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In the South Galaxy, the overwhelming majority of life lives on planets, breathes air, and is carbon-based. All sentient life is carbon-based. However, in the vast reaches of space, there are some animals that float through the empty void, do not breathe (at least not air) and are silicon-based. These include Space Whales, huge whale-like (duh) creatures that inhabit nebulas. Would these Space Whales be edible to the carbon-based lifeforms or would it just be like eating sand?

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  • $\begingroup$ Plants & lichens can derive sustenance (minerals they need at least) from rock & they're carbon based, would a symbiotic relationship (some form of lichen like gut flora perhaps) or farming situation (where lichen is grown on your space whale then harvested) suit your requirements? $\endgroup$ – Pelinore Jan 5 at 17:16
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    $\begingroup$ By "eat" I assume you mean "consume for the purpose of absorbing nutrients or water to keep oneself alive" and not simply "can you eat styrofoam?" to which the answer is "yes, but it'll just constipate you before contiuing its eternal journey." $\endgroup$ – JBH Jan 5 at 20:58
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    $\begingroup$ Since Si cannot replace C in toto or even at all for life you might consider to detail to which extent the alien life is silicon based. They might have carbon proteins for instance.... $\endgroup$ – Alchimista Jan 5 at 23:25
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    $\begingroup$ My guess (which is why I'm not putting this in an answer) is that you'd need an entire complex ecosystem of carbon based life forms to do this, in the same way we have simple ecosystems that turn forms of carbohydrates that are inedible to humans (grasses) into edible meat (deer, antelope, cattle, etc.). You'd probably need to begin at the microbial level, with bacterial analogs that specialize in one or two of the silanes bobtato mentions in his response below. Then these could be in the gut of a carbon-based ruminate analog that's edible to humans? $\endgroup$ – Jaycie Beveri Jan 5 at 23:29
  • $\begingroup$ @JBH agree. Perhaps the OP could clarify whether it is about eating, or digesting. $\endgroup$ – NofP Jan 6 at 2:27
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Maybe some part might be edible.

buffalo tongues

https://allaboutbison.com/bison-in-history/1800s/1861-1868/

During the mass slaughter of the western herds of buffalo (American bison), many thousands of animals were killed just for the tongue. The rest of the animal was left where it fell to rot.

You could have something like this with your space whales. It sounds like it would help your story if they could get eaten by carbon based creatures. Maybe the vast bulk of the space whale is essentially silicious mineral matter but one tiny organ is carbon based - maybe the eye, or a gland in the brain. That part is super tasty and a prestige food for jaded rich people who are tickled by the idea of an enormous ancient being dying so they could eat its eye.

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    $\begingroup$ I can't help myself and must point out that the very next item is "green paint," which might actually be more akin to space whales than buffalo toungues. I'm just sayin'. 😀 $\endgroup$ – JBH Jan 5 at 21:00
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    $\begingroup$ @JBH - it is kind of weird that only green paint would be up for auction. $\endgroup$ – Willk Jan 6 at 2:59
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    $\begingroup$ @Willk Now we just walk into a paint store or big box store and pick a color from thousands of choices and they mix it up on the spot. Not that long ago, each significant (not necessarily "primary") color came from a very different animal, vegetable or mineral source and it could easily be that some would be more or less rare/valuable than others. $\endgroup$ – manassehkatz Jan 6 at 14:58
  • $\begingroup$ Note also the subsequent 'verdigris' item. This is the pigment that makes the paint green. $\endgroup$ – mcalex Jan 7 at 3:37
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We are not able to digest silicon based materials. See for example rice hulls:

Rice hulls are the coatings of seeds, or grains, of rice. The husk protects the seed during the growing season, since it is formed from hard materials, including opaline silica and lignin. The hull is mostly indigestible to humans.

Since your life forms are also silicon based, I doubt a human would able to metabolize any part of their bodies, we simply lack the chemicals to break down the molecules making up their bodies.

