
We May First Find Aliens on Eyeball Planets - dnetesn
http://nautil.us/blog/-forget-earth_likewell-first-find-aliens-on-eyeball-planets
======
nabla9
The background for the article is 'tilt erosion time' and the large number of
tidally locked planets in the habitable zones of numerous low-mass stars. Many
new discovered planets are tidally locked: Kepler-438b, Kepler-442b, K2-3d,
K2-155d. It was previously assumed that tidally locked planets would not be
habitable. New climate modeling seems to change this view.

No snowball on habitable tidally locked planets
[https://arxiv.org/abs/1705.08904](https://arxiv.org/abs/1705.08904)

Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally
Locked Planets
[https://arxiv.org/abs/1307.0515](https://arxiv.org/abs/1307.0515)

Tidal obliquity evolution of potentially habitable planet s
[https://arxiv.org/pdf/1101.2156.pdf](https://arxiv.org/pdf/1101.2156.pdf)

~~~
jerf
"New climate modeling seems to change this view."

And this modeling was confirmed to be accurate... how, exactly?

This strikes me as a classic case of goosing the model until it says what you
want it to say, and then getting in the news. We have no reason to believe
these models. We have no reason to believe prior models, either. We have no
reason to have any confidence in our ability to model a tidally locked planet,
of unknown and arbitrary chemistry, around an unknown star, for unknown
periods of time, with unknown orbital characteristics across geological time,
with zero data points. We particularly have no reason to believe in any
estimates of how long such a system could last; it doesn't seem to do life
much good if there's a place for it to exist for a couple of million years,
followed by freezing. The simulation is almost certainly unstable here; very
small changes in the stability of this configuration will have massive changes
to the result over even a few million years.

There's also more to life than just a comfortable temperature. Life is
possible on Earth in part because we have a moon and plate tectonics keeping
this stirred up, so some of our vital nutrients don't just sequester
themselves somewhere chemically convenient after a couple of million years and
then hang out there for the rest of the planet's existence. Do these types of
planets have a solution for that? We have no idea. (One advantage of the
Earthlike planets is that we do in fact have an idea... we know it's at least
possible once.)

~~~
nabla9
>We have no reason to believe these models ....

What is your level of expertise or knowledge of planetary astrophysics and
climate modeling?

~~~
jerf
Sufficient to know our data point count is zero, and the model can not
possibly have been verified against anything.

This does not require extensive study.

Furthermore, as a bona fide, credentialed expert in computer science, I
observe with the full power of my credentials that other fields frequently
abuse modeling to get into the news, and that as I said, this shows all the
hallmarks of being one of those. There is a profound, mathematical way in
which models simply spit back out at you what you put in. This profound
mathematical understanding seems to be broadly lacking, and it makes people
grant _wildly_ excessive credence to unverified models. As just a single _for
instance_ , I expect you have _no idea_ how many models they ran that produced
lifeless planets until they finally found one that yielded a result conducive
to life. Given the almost-certainty that these systems are deeply, deeply
unstable, I expect it is almost certainly the case that they had a large
number of runs where the system simply ran away in one direction or another.

Edit: I challenge the downmodders to produce a single data point about an
eyeball planet in a habitable zone and demonstrate a model that correctly
represents it. "We have to have data before we can verify a model" is not some
sort of wild anti-scientific statement; the belief that a model _can_ be
trusted without validation is the wildly anti-scientific position!

If some of you are mistaking this for a position on the climate debate, note
that we _do_ have data for Earth's climate. Not as much as we might like
(could always use more!), but it's certainly much greater than zero. You can
literally get more than zero data just by walking outside and observing the
temperature right where you are. This point has nothing to do with the climate
debate on Earth.

~~~
ashelmire
I mean, you’re not wrong, despite the hivemind’s disapproval. Math and CS are
our fields, and that’s what these other fields are using and abusing, and many
of us have significant cross-disciplinary expertise and experience that gives
us good intuition about bullshit. The lack of skepticism is why the
replication crisis is such an issue... your first reaction to any publication
should be doubt.

~~~
yongjik
A bunch of programmers talking crap on astronomers because "Math and CS are
our fields"... Oh geez.

Somewhere in an alternative universe, there must be an astronomers' forum
talking crap on developers because Heartbleed and Spectre show they all
misunderstood Goedel's theorem, and believe me, I totally know what I'm
talking about, I use computer every day.

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fiblye
The most interesting thing that came to my mind reading this was how different
life would be without any distinction between night and day. If the amount of
sunlight reaching the planet were consistent at all times, would life
(assuming it followed an evolutionary path like earth's) still evolve to have
frequent sleep or rest periods?

