0
$\begingroup$

Would silicon-based aliens' biochemistry cause them to look any different than the carbon-based humans that we have in the real world? If so, what could they possibly look like?

For further clarification, these aliens are their world's equivalent to humans at least in that they are sapient, have the same intelligence level as us, and stand upright, although I have not yet set in stone what number of legs they have, nor what kinds of limbs they have for legs (e.g. human-like, arachnid-like, tentacles, etc.)

Improve this question
$\endgroup$
14
  • 3
    $\begingroup$ What do carbon-based lifeforms look like? Worms, jellyfish, humans, dinosaurs... which atom forms the primary structural component of macromolecules is just about the least significant contributor to the range of forms that creatures can take. $\endgroup$
    – Logan R. Kearsley
    Commented Dec 5, 2021 at 19:05
  • 1
    $\begingroup$ What specific biochemistry? And how is this question different from the other dozens of questions about silicon-based lifeforms? (And anyway, what common look do the carbon-based lifeforms on Earth have? What is the common look of a Sequoia tree, a slime mold, a colony of ascidians, a bee and a tiger?) $\endgroup$
    – AlexP
    Commented Dec 5, 2021 at 19:07
  • 1
    $\begingroup$ The most important thing to is to make clear with what you are comparing them. That is, what is the meaning of the words "different than the carbon-based lifeforms". As far as I know, the carbon-based lifeforms we have here on Earth do not have any kind of common look. How is an oak tree similar to a jellyfish? Second, you need to specify the fundamental building blocks of the biochemistry. How do they obtain energy? What are their bodies made of? How do they store energy? $\endgroup$
    – AlexP
    Commented Dec 5, 2021 at 19:26
  • 2
    $\begingroup$ @Jarren_Takar Diatoms (or at least their shells) actually are made of glass (amorphous silica), as are the cell walls of many plants, but those are carbon-based organisms. Meanwhile, you are not a graphite-monster or diamond-monster, despite also being built out of carbon. So why should silicon-based creatures look like rock or glass? $\endgroup$
    – Logan R. Kearsley
    Commented Dec 5, 2021 at 19:36
  • 1
    $\begingroup$ @LoganR.Kearsley: Could please give an example of plant with cell walls made of silica? It would be much appreciated. (All I know is that some grasses for example have a small amount of silica or organosilicon in their cell walls, but I know not of any plant where the cell walls are made mostly of a silicon-based material.) $\endgroup$
    – AlexP
    Commented Dec 5, 2021 at 19:49

2 Answers 2

Reset to default
4
$\begingroup$

Complex silicon polymers generally fall into two classes: those that are inert in water, or those that are unstable in water.

The same applies to simpler silicon compounds: silica is almost entirely inert in water (it does dissolve as silicic acid, Si(OH)4, which makes it bioavailable... but only in very low concentrations, and no naturally-evolved terrestrial organism actually breaks the Si-O bonds to use it for anything more interesting than redepositing silica structurally); and silane, SiH4, rapidly hydrolyses.

So, simply by knowing that your aliens are silicon-based, we can immediately conclude that they do not use water, and they do not live in a similar temperature/pressure regime as we do on Earth. You won't be shaking hands with them without one or both of you being in a pretty hefty spacesuit!

Your aliens might well be extremely cryogenic, existing in liquid nitrogen and/or eutectic mixtures of organic solvents. Or slightly less cryogenic, relying on high-pressure anhydrous ammonia. Or somewhere between "uncomfortably warm" and "lethally hot", with bodily fluids based on fuming sulfuric acid.

Unfortunately, there's not much farther we can go from there. All of these fluids are transparent, so there's no barrier to fluid-filled eyes like we have--but also no barrier to pit-eyes or compound eyes. None of them are associated with atmospheres so dense or gravitational environments so different from ours as to significantly alter the mechanics of walking. None of them necessitate that large creatures be cold-blooded or warm-blooded. None of them would constrain the colors available through structural or chemical pigmentation. And similarly, this level of detail provides no chemical constraints on what the ecology in which your aliens evolved might look like, so you can't make inferences from that, either.

So, basically... they can look like whatever you want, as long as you can justify that appearance according to other constraints, common to all sorts of life.

Improve this answer
$\endgroup$
1
  • $\begingroup$ Thanks for the info, man! :) $\endgroup$
    – Jarren_Takar
    Commented Dec 6, 2021 at 1:15
1
$\begingroup$

They will either have one-or-more holes to take in food and excrete waste OR a way to absorb energy from light and absorb nutrients. They will have to obey a cube-square law for body size so they don’t overheat. Beyond that, assuming silicon is viable for life, silicon life will be as widely varying as carbon-based species.

Improve this answer
$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .