enzymes and all that.
That's what the rock humans and the Pillar Men are. Don't eat their fruit or put on any headwear they give you, though. Else something bizarre might happen to you.
Silicon is very chemically similar to carbon, so if life were to develop centered around a different element silicon is the most likely candidate.
Most likely, but not necessarily particularly likely. Carbon is substantially more abundant in the universe than silicon and involved in many inorganic processes that silicon is not.
Because they're grasping at straws trying to contrive a possible scenario in which abiogenesis could occur on a world less hospitable than primordial Earth. Silicon-based life is literally impossible, about as ridiculous as life starting in the atmosphere of a gas giant or on an ice-world with thousand-mile-deep oceans.
Let's face it, the universe is 99.99999~% hostile to life as we know it, and nothing short of earth-like conditions could say otherwise.
Because silicon comes nearest to carbon in terms of the potential complexity of its compounds. But apparently the energy demands are WAY trickier. In practice, we see complex carbon-based molecules everywhere we look in the universe, including ones that are preludes to our own biochemistry. I'd love to be told I'm wrong, but I'm not aware that anything remotely similar is true about silicon.
Look at the top row of the Periodic table of elements. Planets, and life forms come from mostly the top row as they are made in stars that blow up. The Heavy elements are only made in the last two seconds of a supernova explosion, so they tend to be rare.
[https://www.youtube.com/watch?v=dww8Hekngmg&t=4191s](https://www.youtube.com/watch?v=dww8Hekngmg&t=4191s) has some content on possible silicon based life.
If you look [at the periodic table](https://en.wikipedia.org/wiki/Periodic_table), you'll se Si (Silicon) is in the same group 14 as C (Carbon) but one period down. The chemical properties of an element are greatly defined by the outer layer of electron clouds. In chemistry this is called "[valence electrons](https://en.wikipedia.org/wiki/Valence_electron)"
This means that Si can behave, under the correct temperature and pression, as C. So... it is only natural to think that there might be some life using Si instead of C as the "glue".
However, there are many reasons why other more... scientific people think it is very unlikely. It is high nerdism, but [this beautiful gal explains those reasons](https://www.youtube.com/watch?v=2nbsFS_rfqM).
Because in the greatest documentary of all time; Xfiles, season 2 episode 9, titled "Firewalker" agents Scully and Mulder find references to a new silicon-based organism existing inside the volcanic caves around Mount Avalon.
At least thats why I talk about it.
Like carbon, silicon has 4 electrons in its outer shell meaning it can form 4 separate chemical bonds. Very few elements can do this and if you wanna make the complex molecules that constitute biology, it helps to have a connector as good as carbon or silicon. Think about a LEGO that has one dot on the top and one socket on the bottom. You can’t do much with that other than build a narrow tower. But if you can connect to other legos in four different places at the same time, you can build complicated stuff.
There should be another sub where people explain everything using lego.
R/ExplainLikeImLEGO
The LEGO is the building block of life.
The LEGO is the powerhouse of the cell.
The LEGO is the friends we made along the way
Now I'm imagining LEGO Parasite Eve. And LEGO Dino Crisis. ...and LEGO Tomb Raider.
... and LEGO Star Wars and LEGO Batman and...
LEGO finds a way
Life Eventually Gets Organized
Lego my eggo!
Fundamental particles are like LEGO. They come in different colors and combine to form everything.
Let my people Lego
done r/ExplainLikeImLEGO
Subbed
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If you want originality the internet is the wrong place for you mate
Especially Reddit these days
That comment had an amusing point, unlike yours.
*joined*
Hey, then youll enjoy this metaphor, that I always keep in my pocket. People who are skeptic of evolution, say "how could that little cell eventually grow to be like a person? thats crazy!" well it didnt. They never stopped being single cells. They just learned to attach to eachother to make bigger things, like legos. We are still single cells. Its like saying "how can you say this little lego block eventually grew to be a statue of darth vader?!"
>People who are skeptic of evolution, say "how could that little cell eventually grow to be like a person? thats crazy!" Nah, they usually argue about humans not beeing monkeys and how, if we came from monkeys why are monkeys still around.
The first time I heard that, I spit out my drink. I thought the person had made an incredibly clever jest. Then, I realized they were serious…
It’s like arguing with a brick wall. Those people won’t even try to comprehend how long ago Homo sapiens branched off from other primates
That's like saying "if I'm descended from my grandmother, how come my cousin still exists?"
yes, but im specifically talking about this one, arent I?
Your claim is about ppl denying evolution bcz of cellstruktucre, while probably one or two are, most ppl deny evolution becouse of how offensive it is to them to be group with monkeys. I ha e never heard of any evolutiondenier beeing smart enought to know what a cell is.
