Saturday, March 23, 2024

The Iron Snow Beneath Your Feet

 US Wondering When to Plant? There’s a Map for That The Allegheny Front

How English has changed over the 1000 years

‘That’s What US Capitalism Does Right Now. It Jettisons Its Elders.’ FAIR


Homelessness and Mental Illness: Medicalizing a Housing Crisis Journal of Human Rights and Social Work


Why We Search for Silver Linings Nautilus

The Bezzle


I recently read Cory Doctorow’s new novel, The Bezzle. (FYI his publisher sent me a copy.) It’s the follow-up (and in the story’s own timeline, a prequel) to Cory’s excellent tech-themed thriller, Red Team Blues. The hero of Red Team Blues is Marty Hench, a forensic accountant who loves barbecuing, whiskey, and exposing elaborate financial scams, especially cryptocurrency ones. He’s in his early sixties and gets called in by a vastly wealthy friend to retrieve the crypto-key an international crime family is after. It’s a thrilling ride that got me back into reading the first time covid fried my brain. Red Team Blues is also fascinating on crypto and cyber-security, and its attention to cultural and sociological detail is lovingly rendered, line by snappy line. The Bezzle takes Marty back to the dot com boom. Same guy, very different novel. Utterly worth your time.

First, the title. ‘Bezzle’ was coined by JK Galbraith to describe the blissful and often long moment when an embezzlement has occurred but before it’s been discovered. The embezzler has his money. The victim still thinks he has his. It’s the gravity-defying interval when Wile E. Coyote is running on air and hasn’t begun to fall.
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Okay so, we all know how the Earth ends, right? In six billion years or so, the Sun swells up into a red giant, and the Earth gets melted. Pretty straightforward.

But it turns out that /life/ on Earth will end long before that. There are reasons to think that the biosphere will collapse about a billion years from now — long enough!  But still long before the planet itself gets melted.

Why? Basically two reasons.

First, long before the Sun blows up into a red giant, it will get brighter.  You remember from grade school how the Sun is fusing hydrogen into helium to produce energy?  Well, helium is denser than hydrogen.  So over time, as helium builds up, the Sun’s core gets denser.  And — up to a point — denser means hotter, and hotter means more energy.  So over geological time the Sun very slowly gets brighter.  “Very slowly” here meaning, about 1% brighter every hundred million years.  Stegosaurus lived under a sun that was about 1% dimmer.

Okay, so in about a billion years the Sun will be around 10% brighter.  As it turns out, that’s about the maximum extra energy the biosphere can absorb.  Beyond that, we start to get a runaway greenhouse effect, and the Earth turns into another Venus.  The error bars on the models are pretty large, but it looks like, yeah, about a billion years.

(Just to be clear: this has nothing to do with climate change / global warming.  Climate change is not going to turn us into Venus, a planet with a dense poisonous atmosphere whose surface is hot enough to melt lead.  There is simply no way we can pump enough greenhouse gas into the atmosphere to do that.  Melt the ice caps, sure.  Raise sea levels catastrophically, expand deserts, cause a mass extinction, sure sure.  Render the planet uninhabitable, no.  Totally different thing.)

By a curious coincidence, there’s a completely different process that will /also/ crash Earth’s biosphere in about a billion years, give or take.  That is the expansion of the Earth’s solid core.

Again, back to grade school: remember that diagram of the Earth’s interior in your textbook?  Solid iron core in the center (“the size of the Moon, as hot as the Sun”), surrounded by a liquid “outer core” of hot molten iron, all wrapped in a “mantle” of gooey half-molten rock?  Okay, so the interior of the Earth is fantastically hot.  But that heat slowly escapes through volcanoes and earthquakes, meaning that over geological time the Earth is cooling down.  This cooling gets expressed as a slow, gradual expansion of the Earth’s solid core.  Basically the solid inner core is growing by about 1 millimeter per year — a meter per millennium, a kilometer every million years — into the liquid outer core.

(“But doesn’t that mean the solid core was smaller in the past?”  Yes it sure does!  In fact, the Earth’s solid core is a lot younger than the Earth.  For its first couple of billion years of existence, Earth probably didn’t have a solid core at all.)

Here’s the thing: the liquid outer core is where Earth’s magnetic field is generated.  The details are complex, but basically there are convection currents moving up and down in the molten iron, and that’s where the magnetic field comes from.  But once the Earth’s liquid core gets too shallow, those currents will break down.  Current models suggest that will happen around a billion years from now, give or take.

No magnetic field means no protection from various sorts of horrible radiation coming in from space.   That’s not necessarily game over for the biosphere, but it’s very bad news for anything that doesn’t live underground or underwater.

Again, the error bars are large, and we’re talking about /around/ a billion years.  So there’s still time to clean your attic, yeah?

But!  Here’s a fun complication.  I mentioned the solid iron core is growing, right?  Okay, so just how does it grow?  Well, apparently it grows like a glacier grows, from the accretion of snow.  Crystals of solid iron “snow”, forming in the liquid outer core, softly snowing down.  This paper here looks at the details of that mechanism.  What they find is that snow occurs at different places and different times throughout the liquid core:  “crystallization and the associated buoyancy flux would be strongly heterogeneous in time and space”.  Most of the time, the snow melts again before it reaches the core.  (This happens in Earth’s atmosphere, too.  Ever seen a distant cloud with rain or snow coming out of it, but disappearing before hitting the ground?  The technical term is “virga“; you might have heard them called “jellyfish clouds”.)

The fun complication is… Earth’s core probably has *weather*.  Makes sense, right?  It’s a fluid with lots of heat energy moving through it, plus also it’s rotating.  Differential density, Coriolis force, and oh yeah magnetism probably plays a role.  The Earth’s liquid core has convection cells and iron snow.  And quite possibly it also has storms, some equivalent to thunderstorms and hurricanes.  Except this is happening a couple of thousand miles beneath your feet and, you know, in a dark sea of molten iron.  

And where there’s weather there may be climate.  This sort of thing may explain why the Earth’s magnetic field wanders around, occasionally hiccups a little, and every few hundred millennia simply flips right over.  This is an active field of study right now.

But anyway!  Iron snow, beneath your feet.