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is the magnetic field harmful if its strong enough? or harmful no matter what strength? -----Original Message----- From: Dr. Peter Charles [mailto:] Sent: Wednesday, January 24, 2001 3:39 PM To: Subject: RE: [BasicX] very OT- electromagnet Mathew- Technically speaking, the person who administers the test should also not know which one has the magnet, for it to be truly "double-blind." As an irrelevant aside--I'm not entirely sure that people can't sense magnetic fields. I had an MRI of my head several years ago and was nauseated and disoriented for about 4 hours afterward. This is, of course, entirely anecdotal and an N of 1, but it was quite striking. peter Peter C. Charles, Ph.D. Research Assistant Professor Department of Microbiology and Immunology Rm. 730 Mary Ellen Jones Building, CB# 7290 UNC Chapel Hill, NC 27599-7290 Caesar si viveret, ad remum dareris. -----Original Message----- From: Matthew Daughtrey [mailto:] Sent: Wednesday, January 24, 2001 4:05 PM To: ' Subject: RE: [BasicX] electromagnet If we were that sensitive to magnetic fields then MRIs would just be killing people. Give yourself a double-blind test; have a friend cover one magnet and another object with identical sheets of paper without you seeing so you can't tell which is which. Do this test 10 or 20 times and note the results. The more tests you do the closer your guesses will be 50% one paper, 50% the other. eGroups Sponsor <http://rd.yahoo.com/M=168002.1291681.2888959.2/D=egroupmail/S=1700005378:N/ A=564956/*http://www.columbiahouse.com/gateway?token=7415> Choose 3 DVDs for $0.49 each! Choose 3 DVDs for $0.49 each! <http://us.adserver.yahoo.com/l?M=168002.1291681.2888959.2/D=egroupmail/S=17 00005378:N/A=564956/rand=236186993 [Non-text portions of this message have been removed]

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>Mathew- > >Technically speaking, the person who administers the test should also not >know which one has the magnet, for it to be truly "double-blind." As an >irrelevant aside--I'm not entirely sure that people can't sense magnetic >fields. I had an MRI of my head several years ago and was nauseated and >disoriented for about 4 hours afterward. This is, of course, entirely >anecdotal and an N of 1, but it was quite striking. Hi Peter,... Wow, you sure don't have anaemia then!? [all that iron in your blood!] :-) Seriously though, did they administer any tracer drugs without you knowing about them? Some of those have nastyish side effects. What about what you ate a few days before? Something in the blood? I am also of the mind that organic beings can detect some amount of magnetic field (whether consciously or not), and haven't closed the book on that. There's some folks who reckon that migratory birds that can find their way blindfolded must rely on magnetic fields (although how they deal with local changes of field I don't know). Humans? Dunno, I've never felt one, but that's hardly conclusive! David. _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

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Aaron- The field strength of the magnets used in MRI is phenomenally high. I didn't say that they were "harmful," just that they may have been detectable by human senses. As Mathew pointed out- MRI would not be nearly so popular if it were dangerous. Now rolling your own electromagnets to run off of line voltage is <<<<VERY>>>> dangerous. Buy something (there are rare-earth magnets with very high magnetic field densities available inexpensively, as well as commercially available electromagnets). If you aren't absolutely sure of what you are doing, don't go plugging things into 115 V AC mains! Best rgards- peter ----- Original Message ----- From: Aaron Sulwer <> Date: Wednesday, January 24, 2001 5:16 pm Subject: RE: [BasicX] very OT- electromagnet > is the magnetic field harmful if its strong enough? or harmful no > matterwhat strength? > > -----Original Message----- > From: Dr. Peter Charles [mailto:] > Sent: Wednesday, January 24, 2001 3:39 PM > To: > Subject: RE: [BasicX] very OT- electromagnet > Mathew- > > Technically speaking, the person who administers the test should > also not > know which one has the magnet, for it to be truly "double-blind." > As an > irrelevant aside--I'm not entirely sure that people can't sense > magneticfields. I had an MRI of my head several years ago and was > nauseated and > disoriented for about 4 hours afterward. This is, of course, entirely > anecdotal and an N of 1, but it was quite striking. > > peter > > Peter C. Charles, Ph.D. > Research Assistant Professor > Department of Microbiology and Immunology > Rm. 730 Mary Ellen Jones Building, CB# 7290 > UNC > Chapel Hill, NC 27599-7290 > > Caesar si viveret, ad remum dareris. > > -----Original Message----- > From: Matthew Daughtrey [mailto:] > Sent: Wednesday, January 24, 2001 4:05 PM > To: ' > Subject: RE: [BasicX] electromagnet > If we were that sensitive to magnetic fields then MRIs would just > be killing > people. Give yourself a double-blind test; have a friend cover one > magnetand another object with identical sheets of paper without > you seeing so you > can't tell which is which. Do this test 10 or 20 times and note the > results. The more tests you do the closer your guesses will be > 50% one > paper, 50% the other. > > > eGroups Sponsor <http://rd.yahoo.com/M=168002.1291681.2888959.2/D=egroupmail/S=170000537 8:N/ > A=564956/*" > target="l">http://www.columbiahouse.com/gateway?token=7415> Choose > 3 DVDs for > $0.49 each! > Choose 3 DVDs for $0.49 each! > > <http://us.adserver.yahoo.com/l? M=168002.1291681.2888959.2/D=egroupmail/S=17 > 00005378: > > [Non-text portions of this message have been removed]

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>Aaron- > >The field strength of the magnets used in MRI is phenomenally high. I >didn't say that they were "harmful," just that they may have been >detectable by human senses. I think Aaron's question was more if you knew whether long-term exposure to magnetic fields was harmful only if the strength was above a certain level. Not specifically MRI, but in general. For example, photoelectric effect. If the frequency (wavelength) is below a certain critical frequency, no amount of light intensity will eject photoelectrons from the active material. However, once the critical frequency is exceeded, the number of photoelectrons ejected depends on the intensity of light. He was asking if there is some lower threshold of magnetic field strength below which one can safely be exposed "forever" without any harmful effects. I'd say that the field strength of the earth's mag. field at the surface would have to be a definite lower bound on that. :-) That sort of thing. I think. David. _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

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David- I was not given any tracers or contrast media. Of course, I could simply have been ill from something I ate (I was living in the Bronx at the time, and had an inexplicable fondness for foods served out of trucks idling by the curb!). There were no controls, and I was certainly not blinded to the fact that my head was stuffed into that clunking, grinding tube for the better part of an hour ;) Just an unconfirmed, perhaps interesting, observation. But if humans are sensitive to magnetic fields, MRI would be the place to notice the effect! Best regards, peter ----- Original Message ----- From: "David Emrich" <> Date: Wednesday, January 24, 2001 10:14 pm Subject: RE: [BasicX] very OT- electromagnet > Hi Peter,... > > Wow, you sure don't have anaemia then!? [all that iron in your blood!] > > :-) > > Seriously though, did they administer any tracer drugs without you > knowing > about them? Some of those have nastyish side effects. What about > what you > ate a few days before? Something in the blood? > > I am also of the mind that organic beings can detect some amount > of magnetic > field (whether consciously or not), and haven't closed the book on > that. > There's some folks who reckon that migratory birds that can find > their way > blindfolded must rely on magnetic fields (although how they deal > with local > changes of field I don't know). Humans? Dunno, I've never felt > one, but > that's hardly conclusive! > > David.

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