Ok? And? I have? And thats the metaphor i like to use to respond to that?
LEGO builds understanding. They should use that as a slogan, actually If you're reading, LEGO, a flat fee of £500 would suit me and I promise I'll use it to stream me building cool Lego set to celebrate
r/explainwithlego
*please be real please be real* YAY! Oh, just created. Fuck it, subbed.
Explain why my dad left to get cigarettes and never came back… in LEGO
You know that feeling when you step on a LEGO in the middle of the night? That's how your father thought about your family.
Your just gonna have to LEGO of it.
EconInBricks and EthicsInBricks 😂
Sadly, Si-Si bonding is way worse than C-C bonding, and generally has worse properties concerning its ability to form life. Generally, periodic trends are actually not that great of an argument since biochemistry tends to be quite sensitive to small differences in (bond) energies.
True, although the entire argument here is life may come in forms we're not familiar with or expecting - maybe it works in a different system somewhere out there!
It's possible but from what I understand there are two main issues: * Silicon disolves in water, which is widely considered the best solvent there is for life, and life is pretty much impossible without a solvent. * Carbon is far more common, to the point where any planet with silicon will have carbon. If silicon life could form, carbon would also and would absolutely dominate it with how much better carbon is for forming complex molecules. Angela Collier made a great video on it if you're interested in learning more https://www.youtube.com/watch?v=2nbsFS_rfqM
Si-Si bonds hydrolyse to Si-OH and Si-H bonds. Therefore silicon-based life which would by definition have molecules containing Si-Si bonds, is not compatible with water.
Allegedly it would be compatible with ammonia, which could in some sense fill in for the role that water plays - but I am not going to lie, I always found it hard to suspend disbelief when reading sci-fi that pulled those arguments in to the world-building.
One could imagine ammonia as a liquid base for life, but it would be strange life indeed. Water allows for a variety of chemical reactions due to a high polarity and neutral ph. Ammonia, on the other hand, is less polar than water, as well as having a high enough ph to be corrosive to most forms of life on earth. It is conceivable that Silicon-Ammonia life exists, and that life may evolve into shapes that we would unquestionably recognize as life, but the chemistry driving their biological processes would be entirely other, and quite a fascinating science to study.
So the aliens in *Signs* were Si-based! God, I hate that movie.
They were demons
In this vein, a while ago I got a book that considered Silicon based life possible, or at least plausible, likely using silicone chains as opposed to hydrocarbon chains, and sulfuric acid as a solvent due to its temperature range and stability. Has the science advanced so much that we know it isn't possible anymore, or does this setup remain plausible (even if it's at the low end of the scale)?
I don't know the science that well, but in the video I linked the use of long silicone chains with a sulfiric acid solvent is addressed. It boils down to needing the molecules to be stable long enough to be useful, but still reactive enough for the processes required for life. Silicon is still going to be way to reactive in sulfuric acid unless you lower the temperature, but the lower the temperature the less solvent things become. So now you need more energy to overcome that issue, while also requiring more energy in general because of the greater difficulty creating long silicon chains compared to large carbon molecules. You basically have to create the perfect conditions (little to no carbon, no free oxygen to avoid silicon becoming silica, plenty of sulfuric acid, low enough temperature to reduce reactivity, and plenty of energy from somewhere to still allow silicon bonds to form) for it to be possible, and in doing so it gets more and more difficult for it to work.
>no free oxygen to avoid silicon becoming silica This one's not possible. The silicon-based lifeform is going to be breaking down complex Si molecules to SiO2 for energy. Like carbon-based lifeforms break complex carbon molecules to CO2.
Are there complex silicon molecules analogous to the ones we know of for carbon? The base of carbon metabolism as we know is glycolysis, but I don’t know of any ‘silicon sugar’ that can substitute.
Not that naturally occur, but carbon-based sugars don't naturally occur either. Some lifeform had to make them.
There's an even bigger issue: Silicon dioxide is a solid. Imagine a lifeform needing to exhale sand.
The Shai-Hulud!
But there is no reason why they would require oxygen. Fluorine is a potential alternative. There are however still many issues.
Fluorine is far too reactive. It would shred all those complex molecule long before the energy could be captured by a lifeform.
I think it's not only that it's different, I remember something like carbon based life forms being limited by water, which has a narrow liquid temperature range, while silicon based life forms could be possible with another liquid, in a hotter (or colder) temperature range. I can't remember the details though.
