al@gtx.com (Alan Filipski) (04/09/91)
There was an interesting letter in the 7 Feb 1991 issue of Nature
entitled "levitation of organic materials". The authors, E. Beaugnon
and R. Tournier of the CNRS in Grenoble, report that they have
levitated many kinds of weakly diamagnetic materials such as wood,
plastic, water, ethanol, and acetone in strong magnetic fields. The
levitation was done at room temperature within the 5 cm cylindrical
bore of a "hybrid" magnet (I put "hybrid" in quotes because I don't
know what it means in this context). The field strength used to
levitate water, for example, was about 27T, generating a gradient of
the square of the field of about 3000 T^2/m. The authors explain that
this gradient is related to the force produced on a given diamagnetic
object.
I'm curious about the possibility of generating gradients like this on
a large scale so that, say, a person's body could be levitated. Given
the above numbers, would this be technically possible? Would the
great field strength or gradient thereof have any significant effect
on, say, electrical activity in nervous tissue or other life processes?
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( Alan Filipski, GTX Corp, 8836 N. 23rd Avenue, Phoenix, Arizona 85021, USA )
( {decvax,hplabs,uunet!amdahl,nsc}!sun!sunburn!gtx!al (602)870-1696 )
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P.S. I am cross-posting this to talk.origins because there has recently
been discussion there of some crackpot quasi-Velikovskian theory of
wierd gravitational or electromagnetic effects allowing dinosaurs to
grow huge. I thought this might fan the flames there a little.wreck@fmsrl7.UUCP (Ron Carter) (04/13/91)
In article <1489@gtx.com> al@gtx.UUCP () writes: >I'm curious about the possibility of generating gradients like this on >a large scale so that, say, a person's body could be levitated. Given >the above numbers, would this be technically possible? Would the >great field strength or gradient thereof have any significant effect >on, say, electrical activity in nervous tissue or other life processes? Hell, yes. Just think of the phenomena you have in the body: mildly-conductive fluids moving through tubes in a mildly-conductive matrix. Now 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 of DC current (pulsating in the arteries, closer to continuous in the veins). I'm not sure if the currents would be enough to short out the neural circuitry which controls the heart, but I wouldn't want to find out personally. It sounds dangerous. Yes, I'm a real double-E.
naqvi@ucselx.sdsu.edu (Shahid A. Naqvi --Hercules--) (04/13/91)
In article <40065@fmsrl7.UUCP> wreck@fmsrl7.UUCP (Ron Carter) writes: >In article <1489@gtx.com> al@gtx.UUCP () writes: >>I'm curious about the possibility of generating gradients like this on >>a large scale so that, say, a person's body could be levitated. Given >>the above numbers, would this be technically possible? Would the >>great field strength or gradient thereof have any significant effect >>on, say, electrical activity in nervous tissue or other life processes? > >Hell, yes. Just think of the phenomena you have in the body: >mildly-conductive fluids moving through tubes in a mildly-conductive >matrix. Now 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 of >DC current (pulsating in the arteries, closer to continuous in >the veins). > >I'm not sure if the currents would be enough to short out the >neural circuitry which controls the heart, but I wouldn't want >to find out personally. It sounds dangerous. > >Yes, I'm a real double-E. I think such an experiment would detonate the vessels or nerves before it could levitate the body. Your soul would levitate before your body can!!! Shahid, SDSU,EE
throopw@sheol.UUCP (Wayne Throop) (04/15/91)
> 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. 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. -- Wayne Throop ...!mcnc!dg-rtp!sheol!throopw
sbishop@desire.wright.edu (04/15/91)
In article <1991Apr12.222942.12775@ucselx.sdsu.edu>, naqvi@ucselx.sdsu.edu (Shahid A. Naqvi --Hercules--) writes: > In article <40065@fmsrl7.UUCP> wreck@fmsrl7.UUCP (Ron Carter) writes: >>In article <1489@gtx.com> al@gtx.UUCP () writes: >>>I'm curious about the possibility of generating gradients like this on >>>a large scale so that, say, a person's body could be levitated. Given >>>the above numbers, would this be technically possible? Would the >>>great field strength or gradient thereof have any significant effect >>>on, say, electrical activity in nervous tissue or other life processes? >> >>Hell, yes. Just think of the phenomena you have in the body: >>mildly-conductive fluids moving through tubes in a mildly-conductive >>matrix. Now 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 of >>DC current (pulsating in the arteries, closer to continuous in >>the veins). >> >>I'm not sure if the currents would be enough to short out the >>neural circuitry which controls the heart, but I wouldn't want >>to find out personally. It sounds dangerous. >> >>Yes, I'm a real double-E. > > I think such an experiment would detonate the vessels or nerves before > it could levitate the body. Your soul would levitate before your body can!!! > Shahid, SDSU,EE You people may have missed the heated discussion that has been going on in talk.origins. There is a Velikovskyite who keeps insisting that in 'andeluvian times the felt effect of gravity was lighter'. He keeps changing his stand on exactly what the mechanism is that could cause this but most of the time he's trying to use magnetism. Anyway he keeps saying that anything larger than an elephant would be too heavy to stand up in the current gravity.
