Ask Lemmy

sentience. I think it usually immediately leads to suicide

Pushing Ice by Alastair Reynolds is one of my favorite scifi books and it deals with this question in an interesting way. It proposes that Time is the great filter. Life exists in this galaxy, but intelligent life is so fleeting when considering galactic distances that the probability of one sentient lifeform finding another during their "peaks" is vanishingly small. Extinction, societal collapse, evolution to a higher form, whatever you want to imagine, it all gets in the way of the fantasy of meeting a thinking being from another planet.

I don't think there is a single universal Great filter, and living and then potentially sentient beings with various traits will face various obstacles.

First, life needs suitable materials for polymers and a lot of energy. Most places don't have both.

Next, basic blocks of life that would be self-replicating and adaptive should be randomly generated, which is extremely unlikely and literally took over a billion years on Earth, a planet with generally great conditions for such process.

Then, those blocks should be able to get together to form complex structures - ideally, many separate ones, so that one event wouldn't destroy the entire effort. Earth had it easy, with billions of super simple life forms.

Next, assuming life survived up to this point in a potentially unfriendly and ever-changing environment, bombarded by UV light and exposed to myriad of sources of damage, it should not destroy itself or environment too badly to never recover. Earth had periods when life generated too much carbon dioxide or too much oxygen (yes, that too was a thing), and those were critical points at which our story could very much end.

Then, life has to evolutionize and get into complex forms, either by forming multicellular organisms or by making a cell a powerhouse of everything.

Then, life has to get sentient, and some kind of response system should be available and get highly complex.

Then, most of the sentient creatures just won't be tribal, and civilization requires society and a common effort.

Then, many more won't be expansionist, and will die out in some small region.

Many also won't be competitive, which would slow down evolution.

For those species who are competitive, they shouldn't destroy each other while they're at it, and this is currently one of the risks of our own.

And after all that, they should develop space travel and either get as developed and decisive and resource-rich as to send a generational ship to some random planet named Earth populated by genocidal monkeys, or to somehow hyperdrive here. They can very much decide it's not worth it, and they may be so far away we couldn't see signs of their civilization.

I'm starting to wonder if its LLMs. An AGI is something we would be incredibly cautious around and is really no more likely to be psychopathic than any other living thing, the vast majority of which are not. LLMs on the other hand are pushed into every role techbros can shove them into while having less understanding of what they do than a housefly, the potential for damage is immense if someone decides to put one in charge of something important like infastructure or weaponry.

If there really is a cosmic web and information flows through it, the other solar system will know that we're coming to destroy another world, but it will have developed defensive techniques against a known disease, humans. The same our immune systems does to known viruses.

I went a bit creative with this one.

I don't think life is rare, nor photosynthesis, but complex life might be. A planet needs to be really thriving with life for it to be worth it to go down the path to something like animals

But I think the bigger filter is much stranger.

Humans are a hive-like species. We're not just social - we're insanely interdependent, we don't function on our own and yet we've ended up in this place where we (often) try to individually succeed, even at the cost to our community

We're greedy enough to want the stars, yet interdependent enough we could only swarm over them in endless numbers

There's many problems with the fermi "paradox", but personally I think one of the largest is assuming all species would spread like a cancer blotting out the stars

A more individualistic and long lived species might instead be careful explorers, taking what they need and leaving little sign of their passage. A more communal species might be careful and control themselves to not destroy pointlessly. They might also feel no desire to contact other species

We're just the right mix to want everything a star could give, and to want to find others at great energy cost