The Fermi Paradox ("Where are all the aliens?")

[Poppy]

I voted for ...
They have colonized the galaxy, but we can't see them.

[Kyng]

Well, a simulation suggests that it wouldn't take too long to settle a galaxy, even with slow ships (i.e. no warp drives or other FTL travel). Just by sending multiple ships from each newly-colonised star, and exploiting the power of exponential growth, it's possible to colonise the entire inner part of a galaxy within a billion years:

https://gizmodo.com/aliens-wouldnt-need-...1847101242

Still, it doesn't look as though anybody's actually done it .

[SpookyZalost]

Kyng honestly if humanity began constructing a dyson swarm, we'd have the energy to accelerate photon sail based ships to nearby stars at near light speed and expand rapidly.

if we sent robots who's only purpose was to go to another star, find resources, and build dyson swarms then repeat, they could lay the ground work for a type 1.5 to type 2 civilization in short order, one that could expand quickly.

the bigger issue is, what is preventing anybody from doing this.

Kurtzgesagt actually did a very informative video on the great filter.

[Photon]

Well, I'd say that life itself is a great filter because we don't see comets crashing into planets to create water and start life in a planet everyday. Other than that, there are others, like intelligence, temperature (most important probably).

Michio Kaku, author of the book "The future of humanity" went on to say that being born on land itself might be a great filter as life beneath ocean (Eg. Europa) might think the the ocean as their universe. They might not imagine such a world outside their ocean, which is actually...pretty realistic .

[Kyng]

Well, I'd say that life itself is a great filter because we don't see comets crashing into planets to create water and start life in a planet everyday. Other than that, there are others, like intelligence, temperature (most important probably).

Michio Kaku, author of the book "The future of humanity" went on to say that being born on land itself might be a great filter as life beneath ocean (Eg. Europa) might think the the ocean as their universe. They might not imagine such a world outside their ocean, which is actually...pretty realistic .

Quite possibly . Comets crashing into planets isn't exactly rare; however, you're certainly not going to get life every time it happens . (On its own, it doesn't get you life: it just gets you one of the pre-conditions for life, and then several other things have to happen before life comes into existence)

Of course, we probably need to search more planets before we can get a good idea of just how rare life is!

[SpookyZalost]

That's the real catch, there's known unknowns that are preventing us from knowing the unknown unknowns...

in other words, we only have a sample size of one planet, earth.

though with the potential discoveries on Venus, Titan, and maybe mars...
and of course underneath at least one of the dozen frozen moons/planetoids with liquid water oceans beneath their frozen surfaces.

however as it's plausible that sol had 3 planets with liquid water on their surfaces at some point (Venus, Earth, Mars), it's not that unlikely provided the energy existed for it to form.

[Kyng]

Isaac Arthur may be known for his series about the Fermi Paradox; however, he's certainly not the only science YouTuber to have covered the series.

Here, John Michael Godier presents a video outlining the "Interdict scenario":



Essentially, this solution posits that there are many alien civilisations, and they have expanded across the galaxy and fought wars against one another in the past; however, diplomacy eventually took over, and we now live in a golden age of galactic peace. These advanced aliens view knowledge as extremely valuable; and they see developing civilisations (like us) as a non-renewable source of knowledge; so they do everything they can to protect us. That means hiding themselves from us until we're ready to interact with them - so, essentially, this is a form of the Zoo Hypothesis .

Indeed, it's possible that they deliberately stay away from any planets that we humans would consider 'habitable', in case primitive life forms there. By now, the aliens themselves aren't even living on planets any more: they're advanced enough to have built O'Neill cylinders for the overwhelming bulk of their population. Perhaps they're building these around larger stars - which: a) output more energy for them, and b) are ignored in our searches for life (since they're too short-lived for advanced life to evolve in their planetary systems).

Of course, there are problems with this solution. I already listed some of these in the "Zoo Hypothesis" and "Prime Directive" posts: mainly, it'd be very difficult for any alien empires to stay hidden, because it only takes one rogue alien to expose the entire empire. A further problem with this scenario is that it's untestable: if aliens are indeed using all their advanced technology to make themselves undetectable to us, then how can we tell the difference between aliens that are hiding, and aliens that don't exist?

Finally... there are some unsettling thoughts that come from this. If aliens value knowledge, and are curious about our culture, then have they recorded our entire planet's history? Do they have their own 'Earth zoos', populated with dinosaurs, woolly mammoths, dodos, and even humans??? Are we part of some alien empire that we don't even know exists? And, if so, will our overlords end up going to war with some other alien empire - putting us right in the crossfire of a clash between two civilizations vastly more powerful than our own???

I think I prefer the "Aliens don't exist" solutions, to be honest

[SpookyZalost]

Kyng so you know how I feel about aliens existing and the probability of it...

but let's talk hypotheticals.

let's say the above posited scenario were true here's where I see a few problems.

first, how do we know they haven't already wiped themselves out, it really depends on where they are relative to us.

second, if they did disappear some day, would we actually notice?

probably not...

one of my favorite scenarios in Stellaris is the idea that an ancient or fallen empire is watching over a primitive civilization and acts as their benefactors, keeping a region safe from threats until said empire is ready to join them.
That's an awesome story but unfortunately there's just no evidence to support such a theory, mostly because there's too many things that can be explained by natural causes going on to have the interdict and human zoo scenarios make sense unless said civilizations are type III or greater making their existence indistinguishable from nature.

so if they did exist... they likely do not any longer or are no longer manipulating or monitoring this planet.

[Kyng]

Kyng so you know how I feel about aliens existing and the probability of it...

but let's talk hypotheticals.

let's say the above posited scenario were true here's where I see a few problems.

first, how do we know they haven't already wiped themselves out, it really depends on where they are relative to us.

second, if they did disappear some day, would we actually notice?

probably not...

one of my favorite scenarios in Stellaris is the idea that an ancient or fallen empire is watching over a primitive civilization and acts as their benefactors, keeping a region safe from threats until said empire is ready to join them.
That's an awesome story but unfortunately there's just no evidence to support such a theory, mostly because there's too many things that can be explained by natural causes going on to have the interdict and human zoo scenarios make sense unless said civilizations are type III or greater making their existence indistinguishable from nature.

so if they did exist... they likely do not any longer or are no longer manipulating or monitoring this planet.

Exactly. While the idea is interesting, it can't be regarded as 'scientific', simply because it's untestable and unfalsifiable.

If there really is an advanced civilisation out there, and it really is hiding itself from us... then, what evidence would we expect to see? If they're sufficiently good at hiding, then the answer is probably none at all.

Although, if they had died out already, then I do wonder whether they'd be able to stay hidden . I suspect that at least some of the things they'd do to hide themselves from us would consume massive amounts of energy (for example, Godier suggested they'd cloak their inhabited planets with lasers) - and, when the energy runs out, we should be able to see some of their ruins.

[SpookyZalost]

Kyng well the closest I can think of is zeta reticuli B.

See the star has an anomalously low level of beryllium, a material that's possibly useful for building Dyson swarms, that combined with the unusual age difference between the binary pair, and the debris cloud and you could see how it might look like a late stage type 1 civilization.

That and the Betty and Barney hill case has it listed on the supposed map that they were shown during what was described as a peaceful first contact event.

Real or not it's intriguing.