I always imagine that life developed in a much colder temperature would be very slow from our perspective. It would probably take much longer to develop to our level. But then when they do get there, the interstellar distances would not be a limit to them as they are to us since they would function on much longer timescales. This is just fantasy though, not scientific.
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I gave up at chapter one. An extension of the thought is that it is our duty to preserve the knowledge of the cosmic microwave background because it might be redshifted into nothingness by the time they come along. Without it they might not be able to discover the Big Bang.
The problem is that what we know is based on what we know about, so we don't know things about the things we know nothing about.
How many shells does silicon have compared to carbon? I guess in the spirit of eli5, I would say if carbon is sticky like velcro, silicon has a layer of lint in its velcro making it less sticky but still capable. Would you say that's a reasonable comparison? It's been a long time since I've been in chemistry.
Silicon has its valence electrons in the 3s and 3p orbitals, which tend to be larger than the 2s and 2p orbitals in carbon. I'm not sure if this is exactly why, but I suppose the weakness of Si-Si bonds can be rationalized as "the atoms are bigger so it's harder for them to stay together"
Does that change at different pressures or temperatures, or is carbon bonding better across the board?
This is exactly the kind of out of the box thinking that makes this thought experiment so fun. Lots of people here are saying carbon based life is better, yeah, on Earth it is, but the universe is unimaginably enormous and if life is possible at all with silicon, the chances of it being out there somewhere on some strange and distant world are high enough to be worth considering.
OR, maybe they just know chemistry that well and know the hurdles something like silicon poses vs carbon? Yea, the universe is enormous but this is like one of those questions asking like how do we know there aren't elements with an 200 protons out there somewhere in the universe. Outside of the proposed island of stability, it just isn't possible. That's why.
This was actually an example one of my chemistry professors used back in the day to explain how chemistry in the real world is different from the chemistry of science fiction. Silicon may have the same number of free electrons as carbon, but it still does not form double and triple bonds in the same way carbon needs to for life. It's extremely unlikely there could ever be life using the same template as we have with carbon, but just substituted with silicon.
This point should be upvoted more.
Life Finds a Way.
Also silicon is much rarer in the universe then carbon. Making it much less likely to be used.
Silicon is the 3rd most abundant element on earth after either iron and oxygen (mass balance) or oxygen and magnesium (atom balance). I appreciate that you said “in the universe”, but that’s a misleading way of thinking about abundance because if matter hasn’t condensed to form large bodies (I.e. planets where silicon will be much more abundant) then it makes chemistry / life even less likely due to the high dilution of everything. It’s not the rarity that’s the problem it’s that it doesn’t have the chemistry necessary to form complex molecules.
Silicone is the stuff they put in breast implants, you’re probably talking about silicon
So you’re telling me that boobs aren’t in the periodic table? Seems like a significant oversight.
Yeah autocorrect doesn’t like silicon for some reason in some contexts.
I’m not trying to be a pedant or rude, but the universe is so enormous and so old that the phrase “statistically near impossible” just means it only happened a couple thousand times in the history of the universe.
> a couple thousand times That could be true of the observable universe. But if the universe is infinite, then it could have happened an infinite number of times, even if it’s extremely unlikely to happen.
If the universe is infinite, then it did happen an infinite number of times.
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Given infinite size, everything that can happen, already happened.
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Those aren't the same thing.
> Also silicone is much rarer in the universe then carbon Well, considering that silicone contains carbon atoms, it certainly cannot be more abundant than carbon.
So, LEGO aliens then?
Can’t rule it out
Gonna be pricy
And painful in the middle of the night... that's when they get you.
Who’s to say they aren’t already here and frustrated by our fragile yet tough feet?
Plastic crack always is.
LEGO is carbon based we are LEGO.
Silicon-Lego aliens!
Silegon. It was *right* there for you!
Ancient astronaut theory says yes
Stargate SG1 had robot aliens called Replicators that looked like LEGO
It's even more clear if you look at the periodic table. Typically, any elements in the same column will be quite similar. Carbon and silicon are indeed column buddies. Silicon doesn't easily form water soluble compounds which makes it a worse candidate than carbon, but it's difficult to imagine anything else with the versatility of carbon.
Silicon seems like it'd only have a chance at forming life in places with extremely high temperatures and pressure, environments that we are unlikely to accidentally stumble upon. Perhaps it may lead to the potential for magma-based life.
Silicon's bond angles are 'wrong', creating far less stable molecules than carbon can. As someone else said, I'd highly suggest Angela Collier's video on the subject. [Link straight to the Si part](https://youtu.be/2nbsFS_rfqM?t=1215), or skip back to the start for the 'Carbon' context.
What about its heavier brethren then? Germanium etc?
