The Earth's core: the enigma 1,800 miles below us | Hacker News Reader

The Earth's core: the enigma 1,800 miles below us

nytimes.com

81 pointsValentineC24 comments

"It’s a place where pressures bear down with the weight of 3.5 million atmospheres, like 3.5 million skies falling at once on your head."

I shouldn't be overly critical, but, well, that one's not working for me.

Yeah, what exactly does the weight of 1 sky falling on your head feel like? Feels pretty decent to me.

1 megabar (roughly 1 million atmospheres) is equivalent to a thousand tonnes of pressure on every square centimeter of your body.

It’s a place where the term “ironclad agreement” has no meaning, since iron can’t even agree with itself on what form to take.

This is good writing to most people. It is fun and interesting, etc. But my brain hates it.

Surely You're Joking, Mr. Feynman! is the kind of fact heavy writing I prefer. But me and people like me are in the minority.

The author of this piece REALLY wants to write fiction. I can appreciate the florid tones in a human interest piece, or in an epic tale, but time and time again, I found myself wanting more information where instead, I got a bit of fluff.

It was well-written fluff, but still. Facts, please!

>As if the inside story of our planet weren’t already the ultimate potboiler, a host of new findings has just turned the heat up past Stygian.

I hope, when old media finally dies, that this sort of "clever" news-writing dies with it.

It is funny how regarding the polarity flip they just say "don't worry, you'll be dead.". Ok that may be true, but what would happen? If the rate of polarity switch is exponential, 10% in the last century could end up being, oh dec 12 2012? Even if that is just a silly mayan thing, what would theoretically happen? We get pelted by radiation?

Generally the models have it becoming fairly distorted in various ways and then strengthening again in the opposite polarity. It never goes to 'zero' because there isn't a model where the core stops moving. But there could be some 'local' poles in addition the primary poles. Think of it 'aurora borealis at the equator' kind of weird but not 'sleeting sheets of coronal mass ejecta raining death on helpless flora and fauna.'

Of course nobody really knows, we have models, we have guesses, we have theories. I've not seen any credible theories that result in the field going away but it doesn't mean they aren't out there.

As I understand it, the opposite polarity isn't a guarantee. The weakened magnetic poles wander for a period of time. Once the magnetic field reasserts itself, the magnetic poles return to the physical poles, and if they're opposite, so be it.

Also, your ancestors went though this millions of times while living long enough to have kids. So, while it may be unpleasant chances are it's just going end up with lightly different lights in the sky and at worse a small increase in cancer risk.

The last one was about 780,000 years ago, sometime around the start of the Middle Pleistocene. The earliest known Neanderthals are about 300,000 years old.

So no, none of our vaguely recent ancestors have lived through one. Plenty of Mammals have though!

Mammals are also your ancestors. And, the reversal takes 1,000-10,000 years so /20 and you get 50 to 500 generations per reversal.

More importantly, the magnetic field can only stop charged particles which don't travel vary far though the atmosphere anyway as in a few feet and they hit something.*

PS: Someone mentioned OMG particles, however they ignore the magnetic field anyway.

Polarity flips take thousands of years, as far as I know. In the middle bit you have loads of poles floating around and the ionosphere is much weaker and very confused, so you get a hell of a lot more radiation at the earth's surface. I also read that there is a minor north pole floating around the South Atlantic at the moment, which could presumably have you sailing in circles if relying on compasses.

> there is a minor north pole floating around the South Atlantic at the moment, which could presumably have you sailing in circles if relying on compasses

That sounds very interesting. Any sources?

By the way, I can almost imagine the beginning of the next Roland Emmerich disaster movie. A ship sinks while traveling in circles. Some clever scientist investigates the accident and deduces that the poles are going to switch next week. Nobody listens, so he must single-handedly save the world as well as his family.

Is the South Atlantic Anomaly - http://en.wikipedia.org/wiki/South_Atlantic_Anomaly

[edit] Found a good description of the effects on compasses from a British Geological Survey article on magnetic reversals:

From these models and extrapolating down into the Earth, it is known that regions of reversed flux at the core-mantle boundary have grown over time. In these regions the compass points in the opposite direction, in or out of the core, compared to that of surrounding areas. It is the growth in area of such a reversed flux patch under the south Atlantic that is primarily responsible for the decay in the main dipolar field. This reverse patch is also responsible for the minimum in field strength called the South Atlantic Anomaly, centred over North-east Brazil. In this region energetic particles can approach Earth more closely, causing increased radiation risk to low Earth orbit satellites.

http://www.geomag.bgs.ac.uk/education/reversals.html

1. The most immediate thing that would happen if that were the case is we'd already know. We could tell if the magnetic field were quickly changing. A lot of instruments people use every day would be affected by major changes in the magnetic field.

