
Is Earthly life premature from a cosmic perspective? - dnetesn
http://phys.org/news/2016-08-earthly-life-premature-cosmic-perspective.html
======
antognini
For some context, Avi Loeb has a certain ... reputation in the astrophysics
community. He's a super smart guy, but he has a habit of writing a ton of
short, very speculative papers. One gets the impression that he's throwing a
lot of ideas out there and seeing what sticks. It can be as valid a strategy
in astronomy as in the startup world, but the downside is that it can be hard
to believe anything he writes.

As far as this paper goes, the most interesting implication isn't mentioned in
the phys.org article. It seems to me that main idea of the paper is to connect
the development of life to the cosmological evolution of the universe. We find
that we live in a somewhat special time, when the universe is just starting to
be dominated by dark energy after having been dominated by matter since
~300,000 years after the big bang. Anytime you see that we live at some sort
of a special time, the Copernican principle leads one to wonder if there is
some underlying reason for this.

The main argument of this paper is that as the universe becomes more dominated
by dark energy, the expansion of the universe accelerates and this shuts off
the flow of gas onto galaxies. As galaxies stop accreting matter, star
formation slows, making it less likely that life will develop in the far
future. However, low mass stars are more abundant and have a longer lifetime,
so even if it takes a longer time for life to evolve in that environment, it's
still, on balance, more likely that life evolves around low mass stars in the
near future ("near" still being tens to hundreds of billions of years). So we
would expect that the typical life form will evolve around a low mass star,
far in the future. Thus, life on Earth seems to have developed early, but
maybe not unusually so, and it's maybe not a coincidence that we happen to
live a little after the time at which the universe became dark energy
dominated. I would file this away in the "interesting if true" category.

~~~
EGreg
_We find that we live in a somewhat special time, when the universe is just
starting to be dominated by dark energy after having been dominated by matter
since ~300,000 years after the big bang. Anytime you see that we live at some
sort of a special time, the Copernican principle leads one to wonder if there
is some underlying reason for this._

I will propose such a puzzle. The moon has been moving away from the Earth at
a certain rate every year. Yet it is only in the time frames of the humans
that we find the moon and the sun roughly the same size, so they can form full
solar eclipses etc.

Is this a coincidence? Surely there can't be any physical explanation for
this.

~~~
taneq
The moon just has to be bigger than the sun to form a total solar eclipse. So
it's not very coincidental as far as I can see.

~~~
samatman
The moon causes both annular and total solar eclipses. That is, it is
precisely far away enough to both completely cover the Sun, and to
incompletely cover it.

~~~
EGreg
Exactly! How do you explain that it's happening during the time of homo
sapiens?

~~~
cbraz
Coincidence?

[https://en.wikipedia.org/wiki/Correlation_does_not_imply_cau...](https://en.wikipedia.org/wiki/Correlation_does_not_imply_causation)

------
danieltillett
The big argument against intelligent life being common (and us not being
unique) is the existence of stars. No civilization more advanced than us is
going to let stupendous amounts of energy go to waste in the form of star
light. If you assume von Neumann probes and Dyson spheres are possible, then
star light is incompatible with the existence of advanced technology.

While life appeared very early in the history of the earth, technologically
advanced life took billions of years to evolve. You require a planet with an
extraordinarily stable climate to allow a technological society to evolve and
I predict this is the filter.

Just one factor contributing to this stability is the need for a very large
moon to keep the axis of rotation stable over billion of years. If the Earth
didn't have its moon the Earth's axis would tip over creating massive climatic
change. The more we look at the universe the more unlikely the stability of
Earth's climate looks.

~~~
Terr_
What if they've got something more-convenient or powerful than going around
messing with each star?

I just imagine an intelligent beaver: "There can't be any other intelligence
out there, just look at all these rivers and streams!"

Meanwhile, humans are enjoying fusion-power and will take a little while to
notice suspiciously-well-engineered beaver dams showing up everywhere.

~~~
danieltillett
I hate to break it to you, but we have already dammed most of the rivers. Any
beaver who thinks that there are no dams around is just one that hasn’t tried
to swim far downstream :)

The argument is really more why is there only one technological species on the
planet - the answer is the first one to arise will displace all the other
potential competitors. This is exactly what has happened on Earth and why any
other species that has a chance of creating a technological civilisation is
not doing so well.

The same argument applies to the universe where the first civilisation that
chooses to take over the universe will displace any competitors that choose
not to. All it takes is one civilisation to spread and the whole universe goes
dark.

