On 5/26/2020 10:51 PM, Jason Resch wrote:
On Tue, May 26, 2020 at 11:16 PM 'Brent Meeker' via Everything List
<everything-list@googlegroups.com
<mailto:everything-list@googlegroups.com>> wrote:
On 5/26/2020 3:33 PM, Jason Resch wrote:
On Wed, May 20, 2020 at 5:14 PM 'Brent Meeker' via Everything
List <everything-list@googlegroups.com
<mailto:everything-list@googlegroups.com>> wrote:
On 5/20/2020 6:39 AM, Bruno Marchal wrote:
> Hi Jason,
>
> When you say that Reality is infinite, are you alluding to the
> (phenomenological) physical reality? Or the absolute reality?
>
> With mechanism, it is very plausible that the physical
reality is
> infinite, as it is a sort of broder of the universal mind
(the mind of
> the “virgin” universal machine).
>
> But even with an infinite physical reality, it is unclear
if we are
> alone or not, in the physical reality. We are numerous in the
> arithmetical reality (which can be taken as the absolute
one, modulo a
> change of universal machinery). But to have alien fellows
in the
> physical reality, you need some homogeneity in that
reality, which is
> not obvious at first sight.
>
> In fact, I get the impression that we might be rare, if not
alone. The
> probability for life might be as close to zero as von
Neumann thought,
> but even the possibility of its evolution requires many
conditions, so
> many that we might be alone in the cosmos (not in the
multiverse, as
> there we have even doppelangers).
I think the evidence suggests that there is a lot of life in
the visible
universe and even a lot of technological civilizations...but
they are so
sparse that we are effectively alone.
Hi Brent,
As promised I've just finished writing about the existence of
life and intelligent life in the universe. I'd appreciate your
thoughts.
Though life could be very rare I describe another possibility,
which is that it miniaturizes and becomes so unlike and alient to
the biological life we're familiar with and looking for that we
don't notice it.
But we do know that even the most microscopic "life", even viruses
grow and reproduce using the same mechanism at the molecular level
as we do: DNA, RNA, mRNA, proteins, ATP=>ADp,... That's really
the basis for thinking that all life on Earth had a single
origin. Even archea and bacteria use the same metabolic pathways.
I agree life will likely start in more or less recognizable ways, but
I believe that after a few thousand or million years of being a
technological civilization, it will reach stages that are
unrecognizable to us. They will most likely be non-biological, and
non-corporeal, living in virtual realities. Computers are substrate
independent and can take many different forms. Moreover they can be
arbitrarily efficient so long as they are logically reversible. There
need not be any significant heat signature.
That's why I said you needed to say what your definition of "life" was
at the beginning. Computers can't be logically reversible and still act
within the universe...so most people would say that can't be life. I'm
not sure a computer can even have thoughts if exists only in a
reversible superposition of states.
https://alwaysasking.com/are-we-alone/
Not just matter, energy, and time. Life needs an entropy
gradient. Your whole section on "Energy" reads as though energy
is consumed. But energy is conserved.
Good point. I meant energy in the colloquial sense (energy
available for useful work). Is there a another word I could use for
this concept that isn't as technical/scary sounding as entropy gradient?
It is low entropy (mostly of sunlight) that is "consumed" by
turning it into higher entropy infrared radiation. The best
theories of the origin of life postulate alkaline vents as the
locus (which are not so hot as hydrothermal vents). Have you read
Nick Lane's "The Vital Question"?
I haven't. Thanks for the suggestions, I will have to read more about
alkaline vents.
I think you make a mistake in jumping right into "what life
needs". You should first define what you mean by life. Life as
we know it: carbon, hydrogen based? Anything that reproduces.
Anything that metabolizes?...what?
You're right, that is an oversight. I will add a definition. Something
like: self-maintaining processes that convey information across
generations.
It took a billion to two billion years for/*eukaryotes*/ to
evolve...not multicellular life. Multicellular life only arose
0.6 billion ya.
Thank you, I will correct this.
Tardigrades are not going to survive on the Moon...that's
fantasy. They don't eat rocks. Surface temperature on the Moon
near the equator varies from -183 degC to +106degC. And there's no
protection from occassional cosmic ray showers. Tardigrades might
survive hours or weeks, but they are not going to survive as a
species on the Moon.
