Author Topic: Episode #669  (Read 2957 times)

0 Members and 1 Guest are viewing this topic.

Offline Isranner

  • Off to a Start
  • *
  • Posts: 43
Re: Episode #669
« Reply #15 on: May 08, 2018, 12:49:29 PM »
I did hear another podcast on the recent Magnetic Fields flipping being unlikely.  There was a brief mention on a flipping occurring at the start of the pre-cambrian and that it may have sparked the Cambrian Explosion.
We have a relatively strong northern magnetic pole and a somewhat weaker magnetic pole...and depending where you are in the southern ocean, you might find several southerns poles.
Those fields will flip at some point in the future.  I'll wonder how we'll deal with it since it takes about 100 years to settle back down and provide the protection we need today from high energy solar radiation.

I haven’t read the study on which the report was based, but it’s my understanding that when the magnetic poles flip, the magnetic field doesn’t disappear (along with the protection against cosmic radiation).  What happens is that the north magnetic pole rapidly migrates to the south and the south magnetic pole rapidly migrates to the north on the opposite side of the globe until the two poles are roughly in the region of the geographical poles at which point the movement of the magnetic poles slows down to normal.
The ‘flip’ occurs too rapidly to be shown in the geological record of the polarity of ferrite crystal in rocks.
During the ‘flip’ the northern magnetic pole might at some time be centred over Tahiti.  The magnetic field still persists and is still providing protection from cosmic radiation, so there’s no mass extinction, either major or minor.

Were I you, I wouldn't trust your understanding much:

«Despite the uncertainties surrounding the polarity reversal phenomenon, there are some characteristics that are well established and involve significant dipole moment changes. First, most reversals are associated with a large drop in the dipole moment that typically occurs before the major directional changes of the field. During many reversals the field intensity drops to about 25% of its normal value at the height of the directional transition (Lin et al. 1994; Tanaka et al. 1995; McFadden and Merrill 1997). Second, the duration of this intensity drop generally lasts 5,000 to 20,000 years (Merrill and McFadden 1999; Valet 2003), while the directional transition is usually shorter, typically lasting 2,000–7,000 years (Bogue and Paul 1993; Dormy et al. 2000; Clement 2004). We note that the rate of paleointensity decrease before polarity reversals is comparable to the present-day moment decrease rate.»

— Olson P, Amit H. "Changes in earth's dipole." Naturwissenschaften (2006 Nov) vol. 93 (11) pp. 519-42
http://pages.jh.edu/~polson1/pdfs/ChangesinEarthsDipole.pdf
https://www.ncbi.nlm.nih.gov/pubmed/16915369

I haven’t read the study on which the report was based

Here you are:

• Brown M, Korte M, Holme R, Wardinski I, Gunnarson S. "Earth’s magnetic field is probably not reversing." Proc Natl Acad Sci U S A (published ahead of print: 2018 Apr 30) 201722110 DOI: 10.1073/pnas.1722110115
http://www.pnas.org/content/early/2018/04/24/1722110115
https://sci-hub.hk/10.1073/pnas.1722110115

Press release:

• University of Liverpool. "Earth's magnetic field is not about to reverse." ScienceDaily (2018-04-30)
https://www.sciencedaily.com/releases/2018/04/180430160437.htm

Press coverage:

• John Timmer. "Flip or Flop? — Earth’s magnetic field may not be flipping: While the magnetic field is changing, geology suggests our poles won't trade places." Ars Technica (2018-05-01)
https://arstechnica.com/science/2018/05/earths-magnetic-field-may-not-be-flipping

• Josh Gabbatiss. "Earth's magnetic field is not about to reverse and trigger global catastrophe." The Independent (2018-04-30)
https://www.independent.co.uk/news/science/earth-magnetic-field-flip-poles-why-not-facts-weak-a8329921.html

• Ryan F Mandelbaum. "The Earth’s Magnetic Poles Are Not About to Flip, and Here’s Why." Gizmodo (2018-04-30)
https://gizmodo.com/the-earth-s-magnetic-poles-are-not-about-to-flip-and-h-1825657854

