So, magnetars have field strengths of around 10^11 T, and you would feel this. Sort of. As you are melting into XRays and so forth…
"In a strong magnetic field, electrons are forced to move along the field lines, but when magnetic confinement squeezes the electron in the transverse direction to less than its de Broglie wavelength then quantum effects become important. The transverse motion becomes quantized with discrete energy levels the Landau levels.
A direct measure of the star’s magnetic field is therefore obtained by detecting an emission line at the frequency of electrons making a transition between the Landau levels. Typically these spectral lines are visible in the hard X-ray region: for example the electron cyclotron line for the pulsar in the binary system Hercules X-1 is at about 60 keV. "
Not quite what the OP asked, but when I was taking E&M in undergrad physics, the textbook claimed that if you put your head in a very, very strong magnetic field and shook it, that you’d be able to taste the currents generated. The instructor thought this was pretty funny.
I read somewhere (Slashdot?) that you can get magnetic implants under your skin. After time your body learns to use them to sense magnetic fields (presumably since the magnets press/tug on your flesh when they come into contact with such fields).
The sounds are made by the movements of the “shim coils” - additional electromagnets that smooth out irregularities in the overall magnetic field being applied to the body inside the magnet to align its proton spins.
There are now some MR scanners entering the market where the shim coils are vacuum sealed and don’t transmit noises nearly as much.
Yup, same principle as the experiments where people wore belts that buzzed when you were facing north, or a set of electrodes on the tongue wired to a camera. The brain is a remarkably plastic organ, and you pretty quickly learn how to integrate the new sense.
Losing access to that sense once you’ve integrated it, however, is a whole different story.
Dude, with a 3T MR scanner, I would not get anywhere near it with a steel piercing. Sure, it would probably be no big deal, but just look at this:
or this:
If the piercings were something non-ferromagnetic, it’s not a problem. However, the MRI techs are trained to be OVER-cautious, because overkill on safety here is far preferable to a little screwup that end up serious hurting someone.
I’ll never forget the day that we had a prisoner who was supposed to get scanned, and he was accompanied by burly sheriff’s deputies who a) were supposed to accompany him wherever he went (including into the room with the scanner, apparently) and b) were not supposed to give up their sidearms. Ultimately I had to tell them that either they were going to check their guns in with the nurse or they would have to leave. It took some negotiations with their supervisor on the phone, and we got it worked out, but I could just see the horrified looks on the techs’ faces as they faced the prospect of someone walking into a room with an MRI scanner with a pistol.
My brother told me he had two digital watches zipped and a few credit cards made useless, before he made a ritual of always leaving his wallet and watch in the truck before entering a clinic. However, he pranked two doctors by betting them $5 that they couldn’t throw their wallets through the hole in the magnet. It was worth the five bucks to know that every credit card and hospital pass was fried in the toss. Now that credit cards also contain RFID chips, I wonder if the field fries those, too.
I’m no physicist, but in rough terms, an electrical generator works by moving wiring through a magnetic field. I’d be willing to bet lobbing an RFID tag through a 3T field would yield a sizeable spike of voltage, and probably enough to fry it.
I work for a large medical imaging company and assit with the service of our MR’s. For magnets with a strange of above 1.5 Tesla (our 3 an 7 Tesla models), there are special procedures that service engineers need to follow to minimize exposure to the strong magnetic fields. Specifically company guidelines requires no more than 2 hours servicing the system per day. Working on the 3 tesla units, service engineers - both company and hospital in-house - report that upon making any sudden movements or gestures with the head, such as rapidly turning around or nodding their heads causes symptoms including dizzy spells, mild blackouts, and stars flashing before them.
On the 7 tesla units we have installed at our facilities including Cleveland the possible effects are considered pronounced enough that patients are not allowed to enter the exam room but are instead wheeled in and out already positioned on the couch to avoid these symptoms.
Intriguing … if the magnetic field is changing rapidly, it can certainly induce current flow in neurons, which is the whole basis for transcranial magnetic stimulation therapies. I wonder if moving your head around inside a strong magnetic field will accomplish the same thing.
When I was a teenager, I built a device inside a handheld plastic box that utilized a couple of transformer ripped out of a neon lights, a wheel that functioned as a switch, and a 9V battery; when you turned the wheel, it would close the circuit and re-open it about twenty times per revolution, thus allowing the transformers to work every time the voltage flicked on and off. I was trying to make sparks jump across a couple of metal posts that stuck out of the box, but it never really worked.
However, when you held the box up next to your head and turned the wheel, you’d see faint … I guess the best word would be “pulses” of light. Not exactly like the spots of light you see when you press on your eyes, but vaguely similar. It made for some wildly entertaining times until one of the transformers died. Good times, good times…
I’m reminded of the episode of House (I think it was the first part of Euphoria) where the good doctor shot a corpse in the head and then stuck the guy into the MRI machine to see if they could, in fact, do an MRI on a police officer who had bullet fragments lodged in his brain. I’ll never forget the way the bullet fragments seemed to ooze up out of the guy’s face and then smash through the MRI machine. Made for some darn good television. And later I found out that lead bullets can have impurities that can render them ferromagnetic, so it wasn’t even completely out of the realm of possibility, at that! Even if it was jazzed up to make it more dramatic and … uh … well, for the sake of darn good television.
Phosphenes.
You can actually generate these with a square wave of about 5 volts, and a frequency of 1 to 100 Hz applied to the forehead.
Earlier thread about phosphenes: What do I see?
Now that I think about it some more, I think I conflated two of my creations in my mind. The one with the transformers was older; later, I used the same box to make something I don’t recall the intended function of, but it used a 9V battery and didn’t have any transformers. But it still used my wheel-switch. It sounds like this inadvertently created the perfect conditions for generating phosphenes: as the wheel switched the voltage on and off at somewhere between 20-40 hertz depending on how fast you turned it, it would (I think) be generating a pretty square wave. I always wondered exactly what was happening.
Got any links to further information about generating phosphenes with a square 5v 1-100Hz foreheadally-applied wave? My curiosity is extremely piqued.
Oddly enough, I’ve been thinking of building myself a USB controlled phosphene generator. There isn’t much online, but Gerald Oster wrote an article which describes using a square wave generator to produce them. It’s in Scientific American, 222(2):82–87, 1970.
Now that credit cards also contain RFID chips, I wonder if the field fries those, too.