How strong would a magnetic field have to be to kill you?
There’s a great joke in Futurama, the cartoon comedy show, about a horror movie for robots. In the movie, a planet of robots is terrorized by a giant “non-metallic being” (a monsterified human). The human is finally defeated by a makeshift spear, which prompts the robot general to say:
“Funny, isn’t it? The human was impervious to our most powerful magnetic fields, yet in the end he succumbed to a harmless sharpened stick.”
The joke, of course, is that the human body might seem much more fragile than a metallic machine, but to a robot our ability to withstand enormous magnetic fields would be like invincibility.
But this got me thinking: how strong would a magnetic field have to be before it killed a human?
Unlike a computer hard drive, the human body doesn’t really make use of any magnetic states — there is nowhere in the body where important information is stored as a static magnetization. This means that there is no risk that an external magnetic field could wipe out important information, the way that it would for, say, a credit card or a hard drive. So, for example, it’s perfectly safe for a human (with no metal in their body) to have an MRI scan, during which the magnetic fields reach several Tesla, which is about 
A computer hard drive stores information in a sequence of magnetically aligned segments.
But even without any magnetic information to erase, a strong enough magnetic field must have some effect. Generally speaking, magnetic fields create forces that push on moving charges. And the body has plenty of moving charges inside it: most notably, the electrons that orbit around atomic nuclei.
As I’ll show below, a large enough magnetic field would push strongly enough on these orbiting electrons to completely change the shape of atoms, and this would ruin the chemical bonds that give our body its function and its structure integrity.
What atoms look like
Before I continue, let me briefly recap the cartoon picture of the structure of the atom, and how to think about it. An atom is the bound state of at least one electron to a positively charged nucleus. The electric attraction between the electron and the nucleus pulls the electron inward, while the rules of quantum mechanics prevent the electron from collapsing down completely onto the nucleus.
In this case, the relevant “rule of quantum mechanics” is the Heisenberg uncertainty principle, which says that if you confine an electron to a volume of size 
In a stable atom, the quantum confinement energy, which favors having a large electron orbit, is balanced against the electric attraction between the electron and the nucleus, which pulls the electron inward and has energy 
This is the quick and dirty way to figure out the answer to the question: “how big is an atom?”.
The associated velocity of the electron in its orbit is 
Who pulls harder: the nucleus, or the magnetic field?
Now that I’ve reminded you what an atom looks like, let me remind you what magnetic fields do to free charges.
They pull them into circular orbits, like this:
The force with which a magnetic field pulls on a charge is given by 
Now we can consider the following question. Who pulls harder on the electron: the nucleus, or the external magnetic field?
The answer, of course, depends on the strength of the magnetic field. Looking at the numbers above, one can see that for just about any realistic situation, the force provided by the magnetic field is much much smaller than the force from the nucleus, so that the magnetic field essentially does nothing to perturb the electrons in their atomic orbitals. However, if the magnetic field were to get strong enough, then the force it produces would be enough to start significantly bending the electron trajectories, and the shape of the electron orbits would get distorted.
Setting 
Distorted atoms
But supposing that you did wander into a magnetic field of 100,000 Tesla, what would happen?
The strong magnetic forces would start to squeeze the electron orbits in all the atoms in your body. The result would look something like this:
So, for example, an initially spherical hydrogen atom (on the left) would have its orbit squeezed in the directions perpendicular to the magnetic field, and would end up instead looking like the picture on the right. This squeezing would get more and more pronounced as the field is turned up, so that all the atoms in your body would go from roughly spherical to “cigar-shaped,” and then to “needle-shaped”.
Needless to say, the molecules that make up your body are only able to hold together when they are made from normal shaped atoms, and not needle-shaped atoms. So once the atomic orbitals got sufficiently distorted, their chemistry would change dramatically and these molecules would start to fall apart. And your body would presumably be reduced to a dusty, incoherent mess (artist’s conception).
But for those of us who stay away from neutron stars, it is probably safe to assume that death by magnetic field-induced disintegration is pretty unlikely. So you can continue lording your invincibility over your robot coworkers.