~~~
WildUtah
Population of apes on Earth:

    
    
         Orang-Utan: 50,000
         Chimpanzee: 200,000
         Bonobo: 35,000
         Homo Neandertalensis: 0
         Homo Habilis: 0
         Gorilla: 100,000
         Homo Sapiens: 7,500,000,000
    

Yup. "The first civilisation that chooses to take over the universe will
displace any competitors that choose not to."

~~~
dogma1138
How many zeros would you need to use to count the ants in the world?

~~~
danieltillett
No species the size of ants can ever smelt steel. They are not competitors for
humans to become Earth's technological primary species.

~~~
Tloewald
Have you read _City_? (Not that it's seriously making an argument the other
way.)

Arguing that smelting steel is the key thing is the typical, we're good at
this therefore this is what matters argument we've been making since time
immemorial.

Humans can't sneak into other organism's bodies and take over their DNA (yet,
to be sure) but viruses can, so humans just don't have a real shot.

------
egypturnash
I was idly looking at "age of universe", "age of earth", and "age of life"
numbers and wondering something like this just the other day. The universe is
only about 3x as old as life on Earth, and we've just _barely_ gotten to the
point where we can make noise nearby worlds can conceivably hear. Radio's a
hundred years old. That's _nothing_ on those time scales.

Look at this diagram of the size of the space that could pick up on our radio
broadcasts with regards to the Milky Way:
[http://www.planetary.org/blogs/emily-
lakdawalla/2012/3390.ht...](http://www.planetary.org/blogs/emily-
lakdawalla/2012/3390.html)

If we get at _all_ pessimistic about the likelihood of life happening, it
doesn't feel like much of a stretch to imagine that we are some of the first
ones. I would _love_ to be proven wrong in this by having some advanced Elder
Race show up and try to help us get out of this short-sighted, self-
destrictive capitalist spiral we're in, but I'm not gonna hold my breath.

~~~
avar
To me the algae vs. alumnae solution to the Fermi paradox seems appealing.
I.e. that life is common, but that intelligent life isn't.

Our sample size of one on Earth supports that. We have millions of species,
but only one has evolved higher intelligence, and there's no reason to think
that it's a successful evolutionary strategy v.s. say being a parasite.

    
    
        > [...]by having some advanced Elder Race show up
        > and try to help us[...].
    

Right, "help". I'm just going to let the history of how advanced civilizations
have treated primitive civilizations here on Earth speak for itself.

~~~
civilian
We could also quote Blindsight by Peter Watts:
[http://www.rifters.com/real/Blindsight.htm](http://www.rifters.com/real/Blindsight.htm)
Search for "Once there were three tribes." and read 10 paragraphs :) The key
quote is:

 _> Equidistant to the other two tribes sat the Historians. They didn't have
too many thoughts on the probable prevalence of intelligent, spacefaring
extraterrestrials— but if there are any, they said, they're not just going to
be smart. They're going to be mean._

~~~
taneq
Even easier, it's the second occurrence of the word "historians". :)

------
fastaguy88
If I were reviewing this paper, I would be quite surprised that there is no
mention of how long it took life to emerge on Earth after there was liquid
water. While the earth is around 4.6 By old, my understanding was that liquid
water was not present until about 3.8 Bya, and that life probably emerged in
the by 3.5 Bya. So, 300 million years for life to emerge in on Earth with
liquid water. I realize it's only one data point, but it seems like it should
inform the probability calculation.

------
jessaustin
_" So then you may ask, why aren't we living in the future next to a low-mass
star?" says Loeb.

"One possibility is we're premature. Another possibility is that the
environment around a low-mass star is hazardous to life."_

Wow that is some hardcore "anthropic" logic. Is the question really well-posed
enough to lead to the latter conclusion?

~~~
ahmedfromtunis
This. Sometimes I feel like such out-of-touch-with-reality 'logic' is why a
lot a people don't trust science anymore.

~~~
whack
Just because something is non-intuitive doesn't mean it's "out-of-touch-with-
reality".

