
There Probably Have Been Aliens - kposehn
https://mobile.nytimes.com/2016/06/12/opinion/sunday/yes-there-have-been-aliens.html?WT.mc_id=2016-KWP-MOBILE-AUD_DEV&WT.mc_ev=click&ad-keywords=MOBILEFULLPAGE&kwp_0=298359&kwp_4=1145468&kwp_1=525833&_r=0&referer=
======
jawns
> Specifically, unless the probability for evolving a civilization on a
> habitable-zone planet is less than one in 10 billion trillion, then we are
> not the first.

1 in 10 billion trillion at first seems like such an incomprehensibly low
probability that our first gut reaction is, "Well then of course there's no
way it could be the case."

But then we must bear in mind that abiogenesis (the creation of life from non-
life) might consist of a series of independent events, each of which is
improbable. And guess how you figure out the probability of all of those
events occurring:

P(A and B) = P(A) * P(B)

So, what's 1 in 10 billion trillion? 10^-22?

Well, if you have a mere eight improbable things that must all occur, and each
has a probability of 1 in 1,000, the total probability is now at 10^-24.

Hmm, 10^-22 doesn't seem quite as incomprehensibly low anymore, does it?

Aside from that, we really have to think hard about what probability means in
the context of the snippet quoted above.

As statistician to the stars William M. Briggs points out, "There just is no
such thing as unconditional probability, or probability without respect to any
evidence."

Because we have insufficient evidence to establish what the frequency of
abiogenesis is, the quoted snippet basically could be rephrased:

For all we know, the probability of evolving a civilization on a habitable-
zone planet could be 10^-22 or 10^-222 or 10^-2222, and if it's less than
10^-22 then we are not the first.

Isn't it strange that in a certain sense, the probability of each of those
probabilities being correct is essentially the same, given our current
insufficient level of evidence?

~~~
neaden
One good example is that as far as we can tell multi-cellular life only
evolved on Earth once. And while life started up on Earth pretty quickly it
took about 600 million years for that life to become multicelluar. It's
possible that we'll someday discover life is relatively common but never meet
anything but amoebas.

~~~
cmrdporcupine
Totally. Not only did multicellular life only evolve once, but eukaryotes
themselves seem to have evolved only once. And they are 1000x more complex
than their prokaryote predecessors. [edit: without any real evidence of
anything convincingly between prokaryote and eukaryote]

It's one thing to say there might have been abiogenesis elsewhere that created
something like the simple self-reproducing energy machines that bacteria and
archaea are. It's another to claim that there is some inevitable progression
from that to complex multicellular life. In my opinion this is a very
teleological, very 'progressivist' notion of evolution that implies that one
inevitably follows from another, and it is not borne out in the reality of
what we know so far about happened on earth and what follows from first
principles.

There may be a lot of complex, self-reproducing systems in the universe. It's
arrogant to assume that any of them have to look anything like what we call
"life" unless by life we mean the simplest single cell organisms. [edit: In
fact it looks like simple prokaryotes evolved _twice_ on earth a "short"
distance in time apart].

~~~
Retric
Multi cellular life has evolved several times. There are several distinct
cases of single called organisms promoting conditions which aid others of it's
species. Causing a colony to form, and then spawn new colonies.

Now, highly complex multicellular life seems to share common descent. But that
likely has more to do with predation than anything else. Further single called
organisms preform horizontal gene transfer to both other single called life
and multicellular life, making things impossible to trace back.

------
dtparr
Am I reading this wrong, or is it basically just making a restatement of the
Drake equation with updated numbers in place? [Edit: and ignoring some terms
to allow for time irrelevance]. I was hoping for something addressing the
Fermi paradox or something more than just a refined probabilistic estimate
with such a definitive title.

~~~
eponeponepon
No, that's exactly it. Those numbers will just keep on getting more precise as
time goes on, though - we'll never know from the Drake equation alone, but
it's the best guideline we have right now.

~~~
dtparr
I suppose, but having more precise terms in the first half doesn't seem to
really do much for us given that the terms dealing with the probability of
life forming can't even really be estimated. This article is basically saying
"surely it's more than 1 in 10^22", but I don't see any hint of why that would
be, other than 'it's such a small chance that it had to be written in
italics'.

~~~
ghaff
Right. What's happened with the Drake Equation is that the terms related to
possibly habitable planets have largely moved to the "almost certainly lots"
realm.

But, as you say, with respect to life (or at least complex multi-cellular
life), we just don't know. But the Drake Equation encourages thinking like,
even it's it's a 1 in a trillion chance _effectively zero!_ , we'd have all
these aliens running around. Because 1 in a trillion = 0 is pretty much what
we're informed by day-to-day usage and intuition.

~~~
JumpCrisscross
> _Because 1 in a trillion = 0 is pretty much what we 're informed by day-to-
> day usage and intuition_

Avogadro's constant is 6.022 x 10^23 [1]. There are a hundred billion sets of
a trillion constituent particles in ever mol of anything. A reaction that
happens to water once in a trillion years would occur 20,000 times a second
for each 18 mL of water.

[1]
[https://en.m.wikipedia.org/wiki/Avogadro_constant](https://en.m.wikipedia.org/wiki/Avogadro_constant)

~~~
ghaff
You're being an engineer :-) Yes, I am aware of those things but those sorts
of numbers do not correspond to day-to-day usage and intuition of most people
(as I said).

