Tim May wrote:
> I made no assumptions of nondifficulty (to use your phrasing).
> This is in fact why I picked the Thogians a few hundred million 
> light-years from us. Now perhaps you think advanced civilizations are 
> even rarer than in this example, there have not yet been any 
> civilizations reaching our level, except ourselves, anywhere within a 
> billion light-years or so of us. Arguing this one way or another was 
> not my point.

It probably does make a point. 10^8 light years still puts the
Throgians close enough that we would have seen their Dyson spheres
etc, regardless of whether they've achieved MWI communication.

> Rather, it is that the effects of MWI communication (or time travel) 
> would likely be enormous and that such a civilization would be expected 
> to expand and show themselves in the (likely) billion or more years 
> they would have had to expand, build Dyson spheres and other cosmic 
> artifacts, send signals, etc.

I don't see this.

> >
> > This also implies that such technological civilisations are also
> > rather diffuse within the Multiverse, _excepting_ of course those
> > which share part of their history with ours (eg the Nazis which won
> > WWII). We have some predictive power as to what those people would be
> > like, since they will be similar to us.
> I'm not following this at all. Why do you think that communication with 
> (or actual travel to) worlds is dependent on our ability to _predict_ 
> things about them?

Only that we can predict they're unlikely to achieved MWI
communication (relative to a completely unknown Throgian-like civilisation).

> I can see an argument to be made that only close worlds can be 
> communicated with, and some folks have argued this, but this argument 
> was not made by you here.


> >
> > So, I for one, would not discount Hal Finney's point.
> >
> What I said was that the point that we have not yet built a receiver or 
> portal says nothing about what others have done. And if there are other 
> civilizations out there and building such receivers or portals is 
> possible, one would expect a fair number of them to have done so. Since 
> the implications of building such portals are, I think, enormous, I 
> would expect a civilization which has built such things to have 
> expanded even more rapidly through their part of the universe than 
> without such things.

This is where I lose your argument. I can't see why an MWI
communication capable civilisation should be able to spread throughout
our universe any faster than a non-MWI communication capable one. And
even if its true, all it does is place tighter bounds on how difficult
it is to create such civilisations.

> --Tim May

A/Prof Russell Standish                  Director
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