Re: Interstellar Information Transmission, was Re: Kurzweil's ...

From: Robert J. Bradbury (
Date: Sat Mar 17 2001 - 12:49:43 MST

On Sat, 17 Mar 2001, Emlyn wrote:

> Firstly, we are talking about the expansion of intelligence after a
> singularity, outwards from this solar system.

Thats one point of my comments -- "intelligence" can't "expand" much beyond
the boundaries of the solar system. You have to follow a thermodynamic
downhill slope and radiate your waste heat outward -- that means that an
MBrain can't get much larger than a solar system (at least in our situation).
You don't *want* to get larger because that increases the internode
propagation delays and drives up your energy costs (if you lose photons
because you can't confine them to a waveguide because you don't have
enough material).

Think of the problem of how much more "intelligent" you would be if you
moved all the neurons in your brain a meter apart.

You can perhaps "duplicate" or "grow" intelligence remotely but the
return on investment seems pretty low because they can only communicate
a small fraction of what they "know" with each other. Now, say you
make the transition from we are now (where interhuman bandwidth is
very low relative to internal bandwidth) to the posthuman state
where inter-posthuman bandwidth is very high (I can "know" everything
that you "know") -- are you going to want to return to the "human"
state where you can't communicate much of what you know at all?

The information cost of leaving the "hive"-mind is very high.
I suspect most would choose never to do it.

> There is a discussion of EM vs matter. How is it possible to expand as EM?
> There's no receiver, no way to kickstart a replicator at the other end.

Sure there is, you construct a probe with enough matter to hold the
MBrain designs, and enough nanoassemblers that some of them are still
functional after traveling through interstellar space. You then launch
swarms of these on interstellar voyages using mass-drivers. (Decelleration
on the far side is a bit trickier but you can use things like magnetic
breaking or simple "tolerance" of crash landing for this to work.
As soon as they have assembled enough of a receiving antenna, they
can immediately start to pick up the information flow for any designs
they couldn't carry "on-board". They then proceed to rapidly turn
the target system into an MBrain or JBrains or Dyson-Nets.

> So are we (I'll be there) not entirely limited to *initial* transmission
> using matter? Damien asked the same question on list a while back, actually,
> and I don't remember anyone answering "you can use em as so ...."

The BIG problem that I wasn't clear about earlier is that given the amount
of "information" that you rapidly get at each end (> 10^40 bits potentially)
one *cannot* communicate any significant fraction of that across interstellar
space using electromagnetic radiation (using any of the "popular" ideas
in SETI, OSETI, etc.).

Major Consequence:
 You can *Never* read Encyclopedia Galactica if it transmitted
 via electromagnetic radiation.

Now, I've thought a bit more about this since I first let my fingers fly
and you may be able to get a bit closer using wavelength division
multiplexing at light and UV frequencies but I'm doubtful it will
solve the problem entirely.

The only way you transmit information around the galaxy is as high
density "matter" packets.

> (There is a possible answer to that, of course; you send out an SI seed
> blueprint in a form that a low-tech civilisation could intercept and use.
> Very dodgy in many ways, though: Is there life out there to receive it?
> Who's going to receive it; low tech friend or scary higher tech SI gobbling
> foe? etc etc)

I've addressed this in previous discussions. You never send stuff out
to regions beyond your "light horizon" because you can't guarantee
what will be there when it gets there. The implication of this is
that any colonization or forking off children is likely to be only "local".

> So it seems that sending modulated EM is not useful, except as follow up
> signals to an initial spread of spores. Except that Robert tells us it is
> too wasteful.

I think you can transmit small stuff like a nanobot design (you do have
GHz data rates) but you *do not* transmit significant fractions of your
knowledge base. If you want high-bandwidth communication you are going
to be hurling asteroid sized "data packets" back and forth. They are
probably quite "pretty" packets as Mike's recent picture showed.

