Can a magnetic field kill you?

The answer is yes. Did you forget what blog you were reading? You know I’m going to dial everything up until it gets lethal. A strong enough magnetic field can turn a human being into a mass of fibrous crystals, which is not, as you might imagine, good for biology.

But for once, I’m going to try to start on the low, sensible end of the scale. Actually, since magnetic fields are a bit unintuitive, being invisible and all (and confusing to some musicians, apparently), let’s get an idea how strong an ordinary, every day magnetic field is.

Well, I turned on my smartphone, did a little math, and discovered that the magnetic field at my desk (probably mostly a result of the magnetic field of the Earth) is about 45 microTesla. Technology is awesome.

Purely for amusement purposes, I have a stack of little breathmint-sized neodymium magnets stuck to the side of my desk. When held one finger-thickness from the side of my smartphone, it registers a magnetic field of 4.5 milliTesla.

Also for amusement purposes, and because my relatives are awesome and have no reservations about getting me weird Christmas presents, I have a pair of 1-inch (2.5 cm) cubic neodymium magnets. They’re N45 grade, which means their surface magnetic field is on the order of 1.3 Tesla, which, somewhat alarmingly, is the same kind of field you get in an MRI machine. According to United Nuclear, where I got them (a wonderful site that will also sell you fun things like CO2 laser parts and depleted uranium. No, I am not kidding.), they’ll lift 110 pounds. I believe it. I’ve actually got two of them, and when they stick together, it takes three people and a lot of leverage and clever thinking to pull them apart. Not quite powerful enough to squish a finger, unfortunately (FORTUNATELY! I meant fortunately! I swear!) but powerful enough that if you should, say (purely theoretically, of course) put a steel seamster’s pin in your hand and hold the magnets on the other side, the pin will stand up and poke you rather painfully.

Now we’re getting into the range of magnetic field strengths that have documented biological effects. People placed in the powerful static magnetic fields of MRI machines (which range between 0.5 Tesla and 4 Tesla) sometimes report a metallic taste, dizziness, and nausea. Rats, however, have been exposed to 9.4 Tesla (same article) for months at a time without detectable health effects. Another study, however, found that after even short (48-hour-ish) exposures to 3.0-Tesla fields, rats had significantly more undersized nuclei in the cells in their bone marrow.

As the fields get stronger, their effects become more pronounced. For instance, this paper (which makes me very happy for reasons I don’t understand) calculates the effect on blood flow of a 10-Tesla magnetic field produced by a high current running through a wire. Since all blood contains ions, and since deoxygenated blood is paramagnetic, meaning it’s attracted to magnetic fields), a strong enough field can actually affect how it flows. In practical terms, this means that your blood’s going to have more trouble moving around. Which might lead to trouble if, for instance, the blood starts to have trouble getting into or out of your heart. And I read somewhere that blood is important.

But when you get up to fields this big, you start running into other issues. Charged particles curve when they move through magnetic fields. Unfortunately for our hypothetical human test subject, who for some reason lives in the world’s largest and most powerful solenoid, biology has based a lot of her important working parts on the movement of charged particles. If you fire a charged particle (say for example the sodium, potassium, and calcium ions that make nerves work, or the hydrogen ions that let your mitochondria synthesize energy-transporting ATP) perpendicular to a magnetic field, it’ll curve. This is probably less of a problem in the case of mitochondria (since mitochondria have a lot of ATP-synthase proteins oriented in different directions) than it is for nerves. A nerve running parallel to the magnetic field is going to find that, rather than flowing nicely through ion channels, that its ions curve into the walls, probably increasing friction, increasing resistance, and making it a lot harder for signals to travel down those nerves. Our test subject is going to be seeing some very pretty colors (and probably eleven-legged spiders, if you’re a Peter Watts fan). That’s not really a problem, since, if you know me, he’ll be dead soon anyway.

And here, we more or less leave the realms human beings have explored, as far as strong, static magnetic fields go. The strongest continuous field we’ve produced (as of this writing in April 2015) is around 45 Tesla. (Produced at the National High Magnetic Field Laboratory, who showed us that, at 14 Tesla, a frog not only lives, but can fly. I’d bet you anything they really wanted to use a pig and make a terrible joke, but couldn’t find a pig to fit in their giant solenoid.) The MagLab can produce a pulsed field up to 100 Tesla, but that only lasts 15 milliseconds, so there’s going to be a lot of weird inductive shit going on, which is frankly the kind of complication I don’t need in my life.