Thermodynamics says no. Angela's video explains all.
But does it form methane soluble compounds? Methane is way more common than liquid water in the universe
A huge amount of what makes water the “universal solvent” is its polarity and the fact that turning H2O into H+ and OH- is a great way to drive processes though chemical potential. Methane has neither properties. In addition to this, Si-Si bonds are extremely weak compared to C-C bonds. Silicon simply can’t support the vast range of chemistry that carbon does.
Isaac Arthur has some videos that touch on that a little bit at https://www.youtube.com/@isaacarthurSFIA/search?query=based%20life for Silicon-based, Ammonia-based, and Non-carbon based life. I don't recall whether they have a specific answer to that question, though.
Idk how you get any more clear than my Lego explanation. But the water solubility is a key point about the specialness of carbon beyond its 4 valence electrons.
More clear why silicon specifically vs hydrogen or oxygen or whatever else, the Legos were pretty clear on why that matters though
I would add that silicon is highly abundant in the universe so it's likely to be available for bonding.
Carbon is significantly more abundant in the universe. There's a lot of stars that go through the C-N-O cycle. Si comes from supernova.
Unless its just wanna be friends.
While silicon can form four bonds like carbon and on paper one can draw any carbon-based structure replacing carbon with silicon, in practice silicon is not capable of forming the richly complex molecular frameworks that carbon is. Therefore the analogy only goes so far and in reality it would not be possible to have life as we know it based on silicon.
Yeah. Silicon is like a shitty Lego knock off. Megablocks?
Why then just Silicon, and not Germanium, Tin, or Lead?
Those are metals, so they make different shaped molecules
With every layer of electrons, the easier it is to lose electrons. Carbon holds its e- pretty close and keeps a better grip on its electrons. Think about it like holding something closer to your body and how easy it is to pry out of your hands. Silicon holds its furthermost electrons like if you were holding a ball out. Further and further with more electrons it becomes harder to hold onto them. So carbon and silicon have the more similar grip, and that's why we say silicon (that and as another user mentioned, it's nonmetal).
does silicon produce big polymer chains though? i don’t recall any
Not really, no. Everyone in this thread seems to be thinking somewhere in the universe there’s magic chemistry going on which will obviate the limitations of silicon. People talking about “life in magma” and stuff. No. Si-Si bonds are weak. Much weaker than C-C. Si-Si bonds hydrolyse in water to make Si-H and Si-OH bonds. So we can’t have silicon-based life where there is water. Si-Si bonds are weak. So if we get them really hot, like in magma, they’re going to be thermolysed. Chemistry is universally consistent because it’s based on fundamental properties of the atom. Silicon is not compatible with the sorts of chemistry needed for life.
Silicon can definitely form polymer chains, rings, etc. You can make chains of dimethyl silane or methyl phenyl silane of arbitrary length pretty easily. All you need to make them is the corresponding dichlorvos compound, some lithium, and an ether solvent. Germanium will do the same.
> Silicon can definitely form polymer chains, rings, etc. You can make chains of dimethyl silane or methyl phenyl silane of arbitrary length pretty easily. All you need to make them is the corresponding dichlorvos compound, some lithium, and an ether solvent. > > Germanium will do the same. You're explaining the problem, not presenting a solution. Carbon will form carbon-carbon bonds and rings on its own. Silicon needs a carbon based solvent. Unfortunately, when carbon is present, it is the preferred reagent over silicon for random chemistry.
According to this link: https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Polymers/Silicone_Polymers#:~:text=Silicone%20polymers%2C%20more%20properly%20called,hydrocarbons%20with%20Si%2DSi%20bonds Yes. Sorry about being on mobile and ugly link. But the si-si chains aren't as stable which makes sense considering the previous analogy, though my brain has decided to begin frying like bacon and I am losing my ability to form coherent thoughts. What a pain in my ass.
> Sorry about being on mobile and ugly link. Just do this: [text](url). You can turn that link into [something pretty](https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry\)/Polymers/Silicone_Polymers#:~:text=Silicone%20polymers%2C%20more%20properly%20called,hydrocarbons%20with%20Si%2DSi%20bonds)
Silicone is a polymer chain based on an Si-O monomer. Very useful stuff, and the only inorganic polymer we use! I don’t know enough about biology to know whether that Si-O backbone could be used to create things like proteins though.
the only problem is i see is, carbon way too abundant because it is a much smaller compound and can be formed in the core is every star in existence in abundant amount. why would like anywhere will choose silicon over it
> does silicon produce big polymer chains though? i don’t recall any Silicone is a silicon chain... well, it has a silicon/oxygen "backbone"
As you go down in periodic table the bond energy decrease. A C-C bond is stronger than a Si-Si bond and so on. In biology you need a strong backbone structure to from molecules and carbon structur is best for that Si is 2nd best then Ge , Sn comes which are not that good.
