
Relax, it'll be 1,500 years before aliens contact us - dnetesn
http://phys.org/news/2016-06-itll-years-aliens-contact.html
======
stcredzero
I think it's ridiculous for us to look for alien _civilizations_. Why would
any intelligent person think that civilizations are stable? I mean, would you
really think such a system is stable: Billions of independent sentient planet-
polluting evolving biological machines with their own goals continually
rewriting their own software (culture) and exponentially increasing their
capabilities and rates of change? That has _Chaos_ written all over it.

Whatever prospers and lasts in the universe as we know it isn't going to be
anything like a _civilization._ It's certainly going to be nothing like our
civilization. In fact, if there is a galactic meta-"society" of some sort,
then one should think they'd disdain a chaotic exponentially-expanding
_civilization_ in much the same was as we'd individually view an incontinent,
incoherent, and violent member of our own species.

The fact that we'd expect other civilizations out there is just evidence of
our own parochial bias. The stark truth of the Fermi Paradox is that
civilizations as we conceive of them simply don't last very long -- which also
matches everything we as a civilization have come to know about systems that
resemble our civilization. If "we" are going to last, "we" will have become
something hard to comprehend and hard to accept by our present day selves.

[https://xkcd.com/638/](https://xkcd.com/638/)

[https://xkcd.com/1377/](https://xkcd.com/1377/)

~~~
erikpukinskis
I suspect you come from a culture that portrays itself as disconnected from
nature. You think of civilization as a kind of nihilistic growth machine that
is totally devoid of meaning. That makes sense. I see a lot of that when I
look at the world too.

But not every civilization is like that. There is a form of civilization which
exists in deference to nature. There is a form of enlightenment which doesn't
worship blind reproduction, but instead worships harmony with nature. It sees
our role as humans not as an all-conquering virus, but as gardeners, shepherds
of life. Not über-wolves, but über-trees. Some people call this "permaculture"
but it has lots of other names, and has existed for millennia.

I think the culmination of human civilization is to reach a kind of pinnacle
of progressive efficiency, combined with an almost regressive reverence for
the past and our bodies and the ecologies which sustain them. I suspect other
alien life may also be similarly inclined.

And this notion you have that planet pollution is the only way to exist is
very sad. It's no better than climate denial. It's arguably more destructive,
because you are suckering in smart people who would otherwise balk at
denialists. I would urge you to spend some time learning about ways of living
which nurture ecologies. There many such traditions, spanning every biome.

~~~
stcredzero
_You think of civilization as a kind of nihilistic growth machine that is
totally devoid of meaning._

Oh, ho! Look who's showing up, projecting some biases! Excuse me, but would
you please point out where I said that we were nihilistic or devoid of
meaning? Please provide a quote. Well, you can't, because I didn't. I was
implying that our current civilization is obnoxious, not nihilist. There are
many children who are obnoxious, but I wouldn't say they are without meaning,
beauty or potential. A child can have all of those and still be annoying as
frack.

 _progressive efficiency, combined with an almost regressive reverence for the
past_

You can eliminate the "almost" from that.

 _And this notion you have that planet pollution is the only way to exist is
very sad._

I never said it was the only way. More projection? Again, my point is that in
a galactic context, there are good arguments for why 21st century human
civilization might come across as a chav.

~~~
erikpukinskis
I said "I suspect" to leave open the possibility I was wrong, which appears to
be the case. I could've been clearer about that (my punctuation is ambiguous,
and "suspect" was not ambivalent enough). I regret not phrasing it as a
straight question.

I would still be interested to know how your position differs from mine and
from my (poor) characterization of you, if you have the time.

------
WJW
I'm always amazed by people thinking it is possible for distant civilizations
to pick up random radio signals (typically television broadcasts) that were
transmitted on earth.

Any signals spreading out in space already has to deal with an inverse square
law due to the wavefront being spread out. However, the amount of noise stays
roughly the same all over the universe (as near as we can tell). This means
that "pretty soon" (depending on the original broadcast power) the signal will
be orders of magnitude weaker the the noise level in any receiver.

There are some techniques to pull up a signal from under the noise floor, eg
using matched filters and the like. This is how GPS works. However, can only
be done if you already know the signal that you are looking for. For GPS, this
is not really a problem since it is well known what signal any given satellite
will transmit at any given time. However, with TV shows (or any similarly
information dense signal), the signal content is by definition not known
already to another civilization.

This is not even going into the fact that high-information signals can be
pretty indistinguishable from noise anyway if you don't know the exact
modulation type and parameters used.

Pretty much the only way aliens will be able to enjoy our television
broadcasts is if they come close enough to visit the solar system anyway, and
by then they might as well land and look at cable TV...

(For more information, take a look at
[http://www.bidstrup.com/seti.htm](http://www.bidstrup.com/seti.htm) or
similar)

~~~
knodi123
Can we rough out a modified fermi paradox equation that substitutes values for
as many constants as possible, and takes into account the issue with the
inverse square law vs background noise?

