Oooo, cool, wheee, fun… (SMACK) ow ow ow ow ow

By Phil Plait | February 27, 2009 4:30 pm

I love magnets. I played with them a lot when I was a kid, and now that I am a mature grownup, I use mature magnets: neodymium or rare-Earth magnets. These are like magnets on steroids, superstrong and a ton of fun.

But they’re also dangerous. They won’t give you cancer or yank out the iron in your blood or anything like that. But because they are so strong, they can attract each other quite, um, forcefully. I’ve had a finger nicked once or twice by them, and it hurts.

But geez, let this guy’s story be a stronger cautionary tale. WARNING: nasty trauma images in there. Don’t eat dinner while reading it. Barf.

Still, I’ll play with my magnets; I have a little ball magnet about 2 cm across that is way too much fun to roll across a floor. I’d love to find a flat frictionless space to roll it, and see how much it deflects due to torque from the Earth’s magnetic field.

But then, I’m a dork. But I have all my fingertips!


Comments (52)

  1. Michelle

    As a computer geek, I sometimes dismantled hard drives. They have magnets in there that are probably not the strongest thing around but they’ve got punch… I’ve hurt myself a couple time with them.

    …And that guy is why I never ever ever play too much with the magnets. Or I at least make sure my hand isn’t in the way.

  2. Reminds me of when, on Mythbusters, Jamie (not to be confused with BA’s Close Personal Friend [TM] Adam Savage) had some and was VERY careful not only in using them, but in warning people about them.


  3. Charles Boyer

    Back in college, I once had a RE magnet used in a radar system that was quite powerful.

    We stuck it to the refrigerator as a goof and I think it is still there. There was NO removing it.

  4. Gary Ansorge

    I just have one question: how many Tesla would that N45 represent?

    Gary 7

  5. Vernon Balbert

    I did some transcribing work for an insurance investigation company for a short stint and one of the cases I wrote up involved a workman putting in wall panels in a room with an MRI machine. The MRI machine wasn’t turned off (they take a LONG time to warm up so they couldn’t turn it off for economic reasons) and the guy moved the wrong way while he was holding on to his electric drill. The magnetic field grabbed onto the driil and smashed against the machine, with the poor workman’s hand in the way. So when they tell you to remove all metal objects from your person before you go into one, don’t try to test what they tell you.

  6. EdZ

    I remember reading this a while ago. Oddly enough, someone I knew mentioned reading this to me earlier this week. I wonder what caused this latest memetic resurgence?

  7. So, um, wouldn’t all those rare earth magnets collectively mess up the plasma currents that hold the earth in its orbit about the sun?

    Why don’t you all just stop lying and admit that such things as these “magnets” don’t exist?

  8. Ouija.

    The biggest neodymium magnet I own is only a few mm across, but it can lift my pocket knife all by its lonesome.

    Of course, I’ve been around other, powerful, magnets. NMR, anyone?

    These sorts of mishaps have ended in tragedy. This is the United Nuclear (A science supplier) page for magnets, if you scroll down, there is this:

    Beware – you must think ahead when moving these magnets.

    If carrying one into another room, carefully plan the route you will be taking. Sensitive instruments like computers & monitors will be affected in an entire room. Loose metallic objects and other magnets may become airborne and fly at great speed to attach themselves to these magnets. If you get caught in between the two, you can be severely injured. These magnets will crush bones in the blink of an eye.

    Two of these magnets close together can create an almost unbelievable magnetic field that can be incredibly dangerous.

    Of all the unique items we offer for sale, we consider these items the most dangerous of all. Our normal packing & shipping personnel refuse to package these magnets – our engineers have to do it. This is no joke or exaggeration – and we cannot stress it strongly enough. You must be extremely careful – and know what you’re doing with these magnets.
    Two Supermagnets can very easily get out of control, crush fingers and instantly break ribs or even your arm if opposing poles fly at each other.

    A small child recently lost his hand when his father left two # 31 supermagnets unattended. The child picked one up and when he approached the other magnet on a nearby table,
    it became airborne and obliterated his small hand.