neufeld@aurora.physics.utoronto.ca (Christopher Neufeld) (04/16/91)
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!"
minsky@media-lab.MEDIA.MIT.EDU (Marvin Minsky) (04/16/91)
In article <1689@sheol.UUCP> throopw@sheol.UUCP (Wayne Throop) writes: >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. > >If I'm mistaken about the field strength involved in MRI, I'd appreciate >being corrected. The fields are only a few thousands of Gauss. There is an MRI machine a few blocks from here that uses a large permanent magnet. Astounding well designed pole pieces, I would say -- considering that my pocket compass is not disturbed when forty feet away from the monster. The huge number might have come from someone converting Tesla to Gauss a couple of extra times.
siegman@sierra.STANFORD.EDU (Anthony E. Siegman) (04/16/91)
I>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. > >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. The ac or radio-frequency field strengths (at frequencies something like 30 to 60 MHz) would be very small, though I'm not sure about terragauss -- that is really awfully small. What you more likely saw, however, was the _dc_ or _static_ field, which is likely to be around 1 _Tesla_, which is the SI or mks unit for magnetic field. One Tesla = 10,000 gauss -- still _far_ below the
throopw@sheol.UUCP (Wayne Throop) (04/17/91)
In article <1689@sheol.UUCP> I wrote: > magnetic fields of between 1 and 2 trillion (as in 10^12) gauss. Sigh. Of course, this displays my abject inumeracy. Apparently, my memory substituted "teragauss" for "tesla". Duh. But then, what's eight trailing zeroes between friends, eh? Anyway, here's some hopably somewhat more correct information, from several sources (including email corrections of my faulty memory as I had requested... thanks all). MRI involves fields of up to 5 tesla. The strongest constant magnetic field ever generated (according to the Guinness Book of World Records) was about 35 tesla, at the Francis Bitter National Magnet Laboratory at MIT. There is some indication in the GBR entry that this 30+ tesla field was applied to living tissue without causing it to be dead tissue, but I can't really make out what was going on by the reference there. (Anybody out there know?) So, we know people can stand up to 5 tesla without apparent ill effects (though perhaps not totally without effect). It is even possible that *some* living things have been subjected to 30 tesla. On the other hand, it *is* likely that at "high enough" magnetic fields, things would start to fry, but it isn't clear at all how high is "enough". And still, as far as I know, no organics levitated, even at 30+ tesla. ( Sheesh. *tera*gauss. What was I *think*ing? What *planet* was my memory at... or maybe a neutron star... ) -- Wayne Throop ...!mcnc!dg-rtp!sheol!throopw
mark@photon.mit.edu (Mark Spector) (04/17/91)
In article <1714@sheol.UUCP> throopw@sheol.UUCP (Wayne Throop) writes: > >MRI involves fields of up to 5 tesla. The strongest constant magnetic >field ever generated (according to the Guinness Book of World Records) >was about 35 tesla, at the Francis Bitter National Magnet Laboratory at >MIT. There is some indication in the GBR entry that this 30+ tesla >field was applied to living tissue without causing it to be dead tissue, >but I can't really make out what was going on by the reference there. >(Anybody out there know?) > >Wayne Throop ...!mcnc!dg-rtp!sheol!throopw The world record is indeed held by the FBNML here at MIT. It uses a big bore superconducting magnet (~15 Tesla) with a Bitter magnet (~20 Tesla) inside. I believe to set the world record they put some iron pole pieces inside of the Bitter magnet to pick up a couple extra tesla. As far as living tissue goes, I heard that a few years ago some bioligist had the idea to put some homing pigeons inside a Bitter magnet and see if they remembered the way home. As I recall he put them in a field of around 15 Tesla and not only did they live, but they found their way home! On a related note, FBNML is currently contructing another hybrid magnet which should break the 40 Tesla mark sometime this summer. Of course, the government in it's infinite wisdom has decided to close FBNML in October, so this magnet probably will not get much use. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Mark S. Spector Internet : mark@photon.mit.edu M.I.T. Room 13-2025 BITNET : mark%photon.mit.edu@MITVMA Cambridge, MA 02139 Telephone : (617)253-6803