
As Planet Discoveries Pile Up, a Gap Appears in the Pattern - pseudolus
https://www.quantamagazine.org/as-planet-discoveries-pile-up-a-gap-appears-in-the-pattern-20190516/
======
rossdavidh
Ok, so we can explain this plus Dark Matter in one shot. Basically, planets
slightly larger than Earth are practically guaranteed to evolve intelligent
life. Intelligent life eventually develops technology that allows them to
shield the existence of their planet, or even entire stellar system, from the
probes of the Evil AI Lifedestroyer. So, all that Dark Matter is just the
intelligent life in the universe, using normal prudence to keep out EAILD (see
above), more or less like most humans live in houses with walls.

So, any system that is not part of Dark Matter yet is either: 1) unconducive
to life (or complex life, anyway) 2) was already zapped by the EAILD 3) like
us, is in a transient state where the EAILD hasn't arrived yet, but we haven't
learned how to cloak our solar system yet either

Again, the key here is that planets just slightly larger than Earth are the
most likely to evolve intelligent life, so they nearly always end up cloaking,
and thus we don't see them.

Enjoy.

~~~
PC_LOAD_LETTER
The problem with this (very interesting and fun) theory is that Earth would
have to somehow be the very last planet to develop such intelligence amongst
the large list of planets within detection range, which seems unlikely.

~~~
jerf
Well, if you want to get technical, the major problem with this theory is that
MACHOs are not a good candidate for dark matter:
[https://en.wikipedia.org/wiki/Massive_compact_halo_object#Th...](https://en.wikipedia.org/wiki/Massive_compact_halo_object#Theoretical_considerations)
Even if you imagine they were all hiding, their previous effects on the
universe are missing.

~~~
rossdavidh
Aha, you must need to erase yourself from your timeline, else the EAILD will
find you from your past traces.

------
Gravityloss
Wouldn't gravity be a good explanation? Once your rocky core grows beyond a
certain size, you start retaining some gas molecule X. If you are too small,
the thermal velocity for the gas X is bigger than escape velocity and thus you
can't retain it. So you generally don't have planets right at the small end of
the X retaining size. They always grow bigger because they sweep all of X.
Also it makes them heavier so they can hold onto X better, even if, say the
sun becomes brighter. What is X? Helium?

~~~
petschge
This is indeed one of the possible theories to explain the Fulton gap, as far
as I understand it. If you have a rocky core that accretes more and more
atmosphere, the atmosphere collapses once it contains about as much mass as
the core and you become much more efficient at accreting more gas and you form
a gas giant.

~~~
vivekd
If this is true, would that mean that life is rare in the Universe? I would
mean that we are an anomaly in that we have the perfect size and core
materials to be able to hold onto some of our atmosphere, but not so big so as
to turn into a gas giant.

Kinda sad to think that there may be nothing but space out there.

~~~
petschge
A planet can have a atmosphere that is sufficient for life, but of negligable
mass compared to the core. In our solar system we have at least 2.5 examples
of that: Earth, Venus and Mars. And that is not counting ocean moons with an
ice crust such as Europa that might be hospitable to life as well.

------
Havoc
They really should have put a nice chart or something in that article. Talking
about the gap without visualizing it is a missed trick

~~~
petschge
Go to [http://exoplanet.eu/diagrams/](http://exoplanet.eu/diagrams/) and
select "Semi-major axis" for the X axis (this is the appropriate analog of
"radius" for an ellipse) and "Planetary Mass" for the Y Axis. Note that the
bottom right corner is empty because we can not yet detect stuff there. All of
the solar systems planets would be in that corner. The Fulton gap is the lower
density region at 0.1 to 0.2 jupiter masses.

