4 ms·

Articles on the fear of the Earth's field flipping are, as expected, not very realistic. The best current knowledge is that it takes thousands of years for the

Articles on the fear of the Earth's field flipping are, as expected, not very realistic. The best current knowledge is that it takes thousands of years for the field to flip and the current fluctuations are within normal bounds. The wikipedia article on the Earth's magnetic field[1] is pretty good. See relevant quote from it below. Scientists recently updated the standard Gaussian coefficients used to describe the Earth's field a bit earlier than the usual 10 year adjustment. This is because the field has changed a bit quicker than the recent past and people are more interested in having a high accurate model these days, among other reasons. The release of this new model is why these kinds of stories are in the news at the moment. The Earth's magnetic field is created mostly by the convecting liquid iron/nickel outer core of the Earth. It is a quite turbulent system and can not be modeled very well for numerous reasons. Here are a few: The pressure and temperature is so high that depth (2900-5100km below the surface) in the Earth that is impossible to create similar conditions on the Earth's surface for more that milliseconds on milligram samples. The only measurements that can be made of the core are from seismic waves passing through thousands of kilometers of the heterogeneous Earth. We have decent measurements for the Earth's magnetic field only since people have been recording compass readings (1600AD or so) and really good global measurements only since satellite readings starting in the 1960's. IAAPM (I am a paleomagnetist)[2] and am happy to answer questions about this topic. "At present, the overall geomagnetic field is becoming weaker; the present strong deterioration corresponds to a 10–15% decline over the last 150 years and has accelerated in the past several years; geomagnetic intensity has declined almost continuously from a maximum 35% above the modern value achieved approximately 2,000 years ago. The rate of decrease and the current strength are within the normal range of variation, as shown by the record of past magnetic fields recorded in rocks." [1]https://en.wikipedia.org/wiki/Earth%27s_magnetic_field https://en.wikipedia.org/wiki/Earth%27s_magnetic_field

Pharmakon 8y ago
When you say the pressure conditions can be recreated for milliseconds, is this using a diamond anvil or some other technique? Beyond that, I just wanted to thank you for this post, and your reply to someone else higher up in the thread. Reading the views of subject matter experts is what drew me here in the first place.
- njarboe 8y ago
  Diamond anvil tech is just advancing into the realm where the pressure of the surface of the outer core can be held for long enough for chemical reactions to reach equilibrium. That is, to be highly useful to see what might be happening in the core. Heating up to high temperatures at the same time is an added difficulty and can only be done for a shorter time periods. I'm not an expert on diamond anvils, but follow the advancements some. It is how we are going to actually get a good idea of the possibilities of what goes on in the deep Earth. It would be really cool if humans decided to try and tunnel the 3000km to the core so we could sample it directly and be able to do long timescale experiments on bulk samples. I don't think physics fundamentally prohibits such a thing. By short time I mean that some physical properties of matter at high temperatures and pressures can be determined by observing high velocity collisions or explosions, but these are short lived phenomena. A lot of effort has been spent on experiments like this for understanding how nuclear bombs behave. Some of those experiments help inform, say, the properties of iron under high temp and pressure and have been declassified so us mere Earth scientists can learn about it.
  - Pharmakon 8y ago
    Thanks for the detailed answer. Can you recommend any good publications, books or blogs that relate to this subject?
    - njarboe 8y ago
      I don't know your background, so it is hard to know what to recommend. If you have a PhD in a subject area then in theory you should have enough general knowledge to be able to effectively read a recent review article explaining the state of the art in some sub-discipline. I can then use the references in that paper to read about the concepts and ideas I am not familiar with and I think are important to understand. Using google scholar (not regular google), I found this recent article "Contributed Review: Culet diameter and the achievable pressure of a diamond anvil cell: Implications for the upper pressure limit of a diamond anvil cell" https://doi.org/10.1063/1.5049720 https://doi.org/10.1063/1.5049720 I would read this to update my ideas about what diamond anvil cells can do right now. Then, if I wanted to actually use one or find out if I should use one, I would talk with one of the authors of a paper referenced in the review paper that I thought was good and dealt with the particular reason I wanted to use one. That was a bit long winded. Hope it helped.

Pharmakon 8y ago

When you say the pressure conditions can be recreated for milliseconds, is this using a diamond anvil or some other technique? Beyond that, I just wanted to thank you for this post, and your reply to someone else higher up in the thread. Reading the views of subject matter experts is what drew me here in the first place.

njarboe 8y ago
Diamond anvil tech is just advancing into the realm where the pressure of the surface of the outer core can be held for long enough for chemical reactions to reach equilibrium. That is, to be highly useful to see what might be happening in the core. Heating up to high temperatures at the same time is an added difficulty and can only be done for a shorter time periods. I'm not an expert on diamond anvils, but follow the advancements some. It is how we are going to actually get a good idea of the possibilities of what goes on in the deep Earth. It would be really cool if humans decided to try and tunnel the 3000km to the core so we could sample it directly and be able to do long timescale experiments on bulk samples. I don't think physics fundamentally prohibits such a thing. By short time I mean that some physical properties of matter at high temperatures and pressures can be determined by observing high velocity collisions or explosions, but these are short lived phenomena. A lot of effort has been spent on experiments like this for understanding how nuclear bombs behave. Some of those experiments help inform, say, the properties of iron under high temp and pressure and have been declassified so us mere Earth scientists can learn about it.
- Pharmakon 8y ago
  Thanks for the detailed answer. Can you recommend any good publications, books or blogs that relate to this subject?
  - njarboe 8y ago
    I don't know your background, so it is hard to know what to recommend. If you have a PhD in a subject area then in theory you should have enough general knowledge to be able to effectively read a recent review article explaining the state of the art in some sub-discipline. I can then use the references in that paper to read about the concepts and ideas I am not familiar with and I think are important to understand. Using google scholar (not regular google), I found this recent article "Contributed Review: Culet diameter and the achievable pressure of a diamond anvil cell: Implications for the upper pressure limit of a diamond anvil cell" https://doi.org/10.1063/1.5049720 https://doi.org/10.1063/1.5049720 I would read this to update my ideas about what diamond anvil cells can do right now. Then, if I wanted to actually use one or find out if I should use one, I would talk with one of the authors of a paper referenced in the review paper that I thought was good and dealt with the particular reason I wanted to use one. That was a bit long winded. Hope it helped.