# EMP question?



## hunter63 (Jan 4, 2005)

Hasn't been much said lately about EMP and it's effects.
I realize that a lot of electronics would be effected.
Stuff like GPS's, phones etc.
My question is what would it do to a compass, as the needle in a magnet?


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## 2ndmouse (Jan 16, 2009)

I wish my lawn was EMO so it would cut itself.


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## Cyngbaeld (May 20, 2004)

I don't think it would affect an ordinary compass any.


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## 2ndmouse (Jan 16, 2009)

For local navigation, a printed map with landmarks will do as well of better than a compass, if you sight off the sunrise/sunset with a shadow stick.

If you are traveling, an shadow stick is a good way to set your direction.


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## ET1 SS (Oct 22, 2005)

The needle of a magnet?

Nothing.

EMP is AC, the eddy currents generated will be AC. So all magnetic fields generated will be alternating. So nothing should become magnetic. An EMP lasts only for microseconds, so nothing should become De-Magnetized.

I do have an industrial Demagnetizer tool, but it puts out a very specific type of flux to do that.


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## texican (Oct 4, 2003)

ET1 SS is right... emp won't affect compasses...

I may be wrong, but I don't think anything in the universe can break the laws of gravity, and magnetism...

If you're life defends on it, forget GPS... get a paper map, and a compass, and learn how to use both independently...


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## Riverrat (Oct 14, 2008)

The only thing I would add to what texican said is to protect your map, seal it in water proofing. Great advice texican.


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## SuburbanHermett (Jan 12, 2009)

What about all of those satellites that are up there orbiting the earth? Will those come crashing down if there is an EMP? If there is no way or no one to tell them to adjust their orbit? [I remember that recently (this past spring?) that there was a problem with a broken (but new) satellite (Japan's? China's?) the size of a school bus that was full of fuel (flourazine?) that was going to crash into the U.S.A. unless someone shot it while it was still at a certain altitude].


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## WanderingOak (Jul 12, 2004)

SuburbanHermett said:


> What about all of those satellites that are up there orbiting the earth? Will those come crashing down if there is an EMP? If there is no way or no one to tell them to adjust their orbit? [I remember that recently (this past spring?) that there was a problem with a broken (but new) satellite (Japan's? China's?) the size of a school bus that was full of fuel (flourazine?) that was going to crash into the U.S.A. unless someone shot it while it was still at a certain altitude].


I would think that falling satellites would be the least of my worries after an EMP. If their electronics are fried, then our only choice when their orbit begins to decay is to either shoot it down, or to be someplace else when they crash.


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## mnn2501 (Apr 2, 2008)

SuburbanHermett said:


> What about all of those satellites that are up there orbiting the earth? Will those come crashing down if there is an EMP?


The law of gravity holds them up, not electronics. As thier orbits deteriorate they will indeed come down, but it won't be an immediate thing due to an EMP, while there are a few big satellites most are about the size of a refridgerator and considering the heat they go through upon re-entry, very few will even make it to earth. The chances of hitting the lottery are much much higher than getting hit by a falling satellite.


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## BTO (Feb 7, 2007)

ET1 SS said:


> The needle of a magnet?
> 
> Nothing.
> 
> ...


If the magnetic field is "AC" or periodically reversing itself and is of significant strength it certainly will demagnitize a magnet. At the least it will diminish its magnetic field strength. A field that alternates has the effect of scrambling the magnetic domains that are exposed to it. Scrambled domains equal no magnetic field or a weakened magnetic field.


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## ET1 SS (Oct 22, 2005)

BTO said:


> If the magnetic field is "AC" or periodically reversing itself and is of significant strength it certainly will demagnitize a magnet. At the least it will diminish its magnetic field strength. A field that alternates has the effect of scrambling the magnetic domains that are exposed to it. Scrambled domains equal no magnetic field or a weakened magnetic field.


A permanent magnet no, a temporary magnet yes.

A old style permanent magnet was from 'lodestone', it's magnetic property comes from the molecular structure, and can not be taken away unless the lodestone is melted to allow the molecules to rearrange themselves.

Ferrite magnets are made from inducing a strong magnetic field and hoping that it rubs off. It will, but it can easily be demagnetized.

The rotor of a generator is usually made from ferrites. Their magnetic field does wear-down over time. But operating that generator re-strengthens the fields, so through operation the fields will remain strong for decades.

A compass does not rely on electromagnetism. Compass' are made from lodestone.