Also, can't you distinguish a lot of signal away from noise using parallax and
paired telescopes?

------
jerf
"Combining the equations for the Fermi paradox and the mediocrity principle,
the authors suggests Earth might hear from an alien civilization when
approximately half of the Milky Way Galaxy has been signaled in about 1,500
years."

Not sure where the paper is, but the Milky Way galaxy is much bigger than
that. The Milky Way is expected to be from 100,000 to 120,000 light years in
diameter. A ~3200ly diameter sphere isn't "half" that.

~~~
drjesusphd
Yeah, the timescale for the Fermi Paradox is millions of years; it'd be a hard
sell that 1500 years can make a dent in it.

~~~
pmiller2
Wikipedia claims that the entire galaxy can be traversed in ~1M years. Life on
earth has been around for ~3.8G years. If life started somewhere in the galaxy
a few million years earlier than that, and evolved into a spacefaring
civilization, it's not too far fetched that they could either have already
been here, or, if they are close enough, they could pick up our signals and
come for a look-see.

~~~
jerf
A while back on HN there was a discussion about whether shooting radio waves
into space was a good idea, because the game theoretic solution to "why are we
alone" might be that extraterrestrial civilizations pre-emptively destroy any
other competition they can identify.

What finally made me reject this hypothesis is that A: you shouldn't actually
wait for intelligent life to develop, because even if humans are somehow
progressing at the fastest possible rate and nothing could be faster, a claim
I would seriously doubt, we're still developing at this rate dangerously
quickly and B: Earth has been broadcasting "I very likely have life!" for not
a century since the invention of radio, but approximately 2.3 billion years,
since the invention of atmospheric oxygen, which is something that should be
possible to determine from great distances by looking at the spectra lines
when Earth occludes the Sun. We're already doing that a bit ourselves, and our
telescopes are _tiny_ compared to what a full Kardashev-1 civilization could
put together, or even what _we_ could put together if this was our top
priority.

Even on the cosmic scale, 2.3 billion years is a Real Amount of Time.

Unless nearly every solar system has life of a similar degree of obviousness
from light-years away, making Earth's signal just noise, we've been
broadcasting that we're at least worth a probe for a long time. I doubt every
solar system has free-oxygen-generating life or any equivalent; you don't have
to believe the "Rare Earth" arguments prove that Earth is alone for it to show
that even with our current understanding of physics, chemistry, etc. it is
very unlikely that every, or even a majority, of systems have advanced life in
them. Given that the limits of technology that we now believe in strongly
suggest that an unopposed "probe" is probably on its own sufficient to
colonize a planet (and thus render it no longer a threat), it remains very
strange that we're here at all, not long since displaced by an aliens.

In a weird way, it would almost make more sense from the Fermi paradox point
of view if we obviously _hadn 't_ developed here and if humans were obviously
aliens-to-Earth, but humans have an immaculate pedigree for being 100% all-
natural Earth-sourced ingredients.

------
chmike
It's apparently easy to get an article published that say that aliens are all
dead, minuscule or not close to reach earth. No one managed to get an article
published that say that aliens have been visiting earth for many years with
UFOs. There seam to be a very strong bias in peer review on this topic.

~~~
drjesusphd
Yes, because scientists tend to be fond of evidence.

~~~
dleslie
As it goes, absence of evidence is not evidence of absence.

I have never in my life seen a mountain gorilla. I am aware of evidence that
shows that they exist, but at my age my grand parents did not have access to
that same evidence; does that mean that mountain gorillas came into existence
when the evidence was found? Almost certainly not, heh, but they would have
been valid in disbelieving in the existence of such beasts.

There could be a person behind me with a knife, poised to slay me; but I am
fairly confident that this is not the case due to a number of factors. On a
population scale, such incidents are vanishingly few, and I took precautions
earlier today to ensure that my home was locked and secured; but that does not
guarantee certainty of my safety. It would be a fallacy, perhaps post hoc ergo
propter hoc, for me to believe in the certainty that there is no such
individual behind me. Until I turn around and observe the empty space, I
cannot lay claim to the existence or non-existence of that individual.

We cannot observe all of Earth all of the time, and we cannot do so for the
Solar system, or lay claim to having done so throughout history. This does not
mean that aliens have visited us, or that they even exist; it means that we
cannot be certain that they don't exist and that they haven't visited.

