[JuettnerDistrib]

> is there really any practical value in this sort of research

In many ways it is too early to do this research, so it is a kind of art (as is a lot of research, imho). As long as only a few people do it, it's cool and useful so we can be aware of our potential future.

On the other hand, since we have no credible evidence of extraterrestrials, it would be surprising to find a civilisation so advanced to build a Dyson sphere. If they can build Dyson spheres, wouldn't they already be all over the place?

Ok, I suppose I should actually go read the paper now...

[awb]

> If they can build Dyson spheres, wouldn't they already be all over the place?

The number I’ve seen quoted is 50M years to colonize the galaxy: http://www.sentientdevelopments.com/2012/01/new-mathematical...

> they calculated that any galactic empire would have spread outwards from its home planet at about 0.25% of the speed of light. The result is that after 50m years it would extend over 130,000 light years, with zealous colonisers moving in a relatively uniform cloud and more reticent ones protruding from a central blob. Since the Milky Way is estimated to be 100,000-120,000 light years across, outposts would be sprinkled throughout the galaxy, even if the home planet were, like Earth, located on the periphery.

It’s actually so fast that advanced civilizations would have had time to colonize the galaxy and go extinct many times over without us noticing.

Or maybe their spheres were built so long ago they’ve already collapsed and been consumed by the stars again.

It’s a great mystery and interesting thought experiment though.

[denton-scratch]

> 50M years to colonize the galaxy

Our ancestors from 50M years ago are all extinct. So a civilisation spreading through the galaxy would have evolved in all kinds of different ways. It's not obvious to me that these diverse evolutionary strands would all still be interested in Dyson spheres, or space travel, or even astronomy.

There's a belief that's hard to shake off, that the properties humans have that we think most important represent some kind of evolutionary pinnacle. Typically, those properties are language, and a large brain for processing language. But if language and a large brain are really such great evolutionary advantages, why are humans the only creatures on Earth that have evolved those properties? Possibly language and a large brain are an evolutionary backwater.

At 0.25% of the speed of light, it would take us 1,600 years to reach Proxima Centauri; but it might take a lot longer to reach a star with habitable planets. We'd definitely need generation ships. After (say) a million years, we'd presumably have evolved to adapt to life on generation ships. It's not obvious to me that such adaptations would leave us fit to inhabit a planet. And perhaps adaptation to life on a generation ship means adapting to eating your fellow passengers.

Given the history of humanity, I find it hard to believe that the population of a generation ship could survive as long as 100 years without war breaking out on-board. We've had large brains and language for about 50,000 years, as far as I can tell; we've been warring the whole time. Maybe large brains and language pre-dispose us to war? If that's right, then it seems unlikely that intelligent life would ever spread far from it's planet of origin.

I'm very sceptical of the idea that any "civilisation" could ever spread far from its home planet. There are two things that we refeer to as a civilisation: a culture, and a species. Culture changes very quickly - over a single lifetime. But on a scale of millions of years, speciation is also pretty quick. So I can't see how any kind of homogenous civilisation or species could spread through a galaxy. They would have diversified before the train even reached its first stop.

So I don't have any insurance against being kidnapped by aliens.

[bryanrasmussen]

Being able to build Dyson spheres does not make them capable of going faster than the speed of light, so any civilization capable of building a Dyson sphere would probably still be clustered around a couple stars and that's it.

Would such a civilization spread to more than one star is actually also a question, or would they control their population rationally stay on their Dyson sphere and only start to move when the star had less than 100,000 years left to go.

Only some Dyson sphere variants, like Shkadov thrusters, are primarily conceived as ways to move around. Which personally seems to me less likely, is a civilization, as well as the ability to construct these objects, also going to have a species level interest in going exploring?

[perihelions]

> "Being able to build Dyson spheres does not make them capable of going faster than the speed of light, so any civilization capable of building a Dyson sphere would probably still be clustered around a couple stars and that's it."

Check your math: this galaxy is ~10^5 light-years in size and ~10^10 years in age.

[caf]

They may not be moving around to explore so much as to keep their solar system safe.

Galactic orbits are far more chaotic than the sedate stable orbits within the solar system - stars closely approach each other on a somewhat regular basis.

[dave_sullivan]

No Dyson spheres, but there are black holes all over the place. Some people think those would make great computing devices, many of their origins are not well explained as super nova remnants, and they efficiently harness energy from companion stars. They have all the properties of Dyson spheres but they actually exist. Maybe with advanced enough physics, intelligent civilizations learn to manufacture and harness black holes, neutron stars, and other dense objects for societal benefit.

[jonathankoren]

> No Dyson spheres, but there are black holes all over the place. Some people think those would make great computing devices

They’re crappy computing devices. Even if you figured out how to program one — and that’s an “if” that would make Sagittarius A* look like a neutrino — there’s no way to read the information out except Hawking Radiation, and that would take 10^70 years.

https://youtu.be/0GLgZvTCbaA (8:36)

[alfiedotwtf]

This is the first time I've heard of this. Wow, yes! A blackhole is far more efficient at consuming energy than a Dyson Sphere... the hard part though is kickstarting the process I guess

[ohyeshedid]

> If they can build Dyson spheres, wouldn't they already be all over the place?

I figure they'd have to be.

They'd need more than a solar system's worth of raw resources to build the sphere. They may need more than a solar system's worth of resources just to build the tools and craft to be able to build the sphere. They're going to need an insane amount of production facilities for various components, and that's going to take a massive amount of resources. That's going to require exploring quite a bit of a galaxy.