[extropy-chat] Dark matter and ET

[Eugen Leitl]

On Sun, Jul 17, 2005 at 11:15:55PM +0100, BillK wrote:

> Other galaxies are irrelevant. Estimates say the Milky Way has around
> 100 billion stars. That's 100,000,000,000. Maybe as many as 400
> billion. Quite sufficient for my purposes, thank you.

Other galaxy clusters would have been irrelevant, if you couldn't see them.
There are no visible holes in supercluster distribution. Gravitational lensing
doesn't show invisible dark blobs, on all scales. 
 
> Galaxies are usually millions of light years apart, with a few
> well-known exceptions. Forget about other galaxies.

You must be mistaking somebody else's mail for mine.
 
> Actually I could agree with this. We *might* be the only, or first,
> intelligent life in our galaxy. But we have a huge number of stars,
> most much older than our sun. So I reckon the odds are against it.
> Life seems to *want* to create itself in this universe.

You can't extrapolate from a sample of one, the one being you. 
All life in this system is causally entangled by originating metallicity,
and crosspollination through impact ejecta.  

I'm not interested in life, only in life that we can currently 
observe -- the intelligent, expansive kind.
 
> Again, light cones are irrelevant for our galaxy. Any expansive
> post-singularity civ will relatively quickly be all over the galaxy.

I don't know why my mail is particularly difficult to understand. 

There are no holes in the sky. Observer emergence-preventing relativistic
expansion wavefronts can only be observed very rarely anyway, given low 
nucleation density, which is even documented through our own history, 
strongly hinting we're a fluke. 

No offense, but please read the above, and understand what it means.
 
> > No. I told you you should see them on GYr scale (and in fact, if you could
> > see them, you'd be dead soon after, or you'd never happened at all, which
> > is a negative anthropic principle factor).
> 
> This is just a distraction. If the 100,000,000,000 stars in our galaxy
> haven't produced an expansive civ to fill our galaxy, then I don't
> care what might be going on in other galaxies. You are not increasing

I don't know what you're trying to do, but I'm trying to get upper bound
of smart expansive life from observation data.

It is perhaps not a good idea to try ignoring observation data which is 
telling you something in glowing letters GLYr high.  

> the odds much by adding more galaxies, millions of light years away.

Aargh! I'm giving up now.
 
> > Anything nonexpansive is irrelevant. Anything expansive you see for a
> > gigalightyear distances.
> 
> That's the point! They are all nonexpansive in our galaxy, or they
> would be all over us already.  Gigalightyear distances are
> gigalightyears in the past (and irrelevant anyway).

[ ] they're not observable because they're nonexpansive
[x] they're not observable because they're not there  

Occam's Razor sez: I will cut you. 

> If we did hit the singularity and decide to expand we would have
> 100,000,000,000 stars in our own galaxy to inspect shortly thereafter.
> But I believe a transcendent civ will have *much* better things to do
> than go on a centuries long plane trip.

They still have a metabolism, and they're still darwinian. The first
makes them observable, the second expansive. 

(If you think they're not darwinian, demonstrate how they ceased to be).

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a>
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ICBM: 48.07100, 11.36820            http://www.leitl.org
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