[ExI] SETI for Post Singularity Civs

[John Clark]

On Thu, Jan 22, 2015 at 12:00 AM, Stuart LaForge <avant at sollegro.com> wrote:

>
> >> Having the entire energy output of 100 billion stars radiate uselessly
>> into infinite space is very thermodynamically inefficient indeed, and yet
>> that
>> is exactly what we observe.
>>
>
> > Not so. We can't *observe* 100 billion stars in our galaxy; not even
> with the HST. We can infer their existence and estimate their numbers using
> statistical methods but we can only *see* maybe a billion at best.
>

And we can also infer how much power all the stars in our Galaxy are
pumping out, and we can observe that by far most of that power is in the
form of low entropy visible light, ultraviolet, and X rays. If ET was
getting work out of the stars (such as in Dyson Spheres) it would have to
convert the low entropy electromagnetic wave to high entropy ones such as
infrared and radio waves, but that's not what we see.


> > Most of the stars in the Milky Way are not visible to us because they
> are dim due to being on the other side of the galactic disk


No, most stars look dim because they ARE dim. Almost all the stars you can
see with your naked eye are more brilliant than the sun even though the sun
is larger than the average star.  The most common type of stars are K and M
class red dwarfs, but they're also the dimmest so not a single one can be
seen with the naked eye. The reason for this is that a star's brilliance is
proportional to the cube of the star's mass, so the rare stars that are
larger than the sun vastly outshine all the far more numerous smaller stars
put together.

>>   "If ET had sent just one single Von Neumann Probe to a nearby star at
>> a speed no faster than what our spacecraft can travel at today then a Von
>> Neumann Probe could be sent to every star in thegalaxy in just 50 million
>> years, a blink of a eye cosmically speaking."
>>
>
> > I am not altogether certain that ET would want to launch a fire and
> forget probe to virally copy himself across the cosmos.


ET may or may not want to make copies of himself but we were talking about
thermodynamic efficiency and the cost of building a Von Neumann probe would
be trivial for an advanced civilization. It would be like one of us
purchasing a candy bar. The cost of launching such a probe to the nearest
star at 25,000 miles an hour, something we can do today, would cost even
less. If somebody did that just once then in just 50 million years, a tiny
fraction of the life of the universe, the Galaxy would look vastly
different from what it looks like today  and ET could harvest astronomical
(and I mean that word literally) amounts of energy. Your explanation of why
we don't see that engineered Galaxy is that out of the billions of
individuals in millions of civilizations no one, absolutely no one,
bothered to buy that candy bar.

Be honest now, does this excuse put forward to explain away the lack of
large scale engineering really strike you as credible? If you knew for a
fact that ET existed but had never seen the night sky is this really what
you would predict the sky would look like?  I don't see an elephant in my
living room so I can reasonably conclude there is not an elephant in my
living room. Sometimes a absence of evidence is evidence of absence.

>>  And if that had happened a blind man in a fog bank could detect ET. But
>> we don't see the slightest hint of ET despite having looked for him with our
>> largest telescoped for over half a century. So where is everybody?"
>>
>
> > Come now. Half a century is a laughably small light cone to base any
> sort of conclusion


I think half a century is plenty of time, in fact I think you could start
making tentative conclusions after half a minute.

> Assuming ET would want to blot out stars, instead of harnessing black
> holes,
>

The amount of energy you could get out of rotating black holes would be
trivial compared with the energy of the stars, especially the big bright
stars, and you're the one who said ET would be worrying about thermodynamic
efficiency, and yet it's letting all that energy radiate into infinite
space.

> dark energy, or other exotic energy sources


If ET has found a way to get work out of dark energy then it knows of some
fundamental laws of physics that we do not, that is always a possibility
but conjuring up new laws of physics to explain why things look as they do
should be the last resort not the first; and in this case there is a
explanation that needs no new physics that can explain why the night sky
looks uninhabited very nicely, namely that it IS uninhabited because we are
the first, after all somebody had to be.

  John K Clark
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