This question assumes that there is complex, intelligent life on some other world other than the kind found on Earth.

Carl Sagan allowed that silicon and germanium might replace carbon, and ammonia is thought to be the next thing that could be a conceivable replacement to water as a solvent.

From wiki - Astrobiologist John Baross chaired a committee of scientists under the United States National Research Council that published a report on life's limiting conditions in 2007. The report addresses the concern that a space agency might conduct a well-resourced search for life on other worlds "and then fail to recognize it if it is encountered".

I saw a science TV show that postulated that Silicon based life might present itself as a rock floating in space (hand wave the possibility). Say we had a method that we could use to recognize that floating space rock as a living being, how would we then interact share complex abstract concepts with it?

Could life based on these other biochemistries interact with humans or would we be poisonous to one another? Could we share sciences? Would we even recognize one another? Or are the things that make us "alive" so different that we couldn't even interact?

This question is probably too broad as written but I thought I'd roll the dice.

EDIT: maybe the question suggests that I'm getting hung up on the "intelligence" part of the scenario. But actually not so much. No matter where we go in the universe the laws of physics will always be the laws of physics, 2 + 2 will always = 4, green will still be green no matter what we name it. On that basis alone we would have some way to start a dialog with another species no matter how alien.

But what if that alien is ammonia based? Wouldn't its body literally be poisonous to us? What if there was an alien that was made of energy? What if there was an alien whose physicality was such that we couldn't even detect it with any of our five senses (a concept I'm toying with now)?

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    $\begingroup$ Provided that we can recognise intelligent life, I can see no reason why we could not interact. The only issue is whether we could recognise each other. It is difficult to imagine this working only one way. $\endgroup$
    – Lee Leon
    Feb 2, 2018 at 19:04
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    $\begingroup$ Recognizing life and recognizing and interacting with intelligence are two different things and biochemistry has little impact on the latter. An intelligence that we cannot recognize or interact with is probably possible but the biochemistry wouldn't be the cause. $\endgroup$ Feb 2, 2018 at 19:40
  • $\begingroup$ It is debatable to what extent we can recognise intelligent life on this planet. We do tend to skew the measurement of intelligence in our favour. $\endgroup$
    – Lee Leon
    Feb 2, 2018 at 19:49
  • $\begingroup$ I'm interacting with people on this site, despite there being no physical contact between us. For all you actually know to the contrary, I AM a silicon-based lifeform :-) $\endgroup$
    – jamesqf
    Feb 3, 2018 at 4:30
  • $\begingroup$ Hmmmm... I'm going to elaborate a little more in the main question... $\endgroup$
    – Len
    Feb 3, 2018 at 16:37

2 Answers 2


It is no less likely that we would be able to interact with an intelligent species with different biochemistry than one with the same biochemistry, and the reason for this is covergent evolution.

All life, by definition, requires energy. All life, by definition, reproduces itself, and imperfect reproduction in an environment with limited resources inevitably leads to natural selection. At this point, you're dealing with game theory, which transcends mere biochemistry and should come up with more or less the same solutions regardless of the underlying physiological mechanisms.

Of course, it's possible for life to develop an entirely unrelatable and unrecognizable form of intelligence, but that's just as likely to occur in carbon-based life as it is in silicon or arsenic based life.

A species with different biochemistry may of course be toxic to us, or live in an environment that we could not survive in (for instance, being much too hot or too cold) but as long as they had access to technology like radio we could still communicate with them at a safe distance.

One issue that may arise due to biochemical differences alone may be the speed of metabolic processes. It is possible that silicon-based life, for instance, would operate much, much slower than ourselves. If the entire planet's ecosystem worked like this due to the basic limitations of its fundamental chemistry, intelligent organisms could survive in their own world but be very difficult (or at least frustrating) for us to communicate with.


I think the answer is "of course." What that looks like is somewhat up to you. So an example that came to mind is the character Tali from one of the Mass Effect games - this is from memory and it's been a while... but the gist was that her species was kicked off their homeworld by AI that they'd created and lived in space for generations. As a whole species their immune systems eventually become compromised and they can't interact with any other race without wearing a protective suit. That's sort of interesting and addresses the issue of races that might be poisonous to one another, but doesn't have a huge impact in terms of how they might interact. To be perfectly fair humans generally wear a limited protective suit (clothes) as a rule when interacting with others and that doesn't seem to limit things much.

The idea of the invisible aliens is really fun, but probably still falls under the same sort of reasoning. You would be able to know that there was intelligence based on the fact that stuff that doesn't seem to be naturally occurring is happening - like seeing a spaceship, the land (or a star or a nebula) being worked into the equivalent of a city, or one of your buds taking a predator laser to the chest. For interaction and communication you'd need to work out some system where you are both manipulating something that you both can see, using special sensors or using some sort of indicator to say "I'm here" like the invisible man wearing visible glasses.


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