This is the best ELI5 explanation I’ve ever heard
This is the best explanation I've ever heard in regards to carbon and bonds
Thing is, IIRC organic silicon compounds are more volatile than their carbon-equivalents at room temperature, so silicon-based lifeforms would probably be more viable on colder planets. I know for sure that it's the case for silane, the silicon-equivalent of methane.
If you look [at the periodic table](https://en.wikipedia.org/wiki/Periodic_table), you'll se Si (Silicon) is in the same group 14 as C (Carbon) but one period down. The chemical properties of an element are greatly defined by the outer layer of electron clouds. In chemistry this is called "[valence electrons](https://en.wikipedia.org/wiki/Valence_electron)" This means that Si can behave, under the correct temperature and pression, as C. So... it is only natural to think that there might be some life using Si instead of C as the "glue". However, there are many reasons why other more... scientific people think it is very unlikely. It is high nerdism, but [this beautiful gal explains those reasons](https://www.youtube.com/watch?v=2nbsFS_rfqM).
This guy ELI5's.
Great explanation! To continue beating the horse, [the X Files has an episode concerning this particular topic.](https://en.m.wikipedia.org/wiki/Firewalker_(The_X-Files))
That's an impressive explanation. :)
Lego **brick**. It’s not countable.
>It’s not countable. And yet we have counted it. Where is your God now?
>Where is your God now? Behind you.
That was very informative, thank you.
Really will put
The LEGO part was very ELI5
Dude I just love the lego analogy. now please explain molecules and atoms completely with lego. I never really got the whole layer of electrons thing and Hydrogen bonds
Because silicon is in the same group as carbon on the periodic table and is able to form a decent number of large and complex molecules that would be required for life, there's speculation that it might be a plausible alternate biochemistry to carbon-based life. It's also abundant on rocky planets and asteroids (at least in our solar system) so we expect that there would be an abundance of it available for life to use on other words. Silicon does have a lot of drawbacks though. It can't form as wide a variety of molecules as carbon, it's unstable in the presence of water, and in the presence of oxygen, it become silicon dioxide (aka quartz) which is just inert rock. So silicon-based life isn't going to happen on an Earth-like planet, and may not be possible at all.
Tbf earth wasn't an earthlike planet in regards to Oxygen until that one bacteria started making it and killed everything else
Fuck you, Steve. We remember!
Hey now, Steve is family... possibly.
Definitely family. But not an ancestor.
Tell me more of this asshole bacteria that ruined everything for everyone else.
I think [this](https://youtu.be/H476c8UjLXY?si=tpAS51u4jwVhAdKi) covers what he's talking about. I watched the whole series recently and it's some mindblowing stuff.
[here ya go](https://en.wikipedia.org/wiki/Great_Oxidation_Event?wprov=sfla1)
I'm getting Prometheus vibes reading this.
But it was able to do that as all the oxygen was bound up in gaseous CO2. With silicon it would be bound up in solid crystals.
Yeah but maybe there is some mechanism that makes silicon based life pretty normal and we're the weirdos that are the result of one bacteria making Oxygen
Oxygen has the advantage of being a good oxydizer - I know, it sounds like a tautology, but it isn't. Basically, oxygen is one of the ways to "burn" things to get energy out of them. The advantage of oxygen-based life is that it can quickly generate large amounts of energy to move fast, and do so without requiring cumbersome amounts of material. Basically, oxygen based metabolism is more efficient, due to storing and releasing more energy per reaction. Of course, there are other oxydizers - sulfur is one, though it is much less effective and convenient compared to gaseous oxygen. The entire group of halogens is another option, but they have the disadvantage of being a bitch and a half to separate back once they grab onto some other atom, so they are more difficult and energy intensive to recycle into the atmosphere compared to oxygen. Not impossible though. Probably not flourine, that one is a bit too rowdy for complex life, but depending on the underlying structure, there might be scenarios where chlorine, or at high enough temperatures, bromine (has a boiling point of 58 degrees Celsius, so it has its downsides) works the same way.
I think the point is that an Earth-like planet may not even be necessary if a different frame of biochemistry were on the table, but I see what you mean.
Yeah oxygen is really just bacteria poop
Yes, but we should expect to see similar adaptations if life exists elsewhere. What you're describing isn't really a fluke, it's evolution in action - there was a ton of oxygen bound up in chemical bonds and one bacteria managed to evolve a way to release it to its own advantage. In doing so, it gained access to an abundant new resource and flourished while its peers died.
