Using Occam: No one has ever reached the potential in terms of technology. I have to agree with ThornEel that the possibility of multiple advanced civilizations existing right now -in this Galaxy- is very small… But that’s just the Milky Way which is nothing compared to the Universe… But then again who knows what we may be able to see in a hundred years (or what our governments aren’t showing us)
It’s true that if some species build terraforming self replicating Terra former millions or even billions of years ago we should have noticed it …
That civilization would need an extremely, extremely organized extreme long term management. Because all those giant long term things you mentions would need several thousands of years to return results. You could say they may live for thousands of years or even be immortal, but that poses other problems they may not have/will be able to overcome. Someone has to be organized enough to have someone or something do something with all that data or terraformed planets that would be available by that time.
To be honest I think every civilization that managed to spread over several light years degenerated after only some thousands of years because of the limitations to technology that may be posed by the laws of nature. Transport times would be too long compared to lifetimes. Information would take to long compared to lifetimes. Colonies would get isolated and may fail at problems the home world has solved eons ago.
For instance we have problems researching organism with extremely long lifetimes because we don’t have the organisation or experience to do that kind of, long term, thing yet. Imagine a project taking several thousands of years.
What I’m trying to say is … the longer something takes … the farther it is apart … the more it is prone to fail. Especially if these distances and time frames are several thousands of factors bigger then what evolution has prepared you for.
Maybe there are galaxies out there with quadrillions of transformers.
I think Aliens can contribute to a great experience. One way of countering the Fermi paradox is to cater to stuff that counters it. For instance showing Alliens in enviroments that we didn’t expect. Showing modes of transportation we didn’d expect. Showing ways of communications we didn’t expect.
All those estimates are allways based on something. If that something is wrong it could be totaly different right before our eyes but we just aren’t far enough to realize it.
Think of it like how it would be for a lone child to find out how to manage to grow to be 100. No clue at the beginning. How would any civilization manage to get to millions of years of existence. Why don’t we see them? … well take what you want from this. I’m too tired to continue my thoughts.
Dyson spheres would be very IR bright. AU scale balls at comfortable living temperatures would show up in IR surveys and stand out a welding arc in a dark room, but would look entirely invisible at other wavelengths. Dyson spheres would be plainly obvious by now.
So if there were ten in the Milky Way … how is the probability that we would have found one of these by now?
I limited the argument to the Milky Way, though it could be extended to nearby galaxies, because distant galaxies are probably too far away for us to meaningfully interact with, even if the interaction was nothing more than looking at traces of galactic engineering.
That said, the opening of Accelerando contains one of the best First Contacts I’ve ever read: it is discovered that most of the Andromeda galaxy has been turned into a giant computer. And no one actually cares, because it’s simply too vast and distant to do anything about it.
Galaxy-scale organization doesn’t have to be a hard limit. Beings on a larger and slower scale would find the galaxy smaller, like the Sun System to us, for example. Or they may scale well. Actually, humans could probably do it somehow too. We can wrap our head around the idea of nanotech, and Von Newman galactic probes wouldn’t be that much complex.
So maybe no civilization can reach more than a few light-years before wasting away, but it seems clear that we could do more (note that humans don’t need to live to see a probe-filled galaxy or galactic megastructures, only to launch it and let it evolve by itself). So if we could do it, it means that it’s not actually a hard limit.
And saying that we simply are special is actually a version of the First Ones answer: we are the first one to be like that.
More specifically, we will be when will begin galaxy-wide stuff. If we do so. If we don’t, the First Ones will probably be someone else in another few billion years. And someone else may have failed to do so before despite potential.
But again, with the Apes vs Angels problem, if they did, they are long, long dead.
Oh, that depends on a number of factors. The mass of the central star, whether we’re only expecting a civilization to build spheres around stars in the galactic habitable zone, whether we’re talking about spheres created by a single civilization, or spheres created by 10 separate civilizations scattered around the galaxy, etc.
Let’s assume the spheres are built around K-dwarf stars (~4000 K, relatively magnetically stable), and that the sphere has a temperature of approximately 20 degrees Celsius (that is, they’re living in the sphere, not just using it as a power plant). The sphere would have a diameter of 0.86 AU and a luminosity approximately 40% of the Sun, with a blackbody spectrum peaked at about 10 micrometres.
Let’s also assume that the 10 dyson spheres are spaced equally around the galaxy at the same distance from the galactic centre as the Earth. This leaves the spheres separated by approximately 15,000 light-years, and puts one within 7500 light-years of Earth. They would have a magnitude of 16 peaked in the infrared. Of course, some of this light is going to be filtered out by telescope filters; let’s round this up to magnitude 20, then, as viewed by telescopes such as WISE or Spitzer. That’s probably a huge under-estimate (it’s probably closer to 17 or 18), but even then the spheres would appear to be hundreds of times brighter than extragalactic IR sources such as LIRGs. Indeed, we should be able to find Dyson Spheres in already existing IR survey data out to a distance of over 50,000 light-years. That’s any within our half of the Milky Way.
Fermilab is actually looking for these, by the way. Nothing with the expected signature of a Dyson sphere has been detected yet.