Technically you can made lodestone from melting ferrite materials and inducing a magnetic field into the liquid metal, and keeping that field in place while you allow the ferrite to cool. Once it cools you will have a permanent magnet that no longer relies upon electromagnetism to maintain it's strength. The only way to demagnetise such a permanent magnet would include melting it.

An EMP should not melt a compass, unless you are really close to the explosion. In which case you first concern is not the loss of a magnet rather it would be the 5,000 degrees that has turned you to ash.


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## BTO (Feb 7, 2007)

ET1 SS said:


> A permanent magnet no, a temporary magnet yes.
> 
> A old style permanent magnet was from 'lodestone', it's magnetic property comes from the molecular structure, and can not be taken away unless the lodestone is melted to allow the molecules to rearrange themselves.
> 
> ...


Not to beat a dead horse, but your concept of a permanant magnet is not exactly correct. Lodestone (magnitite ore) is a naturally occuring subtance believed to have been created/magnitized by the big bang that created the universe. I don't know of any modern compass that uses lodestone.


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## ET1 SS (Oct 22, 2005)

BTO said:


> Not to beat a dead horse, but your concept of a permanant magnet is not exactly correct. Lodestone (magnitite ore) is a naturally occuring subtance believed to have been created/magnitized by the big bang that created the universe. I don't know of any modern compass that uses lodestone.


You can make a temporary magnet from ferric materials using electromagnets, and it will hold a field for a while [hours, days, months]. Inside an automotive generator they use regenerative fields to constantly build those fields, and they will stay strong for decades. Such a magnet will not be used in making compases.

Or you can do it in a furnace and make a magnet that will stay strong permanently. These magnets will be used in making compases.

Fine I used the phrase lodestone in a generic sense and not in a technical sense. 

And the horse continues to run.


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## radiofish (Mar 30, 2007)

But what if you decide to use 'celestial navigation'?? At nightime (with a clear sky) look up at the Big Dipper, and then find Polaris. That is considered 'North'.. The sun rises in the East and sets in the West..

I don't think that a compass would be affected by an EMP pulse.. From the lowly el-cheapo Sporting Goods store types, to the US Military issued compasses that I have here.. I may have to sacrifice an el-cheapo pin-on your clothing compass for scientifc experimentation, and play Dr. Frankenstein in my workshop/ radio room..

If folks would now get hopelessly lost without their GPS gadgets, then how did others find their way with only a rudimentary compass and a map (if they even had a map)????? Let alone figuring in the degrees of magnetic declination, from true North!!!!


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## Jim-mi (May 15, 2002)

Throw a rock into a pond and watch the wave . . .how it diminishes with distance......

Same with a 'man' created EMP pulse.
How strong was it?
How far from it were\are you?


The exception of course is the Sun.


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## texican (Oct 4, 2003)

BTO said:


> Not to beat a dead horse, but your concept of a permanant magnet is not exactly correct. Lodestone (magnitite ore) is a naturally occuring subtance believed to have been created/magnitized by the big bang that created the universe. I don't know of any modern compass that uses lodestone.


Not to beat that horse, but another one...

After the initial inflationary event (before the first second), the only element in the virgin universe was hydrogen. Gravity pulled the hydrogen together, which formed stars. Nuclear fusion created helium and other light elements. Some went supernovae and created all of the heavier elements. Everyone of us is made of atoms formed after supernova explosions. 

[one of my passions is cosmology]


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## zito (Dec 21, 2006)

texican said:


> Not to beat that horse, but another one...
> 
> After the initial inflationary event (before the first second), the only element in the virgin universe was hydrogen. Gravity pulled the hydrogen together, which formed stars. Nuclear fusion created helium and other light elements. Some went supernovae and created all of the heavier elements. Everyone of us is made of atoms formed after supernova explosions.
> 
> [one of my passions is cosmology]


Which can be proven by the fact that many ppl (see politicians for one ex.) are still full of those hot gases.


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## BTO (Feb 7, 2007)

ET1 SS said:


> You can make a temporary magnet from ferric materials using electromagnets, and it will hold a field for a while [hours, days, months]. Inside an automotive generator they use regenerative fields to constantly build those fields, and they will stay strong for decades. Such a magnet will not be used in making compases.
> 
> Or you can do it in a furnace and make a magnet that will stay strong permanently. These magnets will be used in making compases.
> 
> ...