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neaden
I'm kind of tired of these sorts of calculations that essentially boil down to
"The universe is big and old". The idea that maybe millions of years ago
another civilization existed in another galaxy just doesn't seem that
important. And while actually encountering an alien species, especially a
technology using one, would have a huge impact on our culture, philosophy, and
religion one existing in theory doesn't. If you think the only reason that
humans exist is because God created us then it doesn't matter how many stars
are out there because the probability of life evolving on any of them is 0.

~~~
ewzimm
There's the possibility that God created life on Earth but it has evolved
naturally elsewhere through the same processes by which our created version of
life mutates. I haven't seen this argument much, but I could imagine it
becoming more popular with the discovery of alien life. This is just a report
on our most recent astronomical data, but the existence in life in theory
could have a large effect on how much effort we put into searching for it.

~~~
jessaustin
If one must attempt to salvage the idea of divine creation in such desultory
fashion, why not assume that the aliens are the intentional created creatures
of the divine, and _we_ are just the random evolutionary accidents?

~~~
danbruc
That seems as weird as the other way round. Wouldn't it be the simplest
explanation to just say God created life on various planets but didn't tell
anyone about each other?

~~~
jessaustin
Haha I wasn't seriously advocating such a bizarre aition. Rather I was
encouraging a reconsideration of parent's proposal, which as you say is "as
weird". Perhaps my encouragement was too obliquely ironical, as is often the
case.

~~~
gknoy
Today I learned that "aition" was not merely a typo, but rather a new (to me)
word! (cool!)

Aition: a tale devised to explain the origin of a religious observance

------
SeanDav
We can use similar logic to "prove" that in fact we are just living in a
computer simulation.

[https://www.scientificamerican.com/article/are-we-living-
in-...](https://www.scientificamerican.com/article/are-we-living-in-a-
computer-simulation/)

[http://www.bbc.co.uk/earth/story/20160901-we-might-live-
in-a...](http://www.bbc.co.uk/earth/story/20160901-we-might-live-in-a-
computer-program-but-it-may-not-matter)

------
pklausler
One of the (to me) most mind-bending arguments about the absence of alien
civilizations is the apparent absence of self-replicating interstellar probes.
It wouldn't take much more of a tech civilization than we have to launch such
a thing, and it would take only one launch event in all of galactic history to
quickly and permanently permeate the galaxy with them. So where are they?

~~~
neaden
Yeah, Bracewell/Von Neuman probes[0]. You create an AI in a probe that can
communicate in a variety of ways and replicate itself and send it off into
space. IIRC it would conservatively take about a million years for a
civilization to blanket the galaxy in them.

[0][https://en.wikipedia.org/wiki/Bracewell_probe](https://en.wikipedia.org/wiki/Bracewell_probe)

~~~
pklausler
Communication seems to be optional.

~~~
jessaustin
It isn't obvious that communication by such "probes" would take place on a
medium that we can currently sense. Which may be what you meant?

------
drewblaisdell
Something has always confused me about the Drake equation.

The explanation I have heard repeatedly goes something like:

"This equation shows that there should be [massive number] of alien
civilizations in the universe. But where are they?"

This seems to assume that, given the density of civilizations throughout the
galaxy we can determine from [massive number], we should be able to observe
other advanced civilizations. But is that true? If there was a civilization as
advanced as we are somewhere in e.g. Alpha Centauri, would we be able to
detect them?

~~~
jaymzcampbell
You are describing the Fermi Paradox:
[https://en.wikipedia.org/wiki/Fermi_paradox](https://en.wikipedia.org/wiki/Fermi_paradox)
\- there is a lot of interesting reading on that Wiki page.

The usual response I think is that the timescales and distances involved are
simply still too big / spread out that we're still searching for the
metaphorical needle in the haystack.

~~~
eponeponepon
It's also perfectly conceivable that we do just happen to be the first.
Looking less likely with every advance in astronomy, but still possible
nonetheless.

------
oconnor663
> we now have enough information to conclude that they almost certainly
> existed at some point in cosmic history

Is there a term in the Drake Equation for our level of certainty that the
Drake Equation isn't missing some terms?

~~~
tlb
One other proposed factor: the laws of physics may vary across the universe,
so stars in faraway galaxies may not be eligible. But there's a lot of
evidence that the laws of physics are the same as far away as we can see, so
this seems unlikely to me.

There are good reasons to believe that intelligent civilizations are short
lived (compared to cosmological time scales). So the absence of radio signals
from nearby planets doesn't mean it's not worthwhile to send a probe there to
see if there are ruins or something.