    [I’ve spaced it for easier reading]

  9. Timothy from Boulder

    I have a little stack of rare earth magnets on my desk — six polished disks that are about 5mm in diameter and 1.5mm high so the stack makes a rod that is twice as high as it is in diameter. If I try to roll it along the desk in a North/South direction, it immediately makes a right angle turn to travel East/West so that the field (along the long axis) lines up with magnetic north.

    I always comprehended the motion of a compass dial on its needle bearing, but was surprised when I first saw how this stack, the mass of which is not negligible, was so strongly affected.

  10. Cameron

    I agree with Michelle’s comment up there…I once got two hard drive magnets, about a 1/4″ thick each (2-3 times as think as most), firmly latched on to a chunk of my arm. I had already discovered that getting them apart required violently twisting them to get the magnetic fields out of alignment, and as it was on my arm, I didn’t even have the leverage to get at it…I finally gritted my teeth and had a friend twist/rip the accursed thing off.


  11. Chip

    Also those of us with pacemakers – probably not a good idea to play with powerful magnets.

  12. Ooh, that turned my stomach a few times. I’ve used old hard drive magnets on the fridge before, but I’ve never owned a rare-earth magnet. Those things are no joke!!!

  13. Alain

    Someone should give you a few sets of geomag or some of those other ball and rod magnetic construction sets.

    I’ve wasted a lot of time making archimedean solids with the geomag sets, and a lot of money buying yet one more set to do a still more complex archimedean solids.

  14. Ooowww…. Why oh why did those pictures have to be so… big?? Broken finger in your face. Ewww.

    Careful with those magnets Phil. A finger is for life, not just for playtime.

  15. Cindy

    You have to be careful even with the magnets in the kids toy Magnetix (spelling??). More than one kid has died when (I think usually) he swallowed the magnets and they pinched parts of the small intestine together and caused sepsis.

  16. QUASAR

    I’ve seen those kinds of neodymium magnets in a Mythbusters episode, they also said that they have a very strong attraction between two opposite poles! Getting one of your fingers stuck between two of them can be very painfull! And those images were really nasty! OUCH!

  17. I’m just glad it was his finger that fot caught and not some other body part… ewwwww.

  18. jest

    It’s probably just me, but I found his writing to be almost as painful as the images (and how it happened). Ouch, though. OUCH.

    I love magnets. There’s so many cool things you can do with them!

  19. dragonet2

    I have a friend who is a magician and uses magnets for some of his tricks.

    His home now has a rare earth magnet as a permanent fixture on one of the steel framing supports in the basement.

    He told the joke on himself, “I didn’t believe the informational sheet that came with the packaging that said don’t stick it to steel objects. It’s there for good now, I can’t make it come loose.”

    The pictures make my hands hurt. Yikes!

  20. ABC123

    It was a good thing his finger was there or those magnets might have been broken.

  21. Kevin Conod

    He, he I once bought a large rare-Earth magnet and thought “Gee I wonder what would happen if I put this on the fridge?” Oops! :-) I did managed to slip a towel between the magnet and the fridge and then put both feet up on the door, put my full weight on it and pulled as hard as I could. It did eventually pop off after leaving a big gouge in the metal door!

  22. The Chemist: One reason not to let children young enough to put magnets in their mouths play with anything but weak toy magnets is that two small, strong magnets can pin parts of the intestines together and cause necrosis. (This is the nursery school teacher in me who finds this stuff out.)

    I grew up playing with them by putting one in a plastic bag and dragging it around in the sandbox at school, then pulling the bag off to loosen the iron bits into a bowl. Oh, good times, good times.

  23. Chris

    The Chemist quoted “A small child recently lost his hand when his father left two # 31 supermagnets unattended. The child picked one up and when he approached the other magnet on a nearby table,
    it became airborne and obliterated his small hand.