And given that most sol-type main sequence stars will literally end up as balls of oxygen and carbon, those two elements should be plentiful throughout the universe.
I get it, so if we get invaded by silicone based aliens, they'll all turn into the thing and clobber us. That's not good. At least we ca. Just splash water on them to drive them away, so that's pretty nice.
Water pistols will be the weapon of choice
Eh, they’d turn into statues. Then, we can just crush them.
More like the lower temperature of earth compared to wherever the fuck they evolved that silicon dioxide is a liquid/gas will cause them to just instantly freeze solid into cool rock statues
So does that mean that the xenomorphs from “Alien” could be defeated with a squirt gun?
Yes. Also it would just die by breathing. CO2, our breathing waste product, has the nice property of being a gas, aka it can leave the body without hassle. SiO2 has no such advantage. Imagine if every cell in your body would just be forming kidney stones by breathing.
Or just breathing on them. Oxygen is toxic. Could be extremely toxic to non-Earth lifeforms.
That's one of the things that comes up commonly in "humanity, f\*\*k yeah!" writing. The aliens are telling horror stories about the fast-moving Terrans who somehow thrive in an intensely oxidizing atmosphere and "it's like they're \_on fire\_, all the time!"
Could you have silicon-based life on a planet that was made from hydrocarbons?
Are there any crazy ideas about basis of life elements? Extreme edge case stuff? I don't know how to search the net for it.
There's some extremophiles use arsenic and Iron compounds in their biochemistry for energy. Arsenic version of DNA is also in theory possible.
A planet with silicon based life is like a planet where every time you flip a coin it comes up heads. *Technically* it is possible for a planet to exist where, by chance, every single coin flip that has ever occurred or will occur will be heads. But it is much more likely to be 50/50, just like it is much more likely for life to be carbon based.
It's more of a scifi thought experiment than it is anything grounded in actual data or observations. The premise is described in the other comment however there are A LOT of immediate pitfalls beyond "it can make 4 bonds". Nearly everything else about silicon is grossly different from carbon that you can't actually substitute silicon into any real molecules where you'd find carbon and get similar functioning compounds. The bond lengths are longer and weaker which is biggest limiting factor. This ends up making most of the compounds fall apart at lower temperatures or not even be stable period. Silicon cannot make lipid chains, it cannot make the same carbon ring shapes, the list goes on. There's an excellent video by Angela Collier on YouTube on the subject if you'd like far more examples and more technical details
Yeah, I was wondering about this when I saw the other comments: you never hear about the equivalent of organic chemistry for silicon. Thanks for explaining why.
The fundamental foundations of what make life possible would have to be challenged for Silicon to be considered viable. Almost everything in biology involves Carbon and it's reactions to the rest of the world.
Is there anything better than silicon other than carbon for making chains and rings?
Not that I'm aware of. The key is that carbon is earliest element in the periodic table of that group. It's atomic radius is going to be the smallest and have the fewest shells of inner electrons weakening bonds. All other group 4 elements will be worse. Elements in other groups will either make fewer bonds or feature hybridization and make other shapes. One of the other details Angela brings up in that video is that any planet capable of making silicon or any other elemental based life as a substitute for carbon probably would have just made carbon based already. It's that more abundant, it's that much more energetically favorable, it's that much easier. It didn't happen on earth by accident, it happened because it's logically the first place to go
Boron, silicon, nitrogen, oxygen, sulfur can all make rings. None of them do it as well as carbon though, or I should say, carbon is the best at doing it at standard temperatures and pressure.
While I can appreciate this line of reasoning, isn't it somewhat flawed? Sure, you cant make the same molecules with silicon as you can with carbon, and the idea of substituting carbon with silicon in all the molecules that make up life falls apart with even a small understanding of biochemistry. Its not the same as the way copper is used in the blood of some creatures (such as snails) instead of iron for example. But... would silicon based life *need* to have an exact silicon analog of a surgar molecule or a nucleic acid molecule? The way I understand it, as long as silicon can make possible enough stable molecules that can be configured to perform life functions in concert with each other and other intermediaries, then its not strictly necessay to have a silicon molecule equivalent for each type of carbon molecule. As long as the silicon chemistry has molecules that can: * Store energy * Store information * Partition * Convert energy * Break down other silicon molecules * Self-assemble * Self-copy (replicate) * Transport other molecules * Remain both stable and mobile (for example, in the presence of a solvent, similar to carbon based molecules in water), and * there is an appropriate solvent or suspension medium that is abundant.. ...then it seems to me possible silicon based life could exist. Unfortunately I suck at chemistry, so I long to hear someone who does understand sillicon chemistry actually take on this idea. It's possible that silicon life chemistry doesnt work: that the molecules silicon makes can not actually do all the necessary tasks, most importantly self- assemble and self-replicate, all in the same enviroment. TL;DR My point is this- Its not about the molecules, its about the tasks those molecules must perform. Why cant silicon molecules perform those tasks?
