
Plate tectonics not needed to sustain life - dnetesn
https://phys.org/news/2018-07-plate-tectonics-sustain-life.html
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jerf
Based on some unverifiable computer models.

I think I'm just going to start flagging all the science stories that are
press releases about someone's unverifiable computer models.

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Luc
It is indeed a press release so that's not great, but why wouldn't their model
be verifiable? We know the applicable laws of physics, someone else can code
up a simulation and verify the results.

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lordnacho
A simulation is a prediction, not a verification. Verification would be going
out to a load of planets and seeing if they look the way the simulations say.

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jerf
In fact there's been several news stories about extraterrestrial planets over
the past few years, since we're finding more of them now. But the ones we hear
about focus on things like "can they support life". There is nothing per se
wrong with playing with the math and playing with models and trying to get a
sense of the space of possibilities.

Where I get crabby is when the whole process is condensed down to the level
the title is at: "Plate tectonics not needed to sustain life". No. The level
of confidence expressed in those words is _utterly_ unjustified. We have
perhaps a trace more than absolutely no idea. That trace is scientifically
valid and I do not begrudge some planetary scientists fiddling around. But we
must not place excessive confidence in the results.

The inability to practically proof the correctness of a computer model does
not mean it is scientifically valid to then just assume they are correct!

To put it in local terms, that's exactly as valid as expecting a programmer to
just type a few thousand lines of code into an editor, compile, and deploy to
production with no further testing required. Because, in a fairly real way,
this isn't even a metaphor, this is _precisely_ what making such concrete
predictions off of an unproofed computer model is doing. Being unable to test
the correctness of the code does not therefore render it correct. I am
reminded of the classic quote "On two occasions I have been asked, — "Pray,
Mr. Babbage, if you put into the machine wrong figures, will the right answers
come out?" In one case a member of the Upper, and in the other a member of the
Lower, House put this question. I am not able rightly to apprehend the kind of
confusion of ideas that could provoke such a question." by Babbage. I am not
able to apprehend the confusion of ideas that produces this concept that if we
can't test the model, we are justified in assuming it is correct. To my
understanding of science, exactly and precisely the opposite is true.

(Incidentally, I _also_ consider the phrase "Plate tectonics are necessary to
support life" to be completely unjustified! Our one sample of life-supporting
planet has plate tectonics. Our own solar system is at least suggestive of the
possibility that plate tectonics across a long time period may be rare, but no
more than "suggestive" without a lot more data. Given the very-slowly-
increasing evidence that life may be rare in the cosmos, it is suggestive that
rare characteristics of our planet and the rare characteristic of "life" may
be connected. We have some plausible-sounding theories as to why plate
tectonics may be helpful. But we can not say absolutely "they are necessary
for life" by any means.)

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bena
I was not aware that Earth was the only planet to have confirmed tectonics.
That seems really weird. I wonder what the percentage winds up being between
planets with and without tectonics.

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throwaway5752
If you have a rotating spherical body with a (sufficiently) heterogeneous
fluid composition, it seems like you'll get plate tectonics. When you realize
it's just a fluid with convection currents and the surface of the fluid
"freezing", you realize it should be relatively common for across planets for
a portion of their existence.

ps - if any actual physicists out there are reading, I've been curious about
the case of Mars and if tectonics there could have been halted by whatever
caused the hemispheric dichotomony for a long time, in case there's any good
reading/research on that out there to pass along...

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jofer
"Plate tectonics" means something a bit more specific than "convection
currents with the surface of the fluid freezing". In particular, it implies 1)
relatively large stable plates, 2) organized regions where crust is
created/destroyed, and 3) large horizontal movement of those plates relative
to each other.

Prior to ~2 billion years ago, Earth didn't have plate tectonics. You had
large vertical motion (not horizontal), and creation+destruction of crust, but
no organized centers where this was occurring. In other words, you didn't have
large plates and what plates there were did not move long distances
horizontally.

As another example, Venus has tectonic activity (it's periodically resurfaced
and has volcanoes), but it doesn't have plate tectonics. You see regions of
compression and extension, but no subduction zones and spreading ridges.

It's likely that what we call plate tectonics requires abundant water, at
least on "rocky" planets. Hydrous phases of silicate minerals are required for
the very weak faults and localized weak mantle required to have subduction.
Without subduction, you don't have plate tectonics.

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reubenswartz
> Prior to ~2 billion years ago, Earth didn't have plate tectonics. You had
> large vertical motion, and creation+destruction of crust, but no organized
> centers where this was occurring. In other words, you didn't have plates.

Well that would be great evidence that you don't need plate tectonics to
sustain life. ;-)

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jofer
Yeah, the exact start of plate tectonics on Earth is very hard to pin down,
but it's almost definitely after the start of life.

On the other hand, even when Earth didn't have plate tectonics, it probably
never had a stagnant lid, which is what this article is modeling.

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okket
This is 1:1 identical with the press release from the Penn State University.
Maybe link to the original?

[https://news.psu.edu/story/529527/2018/07/30/research/plate-...](https://news.psu.edu/story/529527/2018/07/30/research/plate-
tectonics-not-needed-sustain-life)

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megamindbrian2
Revolving around a sun and rotating at the same time needed?

