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A very smart friend of mine seems to get taken in by junk science. He started telling me last night that the electromagnetic field of the heart can be detected beyond 30 feet. What is the actual distance? Thank you.

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what is the detector? seriously in a vacuum with the right equipment i'm sure it could be quite a long distance. –  shigeta Mar 18 at 16:27
    
I heard such anecdotes from electrical engineering friends. Their circuit was so sensitive that you would see your own heart beat on the oscilloscope just in the vicinity. I don't know what the exact distance was. Perhaps you could as this Q at EE.SE electronics.stackexchange.com ? –  Memming Jun 5 at 14:46
    
The EM field strength falls off as the inverse square of the distance (even in space). The heart operates on mV and mA voltages/currents. I wonder if this is detectable beyond 5 meters using a nearly-ideal detector. 30 feet sounds really far. –  daniel Jul 5 at 15:09
    
In 2010 there was a brief note in LiveScience on a system developed at U. Sussex which detected heartbeats at 1 meter. That was apparently good 4 years ago. –  daniel Jul 5 at 15:14
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The electomagnetic field of the heart actually changes with emotions so there is no fixed range as such (reference). It could also change with temperature and other external magnetic disturbances (reference). The heart generates the largest electromagnetic field in the body which is up to 50 mV/m, and that of the brain and other vital organs up to 5 mV/m. Here is a paper on the exposure of human beings to electromagnetic waves (reference). This paper details some of the current medical treatments focusing on the electromagnetic fields (reference).

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In your first sentence I think you mean "changes with emotions." The E-field falls off as the inverse square of the distance so it loses strength rapidly. There is certainly a range even with an ideal detector. –  daniel Jul 5 at 12:16
    
@daniel yes it is "changes with emotions".. thank you for pointing that out. –  The Last Word Jul 5 at 14:29
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