Thanks for the enlightening discussion!

> The more plausible you make the technology the more you have to explain why we aren't doing these things. We might go back to the moon soon but beyond that we don't have any plausible plans to do anything noteworthy in space, let alone activities that would be detectable from other star systems.

We are doing these things! It's just taking longer than people had expected in the 1960s. But in the timescales we are talking about for the Fermi paradox, an extra 100 years don't make a difference.

Arguably, going to the moon was a big waste of money for some bragging rights. More recently, rocket launch costs have decreased dramatically, and lots of space projects are only now becoming economically feasible. At the moment that's mostly a greatly increased rate of satellite launches, but we can already see asteroid mining on the horizon.

Collecting energy in space and beaming it to earth might also soon become economically feasible. Or perhaps the opposite: putting up a big sunshade at a Lagrange point to counteract global warming.

> I don't know how this relates to the Fermi paradox. Is the argument that "as long as some people are interested there will be a Dyson swarm"?. I don't think that follows.

Yes, you understood that right. As humanity becomes richer and more capable and space flight become easier, we'd need to commit proportionally less and less of our total resources to make a difference.

Compare eg how building something like GPT-4 would have been impossible in the 1990s; would have been Apollo program level expensive in the 2000s; is a major corporate investment at the moment; and will probably be something within the reach of hobbyists in the 2030s.

> I can absolutely understand that. What I don't agree with is that we are on an inevitable path to a Dyson swarm (or similar scale engineering).

I guess that's the crux of our disagreement. I predict the only way to avoid a Dyson swarm would be for humanity to blow itself up completely. (And even an AI singularity that sacrifices everything to the great paperclip maximiser would not avoid a Dyson swarm; just the opposite.)

> They might just be on their planet(s) with eternally stagnant technology.

Some aliens might do that. But to resolve the Fermi paradox, almost all alien civilisations would need to do that. If even one in a thousand have technological paths that are only even a 1% as fast as ours on earth, you'll get Dyson swarms.

It's theoretically possible that aliens might be able to do something that looks like violations of thermodynamics. Just like there's some possibility they might be able to go faster than light. But I'm excluding those possibilities here. (Or for the Fermi paradox to be still acute, it's enough if there's even a small fraction of Aliens who are bound by the same thermodynamics and lightspeed limits as we are.)

> It was a hypothetical. But let's say we don't see dyson swarms, which I am not even sure of, then proper conclusion is that nobody builds dyson swarms and nothing else.

Yes, as far as we can tell, nobody has build dyson swarms. But looking at our own technology, it looks like building dyson swarms should be fairly inevitable, once you have a tool using civilisation. So the conclusion is that it looks like there just aren't any civilisations even remotely comparable to earth.

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To operationalise into something concrete that we could theoretically bet on:

I think a dyson swarm is at least a hundred years out, so that's too far out to bet. But as a precursor, I predict that launch costs per kg to an orbit of your choice will keep coming down; and that the number of launches will keep going up.

See the graph on https://en.wikipedia.org/wiki/Timeline_of_spaceflight#Orbita...

At the moment, we might be in a phase of exponential growth. I'm not sure that will keep on. But I predict at least a sustained linear growth in the total mass to orbit per year over the next few decades.