Fields up to 2,800 Tesla have been produced. Unfortunately, producing them required combining high-energy capacitor banks with high explosives, and the fields obtained didn’t last long, as you can imagine. (If I had access to high-energy capacitors and high explosives, I’d be dead by now.)

And then there’s this big unexplored landscape above 2,800 Tesla. Actually, to be honest, we haven’t explored much of what happens in magnetic fields above around 20 Tesla (that’s where nuclear magnetic resonance magnets operate, which cleverly change the way molecules respond to radio waves, and has been a big help in letting us study the structure of molecules). Safe to say, though, a 100-Tesla field would be enough to make you quite uncomfortable, pull all the metallic objects out of your pockets as you walked past (even if they were something nonmagnetic like aluminum, thanks to electrodynamic effects), make your nerves behave strangely, and possibly stop your heart.

But frankly, nobody much talks about such strong fields. I blame this decline in imagination on the popularity of Angry Birds. I’m not sure why. I think I just had a neuron short out somewhere. Too many magnets in my room, perhaps.

Even so, a few wild-eyed scientists have calculated what happens to atoms under ridiculously strong fields, like the ones found near neutron stars. We’re talking fields upwards of 235,000 Tesla. Fields as high as 100,000,000,000 Tesla, in the case of magnetars (which are absolutely horrifying objects that should make you want to wrap yourself in mu-metal and live in a Faraday cage. Or maybe that’s just me. It usually is.) Under fields like this, matter as we know it turns into something strange.

Remember how I said charged particles tend to veer to the side when they travel perpendicular to a magnetic field? Well, electrons are charged particles, and they’re always moving around when they’re in atoms (which is really where you want them; if you moved all your electrons to, say, your toenail, not only would you die, but you’d probably take a city block with you. I’ve just given myself an idea for my next post…) In these ridiculous magnetic fields, the electrons move pretty much normally along the field lines, but in the directions perpendicular to the field lines, they don’t move nearly as far as usual, which means the atoms turn into extremely thin cylinders.

But there’s another, subtler effect. Quantum mechanics tells us that electrons refuse to occupy the same energy state as other electrons with the same spin. In a helium atom, for instance, you’ve got two electrons in the same orbital, but they have opposite spins, so they get along. Sounds like something from a really awful nerdy romantic gameshow.

Trouble is, in really strong magnetic fields, the electrons all line up with their spins pointing in the same direction. They can’t share orbitals anymore. So the way electrons get added to atoms completely changes.

Chemical bonds are still possible, at least after a fashion: these ridiculous magnetic atoms can bond end-to-end to form chains along the magnetic field. But, because the stupid field is calling all the shots now (I’m starting to get a little mad at all these magnets, to be honest), those chains are unlikely to have very interesting chemistry, since they’re effectively one-dimensional.

Which is bad news for our test subject, whom we’ve now transported for absolutely no reason into the vicinity of a highly-magnetized neutron star. His body will literally fall apart, sliding down along the field lines, crystallizing into atom-thin filaments before crashing into the surface at close to the speed of light and evaporating.

So yes. Magnetic fields can kill you. And in more ways than I thought.


12 thoughts on “Can a magnetic field kill you?

    • Thanks for reading!

      I pretty much have to do a follow-up to this post about changing magnetic fields, because I really want to work out what would happen to a person actually sitting near a rotating neutron star.

  1. Dang, I took chemistry in my sophomore year of highschool and we talked about magnets and it’s effects on atoms, but I never even thought about applying magnets to living beings.

  2. suvideator735 says:

    You should totally send this to Marvel Comics! They’ll have some new upgrades for Magneto !!! 😛 😀

    • Oh man…I’d be trouble at Marvel. They’d kick me out in a week. I’d be begging people to flesh out the biology of the Hulk’s transformation. I’d be blowing the Earth up every issue. And I’d turn Magneto into a neutron star. XD

    • I know, right? In my chemistry class, we hardly even got to set things on fire or blow things up, let alone use lethal magnetic fields. I was understandably disappointed.

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