• Nick Whigham. "New research throws cold water on magnetic pole reversal fears: Warnings abound that we need to “start preparing” for a dramatic magnetic pole reversal, but new research sheds light on our planet’s strange behaviour." News.com.au (2018-05-01)
http://www.news.com.au/technology/science/new-research-throws-cold-water-on-magnetic-pole-reversal-fears/news-story/ca91df281987d1d3a815c8ba4acb1146

• News Staff. "Earth's Magnetic Field Is Not Reversing." Science 2.0 (2018-05-01)
http://www.science20.com/news_staff/earths_magnetic_field_is_not_reversing-232120

Offline bachfiend

  • Not Any Kind of Moderator
  • Frequent Poster
  • ******
  • Posts: 2435
Re: Episode #669
« Reply #16 on: May 08, 2018, 07:55:36 PM »
I did hear another podcast on the recent Magnetic Fields flipping being unlikely.  There was a brief mention on a flipping occurring at the start of the pre-cambrian and that it may have sparked the Cambrian Explosion.
We have a relatively strong northern magnetic pole and a somewhat weaker magnetic pole...and depending where you are in the southern ocean, you might find several southerns poles.
Those fields will flip at some point in the future.  I'll wonder how we'll deal with it since it takes about 100 years to settle back down and provide the protection we need today from high energy solar radiation.

I haven’t read the study on which the report was based, but it’s my understanding that when the magnetic poles flip, the magnetic field doesn’t disappear (along with the protection against cosmic radiation).  What happens is that the north magnetic pole rapidly migrates to the south and the south magnetic pole rapidly migrates to the north on the opposite side of the globe until the two poles are roughly in the region of the geographical poles at which point the movement of the magnetic poles slows down to normal.
The ‘flip’ occurs too rapidly to be shown in the geological record of the polarity of ferrite crystal in rocks.
During the ‘flip’ the northern magnetic pole might at some time be centred over Tahiti.  The magnetic field still persists and is still providing protection from cosmic radiation, so there’s no mass extinction, either major or minor.

Were I you, I wouldn't trust your understanding much:

«Despite the uncertainties surrounding the polarity reversal phenomenon, there are some characteristics that are well established and involve significant dipole moment changes. First, most reversals are associated with a large drop in the dipole moment that typically occurs before the major directional changes of the field. During many reversals the field intensity drops to about 25% of its normal value at the height of the directional transition (Lin et al. 1994; Tanaka et al. 1995; McFadden and Merrill 1997). Second, the duration of this intensity drop generally lasts 5,000 to 20,000 years (Merrill and McFadden 1999; Valet 2003), while the directional transition is usually shorter, typically lasting 2,000–7,000 years (Bogue and Paul 1993; Dormy et al. 2000; Clement 2004). We note that the rate of paleointensity decrease before polarity reversals is comparable to the present-day moment decrease rate.»

— Olson P, Amit H. "Changes in earth's dipole." Naturwissenschaften (2006 Nov) vol. 93 (11) pp. 519-42
http://pages.jh.edu/~polson1/pdfs/ChangesinEarthsDipole.pdf
https://www.ncbi.nlm.nih.gov/pubmed/16915369

I haven’t read the study on which the report was based

Here you are:

• Brown M, Korte M, Holme R, Wardinski I, Gunnarson S. "Earth’s magnetic field is probably not reversing." Proc Natl Acad Sci U S A (published ahead of print: 2018 Apr 30) 201722110 DOI: 10.1073/pnas.1722110115
http://www.pnas.org/content/early/2018/04/24/1722110115
https://sci-hub.hk/10.1073/pnas.1722110115

Press release:

• University of Liverpool. "Earth's magnetic field is not about to reverse." ScienceDaily (2018-04-30)
https://www.sciencedaily.com/releases/2018/04/180430160437.htm

Press coverage:

• John Timmer. "Flip or Flop? — Earth’s magnetic field may not be flipping: While the magnetic field is changing, geology suggests our poles won't trade places." Ars Technica (2018-05-01)
https://arstechnica.com/science/2018/05/earths-magnetic-field-may-not-be-flipping

• Josh Gabbatiss. "Earth's magnetic field is not about to reverse and trigger global catastrophe." The Independent (2018-04-30)
https://www.independent.co.uk/news/science/earth-magnetic-field-flip-poles-why-not-facts-weak-a8329921.html

• Ryan F Mandelbaum. "The Earth’s Magnetic Poles Are Not About to Flip, and Here’s Why." Gizmodo (2018-04-30)
https://gizmodo.com/the-earth-s-magnetic-poles-are-not-about-to-flip-and-h-1825657854

• Nick Whigham. "New research throws cold water on magnetic pole reversal fears: Warnings abound that we need to “start preparing” for a dramatic magnetic pole reversal, but new research sheds light on our planet’s strange behaviour." News.com.au (2018-05-01)
http://www.news.com.au/technology/science/new-research-throws-cold-water-on-magnetic-pole-reversal-fears/news-story/ca91df281987d1d3a815c8ba4acb1146

• News Staff. "Earth's Magnetic Field Is Not Reversing." Science 2.0 (2018-05-01)
http://www.science20.com/news_staff/earths_magnetic_field_is_not_reversing-232120

Isranner,

Your linked articles don’t disprove my understanding that when the magnetic poles flip, that the Earth’s magnetic field doesn’t disappear.  The magnetic field dropping to 25% (if true) during a flip isn’t a disappearance of the magnetic field.

I can’t be bothered hunting up my reference for the magnetic poles migrating rapidly during a flip, but it was on the NASA website.

Knowing what the magnetic poles and the magnetic fields were doing in the far distant past, such as the pre-Cambrian, is difficult, in comparison to which playing 3-dimensional chess is easy.  The tectonic plates bearing the continents are constantly moving around on the Earth’s surface, so the location and polarity of the crystals in continental rocks currently are different to when they were first layed down.  And no oceanic rock is older than about 180 million years old.

I doubt that the pre-Cambrian mass extinction leading to the Cambrian ‘explosion’ (actually radiation) was due to a magnetic pole reversal, as has also been suggested.
Gebt ihr ihr ihr Buch zurück?

Offline Fast Eddie B

  • Frequent Poster
  • ******
  • Posts: 3361
Re: Episode #669
« Reply #17 on: May 09, 2018, 10:43:13 AM »
About magnetic north moving...

Pilots have to be aware of the difference between magnetic north and true north, which is called variation. You measure true course on a chart relative to lines of longitude and latitude, but have to convert to magnetic course since that's what compasses read.

On the charts we use are "isogonic" lines - lines connecting points of equal magnetic variation. They look like this:



That one shows that magnetic north lies 5º west of true north in that area.

A snapshot of isogonic lines at one point in time in the US:



Variation is also shown on airport charts, which also shows its historical rate of change:



As a practical consequence, runways are numbered to the nearest 10º of magnetic bearing. Hence, Runway 9 will have a magnetic bearing of between roughly 085º and 095º. The variation can drift enough over time that its not unusual for runways to have to be renumbered.

Interestingly, that current airport chart differs a lot from that older snapshot from a textbook. Opa Locka is near Miami, and you can see at the time of the snapshot it was very close to being on the agonic line - 0º variation, but is now over 6º west variation.

« Last Edit: May 10, 2018, 11:04:05 AM by Fast Eddie B »

Offline gebobs

  • Seasoned Contributor
  • ****
  • Posts: 633
  • Me like hockey!
Re: Episode #669
« Reply #18 on: May 10, 2018, 08:45:02 AM »
Your linked articles don’t disprove my understanding that when the magnetic poles flip, that the Earth’s magnetic field doesn’t disappear.

Not only that, but Earth's magnetic field varies anyway...


