Bradbury's Many Hypotheses

Robin Hanson (
Thu, 04 Nov 1999 14:37:09 -0500

Robert Bradbury has continued to throw out many hypotheses to explain how a universe full of life could appear so dead.

Robert wrote:

>I think about this and the problem of galaxy "walls".  What if in some
>locations SIs get "lucky" and evolve early.  They are going to use up
>all the resources in their galaxy and then spread out from there.
>[Robert F. has done some estimates that show that SIs can consume the
>resources of a galaxy *very* quickly.]  Now interstellar distances
>aren't very limiting but intergalactic distances *are*.  What you will
>see is regions of space where the SI "locusts" have consumed everything
>surrounded by the regions that they are slowly expanding into.
>If there is a correlation between the "warm COBE regions" and the
>dark regions (without galaxies) then you have a very *interesting*
>situation.  The nice thing is that this is a testable hypothesis
>once we have big databases with the locations of all of the galaxies
>and better resolution regarding the microwave background.

A creative suggestion, but I don't think it works if the radius of these dark regions is presumed to increase at a reasonable constant local speed. Maps of these regions and walls are looking back in time. So we should see the wall widths increasing linearly with radius from here, out to a point when the regions disappear. If the dark regions started growing recently, we should see these effects in the maps. If the dark regions started growing long ago, then the only way to not have everything dark by now is to posit a very slow local speed of growth. And I don't see why probes can't move between galaxies at a substantial fraction of the speed of light, if that space is as empty as it seems.

>SIs don't go out of their way to be "invisible", they are "invisible"
>because the most efficient structures are those that radiate their waste
>heat at the lowest possible temperature. ...
>(a) they do disassemble solar systems; ...
>(c) that our galaxy is by and large a Kardashev Type III civilization
>(with ~90% of the mass astroengineered).

I addressed this argument of yours in detail in Sept., giving specific math models which imply contrary conclusions and challenging you to offer models which imply the conclusions you favor. My last post was Sat, 18 Sept 1999, to which you have not yet responded.

To summarize for others, it is hard to rationalize spending precious mass to carefully drop the radiation for most stars down to very low temps, while not even touching 99% of the light from the remaining stars, and also leaving substantial amounts of useful mass there.

>We are not *energy* constrained! We are construction material
>constrained due to the scaling laws for your radiators. Your
>radiator size scales inversely with T^4 -- low temperature radiators
>require a *lot* of material.

This seems contrary to your earlier explanation for why life is dark. If they are not energy constrained, why try so hard to re-radiate at a low temp?

>For the Prime Directive *not* to be "in practice" you have
>to make a very strong case that the overlords can "salvage"
>a contacted species without "poisoning" it. If you destroy its
>will to survive/evolve (because of an awareness of how
>pointless it is) then you do not want contact. If you
>do have contact and they are aware of it, how do you
>salvage the goals of "uninfluenced" evolution?

You are making the strong assumption that these powers care much at all about observing the undisturbed evolution of lowly creatures like ourselves. You could be right, but it is quite a strong assumption. If we know little that would be valuable to them, they would mostly want "contact" to take over the resources we occupy. Maybe there is demand for a dozen such "zoos" in a galaxy, I don't see why there would demand for much more.

[Replying to Bill Brown:]
>> Stars are terribly wasteful, after all - they convert so much mass
>> into a form that is terribly inconvenient to collect.
>But they *may* just be the best way to produce heavy elements.

This seems like complete speculation. I.e., you have no other reason to believe this than it would make your theory work better. And it would be very surprising if the most efficient factor were exactly the natural factory.

>Defense may be a small requirement because of the difficulty
>of destroying solar system sized sturctures (down to the atomic
>level) across interstellar distances.

This seems like complete speculation in the same sense.

>> If there are big computational problems to solve, converting the
>> whole galaxy to J-brains will give you a better chance of solving them.
>*Only* that subset of all possible problems that can be divided into
>data subsets that can be solved on "local" computational resources.
>A plausible scenario is that they evolve to local limits and then
>go to sleep waiting for more computronium to evolve or something
>worth watching ... occurs.

You have just assumed that virtually the only thing all SIs want is to compute answers to the sort of questions that require high synchronization, and maybe also to watch the universe a little. You have *not* derived this conclusion from other assumptions.

>> No kidding. My question is: "Exactly what factors would create this
>> particular selection pressure, rather than some other one."
>This depends on the "goals" of the species. We are talking conscious
>entities here, so in theory they are free to pick their own goals. ...

I don't think you understand evolution. Selection works regardless of the conscious or unconscious goals of the entities involved. If we work at it carefully enough, we should be able to figure out what kinds of goals selection should favor. Their freedom to pick their own goals is irrelevant.

>> If it is possible to profit from aggression, mobilizing all
>> available resources will be essential to both defense and predation.
>... *Only* if the remote SI/MBrain etc. is designed by you
>to be non-self-modifying do you have a chance of this occuring.
>If it is a conscious self-modifying entity then it may well decide
>its interests & goals are much different from the mission you gave it.

You simply assume it is very hard to create descendants which are highly likely to have very compatible goals. I see no reason to think this.

Robin Hanson Asst. Prof. Economics, George Mason University MSN 1D3, Carow Hall, Fairfax VA 22030
703-993-2326 FAX: 703-993-2323