Ok. I am / was speaking in a technical sense. We can agree to disagree.:hobbyhors


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## BTO (Feb 7, 2007)

texican said:


> Not to beat that horse, but another one...
> 
> After the initial inflationary event (before the first second), the only element in the virgin universe was hydrogen. Gravity pulled the hydrogen together, which formed stars. Nuclear fusion created helium and other light elements. Some went supernovae and created all of the heavier elements. Everyone of us is made of atoms formed after supernova explosions.
> 
> [one of my passions is cosmology]


What does makeup have to do with the big bang theory? Sorry, I couldn't help myself!


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## hunter63 (Jan 4, 2005)

So, I going to hazard a guess here, and assume that there is agreement that a magnetic compass will still work?

I am used to finding my way around with one, but if I didn't have one, I can still get around pretty well without.
Now in the event that all the landmarks are a glass parking lot, I would guess I wouldn't have to worry about it all that much.


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## hunter63 (Jan 4, 2005)

texican said:


> Not to beat that horse, but another one...
> 
> After the initial inflationary event (before the first second), the only element in the virgin universe was hydrogen. Gravity pulled the hydrogen together, which formed stars. Nuclear fusion created helium and other light elements. Some went supernovae and created all of the heavier elements. Everyone of us is made of atoms formed after supernova explosions.
> 
> [one of my passions is cosmology]


Here is my latest theory on who we might have come to be:
http://www.homesteadingtoday.com/showthread.php?t=324681


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## Harvey Gnomegrinder (Dec 16, 2020)

SuburbanHermett said:


> What about all of those satellites that are up there orbiting the earth? Will those come crashing down if there is an EMP? If there is no way or no one to tell them to adjust their orbit? [I remember that recently (this past spring?) that there was a problem with a broken (but new) satellite (Japan's? China's?) the size of a school bus that was full of fuel (flourazine?) that was going to crash into the U.S.A. unless someone shot it while it was still at a certain altitude].



Falling satellites would be a negligible worry because:
1) 70% of the Earth is covered by water,
2) Almost everything in orbit would be destroyed during re-entry and,
3) Even the largest object that made re-entry because its orbit decayed beyond correction was Skylab
A.Skylab

Station statisticsLength82.4 feet (25.1 m) w/o Apollo CSMWidth55.8 feet (17.0 m) w/ one solar panelHeight36.3 feet (11.1 m) w/ telescope mountDiameter21.67 feet (6.61 m)

B) The largest pieces to survive were Oxygen and Nitrogen tanks and they impacted in Australia, even though they tried to direct it toward the Indian Ocean:









Skylab's Grave: Remains of 1st American Space Station in Australia


40 years after the United States launched its first space station, Skylab, the remains of the spacecraft are on display in a museum in Australia near where they landed after the station re-entered Earth's atmosphere in 1979.




www.space.com


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## Alice In TX/MO (May 10, 2002)

Or East Texas









Debris From Space Shuttle Columbia Disaster Found in Texas


Debris from the space shuttle Columbia accident was discovered in a dry lakebed in Nacogdoches, Texas.




www.space.com


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## GREENCOUNTYPETE (Jul 25, 2006)

hunter63 said:


> So, I going to hazard a guess here, and assume that there is agreement that a magnetic compass will still work?
> 
> I am used to finding my way around with one, but if I didn't have one, I can still get around pretty well without.
> Now in the event that all the landmarks are a glass parking lot, I would guess I wouldn't have to worry about it all that much.


as long as you are still alive it should be fine.

nukes have been set off on a number of Islands and Nevada and of course Japan and compasses have continued working since.


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## TroyT (Jun 24, 2008)

GREENCOUNTYPETE said:


> as long as you are still alive it should be fine.
> 
> nukes have been set off on a number of Islands and Nevada and of course Japan and compasses have continued working since.


Powerful long range EMPs are not generated by low altitude Nuke bursts. While there is some disruption to electronic devices near the blast area it's nothing like a purpose built device designed to generate an EMP. The USA first detected the EMP effect with the Starfish nuke tests over Bikini Atoll which knocked out telephones, street lights in Hawaii and disrupted radio communications between Hawaii and the mainland USA. Satellites would be largely unaffected if they survived the blast as they are generally well above the earths atmosphere. It's the atmosphere that is responsible for the EMP's magnification and propagation. There has been very little real world EMP testing done for obvious reasons. Magnetic fields shouldn't be affected by and EMP, a CME on the other hand may - may be a different story.


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