[ExI] Fermi question, was is a FTL drive a dream . . .

[Eugen Leitl]

On Tue, Dec 20, 2011 at 11:29:50PM +0100, Anders Sandberg wrote:

> Yup. However, something we have been thinking about recently is whether  
> we would actually see a dimming front. The classic technosphere scenario  

You would see a dimming front. If you could observe it, which
you couldn't. You're either not there yet, or you never happened
when the wave passed through and made emergence of new life
impossible.

> has lots of colonization probes making short jumps, leading to a front.  

It doesn't matter, as the real limit is the speed of light.

> But you can send probes much further ahead than a few lightyears: while  
> it is likely a bit harder, it doesn't seem that difficulty scales  
> proportional to distance. That means you can have a very high branching  

Cruise is cruise, and background repairs take next to no energy.
If you don't hit debris in transit and can deccelerate on arrival,
the universe's your oyster.

> factor at early stages, using early resources to send probes to every  
> other galaxy (or at least very far away), and then do local filling in  
> once the probes have germinated. This might produce a much less clear  

In order to be able to launch stuff you need to be able to dim the
star. Due to the exponential kinetics the dimming is very sudden.
Total duration is very short, probably under a century.

> front, and maybe even a universal dimming. It also interacts with  
> Robin's cosmic commons scenario.

I don't see how cosmic commons is possible. The assumptions make no
sense.

> The key factors are probe survival as a function of travelled distance  
> (my BOTE calculations of interstellar dust suggested that the mean free  
> path is pretty long) the cost of launching and slowing probes from high  

Especially in integalactic space.

The biggest issue is mass required for slowdown, and resources
required to prepare fuel (antimatter-catalyzed fusion e.g.).

> speeds, and whether you want to do really long range colonization on the  
> off chance that some other civ might get there first.

Dandelions do not care where their seeds fall. You can probably push
10^3 probes simultaneously, if not more. The costs for each seed are
negligible.