Imagine if you go to a bus stop in a completely foreign city/country, and the
bus shows up within 1 minute. There are 2 possibilities. Either

A) The bus usually takes a very long time to come (30+ minutes) and you just
happened to get very lucky, or

B) The bus runs at a very frequent interval, so your 1-minute-wait is somewhat
normal

Statistically, B is much more likely to be true than A. Which is pretty much
what the author is alluding to.

~~~
pliny
You are using priors to decide that B is more likely than A, that is, you are
saying that the frequent bus hypothesis is likely because buses with frequent
intervals are common.

If the bus shows up within 1 second of your arrival then there can be no
discussion of "frequent buses", you were definitely lucky, but only because
the prior for buses with frequency of Order-of (1 second) is so low.

The analogy here is time-to-life and we have 1 data point for that, not enough
to establish credible priors for minimum\mean time-to-life under any
circumstances.

~~~
whack
The point of the thought experiment is to avoid using any priors.

If you have a single data-point of an event E, taking time T to occur, then
there are 2 possibilities:

A) Event E usually takes much much longer than T (>100T), and what you just
witnessed is an anomaly, or

B) Event E usually does take roughly time T to occur, and what you witnessed
is within the range of what usually occurs.

Both conclusions have an extremely high likelihood of being wrong, since the
sample size is so small. But between the 2, conclusion B is more likely to be
true than conclusion A.

------
themgt
What seems to me obvious if one looks at: a) the age of the universe b) the
age of the earth c) the age of life on earth d) the age of aware-enough-to-
look-at-stars-and-wonder-about-aliens life on earth

Is that life itself is relatively "easy" and is likely to be common.

It seems more likely to me that the crucial "filter(s)" are for a species of
lifeforms to cross the boundary into a global, technological civilization.
There appear to be very unique, perhaps somewhat accidental set of
circumstances that led to homo sapiens crossing that rubicon that aren't just
evolution doing a "dial intelligence to 11", but more about an ability for
intelligent individuals to share and store their thoughts and build shared
abstractions and culture over periods much longer than individual lifetimes
(e.g. capability for complex vocalizations and extremely precise control with
hands and fingers; not living in water)

~~~
jseliger
_Is that life itself is relatively "easy" and is likely to be common._

Life appears common, but multicellular life appears to be extremely uncommon
and appears to have evolved only once on earth, at least according to Nick
Lane's excellent (though inadvertently depressing) book _The Vital Question:
Energy, Evolution, and the Origins of Complex Life_
([https://www.amazon.com/Vital-Question-Evolution-Origins-
Comp...](https://www.amazon.com/Vital-Question-Evolution-Origins-
Complex/dp/0393088812?ie=UTF8&camp=1789&creative=390957&linkCode=as2&tag=thstsst-20)).
I can't gauge the accuracy of his claims but the book does not appear to have
been rebutted, at least from what I've found. Given all the discussion about
biology on this thread I'm surprised no one else has mentioned it.

~~~
derekp7
Also, as far as we know, single-celled life also evolved exactly once. This is
one thing I haven't seen a good answer for -- if life came about so early,
that would indicate that it is easy. But since it occurred only once, that
would indicate that it is hard.

The common explanation is that once life evolved and began to spread, that it
would prevent other life from appearing by out-competing it. But there is
plenty of raw materials and sunlight to go around, so I don't buy that
explanation.

The only thing that seems to fit, is that life is hard to evolve, but has
extra-terrestrial origin. If that is the case then life should exist (at least
in bacterial form) wherever a suitable habitat is found.

------
dreen
Wasn't there a time for some time after big bang when the space was on average
a lot more warm everywhere and conditions for life were incredibly more
abundant than now? I remember reading something like this here which would
seem to be an antithesis to this article.

~~~
jessriedel
I think you must be referring to this:

> The "Dark Ages" span a period during which the temperature of cosmic
> background radiation cooled from some 4000 K down to about 60 K. The
> background temperature was between 373 K and 273 K, allowing the possibility
> of liquid water, during a period of about 7 million years, from about 10 to
> 17 million after the Big Bang (redshift 137–100). Loeb (2014) speculated
> that primitive life might in principle have appeared during this window,
> which he called "the Habitable Epoch of the Early Universe" .

[https://en.wikipedia.org/wiki/Chronology_of_the_universe#Dar...](https://en.wikipedia.org/wiki/Chronology_of_the_universe#Dark_Ages)

[http://journals.cambridge.org/action/displayAbstract?fromPag...](http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9371049&fileId=S1473550414000196)

Note that the other, Avi Loeb, is the same from the OP article.

The cosmological dark ages lasted from photon decoupling (when photons started
free streaming and the cosmic microwave background was born) to a few hundred
million years later when the first stars begin to form. Loeb's suggestion is a
narrow window of a few million years when the CMB itself would be the source
of warmth, rather than stars. I'm not sure how matter was distributed on small
scales during that time period.

