[ExI] Silence in the sky—but why?

Eugen Leitl eugen at leitl.org
Mon Aug 26 14:53:56 UTC 2013

On Mon, Aug 26, 2013 at 03:25:23PM +0100, BillK wrote:

> So we don't even need a civ capable of relativistic travel. Just fire

Any nonrelativistic expansion will be completely overgrown by
relativistic expansion. As relativistic travel isn't hard (for
small probes, anyway), this means you can consider nonrelativistic
expansion an early, transient phase which is hard to observe.
Unless you're the point of origin.

> off some probes to spam the galaxy. 10 million years is tiny compared
> with the billions of years existence of the galaxy.

We're not talking about just single galaxies, but patches of
real estate GLYrs across. Stellar systems would go dark very
quickly, so by the time you see half of the sky going dark
(FIR) your own system is already toast. Not a damn thing
you can do about it, unless you're already expansive.
So time interval from observer to expander is very short
(few centuries in our case), and hence you need to be arbitarily
unlucky in order to see half of the sky go dark.

What we're seeing is exactly what we should be seeing. 

> There should be a traffic jam of probes flying past the solar system.

No, the entire visible universe would made from ~AU FIR blackbodies,
but this is not something you could observe, as you would have never
happened in the first place. As you're alive and observing, this
indicates that we're not in anyone's smart lightcone.

> Unless 'intelligence' decides that is a silly thing to do..........

'Intelligence' doesn't decide a damn thing, out of control and
statistics decides everyting.

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