~~~
nnx
This is so intriguing indeed.

Maybe most creatures on such planets would evolve towards unihemispheric
sleep, as some Earth species did (eg. dolphins).

Unihemispheric slow-wave sleep (USWS) is sleep with one half of the brain
while the other half remains alert.

[https://en.wikipedia.org/wiki/Unihemispheric_slow-
wave_sleep](https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep)

~~~
eloff
I was wondering if such creatures would sleep at all with 24 hour daylight.
They might evolve other mechanisms to get the same benefits.

~~~
bluGill
Lions sleep 22 hours/day, even though it is light during many of those hours.

Light/dark is only one factor in sleep, there are others.

~~~
felipeko
Evolution on earth is heavily influenced on dark/light cycles through its
entire history. No evolutionary path that has received this influence can tell
us anything about what would happen, on things that are highly correlated to
it, for one that has never received this influence.

~~~
bluGill
of course, but the reasons lions sleep far more than the day/night cycle
requires are a factor that applies elsewhere, and thus might result in
something similar.

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phaedrus
Imagine if such a planet had a small residual rotation left - any civilization
on it would be constantly rediscovering millennia-old sites as previously
abandoned regions rotated back under the inhabitable region.

~~~
cwkoss
This is a beautiful idea, would love to read a novel based on this premise.

The sort of forced nomadism from "only" having ~1000 years before a location
becomes uninhabitable would make for some interesting dynamics. Real estate at
the leading edge would be very valuable, potentially with some kind of
homesteading dynamic for claiming the land (as nobody has lived there for
thousands of years). Also value of land would depreciate over time because it
would have an 'expiration date'.

~~~
jnmandal
I think its doubtful a society like that would adopt a capitalist land rights
system.

~~~
TooBrokeToBeg
First opportunity is always something to capitalize on.

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3chelon
While I agree with most of the other comments that there's little evidence for
the argument of the article, it is refreshing to see a different take on the
whole "earth-like planets" topic.

I am regularly shocked by how little imagination commentators in the popular
science press seem to have on this subject. Even highly-respected scientists
frequently refer to "requirements" for extra-terrestrial life such as carbon-
based chemistry, the requirement for water, a mechanism of natural selection,
etc, etc. (Actually I consider the last one, posited by Dawkins, to be
probably the closest to the truth.)

I guess it's simply the anthropic principle at work, but even the nature we
see on our own planet far surpasses our imagination often (especially at the
microbial level), so why should we be placing any constraints on the rest of
the universe?

~~~
XorNot
Carbon-based chemistry isn't the worst requirement to throw in there, since
the only plausible analogue - silicon - for example doesn't form stable
analogues of the usual amino acids at room-temperature.

Now it would be reasonable to say "well what about extreme environments" but
we are specifically looking for planets with temperatures and "ambient
energies" similar to ours - so it's reasonable to think that whatever
chemistry is there probably has to follow Earth to a large degree.

If instead we were talking about high-pressure hot Jupiters or something, then
it gets more interesting - but that's going to be something so different we're
unlikely to recognize it at all (what consciousness does sentient life which
evolved in a gas-environment have?)

~~~
mkirklions
Well carbon based compounds are significantly more stable when they grow in
size than any other atom.

That bond stability had to play a gigantic role over the last billion years of
evolution.

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jobigoud
There is a third option besides tidal lock and night/day cycle.

Some moons in the outer Solar System have Chaotic Rotation[1]. These bodies
don't have a fixed rotation axis or period.

There could still be such a Moon orbiting a planet in the habitable zone, or
even a small planet in a belt like structure orbiting close to a red dwarf.

I wonder what lifeforms could evolve when the amount of light/energy received
is unpredictable and varies constantly?

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

~~~
quantumhobbit
Chaotic rotation occurs primarily in bodies that are not spherical. These tend
to be smaller, because gravity forces larger bodies into spheres, and would
have a thinner atmosphere if any due to the small gravity.

Not saying life is impossible on such a moon, but it would be even weirder
than just strange day night suggests.

~~~
mkirklions
But wont millions of years of chaotic rotation cause a large body to become
round?

Thousands of years this sounds realistic, but remember the scale of things is
in billions of years.

~~~
lainga
I believe the chaotic rotation would stop as soon as the body became round, to
conserve angular momentum.