UPDATE:
A number of people have pointed out, correctly, that if you really subjected a body to strong magnetic fields, something would probably go wrong biologically far before the field got so ludicrously large fields as 100,000 Tesla. For example, the motion of ions through ion channels, which is essential for nerve firing, might be affected. Sadly, I probably don’t know enough biology to give you a confident speculation about what, exactly, might go wrong.
There is another possible issue, though, that can be understood at the level of cartoon pictures of atoms. An electron orbiting around a nucleus is, in a primitive sense, like a tiny circular electric current. As a result, the electron creates its own little magnetic field, with a “north pole” and “south pole” determined by the direction of its orbital motion. Like so:
Normally, these little electron orbits all point in more or less random directions. But in the presence of a strong enough external magnetic field, the electron orbit will tend to get aligned so that its “north pole” points in the same direction as the magnetic field. By my estimate, this would happen at a few hundred Tesla.
In other words, a few hundred Tesla is what it would take to strongly magnetize the human body. This isn’t deformation of atoms, just alignment of their orbits in a consistent direction.
Once the atomic orbits were all pointed in the same direction, the chemistry of atomic interactions might start to be affected. For example, some chemical processes might start happening at different rates when the atoms are “side by side” as compared to when they are “front to back.” I can imagine this subtle alteration of chemical reaction rates having a big effect over a long enough time.
Maybe this is why, as commenter cornholio pointed out below, a fruit fly that grows up in a ~ 10 Tesla field appears to get mutated.
Footnote
I have been assuming, of course, that we are talking only about static magnetic fields. Subjecting someone to a magnetic field that changes quickly in time is the same thing as bombarding them with radiation. And it is not at all difficult to microwave someone to death.
[Update: A number of people have brought up transcranial magnetic stimulation, which has noticeable biological effects at relatively small field strengths. But this works only because it applies a time-dependent magnetic field, which can induce electric currents in the brain.]
Trackbacks
- Un campo magnético de 100.000 teslas te desintegraría, literalmente | Misiongeek
- 10 Surprising Things Magnetic Fields Do To Your Brain | Top Secret Writers
- Electron spin and the geometry of the wavefunction | Reading Feynman
- The geometry of the wavefunction, electron spin and the form factor | Reading Feynman
Gravity and Levity 
I bet you’d die first from the iron in your blood migrating from it’s cells at a lower magnetic field than atomic manipulation requires. Redo your calculation and get back to us 😀
There was a joke about this on ST:TNG–someone warns Wesley (of course) that he’d need to be careful because the magnets they were playing around with were strong enough to “”rip the iron right out of your blood.”
+1
X-men anyone? Actually not even magneto could pull this off – The Iron in your blood is not Ferromagnetic, sorry. The Iron in our blood is binded with other compounds so its field become shared atomically and becomes neutral. When Iron is chunked together (like in a magnet), an external field is produced because theres an abundance of flux. Here I found this that explains it in more depth. http://www.revisemri.com/blog/2006/mri-blood-iron-attraction/
On youtube there’s a video of a container with blood on water pushed by a relatively weak neodinium magnet
What about the iron in your blood? Would a strong magnet yank out all the red blood cells? Would it happen before or after your atoms got squshed?
As long as the magnetic field were uniform, meaning that it didn’t have spatial variations in strength, it wouldn’t pull anything in any particular direction. It could orient the iron in your blood (as discussed in the update above), but it wouldn’t pull it out.
On the other hand, if the magnetic field has strong gradients, then it could pull magnetized atoms in the direction of the stronger field.
As far as I understand, though, the iron in your blood isn’t actually magnetized (that only happens when lots of iron atoms are grouped together). So it probably wouldn’t be any more “yanked out” than most of the rest of the atoms would be.
Strong magnetic fields are genotoxic, they break up DNA. In a strong enough field, much less than 100.000 Tesla, and a long exposure, the risk of cancer will reach dangerous levels.
Can you elaborate at all? Do you understand what it is about magnetic fields that causes DNA to break up?
I don’t understand the details, but it seems to be accepted by the scientific community. Here’s a peer reviewed study in which they subjected fly DNA to strong magnetic fields (2-14T) and it produced visible mutations in hair pattern:
Click to access 393.full.pdf
They say it has to do with free radicals or increased chemical reactivity of oxigen species in the presence of magnetic fields. The flies are chosen to be DNA-repair deficient, so any errors are much more likely, it won’t happen in your RMI machine. But it stands to reason similar effects would disrupt DNA replication in humans at levels much lower than 100.000 T.