~~~
mikeash
That saying is nonsense. Absence of evidence _is_ evidence of absence, with a
strength that's determined by how likely it is that you should find evidence
given what you've looked for.

Taking your mountain gorilla example, do you have any in your house? I'm
guessing you'll say "no." Well, how do you know that? Absence of evidence is
not evidence of absence, after all. Yet if you look all over your house and
don't see any, I'd guess you would accept that as sufficient reason to say
that there aren't any in your house. But how can you say that if it's not
evidence of absence?

Now, finding no mountain gorillas in your house is very poor evidence for the
absence of mountain gorillas on _Earth_ , because you'd expect the same
results whether or not they existed on Earth in general. On the other hand, if
you've performed a thorough survey of their actual supposed habitat and didn't
find any (maybe because they were driven to extinction) then you'd have pretty
good (but not perfect!) evidence that they aren't there anymore.

There's essentially no evidence for the absence of aliens in the universe.
You'll see this reflected in the opinion of the experts; many, perhaps most,
say that it's likely aliens are out there somewhere. There's decent evidence
for the absence of aliens around Earth, since we see nothing and we'd expect
to see something, but it's possible they're undetectable. There's great
evidence for the absence of classical UFOs, since they're clearly things we'd
expect to see if they were real (people keep saying they saw them!) but out of
all these sightings, none of them have turned out to be anything remarkable at
all.

~~~
ewzimm
Most of what you're saying is right, but the saying isn't nonsense. It's just
describing the problem that comes up when you can't find evidence of
something. If its presence would necessarily present evidence, as with the
gorilla (unless it's a mutant ninja gorilla), then it's evidence of absence.
If its presence would not necessarily present any detectable evidence, then
it's absence of evidence, meaning that you haven't really learned anything.
With something like aliens, we don't actually know what evidence to look for,
so as you're saying, there's no evidence of absence yet, only absence of
evidence.

~~~
mikeash
It is nonsense, because the saying is absolute. It doesn't say "absence of
evidence is not necessarily evidence of absence." In reality, evidence of
absence sometimes is and sometimes isn't evidence of absence, it depends on
the specifics. The fact that the saying is correct for some cases doesn't make
it sensible, any more than saying "birds don't fly" is sensible because of
penguins and ostriches.

~~~
ewzimm
It's just a cute aphorism that describes one of the main challenges in
science. The "is not" is meant to convey that there are two distinct
conclusions that we can make from seeing a lack of something and that it's
important not to make the wrong choice while evaluating the situation. We
can't automatically say "absence of evidence" or "evidence of absence" as it
suits our preconceptions but need to look deeper into why something is
missing.

~~~
mikeash
Well, every single time I've seen someone use that phrase, it hasn't been to
point out that they're not equivalent, it's been to argue for the potential
existence of something where there's zero evidence for it and lots of
searching you'd expect to turn up evidence.

Case in point here, we are not discussing aliens in general, where that phrase
might be sensible, but rather aliens frequently visiting Earth over a period
of years in the form of UFOs.

~~~
ewzimm
It can absolutely be abused, but that really just proves the point of the
statement, that people tend to make biased and wrong decisions when they don't
apply thorough logic. For clarity, it could have been "absence of evidence is
not sufficient evidence of absence," but it just doesn't sound as nice. But it
in that form and how it's intended by logicians, it's perfectly valid.

~~~
mikeash
My point is that it is never anything _but_ abused. Does a statement really
have a point that's independent from how people use it? Especially when that
use agrees with the statement's literal meaning?

~~~
ewzimm
This seems like a case where something completely legitimate got so abused
that it lost its meaning to many people. It does have a point. It's a classic
phrase used in teaching logic to rebut the logical fallacy of an argument from
ignorance. I think what you've seen is a lot of people using the authority of
something from formal logic to back up their own fallacious arguments.

"The phrase "the absence of evidence is not the evidence of absence" can be
used as a shorthand rebuttal to the second form of the ignorance fallacy (i.e.
P has never been absolutely proven and is therefore certainly false). Most
often it is directed at any conclusion derived from null results in an
experiment or from the non-detection of something. In other words, where one
researcher may say their experiment suggests evidence of absence, another
researcher might argue that the experiment failed to detect a phenomenon for
other reasons."

[https://en.m.wikipedia.org/wiki/Argument_from_ignorance](https://en.m.wikipedia.org/wiki/Argument_from_ignorance)

------
libeclipse
"We are on the third planet around a tediously boring star surrounded by other
completely normal stars about two-thirds of the way along one of several arms
of a remarkably average spiral galaxy."