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edoloughlin
Sun in a fixed position in the sky, impassible ice and desert barriers on all
'sides'. These planets must be full of flat 'earthers'.

~~~
adrianmonk
Two of their most memorable technological milestones might be:

1\. First crossing of the hot side, passing through the point where "sun" is
directly overhead. (Having the sun directly overhead would probably seem very
profound and unusual to them.)

2\. First crossing of the cold side, passing through the opposite point.

Both would have unique challenges. Crossing the hot side would require an
amazing ability to keep cool. You can keep warm by burning stuff and using
lots of insulation, but how do you do the opposite?

Crossing the cold side would have temperature challenges and also very
difficult navigation because of the continuous darkness. Maybe there would be
moon(s) and stars for some light, though.

In both cases, I wouldn't be surprised if the first crossing had to wait until
the invention of the airplane. You definitely aren't doing it by sea the first
time like we did here on Earth.

~~~
zaarn
IIRC from various articles, there might also be hefty storms around the
terminator where the thermal difference between hot and cold plays out...

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koonsolo
Wow this brings back memories!

When I was 18, a group of friends and me were going to create a computer game
based on this tidally locked concept. The story went as follows: An explosion
would occur in a huge spaceship close to such a planet. Both parts of this
ship would make an emergency landing on this planet. One part on the cold ice
side, one on the hot desert side. Both teams would work their way towards the
habitable ring, in a true real-time-strategy (Command & Conquer) fashion.

Needles to say, the game never went further than this concept phase.

Although we did visit a small local game developer here in Belgium called
Larian, to get a feel of running a game development company (must be back in
1998). Larian is now known for the critically acclaimed Divinity: Original
Sin.

~~~
progval
I like it! And you could make sequels where they each develop into a different
civilization with different technologies.

------
chopin
The article explains in length what Eyeball Planets are but gives little
arguments why life should be more abundant there compared to other planets
apart from a vague number argument.

~~~
Tepix
Here are some reasons:

Pro:

\- Red dwarfs are by far the most common type of star in the Milky Way, at
least in the neighbourhood of the Sun

\- Red dwarfs exist for a long time (longer than ten billion years) which
gives life a long time to spring into existence (or start via panspermia) and
evolve

\- Planets in the habitable zone of a red dwarf are tidally locked ("eyeball
planets") due to their small distance to the star

So there is very likely to be a huge number of these types of planets with
stable conditions over a long period of time.

Con:

Flares by the red dwarfs (which are not so rare) could destroy life on these
planets

~~~
Klathmon
>Flares by the red dwarfs (which are not so rare) could destroy life on these
planets

As a layperson, I'm curious how "bad" those flares are. Is it in the realm of
possibility that life that develops on these planets could "hide" from these
flares when they happen, or evolve defenses against them for when they happen?
Or is it more "turn the surface into lava" kinds of events?

~~~
dak1
~100 times the intensity required to kill even the hardiest microorganisms,
bad.

[https://phys.org/news/2018-04-proxima-centauri-flare-
powerfu...](https://phys.org/news/2018-04-proxima-centauri-flare-powerful-
visible.html)

~~~
scarmig
In the places that are exposed to the UV light.

You could have life that's 100m deep underwater, or living in protected
structures (caves, etc). Life could evolve more protections against UV (e.g.
some kind of carapace that the organism resides within).

Maybe the hard part is figuring out a way to use UV-heavy light to generate
energy.

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matte_black
It has been said that the equators of eyeball planets are the most romantic
places in the universe, as they are in a perpetual never ending sunset. Great
place for a honeymoon.

~~~
cwkoss
Would be interesting to see how a real estate market would develop on a planet
like this. My guess:

\- Side of planet closest to sun would be great for solar, agriculture.

\- Equator would be great for retail, recreation - constant sunset makes
everything look beautiful.

\- Just further than the equator might be an idea place for housing - it's
always dark, but short commute to light.

\- Further away from the equator would be cold, which could be useful for
heavy industry (particularly exothermic processes)

I wonder how a society's 'clock' would work without the day/night cycle. Would
people coalesce around a certain common "day" cycle or would everyone be on
different schedules so society operates in shifts?

~~~
matte_black
It’s clear that the equator would be the playgrounds of the rich, where grass
is always green and the lighting always perfect. Properties facing the sunset
would fetch a premium over those facing the dark empty sky.

Going away from the center, properties would get cheaper due to harsher
conditions, the poorest of people living in increasingly hotter and colder
conditions. But they would also live closer to the factories that lie toward
the poles of the planet, making for faster commutes.

Somewhere in the very hottest and coldest extremes, would be a good place to
keep prisons.