I guess the electric activity of the heart first then brain second would be disrupted way before 100k Tesla.
What about the ions in your blood? Even if magnetic field is static, with ions floating on blood there will be current inside your heart. What field intensity is needed to cause heart attack?
I worked at General Atomics on their Doublet III tokamak fusion device which used magnetic confinement to contain the plasma. The magnetic fields were strong enough to cause the images on CRT screens in the control room to ‘collapse’ during a machine cycle. I believe the field produced by the machine during operation was 240 kilogauss (24 teslas). We were pondering the effects on the human body because magnetic ‘healing’ bracelets and such were the rage at the time. We never felt anything, and I’m aware of no effects, ill or otherwise as a consequence of our proximity.
Can you tell me if 1600 micro teslas is dangerous? I have areas in my bedroom emitting these levels with no electronic equipment nearby! It seems to be coming through the walls and it turns on and off at random! I feel like I am being microwaved to death! I was wearing a black cap and I smelled like fabric being heated and looked at the hat the next day and it had white singe marks on it in several areas! Your opinion would be greatly appreciated! Thanks Gil in Texas
Txhoss2@gmail.com
I suspect that bioelectric functions in the body would be disrupted long, long before 100K Tesla has been reached.
Some people have fainting spells from Transcranial Magnetic Stimulation. http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation
Agree with RL’s direction. CNS disturbances would likely occur at sub-lethal/sub-mutagenic levels, possibly something on the spectrum of being tazed, having ECT or TMS.
The joke, of course, is that the human body might seem much more fragile than a metallic machine, but to a robot our ability to withstand enormous magnetic fields would be like invincibility.
The joke is also a reversal of a line from the War of the Worlds, where the martians are impervious to our weapons but are killed apparently by bacteria or the flu. Maybe not the remake, as I haven’t seen it.
Nice. Thanks for raising my level of culturedness.
I once heard a story from a high energy physicist at fern about a colleague who stuck his head in a strong field. He related that there was much purple involved, but that he was unharmed. I fuzzily recall that that same field held a large steel hatch shut with 40000 lbs of force, despite the lock.
But… but… Star Trek told me that a big enough magnet would rip all the iron from my bloodstream!
You wouldn’t be able to walk into a magnetic field of 100K teslas, due to the diamagnetic force, This is a repulsive force generated by the desire of all matter with electrons to keep those electrons in nice circular orbits.
yeah and that means the object would be floating in air right? A floating supermagnetic object with 100k tesla.
> squeeze the electron orbits
Meet the Quarter Crusher!:
http://www.capturedlightning.com/frames/shrinkergallery.html
Nice! Of course, these cool experiments are making use of time-dependent magnetic fields (pulses, really), which give rise to electric fields that induce large currents inside the quarters. A completely static field (that is, one that turned on very slowly) would have virtually no effect on the quarter, even when it got as large as a few Tesla.
I pressume that before you get very close, the larger molecules of your body (dna, proteins, fatty acids, carbohydrates, etc. ) will start to be oriented by the magnetic field (magnetic susceptibility). As result of that probably the first cause of dead would be that your tissues, organs, brain activity, muscles will be rigidly oriented by the field.
It would be nice to set up an MRI scan at a certain distance of a magnestar, where it is still safe for humans or robots. Let’s say at the distance corresponding to 50 or 100 T. Very nice spatially resolved images could be done.
Yeah, that’s what I was hinting at in my update comment. It’s not obvious to me how orbital orientation kills you, but it seems very likely that it would.
And it definitely would be nice if we could set up a hospital outpost next to a magnetar, and use it for great medical imaging. 🙂
Since many people are complaining about symptoms as a result of CERN, disturbing the magnetic fields of the earth, why not analyse their experience since CERN’s cranked up to 6,4VE. What will happen when it reaches 13VE?
I can’t say that I’ve heard about any such complaints. The LHC does use big magnets, but not much bigger than the kind that are already in hospital MRI machines all over the world already.
Many people may be complaining, but nobody has demonstrated any actual effects.