~~~
VLM
"So the absence of radio signals from nearby planets"

Whoa there... The SETI people whom are only occasionally telecom engineers
have a thing about scanning for the simplest carrier waves and that's it.

Note that we only broadcast vestigial sideband amplitude modulated video
signals which had a lovely strong stable carrier for oh maybe 50 years and we
don't broadcast analog TV anymore. Lets be honest that the future for
broadcast radio/TV doesn't look particularly bright so even if the aliens had
the bright idea to use 8VSB modulation when the USA is in view or OFDM when
the euros are in view then they still would see total radio silence from us in
"a couple years". Terrestrial broadcasting is pretty much done.

You need to add a term to the SETI equation that your average civilization is
only going to broadcast "SETI@HOME" compatible radio signals for maybe a
century, probably less.

There's a section of Kraus classic radio astronomy textbook indicating that
detecting Earth during the peak of the analog TV era would still have been
pretty tricky if the aliens used our own "SETI@HOME" modulation.

You feed a baseband thru the wrong demod and you just get distorted noise.

Broadcast seems kinda dead as a concept in a packet switched social media era.
The aliens and us are not going to understand each other on some rather
fundamental levels making USA 2050 compared to USA 1950 look fairly trivial.
Wait... you still use radio waves for communication instead of high frequency
short range gravitic waves? You broadcast to a significant fraction of your
unified population instead of social media via low power point to point
systems? How... retro.

~~~
tlb
Good point: a moderately advanced civilization is likely to have no high-power
baseband communication. Only intentional alien interstellar transmissions are
likely to be powerful enough and decodable.

Earth has made several intentional transmissions
([https://en.wikipedia.org/wiki/Active_SETI](https://en.wikipedia.org/wiki/Active_SETI))
but it's unclear if we'll send any more, because they might attract hostile
aliens.

------
logfromblammo
If an alien civilization existed, but we can never find any evidence of it
existing, does it still count?

The speculation is moot as long as the record of evidence cannot support
within a reasonable confidence interval that only one or more alien
civilizations could have produced it.

Guessing with the Drake equation only helps to determine just how much time
and funding you would like to provide to projects like SETI, that actually
watch for and listen for evidence that would refute the null hypothesis (viz.
no civilizations anywhere outside of Sol System).

All the article really says is that if SETI has enough resources to watch the
entire sky at maximum resolution for an infinite timespan, it will eventually
find something. But I'm certainly not going to sink that much time and money
into it. I'd rather put that money into generation ships, sleeper ships,
robotic seed ships, permanent space habitats, or some combination thereof.

------
eponeponepon
It's nice to see this sort of sentiment expressed more scientifically than
"well come on, this place is huge and old, so... yeah, probably".

But I think it stands to reason and always has. After all, this place is old
and huge, so...

------
pilom
Please add "(2016)" to the title as this article is from last June.

------
sampo
> _Specifically, unless the probability for evolving a civilization on a
> habitable-zone planet is less than one in 10 billion trillion, then we are
> not the first._

Obviously, astronomy theories don't know much about these things, as the sheer
number of stars with planets, and planets in the habitable zones, have come as
a big surprise to everyone.

But still, can we say or guess anything about the age distribution of these
stars and planets, compared to our earth and sun? Is our sun among the oldest
or youngest of those stars which have earth-like planets?

------
Pica_soO
Envision civilizations tombstone: A automated observatory, which searches for
green-zone planets and sends short laser-burst-encoded "Here lies"\- messages
to the probable locations of tomorrow civilizations.

On some far away planet, a circle of far-travelled pulsing light razes with 30
km/s over the clouds, and is interpreted as a answer to the "Where is
everybody?" question, missing the grammatically correct point of a decent
interstellar conversation. The Question is.. "Where was everybody (when we
where around?)"

------
brockers
tl;dr The rough estimates of the number of habitable planets in the universe
just went from 20 trillion to 100 trillion based on the fact that it looks
like almost all stars have planets.

------
Taranis
Paraphrasing Sagan: "Great claims, need great evidence". Real evidence is
always lacking for aliens.

~~~
littlegreenb18
Evidence isn't really the issue here. We're not trying to answer a definitive
question here of whether or not there have been advanced civilizations. We're
trying to reason our way into a statement of probability. Just because it
isn't currently provable doesn't mean it isn't a question worth investigating.

------
JCzynski
Pull the other one, it exists with probability 10^-22.

------
marsrover
> In other words, given what we now know about the number and orbital
> positions of the galaxy’s planets, the degree of pessimism required to doubt
> the existence, at some point in time, of an advanced extraterrestrial
> civilization borders on the irrational.

AKA "Yes, there _might_ have been aliens". Interesting article, sensationalist
headline.

~~~
allemagne
It doesn't seem sensationalized to me. Saying that you'd almost have to be
irrational to doubt something seems as close as a scientist can get to
confirming that thing.

