[ExI] No mirrors, was Deceleration mirrors

Anders Sandberg anders at aleph.se
Mon Sep 21 12:23:53 UTC 2015

My calculations convinced me that there is simply no point in sending 
flesh to the stars. AI/nano probes, rather thin javellins and not 
superrelativistic, seems to be the way to go. Colonizing around denser 
dust clouds rather than trying to spam through them looks like a good 
strategy; in many cases remote galaxies are easier to reach than stars 
in the thin galactic disk.

On 2015-09-21 12:47, BillK wrote:
> On 21 September 2015 at 09:20, Anders Sandberg  wrote:
> <snip>
>> We have looked both at the laser launch and in-flight damage
>> deflection/repair. Some cool problems there (interstellar hydrogen becomes a
>> proton beam when you move fast enough).
> Two conflicting problems there.
> If the ship travels slow, then interstellar debris can be shielded
> against, but travel time takes centuries. This system is OK for AI
> exploration. (So why aren't they here already?).  :)
> By the time humanity is considering interstellar travel we may be AIs
> ourselves, so we might be happy to travel slow. Flesh bodies really
> don't behave well during long-term space travel.
> If the ship travels fast (substantial fraction of lightspeed), then
> interstellar debris becomes a major problem. Possibly even a
> show-stopper. It is not just hydrogen. There is dust as well, some of
> which might be significant bits of rock, cosmic radiation, etc. So the
> ship needs a good shielding system.
> The trouble is that the interstellar medium is not evenly spread.
> Average calculations might look OK until you hit a denser cloud, then
> the ship becomes more interstellar dust. It would be a big help if we
> could map routes first by AI ships and report back to earth. They
> might even be able to sweep routes clear of dust, but over the time
> scales involved the routes may become clogged again.
> I have the feeling though that (excluding magic physics) interstellar
> travel will prove to be too expensive / dangerous / difficult and civs
> find more preferable things to occupy themselves with.
> BillK
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Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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