Sort of like vaccines; there are a lot of people that are alarmists over leterally nothing.
had a MRI and commented was it safer than xrays to the operator
he admitted that they had NO Idea about long term effects of MRI on patients
we were going to be the test pigs over out lifetimes.
and of course seeing as many of the recipients are cancer sufferers , along with other illnesses whos going to sort or even collect long term data globally?
I was under the impression that electrons don’t actually orbit the nucleus. They have a probability distribution. In the case of hydrogen that distribution is a sphere surrounding the nucleus. There is a probability that the electron can even occupy the nucleus. The electrons don’t have defined positions until they are measured. They are “smeared” over the probability space. Is it correct to treat the electron bound to a nucleus as a moving charged particle with the physics that describe moving charged particles in a magnetic field?
Hi Eric,
You are right, of course, that the most accurate way (that we know of) is to think of the electron in terms of its wavefunction, or “probability cloud”, rather than with classical trajectories. But if you do calculate that wavefunction by solving the Schrodinger equation in the presence of a magnetic field, you will find the same thing that I show in the picture above. The wavefunction gets squeezed in the directions parallel to the magnetic field, and becomes “cigar-shaped”.
I took a shortcut, and described the electron motion as a classical orbit. This almost always gives you the right intuition, as long as you remember that the orbits have to be quantized (i.e., their angular momentum has to have units of hbar). This general point was the basis of my recent defense of the Bohr model:
https://gravityandlevity.wordpress.com/2013/10/26/the-bohr-model/
Guys, I just got my 100K Tesla, and it does none of the things you claim here…
It drives smoothly, handles well, and chicks love it.
Very nice, I like it! 😀
Watching Under the Dome on Amazon Prime and just passed the part where there was a magnetic field that was doing some crazy stuff on people and creatures.
This was a terrific simplified physics lesson. I get so excited reading articles about science! Ironically, it only takes a magnetic field of 1T to cause a death. In 2001, an uninformed hospital nurse brought an ordinary oxygen tank too close to an MRI machine, it became a missile, and killed the six year-old patient inside. Ferrous metal objects entering the machine uncontrolled remains the main danger from MRI scanners and the fields they produce.
Wow i learned something new.
Thanks for teaching me something new! Btw Futurama is the best!
The question should include how fast the field was introduced. Because on one hand, it might just cause heat build up that could cook you and electrical currents which could disrupt you. Or if it’s even strong and instantaneous it could just rip the molecules in your body apart kinda like being dropped into a black hole. Hmm… I just wonder which one wouldn’t hurt. I also wonder why I’m answering this question.
I’ve never watched futurama, but maybe I will now;)
Reblogged this on juniorarias12 and commented:
A cosmic formation known as Magnetar which is the result of a star using all of its fusion material collapses into a smaller body with a great amount of mass and rotational speed creating a magnetic field strong enough to rip your skin and whole body apart just by getting Close enough to it.
Like the frog in the boiling water, the sudden application of an intense, but far less than 100K, magnetic field would cause an immediate and intense disruption to bodily processes – particularly brain function – and drop you dead in your tracks. If, even for a second, you can disrupt the flow of electricity through an organic system, the system fails, the electric pathways close, and the organism ceases to function.
Wow that is an extensive analysis!! Respect
Being microwaved to death is somewhere in the middle of my preferences to go. Not the worst, but definitely not the best either.
Enjoyed the read. Thanks, feeling well informed 🙂
cool!!
Reblogged this on rockitsciencemom and commented:
Ha! I love futurama… this was a great read!
This may seem a little far fetched but if you’re reorienting the shape of atoms in your body to disintegration wouldn’t that be the first step in teleportation. The energy of the atoms themselves wouldn’t be destroyed so if you could capture the energy emitted from the collapsing of cells use it for propulsion and then demagnetize at a new location. That’d be pretty DOPE!
You would also somehow have to preserve the information of location, trajectory, and velocity of electrons and bonds, etc. and to somehow replace this information during the “demagnetization”. The molecules, for all we know, will not simply fall into place as expected, unless there is some underlying harmony to the molecular makeup of biological materials that is heretofore undiscovered. Without this information and without some way of forcing all the many atoms to recover their originally intended bonds, there would be no way to turn the dust back into a human being. I do like the concept, though, of using the expelled energy to do something. It makes me wonder if the suddenly broken bonds wouldn’t be accompanied by a flash.
