[HN Gopher] The Planet Inside: Scientists are probing the secret...
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The Planet Inside: Scientists are probing the secrets of the inner
core
Author : Hooke
Score : 35 points
Date : 2022-07-05 05:46 UTC (1 days ago)
(HTM) web link (www.science.org)
(TXT) w3m dump (www.science.org)
| lven wrote:
| The part about the dynamo being 10x lower 500 m.y.a. compared to
| today suggests that the background radiation was 10x higher. They
| point out that lower dynamo leads to more atmospheric loss to
| space, thus limiting biological activity. Butthe the great
| reduction in radiation could be similarly impactful, allowing for
| more manageable genetic mutation.
| orbital-decay wrote:
| Be sure to scroll the article down to the responses, for an
| excellent comment of an actual seismologist who appears to be
| mildly irritated by the usual scientific news cycle.
| jofer wrote:
| That's more of a "you didn't mention my recent research on
| this" than frustration with the "usual scientific news cycle".
|
| (The commenter does have a good point, though -- the writeup is
| on "Hey, these observations conflict. That's weird!", and the
| commenter is saying: "Hey, we published a paper on that
| conflict several years back that we think explains it well, you
| missed that hypothesis when going over papers that discuss that
| conflict". It's kinda their pet theory, and pretty wild, but it
| was still a Science paper/very prestigious/respected.)
|
| This is actually a _really_ excellent general audience summary.
| It's hard to beat Science's non-technical sections like this
| for scientific reporting.
| jofer wrote:
| For a little more context on the "pet theory" part, Wen
| (2006) (The commenter) looks at waves that reflected off the
| same spot at the surface of the inner core 10 years apart and
| proposes that the differences in reflections are because the
| core itself grew by ~1km in 10 years at that location. You
| can also explain these differences by spin (the boundary is
| moving) or a few other mechanisms, but you can't rule out
| "the radial location of the boundary changed".
|
| That's basically the point - spin can explain it, but we've
| measured inconsistent spins. The inner core boundary moving
| around vertically by a few km can explain it, but that is a
| little hard to stomach for geologic reasons.
|
| The issue is that it's _really_ hard to come up with a
| geologically plausible mechanism that would allow 1km of
| vertical solidification over a significant area in only 10
| years that's also compatible with the liquid outer core
| existing at all. The paper proposes that it's constantly
| growing and eroding so the net gain/loss is essentially 0,
| but again, how do you explain that rate of 1km of
| solidification in 10 years geologically?
|
| That's what moves it into the "pet theory" camp. It's not
| crazy, but no one's been able to come up with a convincing
| mechanism for the proposed very rapid growth+erosion of the
| inner/outer core boundary and there are other explanations
| (like spin of the inner core relative to the rest of the
| Earth) that have gained broader acceptance. The comment of
| "Hey, we have an alternate explanation for this that wasn't
| mentioned" is also pretty fair, though.
| lven wrote:
| This got me thinking about the earth's heat flux to the surface.
| It comes from primordial heat and radioisotope decay of thorium
| and uranium. Wild that geothermal energy is really just nuclear
| decay energy, just like the mars RTGs. But disappointing that it
| ain't all that much at just 47 TW, compared to the sun's 200,000
| TW on the Earth's surface. And of those 47 TW, only 14 TW are on
| land. Not even close to enough to power mankind and our 20-40TW
| of primary energy today, and hopefully much much more in the
| future.
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(page generated 2022-07-06 23:02 UTC)