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From: neufeld@aurora.physics.utoronto.ca (Christopher Neufeld)
Subject: Re: Magnetic Levitation of Organic Materials
Message-ID: <1991Apr15.192613.1502@helios.physics.utoronto.ca>
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References: <1489@gtx.com> <40065@fmsrl7.UUCP> <1689@sheol.UUCP>
Date: Mon, 15 Apr 1991 19:26:13 GMT

In article <1689@sheol.UUCP> throopw@sheol.UUCP (Wayne Throop) writes:
>> wreck@fmsrl7.UUCP (Ron Carter)
>>> al@gtx.UUCP () 
>>> [..could..] a person's body could be levitated [..by a magnetic field..]
>>> Would the great field strength or gradient thereof have any significant
>>> effect on, say, electrical activity in nervous tissue [...]
>> Hell, yes.  [...] introduce an enormous magnetic field.  Every moving
>> ion will experience a BxV force, and every blood vessel which is
>> not parallel to the ambient field becomes an MHD generator [...]
>> [...] It sounds dangerous.
>
>Well, I don't know how enormous you folks mean by "enormous".  But
>unless I'm much mistaken in my memory of reading the resulting images,
>MRI (the euphemism for what used to be called NMR imaging) involves
>subjecting a person to magnetic fields of between 1 and 2 trillion (as
>in 10^12) gauss.  The person I saw in the device didn't levitate.  Nor
>fry, nor heart-fail, nor nothing. 
>
   I wish! My experiment would do well to have even a thousandth of that
field. It's almost impossible now to generate continuous fields much in
excess of 30 Tesla, which is 300000 gauss. Maybe the field was being
measured in units of 'gamma'? I think that introduces another factor of
10^7 to the number.

>If I'm mistaken about the field strength involved in MRI, I'd appreciate
>being corrected.  As I said, I remember being somewhat amazed at a
>reading of 1.mumble terragauss on the statistics printed on the image
>output.
>
   I'd have been shocked. It's akin to hearing that the patient's body
temperature is in the high millions of degrees celcius.

>Wayne Throop  ...!mcnc!dg-rtp!sheol!throopw


-- 
 Christopher Neufeld....Just a graduate student  | Flash: morning star seen
 neufeld@aurora.physics.utoronto.ca    Ad astra! | in evening! Baffled
 cneufeld@{pnet91,pro-cco}.cts.com               | astronomers: "could mean
 "Don't edit reality for the sake of simplicity" | second coming of Elvis!"