[ExI] Von Neumann Probes

[Ben Zaiboc]

On 25/01/2026 14:58, BillK wrote:
> Gemini makes the point that once a civ develops controlled fusion power, there will be no requirement to build a Dyson swarm. 

That's an interesting idea.

Wasteful of course, just ignoring all the stellar energy available, but it does open up some options.

How small could a fusion reactor be? We can't really know this yet, but we can make some guesses. I'd guess that 'not small' would be the answer. If the smallest possible fusion reactor would be on the order of a few metres, then small (tens or hundreds of metres) completely independent 'worlds' would be possible that wouldn't even have to be in orbit around a star. They could be home to quadrillions or more minds. They'd eventually need fresh supplies of matter, and to get rid of waste heat, but apart from that, would be pretty self-sufficient, and could exist just about anywhere that physics permits, even in intergalactic space.


On 25/01/2026 14:58, John K Clark wrote:
> If ET is using fusion reactors to produce as much power as a sun does and for as long (I don't see how that would be possible, but never mind) then according to the Second Law Of Thermodynamics it's going to produces [as] much waste energy, in the form of infrared radiation, that a Dyson Swarm would, and we would be able to see that

I don't think anyone is proposing producing as much power as a star does. Imagine a small asteroid-sized object, with a fusion generator or two inside, large reserves of hydrogen fuel, some kind of propulsion system, cooling and lots of data-processing.

Combine that with the ability to slow down your clock speed, and I reckon that's as close to a real-world Star Trek scenario as we're likely to get. You could get to the galactic core and investigate the antimatter fountain in a few (subjective) months. Or zoom off to another galaxy. What's a few hundred million years between friends?

I reckon the significant thing here is that travel on a cosmic scale means permanent severance from your originating civilisation. Once you've left, there's no returning to what you left.

While this won't deter everybody (not sure that it would deter me), I think it would deter the vast majority of non-antisocial curmudgeons. So I suspect that interstellar travel would be a minority pastime, and most intelligent life would stay at home, and enjoy the benefits of trillions of subjective years of leisure and fun.

So, yeah, probably Dyson swarms, for most people. At least until we discover new physics.

Also, no reason that I can see not to have both. Spend a few thousand subjective years whooping it up around your local star for a few weeks, then head off in an asteroid, slow yourself right down, and see what's going on in the Great Attractor, or find out just how empty those galactic voids really are.

-- 
Ben