The Tardigrades were in their tun state where they wrap up their genes
to protect them from radiation and reduce their metabolism by orders
of magnitude. I agree they would not thrive and reproduce on the moon,
but they may exist for perhaps a year (maybe longer?), at least if
some landed in an indentation in the soil where they were shielded
from direct sunlight) and remain revivable. Some recovered tardigrades
in the antarctic were revived after 30 years. I don't know the lower
temperatures on the moon would extend or shorten that time frame.
The Drake equation rewritten in terms of "detectable"
civilizations is wrong because it only considers sending out
signals. To be detectable there has to be a receiver in the
forward light cone. Assuming technologically advanced
civilizations last 500yrs that means two of them have to be
withing detection range during that 500yr band. I'm not sure what
the detection range is within a noisy galaxy but I think it's less
than 100lyr. One problem is that as communication becomes more
technologically advance it becomes less distinguishable from noise.
That's true bout going silent with new technologies, and I mention
that. I would say that the Drake Equation is in terms of "detectable
in principle" rather than "detectable in practice". Detecting unaimed
broadcasts from across the galaxy might require planet-sized detection
dishes. But regardless of whether or not two-way communication is
possible, the equation is based on a constant star creation rate.
Assuming that constant rate applies, then even if civilizations
appear, broadcast for 500 years, then wipe themselves out, the total
number of presently detectable (in principle) civilizations should be
approximated by the equation.
That's very well if you're just aiming to convince people that there are
a lot of civilizations out there in spacetime. But it's useless in
answering Fermi's question. The answer to that question depends on us
being a civilization capable of hearing another one as well as there
being another one near enough in space and time.
"the Arecibo Telescope on the receiving end could pick up the
signal from a distance of tens of thousand of light years–on the
other side of the galaxy."
The other side of the galaxy is a /*hundred*/ thousand light years
away.
But we're about midway to the center. Even if they were as far apart
as possible, the farthest they could be from us and still be in the
galaxy is 70K ly. Perhaps I should say across, rather than on the
other side to be more clear.
"The vast distances implied by being the only intelligence in the
observable universe would, for all practical purposes, mean we are
alone, even if infinite other intelligences exist across our
infinite universe."
I think this is the important take-home point. And it doesn't
have much to do with the observable universe and how many planets
may have life. Even the closest stars are already too far away
for us to not be alone. We might conceivably send a probe to
alpha centauri. We might talk to a technological civilization 50
light years away...but that would be about the limit, 100year
send/reply cycle.
For our present state of technology, and biology, where we live as
bags of meat with 100-year lifespans, those distances are
inaccessible. But for a civilization that uploads their minds into
starchip-like computer chips, effectively copying their entire
civilization and storing them on each von Neumann probes as it
replicates and spreads, they could build a civilization that spans the
galaxy, and is present in every solar system (assuming they had the
will to).
No doubt intelligence is evolutionarily useful...but human level
intelligence, speech, mathematics, technology? It's not so
clear. In fact it may be the kiss of death. You used 500yr as
the life time of a technological civilization...do you think we'll
make another 400yrs?
I think if we can survive the next century, we can last another
million years. But I hold that optimism only because I see
super-intelligence arising in that time, which could intervene to
relieve us from making suicidal missteps.
More to the point, it will replace us completely. But then who knows
what values will motivate it? It may just sit and live in Platonia.
I think you miss one possibility at the other extreme. Maybe there
are aliens that are so big we don't notice them. There was a
scifi story, I believe by the Strugatsky brothers, in which aliens
visit Earth but they are vaporous thin structures of gases and
stand many kilometers tall. They are almost completely
transparent so they are not even noticed at first. And they never
give any sign of noticing us despite attempts to get their
attention. Eventually they just leave as mysteriously as they came.
That sounds like a great story. I'll see if I can find it. Is it
Roadside Picnic? ( https://en.wikipedia.org/wiki/Roadside_Picnic ) It
reminds me a bit of this episode:
https://www.youtube.com/watch?v=3oO3tUVLpIM
No. I think it was well before "Roadside Picnic" and it was short
story...only a few pages as I recall. But Stanislaw Lem has also
written a couple of stories about the radical impossibility of
communicating with aliens, simply because they are so alien.
Brent
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