Offline bachfiend

  • Not Any Kind of Moderator
  • Frequent Poster
  • ******
  • Posts: 2435
Re: Episode #669
« Reply #19 on: May 10, 2018, 09:31:35 AM »
Your linked articles don’t disprove my understanding that when the magnetic poles flip, that the Earth’s magnetic field doesn’t disappear.

Not only that, but Earth's magnetic field varies anyway...




gebobs,

I don’t doubt that the strength of the magnetic field varies.  But estimates of its strength before there were meters which measured it directly are problematic.  You have to find rocks of the right age and determine the polarity of the magnetic crystals (and make allowance for changes in position and orientation of the rocks) and somehow estimate how strong the magnetic field was at the time the rocks were laid down.
Gebt ihr ihr ihr Buch zurück?

Offline gebobs

  • Seasoned Contributor
  • ****
  • Posts: 633
  • Me like hockey!
Re: Episode #669
« Reply #20 on: May 14, 2018, 12:02:58 PM »
gebobs,

I don’t doubt that the strength of the magnetic field varies.  But estimates of its strength before there were meters which measured it directly are problematic.  You have to find rocks of the right age and determine the polarity of the magnetic crystals (and make allowance for changes in position and orientation of the rocks) and somehow estimate how strong the magnetic field was at the time the rocks were laid down.

I was just showing that it changes continually over the geologic record. I'm sure establishing such a timeline is very complicated and really have no idea if it's more or less complicated than a similar CO2 timeline. But I just don't think we have to worry about the field disappearing for a century so we need to start moving into caves.

Offline seamas

  • Frequent Poster
  • ******
  • Posts: 2542
Re: Episode #669
« Reply #21 on: May 15, 2018, 12:00:00 PM »
Regardless of what Perry died thinking, Tony Soprano is dead.
Schrodinger says you are both right.
There's no such thing as denial.

Offline DevoutCatalyst

  • Well Established
  • *****
  • Posts: 1649
Re: Episode #669
« Reply #22 on: May 15, 2018, 12:11:56 PM »
Schrodinger says you are both right.
Go to your room.

Offline martintolley

  • Banned
  • Brand New
  • *
  • Posts: 4
Re: Episode #669
« Reply #23 on: May 23, 2018, 02:38:30 AM »
 Great post. One time I had a pole flip on me. I really thinks the noise clip in Episode #669 are pennies rolling down the spiral wishing well in Los Vegas, NV. Science Child's Museum url=http://www.geometrydash.me/geometry dash

Moderator Comment Broke spam link
« Last Edit: May 23, 2018, 05:19:16 AM by Rai »

Offline keithc

  • Off to a Start
  • *
  • Posts: 10
    • Methods and Music
Re: Episode #669
« Reply #24 on: May 24, 2018, 05:07:31 AM »
On the audio wiring, I heard a story that a speaker manufacturer was exhibiting at an audio show and people were asking where they got the great sounding orange speaker wires from. The answer was that they had managed to turn up at the show without their speaker wires, so they popped across the street to a garden store and bought extension cables for garden equipment and used them.
Cheers

KeithC

read my blog: http://methods-and-music.blogspot.com/

Offline keithc

  • Off to a Start
  • *
  • Posts: 10
    • Methods and Music
Re: Episode #669
« Reply #25 on: May 24, 2018, 05:17:44 AM »
Mistletoe is the punchline to a silly joke.

"What do astronauts get instead of athelete's foot?"
Took me a bit of time to realise that this doesn't work with my British accent, but works fine with a US accent
Cheers

KeithC

read my blog: http://methods-and-music.blogspot.com/

Offline starnado

  • the once and future king of tl;dr
  • Well Established
  • *****
  • Posts: 1569
Re: Episode #669
« Reply #26 on: June 03, 2018, 01:58:22 PM »
Mistletoe berries are white, aren't they? Holly has red berries.
'The little, stupid differences are nothing next to the big, stupid similarities'
Bart Simpson