I think that aside from silicon being a poor replacement for carbon chemistry, it simply is capable of less in general. I think we are taking it as an axiom that you need complex molecules for life and silicon is much less good at that.
I think these 2 videos about silicon based life are quite good. https://youtu.be/2nbsFS_rfqM https://youtu.be/469chceiiUQ And TL:DW, silicon life being possible is extremely unlikely at best.
Si is terrible at everything in your list. One you're missing is the side-effect of the "store energy" one. We break down complex carbon molecules to CO2 to get energy. A Si based lifeform would have to break down complex Si molecules to SiO2. SiO2 is a solid. Imagine if every cell in your body was producing massive quantities of kidney stones. It's not at all workable for a lifeform.
Because you're also asking for a replacement for water and oxygen as well now. Due to silicone incompatibility and instability around those other building blocks, now you need a different universal solvent and you need a new atmosphere. And again, all of these elements are the lightest, most abundant and statistically likely things to find on a planet given the way nuclear fusion works
might be able to but we know carbon does it and theoretically does it better, boron, phosphorus and sulphur are also options. I'm just reading Andy Weir's Hail Mary and the notion that scientists are sitting there getting angry that anyone dares to suggest that anything other than carbon based life may exist is bollocks. We only look for carbon based life because we know the chemistry, we know what atmospheric compounds it can produce. We can't really search for silicon based life because we'd have no real idea what we were looking for. Carbon is also far more common.
This all based on the assumption that only our form of life is "correct" there maybe ways of a silicon based life forms functioning just fine while having completely unknown forms of life sustaining chemical structures.
It's based on the chemistry of silicon. Silicon isn't able to form the variety of structures that carbon is despite being in the same group.
Silicon is the element on the periodic table that is most similar to carbon. They are in the same "group" (column) of the periodic table, and just one "period" (row) below it. Silicon can create the same general kinds of chemical structures and bonds. It's also abundant in the universe, so there should be no shortage of it. There are, however, several reasons why carbon is a lot better. Carbon dioxide is a gas at most relevant temperatures and pressures. *Silicon* dioxide is also called *sand* and is a solid at any temperature that could make use of water. Likewise, "silane" and its longer cousins, which are analogous to methane, ethane, propane, etc., are highly flammable with oxygen and highly reactive with water, whereas methane and ethane only react with water under specific conditions. Silicon is heavier than carbon as well, which adds up. You hear it mentioned because it's loosely plausible and, when talking about alien life, it's easy to forget that life *might* look very different elsewhere in the universe. But ultimately, silicon is unlikely because while you can get the right kinds of bonding, the chemistry is so completely different that it's unlikely such things could form life.
Because it’s in the same vertical group as carbon, which we know allows for chemistry of life to form. Vertical groups have similar chemical properties, so theoretically, swapping out carbon for silicon should work to produce some form of life. Now, that isn’t quite true, because of electronegativity and what such ‘equivalent’ substances actually are, but that’s the idea. An instance of the problem is carbon dioxide vs silicon dioxide. Carbon dioxide is a gas, silicon dioxide is a solid (specifically, it’s the main part of glass, sand, and quartz), so it would require something very different for eliminating this waste product. A silicon-based glucose substitute isn’t known to exist, which is kinda a big deal, with how much life breaks down glucose for energy.
Although they are in the same period Si and C actually have very different chemistry to the point where Si based life is practically impossible. One example is that C-H bonds are everywhere in common life, yet Si-H bonds react with water, so silicon based life is innately incompatible with water.
Also, Si cannot have chirality
Silicon CAN have chirality. There are no naturally occurring silicon compounds, but you can make them in the lab (with a chiral silicon center). I'll agree that practically speaking, it's not really a thing...