    A toddler died due to swallowing a pair of those magnets. He swallowed a pair of small strong magnets that were part of a magnetic building toy, and they pinched a part of his intestines. Other children have been injured in various ways with these magnets.

    With a bit a googling I found the warning about them here:

    As the number of toys with magnets increases, so is the number of serious injuries to children. The U.S. Consumer Product Safety Commission (CPSC) is aware of hundreds of complaints that magnets have fallen out of various toys and at least 33 cases where children swallowed loose magnets and required emergency surgery. In addition, a 20-month-old boy from Seattle, Wash. died.
    If two or more magnets, two or more magnet components, or a magnet and another metal object are swallowed separately, they can attract to one another through intestinal walls. When this happens, parents and physicians may think that the materials will pass through the child. But with magnets this is often not the case. The magnets become trapped in the body and can twist or pinch the intestine, causing holes, blockage and infection in the intestine or blood poisoning. All of which can lead to death.

  24. Roger Wilco

    It’s interesting that they sutured the end of his finger. From what I have read about this recently (er yes, reputable journals) the best treatment is to leave the wound alone as much as possible. If it’s just covered with a dry dressing (to keep out infection) the fingertip regrows (really!). If it’s sown up like this it does not regrow. There is quite a bit of research going on to find why this works for fingertips but not whole limbs, there could be some very interesting results from this research one day.

  25. Dave M

    I don’t want to think about how long it’s been since I took physics, but doesn’t the force between magnets fall off based on the inverse cube of the distance. If there was 1,000 pounds of attractive force at 1 inch, wouldn’t that fall to around 1/2 pound at a foot? For an MRI machine to forcefully grab a drill from a few feet, the magnetic field must have been incredible!

    Audio speakers that are meant to be used near CRTs usually have steel shells around the magnets to redirect the field. I wonder if these are used when shipping super magnets. The post office probably wouldn’t take kindly to packages becoming permanently stuck to their machinery.

  26. Anthony Popple

    As long as we are sharing war stories…….

    I was a physics student at the University of Minnesota in the early 1990s. The lab where I worked had a group that researched medical imaging. They had a compact, but very powerful, magnet for studying PET scans. The medical school was in the process of setting up some new equipment and needed to barrow some specialized power supplies from the lab. A couple of moving guys were sent to pick up the units. They were given very detailed instructions as how they were supposed to remove the power supplies.

    Unfortunately, the movers were very impatient and didn’t like being told what to do. As soon as the lab staff left the room, they attempted to drag one of the units straight across the room within feet of the magnet. The field ripped the power supply right out of there arms and slammed it against the side of the magnet housing. The power supply was nearly crushed flat.

    Luckily, one body got hurt, but it could easily have been a very tragic event. I seem to remember it took a couple of days before they were able to remove the power supply. They damaged the core of the magnet and it took months to repair it. I think they also lost several tens of thousands of dollars worth of liquid helium.

    Of course, the movers had also ignored the instructions to remove their watches and wallets before entering.

  27. jest

    Dave M: I thought about that too (how they’re packaged). Could you imagine? Post man makes it all the way to your front door, and happens to place the package down on a metal handrail… SPANG! Uh oh.

    Mary M: Yes, I’ve actually heard of that happening to children. Something about those little round magnets used in the letters they used to make for fridges (I believe the newer toy letters feature the magnet hidden inside of them, so they can’t be removed from the toy and eaten). It’s amazing how some of us made it past our childhoods eh?

  28. IVAN3MAN

    Gary Ansorge:

    I just have one question: how many Tesla would that N45 represent?

    Grade N45 Magnet — 12,500 gauss = 1.25 tesla (1 tesla = 104 guass).

  29. IVAN3MAN

    Goddamnit, I hit the submit button to soon; that should read: 1 tesla = 104 gauss, not “guass”.

  30. IVAN3MAN

    And that “to” should be too!

  31. Fergus Gallagher

    I have a large granite kitchen worktop to roll my spherical magnet along. But they only travel a short distance before stopping, attracted by the iron… Really cool the way it wobbles from side to side as the iron density changes.