~~~
petschge
Since a lot of people seem to have problems with that plot I have uploaded an
annotated version to
[https://imagebin.ca/v/4hQOkAKo27fq](https://imagebin.ca/v/4hQOkAKo27fq) . The
black dots are data and are correct. The colorful annotations are by me and
might be wrong as I am a plasma physicist, not a planetary scientist. And
unfortunately I can not get the dots for the solar system in there using the
plot interface of exoplanet.eu. But they would be in the bottom right
triangle.

~~~
Havoc
Thanks for this

------
fsiefken
I wonder if a simulation could be made of planet formation in a solar system
based on current data of the different stages for each type and size of star
and the distribution of clouds of gas and matter. Run billions of simulations
and see under what conditions similar gaps appear in planet mass and size.
Perhaps that could provide a clue.

~~~
petschge
People are running models of planet formation. And some people run their model
often enough to do statistics over the outcomes.

The problem is that modelling the formation all the way from micron sized dust
to 100000 km diameter planets is hard (14 order of magnitude in length scale).
No single model does all steps well, most of them do not include some steps at
all.

Note: this does not mean that the models are useless. There is some things we
can already learn and smart people work on improving the models. But as usual,
HN overestimates the power of numerical models. Modeling real life is a bit
harder than launching a ruby web app. And takes MUCH more compute power.

~~~
cardigan
This is so interesting. Because it can't be this hard to do this kind of
physics simulation at the correct level of fidelity if you want to apply RL to
physical problems

~~~
AlotOfReading
What does RL have to do with this? The laws governing gravity are already well
understood and specialized code will always be more computationally efficient
while having less unexplainable behavior. Why would you use a slower, more
opaque method to accomplish the same thing?

------
INTPenis
Well do we know how large the core of gas giants are? Maybe at a certain size
they just attract too much debris and form gas giants.

~~~
scott_s
The planets on the large size of the gap are _not_ gas giants, so that cannot
explain it.

~~~
petschge
Do you have more information on that? "Hot jupiters" are close in gas planets
and the should appear at low semi-major axis, above the Fulton gap.
(Disclaimer: I am not a planetary scientist, but my office mate is and I
learned just enough to be annoying)

~~~
scott_s
Sorry, I don't have any further insight, as my reply was based on information
from the posted story.

------
ianai
How confident are they in detecting planets of earth size? I have a distinct
memory that they weren’t.

~~~
petschge
Depends how close to the parent star and how far that star is from us. But for
earth sized planetes about 1 AU from the star we are rather blind.

~~~
lucb1e
For those who don't know (I don't think it's a common unit): 1 AU is the
distance between the earth and the sun (Astronomical Unit). So apparently
[citation needed] we're blind for earth-sized planets at an earth's distance
from its star.

~~~
petschge
I am not a planetary scientist (my office mate is) and didn't spend much time
looking at the literature. "A Revised Exoplanet Yield from the Transiting
Exoplanet Survey Satellite (TESS)" by Barclay et al.
([https://iopscience.iop.org/article/10.3847/1538-4365/aae3e9](https://iopscience.iop.org/article/10.3847/1538-4365/aae3e9))
might be the citation you are looking for. Figure 14 shows that anything below
1.5 Earth radii is basically invisible to TESS. I can not find a good chart
for the detection limit in the planet size vs star distance plane.

~~~
Fjolsvith
The question that popped into my head in a disturbing manner was whether
beings on those planets could see ours.

------
VyseofArcadia
I've been reading The Wheel of Time at a feverish pace over the last couple of
months. Seeing a headline about a gap in the Pattern was a confusing
experience complete with shock and a sense of dread and a triple-take.

For one brief moment I thought some fool scientist had opened up the Bore.
Light!

------
athrowaway3z
I know very little physics, but perhaps objects have a stable orbit w.r.t.
their mass and objects in the Fulton gap have the highest probability to
interfere with each other and as a consequence distribute their mass to the
outer and inner orbit?

~~~
petschge
Orbits are stable and not sensitive to the objects mass, as long as the mass
is much less than parent star. There is even experimental prove of that. An
upper stage from the Apollo programm ended up in an orbit around that sun that
was basically identical to the Earth orbit.

------
afarviral
Nah, it's probably just aliens destroying planets of the dangerous, life-
harboring, variety. And we're next!