What’s’ the difference between an Electric Magnetic Pulse and a Electro Magnetic Field?
An electromagnetic pulse (EMP) is a short, very energetic burst of radation — similar to an x-ray, microwave, or radio wave. The electromagnetic field is the field that carries this kind of radation. The best I can do to answer the question “what is a field?” is to point you here: https://gravityandlevity.wordpress.com/2010/08/30/our-stability-is-but-balance-freeman-dyson-on-how-to-imagine-quantum-fields/
Thank you I understand. I will check it out though.
Reblogged this on Academic Avenue and commented:
Highly informative article. Really useful for advanced biophysics. The article also elucidates that why implementing powerful MRI technologies is very risky.
I actually think that, if anything, this analysis suggests that powerful MRIs are NOT very risky at all.
Dear Brian, I know that MRI with high levels of magnetic field is not so dangerous for humans … that are human flesh, bone, blood, etc. However, MRI may have to be used during surgical procedures too. Utilizing metallic substances in such environments is highly risky. Although research is ongoing that how most of the metallic surgical instruments may be replaced, scientists and designers have not been that successful insofar. That is why I think MRI technology is a very vital and evolving field of work. Effects of magnetism to human body can be understood from the article. But when a human body requires surgical intervention inside an MRI environment, then things may go troublesome. What is more, some humans may have metallic implants in their bodies. How should they take care of themselves? I am posing these questions from the point of view of healthcare and diagnostics.
Very wrong interpretation of diagram no. 3. How can you possibly even think of comparing Magnetic force to a Nuclear force :0 !!!!!
Great error
I guess I would respond to you like this:
1) I’m not talking about the “nuclear force”, in the standard sense of “the force that holds protons and neutrons together in the nucleus”, but only the much weaker electric force between the electron and the nucleus.
2) It’s my blog, so I can imagine magnetic fields as ludicrously large as I want. 🙂
interesting
Interesting read! I like it
Reblogged this on whatyouneedtolookat and commented:
I need to watch Futurama soon.
Well, I learned something new today. I really like it when this kind of stuff is broken down. Definitely sharing!
That is a great point! : }
You just helped with my comic, thanks!
That would be awsome…. it would replace guns and knives…… someone enters your space and wala!!! They are Polverized…. a bullet is shot at you and it is stoped.
I love lessons from cartoons.
lol
Certain imaging machines profusedly state not to allow magnetic objects near them, like MRI. Could these fields be large enough to yank a pin or plate from the inside of your body loose and out throgh your fleshy bits?
Yes, if you have something ferromagnetic (basically, that contains metallic iron) in your body, then a strong field can pull it around.
But what a lot of people don’t realize is that a pushing or pulling force requires a magnetic field gradient. A completely spatially uniform magnetic field can twist an object, but it can’t push it in one direction or another.
Many people mentioned MRI. Functional MRI, the mode used to study activation patterns in the brain, is based upon a difference in the magnetic properties of hemoglobin that depends upon its state of oxygenation. Deoxyhemoglobin is paramagnetic, while oxyhemoglobin is diamagnetic; and when a part of the brain becomes activated there is a disproportionate increase in blood supply compared to local metabolic needs leading to the increased ratio of oxy- to deoxyhemoglobin that is detected in BOLD-fMRI.
hi ,frnds its Ankit here
frnds a few year back I had heard a news that a person I don’t remember his name and place where he belongs that the too much iron content in his body mades a polarity within his body and because of that his body started acting like a magnet means he was able to attract iron pieces and iron contents as same as magneto does in X-MEN movie but he was able to do that at very small level .so I want to whether it is possible or not ?
No.
Draco
Yes, all nice and well. Iron in our body is a “Bio Iron”. It does really follow physics we know. Just like water in our body is not the water we get from a tap.
i read this and im still pretty confused…but i can say in the few times ive had an mri i definately felt something “weird”
Hmm. I did read somewhere about a 75T MRI being built because they wanted to find out how some piece of hardware worked in such a strong field.
It uses carbon doped MgB2 and cooled it to 4.2K in liquid helium to get such a high field but if scaled up with outer conventional Nb3Ti magnets to supercharge the field we could see if a field this strong would mess with the brain. My theories suggest it could, but this could be worked around by ramping the field from 9T to 75T slowly enough like a decompression chamber.
