Anyone with only mildly better tech than we have now, can see your ecosystem changing over the course of the seasons before you invented fire, let alone built a Dyson swarm. We're just starting to have this capacity already in special cases, though we've not found any sign of an ecosystem, just "boring" diamond rain etc.

A Dyson swarm will keep you safe from any threat smaller than another Dyson swarm — and while you may not be able to "pack it up", you can use one to run to other galaxies… in fact, almost all of them… at close enough to the same time that light cones matter… and get the settlers moving at a significant fraction of the speed of light… and have a lot of redundancy.

I would assume it takes more than a day to build a Dyson sphere. But more to the point from a distant observer's viewpoint the star isn't going to just blink out. The Dyson sphere has to radiate just as much energy as the star produces, so it would probably appear just as a red dwarf. Unless the alien civilization has some way to destroy energy it will be in a constant battle to avoid cooking the inhabitants of the sphere.

> Unless the alien civilization has some way to destroy energy (...)

If the point of a Dyson sphere is to collect energy, wouldn't it be enough to just use it or store it?

To use, not to collect. And thermodynamics appears to say you can't just store it.

A stellar mass black hole might be an interesting "cold end" in this regard… if you can find or make one, but to do that you'd need to start with a Dyson swarm.

> To use, not to collect. And thermodynamics says you can't just store it.

I don't think these semantic games are productive. Thermodynamics says you can transform energy. "Collect" in this context means using energy in a way that allows you to retrieve it in the future. For example, charging a battery or condenser with light with a PV panel, powering a motor that accelerates a flywheel, coiling a spring, heating a material, etc.

Unless your civilization has ways of infinitely storing energy or exporting it somehow you'll need to be in equilibrium over the long term. This means radiating away the waste heat, at stellar scale.

If you have a Dyson swarm, the best way to "store" the power output of a star for later use is to perform star lifting, making the star itself smaller and lighter so it doesn't burn as hot in the first place, with the extra mass being used to construct a collection of gas giants in the same system.

If this kind of thing appeals to a group with meaningful control over a Dyson swarm, given that Dyson swarms and the capacity to make them can also be used to build and power a rapid, direct, and near-simultaneous colonisation of all galaxies in our future particle horizon (with significant levels of redundancy, though obviously we can't determine if "significant" is "sufficient"), you should anticipate the first such group turning almost every star in the universe into a red dwarf (or brown dwarf, for those they don't care to colonise just yet) in very short order.

I don't know if anyone's been looking for signatures of this specific thing; though I am told that "1 AU sphere of room-temperature metal" would be quite easy to spot, if you downsize the stars first then the size of the corresponding room-temperature sphere gets smaller, and I don't have a quantifiable number for "quite easy" nor any sense of scale for how much effort is going into such searches.

> Can't exactly pack it up and run either, not with a medium-sized star in your suitcase.

If you're K2 just take the star and solar system with you. Stellar engines can be used to move stars. https://en.wikipedia.org/wiki/Stellar_engine

Eventually.

Shkadov thruster:

> After a period of one million years this would yield an imparted speed of 20 m/s, with a displacement from the original position of 0.03 light-years. After one billion years, the speed would be 20 km/s and the displacement 34,000 light-years, a little over a third of the estimated width of the Milky Way galaxy.

Caplan thruster:

> Caplan estimates that the Bussard engine would use 10^12 kg of solar material per second to produce a maximum acceleration of 10^−9 m/s2, yielding a velocity of 200 km/s after 5 million years.

Svoronos Star Tug:

> The Svoronos Star Tug can, in principle (assuming perfect efficiency), accelerate the Sun to ~27% the speed of light (after burning enough of the Sun's mass to transition it to a brown dwarf).

Temporal displacement fields: Wrap you star system in one of those and remove from the normal universe with a time shift of a couple of seconds! Let those pesky K2 Dyson Sphere civilisation figure that out!

Tried that, it didn't work; that's how I ended up stuck in this insane reality where JavaScript ate the world, and my nickname is all I have to show for it.

Ah, sucks when this happens, doesn't it?

>but the other K2s will fuck your shit up.

[Citation Needed]