On a serious note; I wonder whether the size of planets has much bearing on
whether life could be started or sustained, or if this is usually trumped by
other factors.

~~~
pedrocr
It would make for good Sci-Fi premise as an explanation for the Great
Filter[1]. Some advanced civilization keeps destroying planets that have life
or are ideal for it but the first heuristic they use to do it fast doesn't
catch all cases. Earth is below the threshold so we get by, for now...

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

~~~
AnIdiotOnTheNet
Why are so many people so in love with the idea that the solution to the fermi
paradox is sapiocide on a cosmic scale? It neither fits the data nor does it
hold any philosophical merit.

~~~
monomyth
We are about to eradicate mosquitos.

~~~
CamperBob2
Because they're an active threat.

------
nemacol
My (totally uneducated) guess is, in the early formation of a solar system the
material is hot and volatile it is all moving around a lot. There are a lot of
large / medium sized bodies moving around they are running into each other,
joining, breaking apart, moving around, etc. In all that chaos, the available
material is tossed around and "excess" material is toss out of the inner
planet orbit.

I am imagining it like pouring a cup of sugar on a dinner plate and shaking
the plate around until the amount of sugar on the plate is sort of stable. The
excess material ends up outside the solar system (Oort cloud / kuiper belt) or
part of gas giant cores and moons.

With that, there is only so much material in the inner solar system to work
with and the law of averages works out and we end up with similar sized
planets.

I would assert a hypothesis that a ratio of material in the inner solar system
is linked, in some way, to the size of the star. That it is unlikely there
will be massive earths out there in the inner solar system because of this
natural distribution of material around a star.

I have no formal training at all. Just an IT nerd that watches a lot of
Kurzgesagt.

~~~
PC_LOAD_LETTER
That would be compelling if there were planets up to a certain size. However,
that's not the case. You have increasingly large planets, a big gap, and then
increasingly large planets again. It's a bimodal distribution, which implies
some other factor at hand than just the law of averages.

------
bjornlouser
There is so much trash orbiting that those planets appear to be more massive
than they are

~~~
mLuby
Or it's a shell world that used to be Earth-size.

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

------
jajag
Two obvious questions, perhaps someone knows their answers:

* Is the gap a measurement artifact? (Presumably not). * Are there other, small gaps besides the Fulton gap discussed in the article?

~~~
petschge
There is no (known) selection effect that would account for that gap. (And
scientists have looked to find such selection effects). And yes, there is
other gaps, e.g. a lack of systems with a planet at 0.2 AU (or rather in the
range from 0.1 to 1.0 AU, separating the "hot jupiters" far in from the
"normal" gas giants further out that we know from our solar system).

------
kazinator
Can someone explain this recurring pattern of elaborate art images produced
for rinky-dink articles? Is that just to try to keep eyes on the page or
something?

------
Robotbeat
Why no graph in this article? It’d be a lot more informative.

------
ekianjo
> While TESS doesn’t yet have enough planets in its statistics bin to confirm
> or disprove the Fulton gap,

You can stop reading the article after that line.

~~~
sidlls
Why? A key part of physics is collecting data. All the line means is the data
are incomplete but _as of now_ suggest a gap that may be interesting to keep
an eye on as new data are observed.

~~~
scott_s
Yes, agreed. We now have a prediction. We will collect more data to see if
that prediction holds. If it does, we'll work on theories to explain it. (Of
course, these two processes will actually happen in tandem, as how things work
in practice is much messier.) They are _not_ looking at the data set and
saying "This anomaly will certainly hold when we get more data, it is now
established fact." They _are_ looking at the data set and saying "This looks
funny, we should keep an eye on it." That is good science.

~~~
jerf
I actually find it hard to imagine the model of science that some people seem
to have is supposed to work, where, apparently, you are supposed to never look
at the real data already collected out in the world and somehow just come up
with hypotheses to be tested from... uhh... err... nothing, apparently,
because looking at pre-existing data is somehow cheating, and, what else is
there?

The "standard model" of science that seems to be embedded in the heads of the
Greater Internet Commetariat is pretty ludicrously nonsensical in a number of
places.