> My second point is, given that you've already got matter out there in some
> form, you've had time to put a bunch of relay stations *out there*, ready to
> relay your signal. A big long (long!) line of them could take a signal from
> one star to the next, without anywhere near the losses or a super death ray,
> could it not?

Yep, the interstellar pony express does seem feasible except when they
have to ride through Amara's clouds of dust. The ablation in those
probably makes them take the long way around.

> What they are powered with is an interesting problem (the energy they receive?),

You want to recover as much as possible. Magnetic braking of the incoming
data packets should get you back most of the launch energy and you simply
recycle the matter for outgoing packets (or perhaps you have clever ways to
do the readout nondestructively, then simply do any necessary rewriting
flipped bits and send the packet on to the next station).

> which should overall use less energy in communicating at (damned near) C

Nope, as the JBIS Project Deadalus study and others that Spike and I have been
bouncing back and forth as your velocity increases so too does your ablation
by the interstellar hydrogen ions. There is a very clear tradeoff between
how fast you want the information and how much of your information carrier
is left when it arrives. [I suppose that one could argue that you
can simply extract matter from your star and use it for the packets
but that is draining your gas tank to talk on the telephone.]

> My third point (I've a disordered mind) is that the cost of EM
> communication might be high, but the speed may justify the cost.

Yes, I agree of course. The question is what information is so valuable
that the communication justifies the expense?
  Transmission: "Hey my sun just went nova!!!"
  Reply: "Really, we predicted that 3 million years ago..."

> Information is important to us; maybe it'll be important to giant
> spaceborn brains? Timelines often makes the difference between
> information and noise. Waiting for your sub-c message-in-a-bottle
> may not be an option, if others are communicating at light speed.

If you want to communicate large volumes of information you only do
it with EMR if you are in *very* close proximity (sub-lt yr distances).

You can use IR (or radio) to transmit through the dust clouds that
your information transport packets can't go through but the data
rate is going to be pretty darn low.

I think this may resolve the Fermi Paradox -- SIs only fork off
children when they get *very* close to something (solar system,
brown dwarf, etc. that can be rapidly turned into something
that can "hold" a download of >10^40 bits. You have to be
close enough to it so that you can align billions of lasers and
receiving antennas such that you don't waste the energy involved in
the information transmission and can get the foundation data for
the child across the void while you are still in close proximity.

This doesn't happen very often because stars don't get that
close that often and navigating an MBrain into close proximity
requires the expenditure of a lot of energy and possibly mass
and takes a very long time (millions of years minimally).

Now, this would "predict" that the center regions of galaxies
should grow dark more rapidly than the outer regions of galaxies
(more close enounters providing more forking opportunities).
I don't believe we are observing that. Perhaps SIs close to
the centers of galaxies have more to worry about like how
to minimize the cost of staying out of the black hole over
the very long term. They can't afford to worry about offspring,
in large part because they are more concerned about their long
term survival. Now *this* gets very interesting because it implies
one possible path civilizations might follow is "star hopping"
*away* from the center of the galaxy. You don't "fork" at all --
you transfer yourself en-mass to stars that are "outward" bound.
I'm pretty sure that I wouldn't want to be on the MBrain Titanic
as it gets sucked into oblivion. Now, this *would* explain
why there seems to be more "dark matter" in the outer regions
of the galaxies -- those are the neighborhoods where one
can expect to survive the longest. Long term, you are looking
for a travel path that minimizes getting sucked into a black
hole or colliding with another star and allows you the greatest
opportunities to pick up elements that are in short supply
(and possibly allows forking opportunities) until you can make
it to the "safe" region of intergalactic space.

In case this isn't clear, the implication (if this is correct)
is that advanced civilizations do *not* expand at a velocity
remotely approaching 'c'. They expand at the rate at which they
can arrange convenient (read inexpensive(?)) interstellar 'forking'
opportunities. Those probably only occur once in a blue moon.


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