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  • $\begingroup$ If I understand the concept of silicon based lifeforms correctly (which I may not of course) the silicon (among other things) replaces the carbon we as carbon based lifeforms use for the forming of complex bonds in DNA, also silicon doesn't easily form bonds with oxygen so it's unlikely to be used for some form of respiration even if used elsewhere in the organism in places we use carbon : so if the "silicon life" is just using the silicon for DNA there might not be any reason to suppose it's "cells" & proteins might not have some digestible components for carbon life forms? $\endgroup$ – Pelinore Jan 5 at 16:56
  • $\begingroup$ @Pelinore, carbohydrates are also based on Carbon, like also proteins and lipids. A Silicon based life form would replace Carbon with Silicon everywhere $\endgroup$ – L.Dutch Jan 5 at 16:59
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    $\begingroup$ Can we easily extrapolate the inability of humans to digest silicon based materials to all carbon based lifeforms? That is, is the inability to digest rice hulls just something humans can't do, or it that something intrinsic to carbon based lifeforms? $\endgroup$ – Abigail Jan 5 at 17:04
  • $\begingroup$ "A Silicon based life form would replace Carbon with Silicon everywhere" I guess that does make sense, the primary assumption of silicon based life is that it evolves in a carbon poor silicon rich environment after all. $\endgroup$ – Pelinore Jan 5 at 17:09
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    $\begingroup$ @Pelinore "… silicon doesn't easily form bonds with oxygen …" – Oxygen compounds (e.g. silicates, silicon dioxide) actually are the most abundant form of silicon. $\endgroup$ – Loong Jan 6 at 9:55
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The majority of the nutrients we need (proteins, carbohydrates, fats) are carbon-based, and silicon-based life is presumed to have incompatible analogs instead (with silanes replacing alkane groups).

Silicon-based organic analogs are often biologically inert (on Earth), which is why they're used for things like medical implants and cookware. Eating space whale meat wouldn't nourish you, but it probably wouldn't harm you either, at least in moderate amounts. Like clay eating (pica), it could become a problem just in mechanical terms if you eat too much of the stuff.

Space whale might contain one or two things you do need – most obviously water, but also salt and trace elements like iron and magnesium, which might be in forms that your digestive system could extract.

So, no, you couldn't live off it; but in starvation conditions it might be slightly better than sucking a button.

(Of course, if silicon is replacing carbon, the chemistry might be different in other ways. If, by the same logic, oxygen were replaced by sulfur, then you would have hydrogen sulfide instead of water, and then the space whale meat would be highly toxic and bad-smelling)

Edited to add:

I suppose another reason to eat space whale would be if it tasted good. But I suspect that silicon-based meat would not taste of much of anything. Our sense of smell (and taste) is known to be largely based on the shape of molecules, and because silicon atoms are larger than carbon atoms, the silicon-based analogs of tasty molecules would not fit taste / smell receptors designed for the carbon-based versions. Also, silicon-based "organic" molecules tend to be much more water-repellent. I imagine it would be like eating flavorless, oily clay or rubber.

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Humans eat for two different reasons:

  1. Energy. We need energy to survive. To get it, we eat plants, or animals which ate plants, and then, through the Calvin and Krebs Cycles, convert Adenosine Diphosphate (ADP) to Adenosine Triphosphate (ATP). The extra phosphate in ATP stores energy. We then burn that ATP back into ADP to harness it. The number of basic types of foods that can give us energy are very limited, and all of them are carbon based, as carbon is needed in the Calvin and Krebs Cycles. Silicon-based lifeforms would most likely have no caloric value for human digestion.

  2. Nutrition. Humans need 20 different types of amino acids to survive. We can make 12 of them, leaving 8 which we must "harvest" from other organisms. These eight are called the "essential amino acids." Many other animals are capable of making them, so by eating them, we satisfy our needs. The only plant conclusively found to have all eight is quinoa, and flax seed is a maybe. Silicon-based lifeforms would not have these amino acids, as all of them contain carbon. This is what makes us carbon-based.

There is no reason, therefore, for humans to want to eat these. It would likely give them indigestion. However, there are other reasons people might be hunting space-whales. In the 1800s, whales were killed for their oil, which was used in lamps. Perhaps these space-whales contain a critical energy source. There are plenty of reasons why they might be hunted, and I would consider using one of those in your world.

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On earth some bacteria living extreme environment are able to use non-organic material like rocks to live like pyrite (FeS2). https://en.wikipedia.org/wiki/Lithoautotroph As mentionned previously Sulfur would be replacing oxygen for silicium-based organism so why not a kind of complex organism based on extremophile example could use it in a non traditionnal way to extract energy.

As you'll see there is a lot of extremophile bacteria kind and we'll discover more and more. https://en.wikipedia.org/wiki/Extremophile So if you can exhibit a way to extract energy from your silicium-based organism using organic chemistry you can imagine an organism able to support it.

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