# [ExI] Silence in the sky-but why?

spike spike66 at att.net
Mon Sep 2 14:48:46 UTC 2013

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-----Original Message-----
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Eugen Leitl
Subject: Re: [ExI] Silence in the sky-but why?

On Sun, Sep 01, 2013 at 04:23:46PM -0600, Kelly Anderson wrote:

> But how many millions of years would it take to get it moving at a
> reasonable speed? Have you done those calculations Spike?

I have done the calcs on it, takes 20 million years to get to the nearest
star from here, doesn't ever get up to a reasonable speed for interstellar
travel.  The speed once it reaches the nearest star is about 200-ish meters
per second, about the speed of a Booeing 737.  The real magic is that you
can deflect off of the nearest star gravitationally, and pick up some of its
orbital velocity around the center of the galaxy.  This is a good idea,
since with this scheme you can't actually stop at the target star; you just
go zooming on past.  But it isn't really like flying over Salt Lake City on
your way to Denver, for you leave behind some MBrain nodes at the target
star, so they use the metal that is there and start a new MBrain.

> but assuming you take half the mass of the asteroid belt and build
> these things out of it... what kind of acceleration would you get?  Kelly

The sample calcs I did require about 20% of the asteroid belt and max
acceleration is in the pico-G range as I recall, which is why I used the
units meters per square year rather than an alternative picometers per
square second.  This whole notion isn't for the impatient types, who insist
on rushing around in the lifetime of a particular species.

>...You're competing against relativistic craft ~kg to ~ton range, capable
of 1-10 g acceleration... Eugen

That depends on what your definition of "compete" is.  The other fast
species can do their thing, while the MBrain goes about its business on a
different time scale.

> The other thing is how would you agree which direction to go? ...  Kelly

What you mean you?  You and I wouldn't need to agree.  The MBrain makes that
decision without consulting humanity, and does what it collectively decides
to do.  If your question is how does an MBrain decide things and can you
have competing MBrains around the same star, my answer is I don't know and I
don't know.  But MBrains are smart, so I would trust them to do the right
thing.

>I'm guessing humanity would want to move to the outside of the
galaxy...Kelly

Perhaps.  Metal is very valuable in this scheme, but the outboard guys can
carry metals inboard with them.  The MBrain as photon rocket notion carries
all the planets and everything else in there along for the ride.

>...Humanity that chose to become solid state or begat solid state will go

Ja, if that becomes reality, this other scheme is likely a nonstarter.  But
humans to solid state is pie in the sky tech, whereas we have everything, or
durn near almost everything we need right now to build an MBrain.  MBrain
tech is now potatoes on the plate technology.  If humanity suffers a peak
collective intelligence and starts declining (I can think of several
mechanisms that could cause that) then we may never achieve human
intelligence to solid state, and if not, we may never get out of the cradle.
But if we create the means of converting the asteroid belt to an MBrain,
then we start along the 20 million year journey to the next star, then the
next intelligent life form will see a star coming at a couple hundred meters
per second, realize there are wonderful opportunities, etc.

Kelly more directly to your question, it could be that the original MBrain
merely gets programmed to head off to the nearest star, with the MBrains
never having anything like intelligence.  The nodes just do what they do,
like 6E26 chess computers, never developing intelligence or ever wanting to.

> ...but seriously, how would you figure out the right
> direction to go? Ok, you might be able to compute a good direction
> with regards to the imminent collision with the Andromeda Galaxy...
> :-)
Kelly_______________________________________________

OK Kelly and other MBrain fans, here's your assignment: propose a direction
to start.

Considerations:  as I noted before, the luminosity of a star on the main
sequence scales as the 3.5 power of the mass, so if you double the mass of a
star, its luminosity goes up by about 11 but its mass doubles, so the
acceleration available with an MBrain goes up by five and some change.  With
that information, we want a star which we can combine with ours and still be
on the main sequence, for causing a supernova could spoil an MBrain's whole
eon.

I haven't worked out the details on whether colliding two stars would cause
a nova (note difference between nova and supernova.)  I suspect any star
collision would cause a nova, but that is not a show stopper I wouldn't
think.

There is another thing I thought of.  Just as it might be possible to
combine two stars, it might be possible to collide two stars in such a way
as to create a smaller star.  If for instance you have a 1 solar mass star
colliding with another 1 solar mass star, you might be able to arrange the
collision to create a 1.8 solar mass star and a 0.2, the smaller one going
zinging off with enormous velocity.  Why would you do that?  We only have a
few billion years before main sequence stars start to go red giant, and even
less than a paltry billion years for the bigger stars.  But if you take a
star on the main sequence and remove some of the mass, its lifetime is
extended enormously.  The resulting star becomes more difficult to steer,
because the luminosity available for the MBrain to deflect is lowered by a
factor of about 280 and the mass is lowered by a factor of 5, so the
available acceleration is lower by a factor of about 56, but the star's
lifetime is extended by a factor of about 25.  So with that technique we are
partially freed from that tight deadline only a few billion years away and
approaching rapidly.

MBrain star steering is not for impatient types who expect everything to
happen in this particular geological age.  It helps to look at things from
the perspective of the Nuvvuagittuq greenstone belt.  All these eons, the
greenstone watched these life forms pop out of the sea, swarm all over the
place, run around in circles, accomplish nothing from the perspective of
moving off to the nearest star and joining the others, or if there are no
others, then becoming the others.

spike

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