# Geeky, but a bit of fascinating history - Degaussing ships to avoid mines in WWII **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [November 4, 2013, 1:42am UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021 "2013-11-04T01:42:54Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [November 4, 2013, 1:42am UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/1 "2013-11-04T01:42:54Z")
[Pretty interesting](http://www.fas.org/man/dod-101/sys/ship/weaps/degaussing.htm) overview of using degaussing to avoid mines. > [@](#): > > The effort to defeat these magnetic mines took several forms. One such approach was to attempt to negate the magnetic signatures of metal ships through a process known as “degaussing,” as described here: > A steel-hulled ship is like a huge floating magnet with a large magnetic field surrounding it. As the ship moves through the water, this field also moves and adds to or subtracts from the Earth’s magnetic field. Because of its distortion effects on the Earth’s magnetic field, the ship can act as a trigger device for magnetic sensitive ordnance or devices which are designed to detect these distortions. The degaussing system is installed aboard ship to reduce the ship’s effect on the Earth’s magnetic field. In order to accomplish this, the change in the Earth’s field about the ship’s hull is “canceled” by controlling the electric current flowing through degaussing coils wound in specific locations within the hull. This, in turn, reduces the possibility of detection by these magnetic sensitive ordnance or devices. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [November 4, 2013, 3:16am UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/2 "2013-11-04T03:16:33Z")
Misunderstood origin of the “Philadelphia Experiment.” ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [November 4, 2013, 4:51am UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/3 "2013-11-04T04:51:14Z")
Check out “dazzle paint” which I came across recently for the first time, for another bit of unusual wartime evasion. ---
**Author:** ![yoyodyne](https://avatars.discourse-cdn.com/v4/letter/y/a9a28c/32.png) [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)\ **Post date:** [November 4, 2013, 2:01pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/4 "2013-11-04T14:01:47Z")
Submarines still do [deperming](http://en.wikipedia.org/wiki/Deperming). ---
**Author:** ![tonyfop](https://avatars.discourse-cdn.com/v4/letter/t/85f322/32.png) [@tonyfop](https://boards.straightdope.com/u/tonyfop)\ **Post date:** [November 4, 2013, 2:14pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/5 "2013-11-04T14:14:39Z")
When I got my Enlisted Surface Warfare Specialist Qualification aboard USS Kearsarge in 2008 learning about the degaussing system was part of the qualification. You can see it here in the Personnel Qualification Standard page 61, items 109.23 and 109.24[http://www.desron.herrickmi.us/esws.pdf](http://www.desron.herrickmi.us/esws.pdf). While I have forgotten most of it now, I seem to remember that the purpose was anti-mine as well as taking care of all of the electronics onboard the ship and on the aircraft landing on the ship. We had to learn where all of the windings were, and where the different controls were. ---
**Author:** ![Kimballkid](https://avatars.discourse-cdn.com/v4/letter/k/b5a626/32.png) [@Kimballkid](https://boards.straightdope.com/u/Kimballkid)\ **Post date:** [November 4, 2013, 5:19pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/6 "2013-11-04T17:19:35Z")
[Here’s](http://travelphotobase.com/v/USAL/ALMB073.HTM) a picture of the degaussing room on the USS Alabama. ---
**Author:** ![aruvqan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aruvqan/32/2891_2.png) [@aruvqan](https://boards.straightdope.com/u/aruvqan)\ **Post date:** [November 4, 2013, 8:12pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/7 "2013-11-04T20:12:21Z")
> [@yoyodyne](#): > > Submarines still do [deperming](http://en.wikipedia.org/wiki/Deperming). Which sucked for the guy who left his wallet on the US Spadefish that one time … 😛 ---
**Author:** ![Mr.Goob](https://avatars.discourse-cdn.com/v4/letter/m/c77e96/32.png) [@Mr.Goob](https://boards.straightdope.com/u/Mr.Goob)\ **Post date:** [November 4, 2013, 10:50pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/8 "2013-11-04T22:50:08Z")
**Tonyfop** beat me to it, I was going to say as of 1992 ships still had the gear in use. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [November 5, 2013, 3:40pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/9 "2013-11-05T15:40:22Z")
> [@Amateur\_Barbarian](#): > > Misunderstood origin of the “Philadelphia Experiment.” Oh, I was going to make a joke about this, but it’s true?! ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [November 5, 2013, 3:45pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/10 "2013-11-05T15:45:28Z")
> [@AaronX](#): > > Oh, I was going to make a joke about this, but it’s true?! Almost certainly. Someone misunderstood the then-new notion of degaussing ships (which was, I believe, semi-secret during the war) and making ships “invisible” to mines turned into all kinds of nonsense about teleporting invisible ships around. There may have even been an accident with the gigantic equipment (100-foot coils powered by high voltages) that introduced the other facets of the legend. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [November 5, 2013, 3:51pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/11 "2013-11-05T15:51:46Z")
I’m going to assume the bits about people disappearing and getting stuck in the walls are exaggeration. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [November 5, 2013, 4:05pm UTC](https://boards.straightdope.com/t/geeky-but-a-bit-of-fascinating-history-degaussing-ships-to-avoid-mines-in-wwii/673021/12 "2013-11-05T16:05:06Z")
> [@AaronX](#): > > I’m going to assume the bits about people disappearing and getting stuck in the walls are exaggeration. It’s an urban legend/paranormal claim. Like many of such, it’s based on the faintest grain of truth but a few decades of embellishment have obscured that.