~~~
cwkoss
If enough capital is available, I'd expect the rich to grade the equator so it
slopes towards the sun, allowing for more real estate to get sunny views.

------
jaddood
This kind of reminds me of Norwegian mythology where, as far as I can
remember, there was an icy world in the North and a fire in the South, and as
the fire melted the ice, a thin strip of life began forming.

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chefandy
Man, living on an eyeball planet sure would be convenient for producing solar
energy.

~~~
macintux
I wonder whether you'd ever achieve the level of technology required to take
advantage of it, though. Mining would be brutally difficult outside the
habitable zone.

~~~
svachalek
On a planet the size of Earth, or a few Earths, it seems the habitable zone
should be large enough to develop a major civilization, no?

~~~
macintux
No idea. It just seems based on our own experience that resources aren't
likely to be evenly distributed.

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greggarious
The article reminds me of another[1] HN article... this one says such a planet
might be covered in oceans. I wonder what kind of life develops on an ocean
planet? :)

(This is all idle speculation but it's fun to think about)

[1] "Group of scientists suggest that octopuses might actually be aliens "
[https://news.ycombinator.com/item?id=17110874](https://news.ycombinator.com/item?id=17110874)

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throwaway1982x
I find that it completely unlikely that 'eyeball' planets would have a life-
supporting zone.

Over geological time period, the zone is likely to suffer unpredictable and
novel variability which is not conducive to developing life.

~~~
jameshart
Geological-timescale variability is VERY conducive to evolution.

~~~
XorNot
We also don't have timescales for abiogenesis in a sterile environment - i.e.
given the right ingredients and energy input, no existing life forms...how
long does life take to appear? There's no particular reason that timescale has
to be very long - and we know life on earth got started pretty damn quick
after the planet cooled off enough (EDIT: in the sense that the planet is ~4
billion years old, the earliest life is dated to 3.5 billion years old, so the
number is somewhere between a little over 0 and 500 million years).

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wainstead
A pretty good short story set on a tidally locked planet is "Weep For Day" by
Indrapramit Das.

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kensai
True thing. In "Another World" it looked totally different, both in fauna and
flora.

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samatman
If only Hal Clement were around to write hard science fiction set on an
eyeball planet...

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trhway
Life, at least it's origination, requires cycling - this is what allows for
the original buildup and release of entropy gradients which follow spacetime
trajectories different from the ones of the dead matter. For example you get
cells (and especially precells) to get divided by temperature cycling.

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mrhappyunhappy
This would make for a great blockbuster movie. Something mad max-esque

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pulsarpietro
I would have added "maybe" at the end of the title :-)

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madeuptempacct
Would this eyeball planet structure affect geography? I.e. would the terrain
be flatter? Would there be more or less volcanoes? No blanket statements could
be made because it would depend more on composition?

------
John_KZ
That's a lot of assumptions based on top of other assumptions. All asserted as
the truth. I'd be more willing to listen if the author was aware of this
potential for error.

~~~
nkozyra
The argument seems to stand on the greater risk to life on a planet with
relative axial rotation. So one without is more likely to have "sweet spots."

As an earthling this is probably the first thing you think about when you read
about Mars - too hot for life in the day, too cold for life at night. But that
makes way too many assumptions relative to _human_ life. It assumes nothing
could be rigid enough to adapt to day and night extremes greater than Earth's.

It seems to me the greatest challenge to thinking about potential life outside
this planet is being mentally bound to the constraints of life on this planet.

~~~
simias
>It seems to me the greatest challenge to thinking about potential life
outside this planet is being mentally bound to the constraints of life on this
planet.

I always felt the same way about astronomers linking liquid water with life
but then again where do you start if you don't use the only known instances of
life in the universe as a template? Maybe it happens that there's a viable
evolutionary path for sentient Nitrogen clouds but how would we know that?

Furthermore it doesn't sound too absurd that the very complex chemical
constructs necessary for life would have a greater chance to stabilize in less
extreme environments with a smaller temperature amplitude. Especially if
you're looking for complex life and not merely microbes (which tend to be a
lot more resilient).

~~~
ekianjo
The rationale is because carbon chemistry is the richest chemistry out there.
Other elements are not nearly as flexible to sustain complex molecules while
maintaining the possibility of reversability in chemical reactions. Thats
actually a very sound argument.