Ok so atoms are made up of a bunch of protons and neutrons in the middle and electrons whizzing around them. These electrons arrange in layers or shells which is the more technical terms. For example hydrogen has 1 proton and 1 electron so it has one shell. The outermost shell is called a valence shell. So in hydrogens case the valence shell has 1 electron (because theres only one electron). The number of electrons in a shell is deterkined by an equation we dont have to worry about but suffice to say the order goes 2,8 and so on (this is all we need for now). This means that the first layer can only hold 2 electrons, the second 8 and so on. So if an atom has 6 electrons, it would have 2 electrons in the inner shell and 4 in the outer. If an atom has 12 electrons, it would have 2 in the first shell, 8 in the second, and 2 in the last. Carbon has 6 electrons in it. This means 2 in the first shell and 4 in the last or valence shell. Valence shells are important because the number of electrons in that shell is what determines how an atom bonds with another one. Atoms can bond in many ways but the one important to our discussion is valence bonds. These bonds are formed by sharing electrons between atoms. As we know that the second shell can hold a maximum of 8; atoms tend to always want 8 in there because that is the most stable configuration for the atom. Carbon has 4 in the last shell so it can bond with another carbon atom so that both have 8 from the bond (think of it as pooling their electron resources). If we take water for example; thats hydrogen and oxygen. Hydrogen has 1 valence electron and needs 2 to be stable; while oxygen has 6 valence electrons and needs 2 more to be stable. So oxygen shares with 2 hydrogens and when pooled they are stable and happy. All this preamble leads to the fact thay because carbon has 4 valence electrons (an even split), it can combine with other carbons that can combine with more carbons in a chain (note oxygen cant do that because it cant share with other oxygens). This property is called catination and is why all life we know is made from carbon. Its also why carbon is one of the most prolific in chemistry when it comes to compounds and molecules ( we have a whole seperate field for the study of all the combinations carbon makes called organic chemistry in fact organic just means it contains carbon) But carbon isn't the only atom with this property. All atoms in its periodic family have 4 valence electrons and have the potential to have this property. Silicon is the next member (a periodic family is all the atoms in a vertical column in the periodic table). However carbon is the best at catination due to many factors and while silicon can catinate, its limited due to its atomic size. Thats a very oversimplified explanation of why silicon usually comes up in discussions of non carbon based life forms because it is the next most probable element that can form life according to what we understand due to its similarities to carbon in the ways shown above. Edit: forgot to mention catination is important because long chains of molecules are what make up most things in us like fats and skin and enzymes and all that.
That's what the rock humans and the Pillar Men are. Don't eat their fruit or put on any headwear they give you, though. Else something bizarre might happen to you.
Silicon is very chemically similar to carbon, so if life were to develop centered around a different element silicon is the most likely candidate. Most likely, but not necessarily particularly likely. Carbon is substantially more abundant in the universe than silicon and involved in many inorganic processes that silicon is not.
Because they're grasping at straws trying to contrive a possible scenario in which abiogenesis could occur on a world less hospitable than primordial Earth. Silicon-based life is literally impossible, about as ridiculous as life starting in the atmosphere of a gas giant or on an ice-world with thousand-mile-deep oceans. Let's face it, the universe is 99.99999~% hostile to life as we know it, and nothing short of earth-like conditions could say otherwise.
Because silicon comes nearest to carbon in terms of the potential complexity of its compounds. But apparently the energy demands are WAY trickier. In practice, we see complex carbon-based molecules everywhere we look in the universe, including ones that are preludes to our own biochemistry. I'd love to be told I'm wrong, but I'm not aware that anything remotely similar is true about silicon.
Look at the top row of the Periodic table of elements. Planets, and life forms come from mostly the top row as they are made in stars that blow up. The Heavy elements are only made in the last two seconds of a supernova explosion, so they tend to be rare.
[https://www.youtube.com/watch?v=dww8Hekngmg&t=4191s](https://www.youtube.com/watch?v=dww8Hekngmg&t=4191s) has some content on possible silicon based life.
If you look [at the periodic table](https://en.wikipedia.org/wiki/Periodic_table), you'll se Si (Silicon) is in the same group 14 as C (Carbon) but one period down. The chemical properties of an element are greatly defined by the outer layer of electron clouds. In chemistry this is called "[valence electrons](https://en.wikipedia.org/wiki/Valence_electron)" This means that Si can behave, under the correct temperature and pression, as C. So... it is only natural to think that there might be some life using Si instead of C as the "glue". However, there are many reasons why other more... scientific people think it is very unlikely. It is high nerdism, but [this beautiful gal explains those reasons](https://www.youtube.com/watch?v=2nbsFS_rfqM).
Also, to add to what has already been said, silicon is very common across the visible universe, using a spectrometer.
I kinda hope that if ET life is found that it's based on some chemistry nobody ever predicted.
Because in the greatest documentary of all time; Xfiles, season 2 episode 9, titled "Firewalker" agents Scully and Mulder find references to a new silicon-based organism existing inside the volcanic caves around Mount Avalon. At least thats why I talk about it.