[nachomg]

You made me remember how I was ridiculed by my teacher by asking if there was a possibility that life could be based on other thing than carbon. Granted, as I grew older and learnt a little bit more about the chemistry of carbon I realized that it had almost magic properties for life, but I wondered for long time why he reacted that way.

[cmccart]

Ridiculing genuine curiosity is a terrible behavior from teachers... why stifle inquisitive minds? Anyway, you may already be familiar with these proposed biochemistries, but there has been a lot of speculation on this exact question over the years:

https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...

[booleandilemma]

I think it's simply that the teacher feels insecure.

[brabel]

You probably triggered some memory. Perhaps, a student who insisted they knew more than the teacher and pushed some ignorant argument too far... so when you suggested the idea, and perhaps tried to push a bit more consideration, the teacher found himself re-living that bad experience and treated you like you were the other student, even if you yourself didn't push the matter beyond an acceptable level.

It happens to the best of us.

[gus_massa]

Boron and Nitrogen may have a chance. They form long weird molecules that are stable. Is it possible? I don't know. Can they compeat with Carbon base life? Perhaps no. In a weird planet where almost all the Carbon is sequestred by some weird chemical composition of thee rocks, can Boron or Nitrogen life have a chance. I don't know!

(My guess is that we still need a few thousand years to answer these questions. We still don't understand too may details about Carbon based life. I'm not very optimistic.)

[pfdietz]

Boron is scarce; it's one of the x-process elements, and those inherently have low abundance (although the boron-to-carbon ratio in the Earth's crust is enhanced over the solar system ratio, I believe.)

Boron nitride is weirdly analogous (indeed, isoelectronic) to carbon in that there's a graphite-like form (hexagonal BN) and a diamond-like form (cubic BN).

One thing that would hold back BN life is that by themselves B and N form more stable compounds than carbon does. Nitrogen in particular forms molecular nitrogen, which is annoyingly tightly bound.

[gus_massa]

Too many nitrogen together make you go to the list of https://www.science.org/topic/blog-category/things-i-wont-wo... I'd try to be far away from a planet with living things made of nitrogen chains.

[__MatrixMan__]

I wonder to what extent they'd need to compete at all, they'd probably have a different diet. Maybe there are carbon life forms out there living mutualistically with boron-nitrogen life forms.

[gus_massa]

I don't expect a mix of Boron and Nitrogen. Only Boron in some planets and only Nitrogen in another planets.

We [1] can eat things with Nitrogen, so I expect a competing form to be completely eaten if they are less effecient.

I don't know enough about Boron chemistry, but if there were enough of them we will eat them too, unles they eat us first.

The first stages of living things are probably very ineficient. If you need a year to make a viable copy, a previus life form will probably eat you before that. I think that two independent origins of life in tha same planet are impossible.

[1] If you include bacteria and archea in "we". And even we (humans) can eat some compound with nitrogen, in particular proteins that mix carbon and nitrogen.

[0x00_NULL]

Silicon has almost the exact same properties as carbon. At high temperatures, carbon chains can’t form, but silicon chains can. In a high-temperature or high-pressure range, silicon might for a basis for life, analogous to carbon for us. So, not only was that question not stupid, it was profound.

Look at silicon on the periodic table. All of the things that make carbon great, basically silicon has almost exactly, except it needs a high temperature for most of those properties to be expressible.

That teacher didn’t know what he was talking about. Ridiculing a student for questions is such detestable behavior. The silliest questions can end up being the most insightful. I really despise teachers like that.

Here is a paper all about how your question was actually wonderful.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345352/

[zdragnar]

Silicon has only superficial similarities to carbon. Even at high temperatures, water and oxygen prevent silicon from substituting for carbon in any of what we are familiar with as organic molecules.

Your linked paper points out that the only viable solvent that supports a large variety of silicon chemistry is sulphuric acid, and even then it would need to be very poor in oxygen since silicon-oxygen bonds are so strong it ends up being much more strongly preferred over si-si bonds.

It makes for an interesting conversation, but I can't imagine spending an entire class going over what amounts to a massive distraction from the lesson plan.

All that's left is going to amount to an effectively dismissive answer, I suppose (though I agree that teachers who are intentionally dismissive are doing it wrong).

[0x00_NULL]

Wouldn’t an environment that has a significant sulfuric acid content naturally also a relatively limited free oxygen?

I’m thinking of Venus. That sort of environment would satisfy all criteria and would also start to get into the temperature ranges that would make Si-Si bonds possible.

That would at-least bracket the types of planets and their history to a useful extent.

[zdragnar]

Sulphuric acid actually has a lot of oxygen and hydrogen in it, and the presence of any metal or even high enough temperature will cause it to break up.

In a lab, it makes for a good solvent, but any place that has sulphuric acid will have both water and oxygen.

Venus, notably, has little to none of both. What free oxygen that does exist is from CO2 and CO breaking down in the atmosphere from the intense and extended venusian day. Most of the sulphur on Venus is sulphur dioxide (a tiny percentage of the atmosphere), and water vapor is a measly 20ppm.

Even if all of that water was sulphuric acid (which it may well be), there's simply not enough of it staying still long enough to form the repeating patterns of chemistry that might reasonably be called life.