# If the earth's magnetic field reversed what would be affected other than compasses? **URL:** \ **Category:** Factual Questions\ **Created:** [December 10, 2005, 3:04am UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993 "2005-12-10T03:04:46Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [December 10, 2005, 3:04am UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993/1 "2005-12-10T03:04:46Z")
Per the article below say it did flip, would anything substantive be affected other than compasses and the northern lights? [Earth’s Magnetic Pole Drifting Quickly](http://www.breitbart.com/news/2005/12/09/D8ED22880.html) > [@](#): > > The magnetic poles are part of the magnetic field generated by liquid iron in Earth’s core and are different from the geographic poles, the surface points marking the axis of the planet’s rotation. Scientists have long known that magnetic poles migrate and in rare cases, swap places. Exactly why this happens is a mystery. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [December 10, 2005, 3:19am UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993/2 "2005-12-10T03:19:46Z")
IIRC there’s a period of low to no magnetic field as it flips; this would allow a fair amount of ionizing radiation to reach the surface and likely cause cancers/birth defects. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [December 10, 2005, 3:57am UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993/3 "2005-12-10T03:57:29Z")
The earth’s magnetic field is composed of a dominant dipole field plus other, weaker fields with more poles, 4, 6, etc. It is the dipole field that has a north magnetic in Canada and a south magnetic somewhere in Antarctica. The current theory as to the cause of the fields is convection currents in the earth’s core. Those currents never cease but they could become more disorganized in such a way as to reduce the dipole field. However according to the US Geological Survey people who studied the fields and established the reduction of the dipole field, the total magnetic energy is just about constant. The energy that was in the diplole field is being shifted over to the higher order fields[sup]\*[/sup]. The total field strength is just about the same but it is distributed differently in the various modes. (The Geological Survey work cited is quite old [1968] and there might be newer data available that I can’t find.) It seems unlikely that the _total_ field will disappear but the dipole field very well could. The dipole field might also merely change polarity rapidly, say over a few hundred years, without going through zero field strength. I don’t believe there is any evidence of serious die offs that coincide with reversals of the dipole field. \*_Scientists Confront Creationism_, Laurie R. Godfrey, Editor, W.W. Norton, NY, NY. A compendioum of scientific articles on various claims of creationists. The magnetic field information is in Chapter 4 by Prof. Stephen G. Brush, Univ. of Maryland. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [December 10, 2005, 4:02am UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993/4 "2005-12-10T04:02:36Z")
Some of the many previous threads on this topic: > **[Magnetic Polar Shifts](https://boards.straightdope.com/sdmb/showthread.php?t=267902)** > > yeah, i know, this has probably been discussed before; but i have some specific questions that i don’t feel like reading 3 entire threads to find the answer. my first question is, what exactly causes them? i have been told by one of my high school... > **[How is the earth's magnetic field flipping going to knock out the US power grid?](https://boards.straightdope.com/sdmb/showthread.php?t=266191)** > > Even if it does, per this article, how is that going to affect the power distribution grid? The earth’s magnetic fields is extremely weak compared to AC land lines. How would a magnetic polarity flip blow anything out? NYT: COLLAPSE OF THE EARTH’S... > **[The Next Magnetic Reversal?](https://boards.straightdope.com/sdmb/showthread.php?t=157879)** > > It seems to be quite well established that the Earth’s magnetic field reverses polarity about every 100,000 years, and that the last one was about 100,000 years ago. That means that “soon” – in geologic terms – we’re due for another magnetic... > **[The poles and their occasional switch](https://boards.straightdope.com/sdmb/showthread.php?t=141682)** > > My understanding is that occasionally the magnetic poles of the earth do a flip-flop. Here are my questions: Which pole, currently, is the positive, and which the negative? Considering that we haven’t had a polarity swap in recorded history (we... > **[Earths Magnetism](https://boards.straightdope.com/sdmb/showthread.php?t=125814)** > > I read on several internet sites recently that the Earth’s magnet field has weakened over the last 150 years that it has been measured. Could this have something to do with the non-polarized collection of ferrite materials in big cities or due to... From that last thread: > [@](#): > > > [@scm1001](#): > > > > David you seem to be right > > > > [http://www.newton.dep.anl.gov/askasci/env99/env034.htm](http://www.newton.dep.anl.gov/askasci/env99/env034.htm) > > > > “The magnetic field does not protect the earth from solar flares. It simply guides the ions of the solar wind to the polar regions, where their energetic collisions with the upper atmosphere produce the luminous plasma known as the Northern and Southern Lights (Aurora Borealis and Aurora Australis). It is the earth’s atmosphere that actually prevents the solar wind from reaching the surface, and that is independent of the magnetic > > field.” > > > > However all those animals and birds that use the magnetic fields for navigation are in for a shock! ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [December 11, 2005, 5:28am UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993/5 "2005-12-11T05:28:12Z")
Speculation: All the bipolar people on earth might undergo a dramatic change in mood and thinking. That would apparently include the folks who made the polar bears/penguins ads for Coca-Cola. Fiction: Check out Ken Kesey’s novel, _Sailor’s Song._ Besides being a brilliant book, it has a climax that seems to deal with shifting polarity. Aaaaand Og knows what else. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [December 11, 2005, 2:37pm UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993/6 "2005-12-11T14:37:57Z")
What I want to know is when they will start blaming the USA for it. ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [December 11, 2005, 4:09pm UTC](https://boards.straightdope.com/t/if-the-earths-magnetic-field-reversed-what-would-be-affected-other-than-compasses/334993/7 "2005-12-11T16:09:32Z")
> [@David Simmons](#): > > The earth’s magnetic field is composed of a dominant dipole field plus other, weaker fields with more poles, 4, 6, etc. It is the dipole field that has a north magnetic in Canada and a south magnetic somewhere in Antarctica. Nitpick: The higher modes of a magnetic field are usually decomposed into quadrupole, octopole, hexadecapole, etc. contributions — i.e. 2, 4, 8, 16, etc.