Silicon Life Discussion

[bartekkru99]

We all know that te base of all life on Earth is... pretty much carbon along with his friends hydrogen, oxygen and sometimes even nitrogen and sulphur and some other elemnts that aren't that important as those five guys. But... is it the only way for life? Most of us most likely heard about a theory, that somewhere in the univerese there could be life, but not like our carbon based life, life that is a bit different... Where the element of life is silicon. What do you think about it?

I personally think, that it could be trueI. f we look at the table of elements we can see, that silicon is right below carbon, it has four valence electrons, which means, that it can create four bonds. The simplest of organic compounds are hydrocarbons and the simplest of them is methane, but silicon can form very, very simlar compounds, ok almost identical and they are called hydrosilicons... Tere are three groups of hydrosilicons:

- Silanes... sounds kinda familiar... doesn't it? http://en.wikipedia.org/wiki/Silanes

- Silenes... I think, that I've heard something simlar before, hmmmm... http://en.wikipedia.org/wiki/Silenes

- And Silynes? I don't know how to spell it.

What do you think? Would it be cool to see creatures breathing out sand particles, or long protein-like structures with silicon atoms instead of carbon?

[CaptainKipard]

Practically speaking, carbon is so much more abundant in the universe that carbon life forms are simply inevitable. It's just a matter of resources. Life finds the most efficient way it can.

[bartekkru99]

Practically speaking, carbon is so much more abundant in the universe that carbon life forms are simply inevitable. It's just a matter of resources. Life finds the most efficient way it can.

I agree, but still, silicon is also pretty abundant, at least on Earth.

Oh and leaving alone chemistry stuff, but would it be possible to form kind of "organic transistors" inside the cell of extra-terrestial? Boosting nervous system, or carrying genetical data?

[Kryten]

Practically speaking, carbon is so much more abundant in the universe that carbon life forms are simply inevitable. It's just a matter of resources. Life finds the most efficient way it can.

Universal abundance values aren't terribly relevant at planetary scale; the planet you're currently sitting on has well over a thousand times as much silicon as carbon.

[sal_vager]

No idea if silicon life is possible, but I'd assume it'd need a fluid just as much as carbon based life does, and h20 may not be the most suitable.

[KerikBalm]

http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Silicon_biochemistry

"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.[6] Moreover, where it does interact with other atoms, silicon creates molecules that have been described as "monotonous compared with the combinatorial universe of organic macromolecules".[6] This is because silicon atoms are much bigger, having a larger mass and atomic radius, and so have difficulty forming double bonds (the double bonded carbon is part of the carbonyl group, a fundamental motif of bio-organic chemistry).

...

"Finally, of the varieties of molecules identified in the interstellar medium as of 1998, 84 are based on carbon while only 8 are based on silicon.[8] Moreover, of those 8 compounds, four also include carbon within them. The cosmic abundance of carbon to silicon is roughly 10 to 1. This may suggest a greater variety of complex carbon compounds throughout the cosmos, providing less of a foundation upon which to build silicon-based biologies, at least under the conditions prevalent on the surface of planets.

...

Also, even though Earth and other terrestrial planets are exceptionally silicon-rich and carbon-poor (the relative abundance of silicon to carbon in the Earth's crust is roughly 925:1), terrestrial life is carbon-based. The fact that carbon is used instead of silicon, may be evidence that silicon is poorly suited for biochemistry on Earth-like planets."

[bartekkru99]

BTW, I've just started with biochemistry at school, so some things will not be so obvious for me for now.

[CaptainKipard]

Damnit... Well at least I learned something new.

By the way there was a similar discussion here not too long ago.

[-Velocity-]

I am highly doubtful silicon life exists anywhere, at least, not naturally-evolved chemical life. Perhaps mechanical life-forms could exist that use silicon "brains", but I doubt that too, mostly because I think we'll eventually find that silicon microfabrication is not the best material and method for building logic circuits. You also need a massive set of infrastructure to produce one silicon IC. Our brains are several thousands of times faster than a desktop computer (in terms of equivalent processing power) and something like a million times more efficient. Quite amazing, really.

Chemically though, silicon is vastly inferior to carbon for chemical life forms, and it's hard to imagine that silicon life could exist anywhere. As it's been pointed out, anywhere you have silicon, you also have carbon....

[Idobox]

Another important thing is that CO2 is a gas, but SiO2 is a solid, known as quartz, sand or glass depending on the structure. It is much, much easier for biology to happen with fluids than solids, and that will generally favour carbon over silicon.

A less extreme option would be life that is mostly carbon based, but also extensively uses silicon chemistry.

[mmottet]

The fact that silicon has four valence electron doesn't mean it has a similar chemistry.

The main problem would arise when you start considering higher order bonding. Carbon readily makes double and triple bonds, allowing for a very rich chemistry. Silicon... not so much. Sure, you can find molecules such as Si2H4 and Si2H2. But the bonding scheme is very different.

If we take C2H4 and tear the double bond apart. We end up with two fragments CH2, sp2 hybridized, with one electron in the free sp2 and one electron in the pz. This is the electronic ground state of the fragment. Let's go to silicon and do the same. For simplicity, we'll assume the fragment is also in a sp2 hybridization. What you will obtain is 2 electrons paired in the free sp orbital. So what do we need to make a carbon style double bond? First we need to unpair the two electrons and place them in both orbitals and bring two fragments together. Problem is, the cost of unpairing the electrons in two fragments is higher than the energy released by forming the bond. What really happens is that the two filled orbitals will overlap with the two empty orbitals and form what is known as dipolar or dative covalent bonds.

So yes, silicon is just below carbon in the periodic table, but a chemistry based on silicon would definitely lack some of the versatility that carbon based chemistry can bring.