2. The magnetic field could completely disappear and we wouldn't get bombarded by radiation. The atmosphere itself protects us from radiation. Remember all that talk in the '90s about the ozone layer and how we'd get irradiated if it disappeared? That's in the atmosphere. The magnetic field doesn't do much for that AFAIK.

3. Based on the same evidence that leads us to believe the polarity switches, we believe it doesn't happen quickly. We are talking about a geological timescale here. The field won't flip by the end of the year any more than a new mountain will appear by then.

4. I think the biggest consequence if the field suddenly flipped is that we would have to fix a lot of navigational equipment.

5. You're more likely to get killed by the consequences of silly superstitions — say, based off a calendar ending on a particular date — than you are from a magnetic field polarity reversal.

In rough agreement with you, but have a quibble about your second point. As far as I understand it, while the lower atmosphere does provide significant protection, the ionosphere does have a substantial role to play as well.

Here is a very brief outline of this from everyone's favourite experimental nutter-magnet/atmospheric testing facility, HAARP: http://www.haarp.alaska.edu/haarp/ion3.html

[edit] Just thought and realised that the ionosphere is very little to do with the issue. I should really be talking about the magnetosphere and how it helps protect us from highly energetic particles in the solar wind. So my quibble still stands, but my reasoning was a big steaming pile of monkey poo.

Charged particles are the only thing affected by the earths magnetic field and they tend to be absorbed easily. Especially when they would need to get though 10+ miles of dense atmosphere to get to us.

Alpha Radiation can travel a few inches in the air.

Beta Radiation can travel a few feet in the air but far less than 50% can make it though 100 feet of air. So for 1 mile of atmosphere you would leave 1/2^52 of them.

But at ground level, cosmic radiation accounts for apparently an average of around 11% of ionising radiation exposure and this is measurably affected by the interaction of the solar wind with the magnetosphere according to experiment, or at least according to the nice graph on this page - http://www.sievert-system.org/WebMasters/en/contenu_rayonnem...

[edit] I think I remember reading somewhere that a strong magnetosphere also reduces the erosion of the atmosphere, but I suspect that this would not be a particularly important effect over the timespan of a magnetic flip, otherwise we would not be here to worry about it.

[edit] Have just gone and had a good look at this and it would appear that while there is an increase in cosmic rays at the earth's surface when the magnetic field is reduced, this basically has negligible effect when compared to other sources of ionising radiation exposure - http://www-istp.gsfc.nasa.gov/Education/FAQs7.html#q104 - so I was talking monkey poo all along. Oh well. Quibble revoked.

However I did learn a little bit about oh-my-god particles while looking into this - http://www.fourmilab.ch/documents/OhMyGodParticle/ - which are really, really cool. :)

The BBC did a great Horizon documentary on The Core recently where they visited some researchers and looked at some shiny machines which attempted to replicate the conditions at the core and grow iron crystals or something. It talks about local variations in the earth's magnetic field as well. I recommend it.

I would go for D) Scientists dont have a clue.

Because despite all human hubris, we are pretty much in the dark ages. When we have learned how to sustain ourselves without raping the planet, then maybe we can at least be called civilized. Although still a very primitive species.

Humans dont like viewing themselves as primitive and limited, but we very much are. We are unaware of the alien species constantly being around us, we think 90% of the DNA is "junk" because we dont understand what it does, we call space "empty" because we dont see whats there, etc.

Its all very much based on hubris and ego. Very very primitive. I often feel like Im watching a society that is completely nuts. Valuing paper more than the planet that is giving us life every second of every day (!).

Ok, rant over... its just mind boggling...

I think you have that tin foil hat on a little too tightly.

Everything is primitive, in that it is the origin for the things to come. The way I think of the situation is that our species and its civilization are frightfully young, with all the arrogance and naïveté that entails. Here's hoping we're not the kind of teenager that kills ourselves by crashing the family car.

If heat is coming up 3x faster than expected, isn't there a good chance that this could have a material affect on global climate? Perhaps this is yet another significant piece of the chaotic climate record.

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