~~~
civilian
Does Loeb address whether there would have been oxygen and carbon 10-17
million years after the Big Bang? I thought that the heavier elements formed
much later, and had to be forged in the center of stars. Our first generation
of stars appeared 560million years after the Big bang. (Reference is the same
wiki article you linked)

~~~
jessriedel
He talks about it in the paper. Basically, depending on your assumptions about
nongaussianity of the primordial perturbations, there were at least a few
stars simply by accident in the early universe.

------
DannyB2
> Stars larger than about three times the sun's mass

> will expire before life has a chance to evolve.

Protip: if you are looking to hide the existence of your civilization, a good
place would be in the vicinity of one of these.

~~~
Aelinsaar
Definitely. No need to be worried about what orientation you are in relation
to a hypothetical observer either. Then again, you could sit in a molecular
cloud, or near something really exotic like a neutron star of some variety to
REALLY hide over longer time scales.

------
Meegul
"...chances of life are 1000 times higher in the distant future than now."

I still don't see this as a solution to the Fermi paradox, considering the
billions (more?) of planets in our galaxy.

~~~
agentgt
There was a discussion thread a while back about this on HN [1].

The first argument is a fairly weak argument/theory but about the same
strength as most of the other common arguments/theories.

To me the strongest argument that there is a paradox is the idea of probes
that can replicate. That it would be fairly easy with some sort of advance but
not FTL technology to easily deal with the size and expansion of the universe
(of course I could be full of it on this as I haven't looked into this idea in
some time).

Basically why haven't we run into a probe yet?

[1]:
[https://news.ycombinator.com/item?id=9916085](https://news.ycombinator.com/item?id=9916085)

~~~
openasocket
The Neumann probe idea has one flaw: it's assumed the probes will propagate
and spread largely unimpeded. However, any interstellar civilization which
encounters a probe is going to capture it and analyze/destroy it. They would
not allow it to float though their territory and replicate. At the least they
will intercept any that enter their territory; if the civilization gets
annoyed they may embark on a campaign to wipe out as many as they can. Which
leads us to two possible explanations, assuming a civilization has already
sent out probes:

1\. The civilization was bordered on all sides by other interstellar
civilizations, which stopped the probes from spreading.

2\. Our civilization is bordered on all sides by other interstellar
civilizations (or perhaps is in a remote backwater of a civilization, like
uncontacted indigenous tribes in the Amazon), which stopped the probes from
reaching us.

There's even a third, somewhat stranger and less likely option:

3\. Some civilization is profoundly annoyed by Neumann probes, and has devoted
themselves to destroying them everywhere. They made their own stealthy fighter
probes, which wander deep space destroying any probes they may find. Perhaps
they are keyed in to one specific model of probe that annoyed them, or perhaps
will target any unmanned spacecraft with certain properties.

~~~
agentgt
4\. I would add an even stranger 4th option in that given the probes are
sufficient intelligence they perhaps "evolve" into an uncontrolled state.

That could mean as simply as getting stuck like in local minimum in the hill
climbing algorithm or something extremely complex as a probe like civilization
(aka Star Trek 1 but in this case no longer cares about space exploration).

~~~
mcbits
5\. The von Neumann probes are microscopic and densely packed with a chemical
structure encoding the information needed to reproduce in a variety of
environments. Occasionally some of them mutate and get stuck in a planet's
gravitational well, where they keep reproducing and mutating into who-knows-
what. The urge to explore the cosmos is never completely lost, and eventually
they reach a state where it's possible to continue the mission.

------
JoeAltmaier
The universe may only be 20B years old. It takes our galaxy 250M years to
rotate once. So the universe is only something like 80 galactic years (days?)
old. It is still early innings.

------
dannylandau
Very recent video profile on Avi --
[https://www.youtube.com/watch?v=SKLMXdZNmZk](https://www.youtube.com/watch?v=SKLMXdZNmZk)

------
singularity2001
I thought the very fact that complex organisms can be traced back to the
Archean hints at cosmic origins of live on earth. Also no signs of a 'RNA-
world' on this planet?

