Question about EM Spectrum, and EM Fields

[jjrakman]

How's this?

 

[Klaynos]

Yep that shows it.

 

It's right on the far left, 10² is 100 so halfway between there and 0

[jjrakman]

Thanks very much for your help!

[jjrakman]

One other question.

 

The body also gives off EMF as does the Earth and other biological life forms. What portion of the electromagnetic spectrim do these natural EMF's lie?

 

Also, how can one discern between an artificial EMF and a natural EMF, what properties makes them different?

[Klaynos]

The EMF given off by "natural" things and be in any part of the spectrum pretty much.

 

And there's no way to tell a photon generated from a light bulb at 550nm is the same as one generated by the sun at 550nm.

 

But if you look at a larger spectrum than a single frequency you can often make a guess at the origins. I for example know what my lightsource should look like, and I know what effect having the lights turned on in the room does to it, and I can make guesses looking at other peoples kits as to what part of their spectrum is due to having floresant lights in their lab.

[jjrakman]

I guess I'm primarily concerned with the low frequency area.

 

Would it be safe to assume that an AC EMF field is usually artificial whereas a DC EMF field is usually natural?

[swansont]

I guess I'm primarily concerned with the low frequency area.

 

Would it be safe to assume that an AC EMF field is usually artificial whereas a DC EMF field is usually natural?

 

 

No, it would be extremely unsafe to make that assumption. The sun dumps ~ a kilowatt per square meter of AC EM radiation on the earth. You emit of order 100 Watts of an AC EM field. However, if you were to detect e.g. a 60 Hz signal (or 50 Hz where that is used), then it's likely it was man-made.

 

However, as Klaynos already said, a photon is a photon. The source makes absolutely no difference — you can't tell by looking at the photon, and the photons will interact in exactly the same way.

[jjrakman]

O.K., so how can these meters be able to differentiate between artificial EMF and natural EMF?

 

http://www.trifield.com/EMF_meter.htm

 

http://www.trifield.com/EMF_natural.htm

 

What am I missing here?

[swansont]

O.K., so how can these meters be able to differentiate between artificial EMF and natural EMF?

 

http://www.trifield.com/EMF_meter.htm

 

http://www.trifield.com/EMF_natural.htm

 

What am I missing here?

 

They can't.

 

I'm guessing that these are being marketed to gullible ghosthunters or other "paranormal researchers" who do think there's a difference.

[phoglite]

I'm attempting to understand their difference, and their relationship.

 

 

Here's how I understand it... maybe it will help.

 

1.) Magnetic fields and electrons have a special relationship. A moving electron creates a magetic field and moving a magnetic field can push or move an electron. For example - you have a piece of conductive wire which has lots of electrons (all atoms have electrons) and move a magnet over it - electrons get pushed along the wire (this is how a generator works to make electricity). You can reverse this by running electric current through a wire (electrons flowing) and it will create a magnetic field that can push a magnet (this is how motors work).

 

2.) DC current involves pushing the electrons along the wire continuously... while AC (alternating current) involves pushing the electrons a little bit and then jerking them back the other direction - over and over. This back and forth action can usually be measured in number of cycles per second or the frequency - hertz.

 

3.) This frequency can vary and depends on what is moving those electrons back and forth (all the while shifting the magnetic field it generates back and forth). This frequency is how you would categorize the particular place on the EM spectrum that you're trying to relate to.

 

Household AC current might be at 60 hz because the electrons flowing into any AC device are moving back and forth 60 times per second, while generating a corresponding disturbance in the electromagnetic field. Organic or "natural" sources of EM fields are likely continuously changing the frequency at which they move their electrons around so it's hard to say where they would fit in a chart since they may move all over the thing. Hope that helps!

 

-phog

[jjrakman]

I've been doing a little more readin on this Natural EMF Meter, and it claims to be able to detect weak DC fields, while ignoring AC.

 

I've played with one myself, and have seen it work. Insomuch as when a person walks about in a room, the needle will go off, seemingly detecting a person's movements. Whether it's actually detecting my movement itself, or the bioelectric field I'm putting off I suppose is up for debate. But the other settings on the meter do seem to do as advertised.

 

Would it be safe to say then, that AC is almost always artificial, while weak DC is mostly natural?

[Klaynos]

Would it be safe to say then, that AC is almost always artificial, while weak DC is mostly natural?

 

I'd say no... it's safe to assume that 50Hz or 60Hz is probably artificially as that is what AC power in most countries runs at.