If anyone wants to test it on a human I can volunteer as long as I get a copy of the data 🙂
I am a Pediatric Gastroenterologist and I find children who swallow 4T magnets, such as Bucky Balls, and the magnets perforate through the tissue. Current theory is that two magnets are swallowed at different times and the attraction traps tissue in between causing the perforations. However, I have seen a single magnet burrow a deep hole in the stomach wall in 2-3 hours without perforating. Is there something about the magnetic field in contact with the tissue that would make it susceptible to disintegration? Any thoughts?
I don’t see how a magnetic field, by itself, would damage tissue. Maybe there’s something dangerous about the metal used in the magnet (or its coating).
i gues that magnet John Grunow MD talk about was probably neodymium magnet and these are nickel plated often, maybe thats the source of a problems…
I see a lot of discussion covering the magnetic field and magnetic pull.
The first question would have to be:
Can you make a large magnet that has an opposite effect, what I mean is, a magnet that pushes instead of pulling, and would the effects essentially be the same? Referring specifically to the static magnets you described
The second question is: If it is possible to build a magnet whose main function is to push and not pull, would the magnetic field have the “needling effect” that you described, or would it then cause a pancake effect, or something of that nature?
Basically, would it be as harmful, more harmful, or the same?
I am assuming that a static magnet requires (at least) two poles to operate correctly.
The “pull” isn’t a thing in its own right. The reason a magnet’s north AND south pull when ferrite is in proximity is because the field polarizes/orients the atoms in the ferrite, and opposite magnetic poles attract each other. Therefore it is not possible to have a time-stable magnetic field which ‘pushed’ ferrite away. You’d have to rely on a time-varying field and the ferrite’s hysteresis curve to accomplish anything like pushing ferrite using magnetic fields.
I have heard that at around 10T-15T problems with the nervous system start. Once the nerves have been disrupted by the magnetic field, the effect does not go away immediately when the field is turned off. There’s also the effect of bio magnetic resistance, where living material tends to float above strong magnetic fields. I’v seen insects float above a magnetic field. The field has to be very strong.
When you press two magnets together, so that they repel each other, you can feel the pressure. I had often as a child, thought that it almost felt like a balloon that with enough force, would go “pop”. Is it possible to make that “pop” happen? if so, how much energy would be released, and what types of energy?
This is a great question. Any time a magnet is pointing against an applied magnetic field (as happens when you push two north poles or two south poles together) there is indeed a “pressure” associated with their repulsion. If the applied magnetic field is strong enough, then it can make the permanent magnet “pop”, just like you suspected. Here a “pop” means that the polarization of the magnet is suddenly flipped to align with the applied field. The required field strength to make this happen is called the “coercive field”. You can read a little bit about this phenomenon here, for example: http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/magperm.html
I wonder how strong the magnetic field would be for the spaceship (with people inside) orbiting the neutron star in Robert L. Forward’s “Dragon’s Egg.” As I recall it orbited about 5 times per second at a distance of 50 miles or so, and used masses around the ship to reduce gravitational tidal forces.
Typo: F_E ~ – e^2/(ε_0 r^2).
Fixed. Thanks!
I was intetested in knowing if pulsed at 30,000 volts, would this do any harm to human body?
Is 251 micro real as harmful to the human body?
Is 251 micro teslas harmful to the human body?
I think it would take between 10-15 Tesla’s to create a problem in the head in relation to the magnetic impulses running the brain, where the only thing to fix the pain caused by the Teslas, is an MRI (learned from experimentation & experience)
I think something would likely go wrong with your H2O because the shape of the water molecule is very critical to its liquid properties and any magnetic distortion might increase viscosity or decrease it causing you to bleed out.
As someone with what you might consider “good coverage” when it comes to tattoos, and who has had many MRI’s…. I can assure that neither MRI image fidelity, nor income, have ever been a problem.
Imagine, in this day and age, holding such a miserable and archiac belief system. It’s that sort of mindset that holds us back, and demonstrates that as a species, we have a long way to go.
I think you’re looking at the wrong thing here. You’re considering what it would take to rip an electron off it’s atom, but the bonds between atoms are generally far weaker. Molecules will be disrupted long before atoms are.