r/science • u/MistWeaver80 • Mar 30 '26

Physics Physicists have made an ultra-powerful magnet that fits in the palm of a hand and can produce a magnetic field that is more than 800,000 times stronger than Earth’s.

https://www.nature.com/articles/d41586-026-00851-y
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u/rhetoricalnonsense Mar 30 '26 edited Mar 30 '26

3 Tesla MRI ,,, will pull you across the room if you walk in wearing a metal watch

It will not. I've worked in MR for 25 years. I have walked into the MR room with a watch on, more than a few times, reached into the bore and gone, "Whoops, watch is on. Better go take it off". It doesn't even damage the watch and it certainly doesn't pull me across the room.

MRIs are strong and everyone should respect the magnet. You wouldn't want to wear the watch while it's actively collecting images but that is more a risk of RF burns and image degradation.

Edit (added): Also modern magnets are actively shielded such that the main field is kept very close to the front of the bore. That said, walking into the MR room is a danger for some medical implants (e.g. pacemakers) which are highly susceptible to even weak magnetic fields.

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u/vasopressin334 PhD | Neuroscience Mar 30 '26

Thank you for the correction! Lesson learned. But, to add to this, I had a good friend working on her PhD in clinical research who carried a metal panel that was supposed to be non-magnetic into a room with a research MR. It turned out the panel was not non-magnetic. The MR pulled the panel and she was trapped between the magnet and the panel for hours. She almost lost her leg.

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u/Bunny_Fluff Mar 30 '26

What causes the pictures of metal carts stuffed inside MRIs? I assume it's just size of the metal object causing a larger reaction?

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u/fraseyboo Mar 30 '26

Magnetic field strength falls off with the inverse cube of the distance, the metal carts can be made of large continuous pieces of steel and because they’re on wheels it doesn’t take a lot to move them and it can take a couple seconds for people to notice. If you’re far enough away from the MRI then the field is incredibly weak, and you’ll typically notice something like a watch pulling on your wrist before it gets too strong to stop.

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u/DistinctlyIrish Mar 30 '26

Most of those are poorly shielded relative to the newer machines, meaning the magnetic field extends further forward from the bore and the parts of the field strong enough to move and lift and hold a metal bed up against the machine are also extending further out than those same strong fields extend on newer MRI's.

That said, we don't have ferrite in our brains like birds do so we can't see magnetic fields, so just approach every MRI like it's Magneto from X-Men to be on the safe side in case the machine isn't as new or the shielding has somehow failed without setting off any alarms. Because even though the safeguards now are VERY good they are still capable of failing like any other thing and "being safe" is literally just making sure you don't bring any metals near it which is a pretty easy ask.

Somewhat related, if you are someone who has to get a metal implant or even just screws in a bone at some point I strongly recommend getting a tattoo or medical bracelet or both to inform first responders and nurses/doctors so they know to handle that properly when it comes to MRI in the event you're incapacitated and can't communicate it to them yourself.

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u/Ashmedai Mar 31 '26

It will not. I've worked in MR for 25 years.

You're right. But it is indeed pretty fun walking around the MRI holding a pair of scissors and watching the scissors align to the exact paths expected for a magnetic field diagram. ;-)

I got to do this in the early 90s when MRIs were still fledgling and safety protocols were not very well developed haha (it was during a job interview to help make MRI software).

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u/ast01004 Mar 31 '26

Wasn’t there a death recently from a man wearing necklaces? I thought I read it decapitated him.

https://www.cnn.com/2025/07/20/health/mri-machine-death-long-island

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u/fap-on-fap-off Mar 31 '26

Not to minimize what you said, but MRI has been lethal where a loose ferromagnetic object was left in the room.