  32. MadScientist

    A friend of mine caught his fingers between two toroidal samarium-cobalt magnets (that was about 10 years ago). I rescued him using two large screwdrivers then heard from another friend on the following weekend that he’d gone and done it again. Some people never learn. I guess he at least kept the magnets above waist level – pity really because I could have had a funnier story to tell.

  33. “These are like magnets on steroids”, ahhaha :D.
    and “usch” as we say in swedish, to the pictures.

  34. Naomi

    Oh, I’m so glad I wasn’t eating when I saw those pictures o.o

    Neodymium magnets are hardcore. In the physics lab, we had a small roll of disc-shaped ones now permanently stuck together – I was wearing fairly loose trousers, put the roll in my pocket as an experiment, and walked by a metal table leg. It physically dragged me a foot to the side! (I was very very careful to keep my hands well away – if my hand had been caught between the roll and the table leg, the bones WOULD have been pulverised.)

    Like volcanoes and radioactive materials, neodymium magnets are dangerous but AWESOME.

  35. Jessica

    Thanks for the warning (I switched off the “Show Pictures” option before following the link!). OUCH. Magnets are interesting, but I don’t think I’d like to go near strong ones after hearing all these stories! >_<

  36. LionDancer

    Mike M:

    Don’t you mean inverse square not inverse cube??

  37. Lee Hadley

    That is possibly the grossest thing I have ever seen. Thanks Phil.

  38. I had no idea that a magnet could be any where near as strong at that. An electric magnet maybe, but not I know about the rare earth stuff – crumbs!

  39. Bennihana123

    Oh my sweet juicy Jesus. I’m going to go vomit now.

  40. Torbjörn Larsson, OM

    Well, I don’t doubt that you can get quite a wallop from magnets. In fact, I’ve had my fingers pinched as well (but no injuries).

    The warnings about ingesting magnets sounded far-fetched though, but there were papers on the net not only surveying magnets but their characteristics vs medicine. For example, I found this CDC report, including references, case studies, radiographs of magnets causing bowel problems, and statistics.

    Don’t you mean inverse square not inverse cube??

    It is AFAIU true that long range forces like magnetic fields must fall of as the inverse square of distance from a source in a 3D space, or they wouldn’t be long range (go to infinity as a solution to a source Laplacian).

    But he was describing (bar) magnets, which are roughly dipoles as seen from outside the bar, i.e. can be approximated by a source and an equivalent sink in the ends, or as two opposed sources if you will. Far away from a magnet the field will then go, I think, as an electric dipole field does, which is extinguished faster, as an inverse cube of the distance.

  41. But… but… I don’t get it! Shouldn’t magnets that powerful have healed him instantly?

  42. Daniel J. Andrew

    I’ve seen advertisements for powerful rare earth magnets. I thought it was just hype. I had no idea they could be that strong. Think I’ll get one. Not two. Just one. I’m a klutz, two will kill me.

  43. Donnie B.

    My brother uses an expression that perfectly describes the sensation produced by looking at pictures like those: “butt willies”.

  44. Kyle

    OK I must be the only medical person in here, former paramedic, but I thought the pictures were cool. Always hated having to take patients into a MRI, took 5 minutes to pull all our metal off and then put it all back on. Only ever had the snaps on my pockets pop open.

  45. Mark Hansen

    Just Al, maybe they work best when used in a homeopathic fashion. The further the magnet is away from you, the better it works. In this guys case the proof is in the photos.

  46. Alex Besogonov

    Torbjörn Larsson:

    It’s more complex. Magnetic field generally diminishes according to inverse cube law ( ), but in some cases it can even be inverse fourth power.

  47. Gary Ansorge

    Thanks. That was useful.

    GAry 7

  48. Units geek

    Somebody should let them know that a “force” of 700 lbs is *never* equal any amount of kilograms. 3,113 Newtons maybe…

  49. Ryan

    Is it bad that after seeing that website I want some of these?

  50. Master Meadows



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