7 ms·

We didn't evolve to have the warning mechanisms for modern life. Tell a person there's a tarantula or a cobra in the next room and not a second will go by with

We didn't evolve to have the warning mechanisms for modern life. Tell a person there's a tarantula or a cobra in the next room and not a second will go by without them being deeply aware of this information. Tell them it's a 3 tesla magnetic field and they'll run in carrying a piece of sheet metal and a pocket full of ball bearings.

HelloUsername 1y ago
https://en.wikipedia.org/wiki/Darwin_Awards https://en.wikipedia.org/wiki/Darwin_Awards
sippeangelo 1y ago
This doesn't track to me. People have been irrationally afraid of things since the dawn of time, based purely on hearsay (see religion). And surely even the simplest of language serves to warn about unseen dangers. Entering the MRI room myself I was very familiar with the dangers of bringing metal inside, to the point where I would second guess myself and my own body. "What if my leg bone actually has metal in it for some reason?!"
- Karawebnetwork 1y ago
  > "What if my leg bone actually has metal in it for some reason?!" I have a titanium plate in my head, so it's not magnetic. When the MRI tech asked if I had any metal in me, I said I had titanium on my skull. She asked if I was sure it was titanium. I knew it was, but I was nervous, so I said, "I think so." She half-joked, "Well, if it's not, we'll find out real quick." It was titanium. But they never really double-checked or anything. Part of me thinks that because of my age, she could tell it wasn't iron or anything dangerous. But another part of me feels like she honestly didn't care that much and meant it when she said we'd find out fast.
  - octopoc 1y ago
    Wouldn’t your head have started to get pulled towards it as you approached, so maybe you could stop approaching once you felt something weird going on in your head?
    - trod1234 1y ago
      Powerful electromagnets don't work like that. They may switch on and off, and if you are in range, the motion is almost instantaneous. Its not like in the movies where you have to be right up on it, and certain materials may attract at higher rates depending on the amount of ferromagnetic materials affected by the flux. Field flux lines may also be warped depending on the geometry so its possible the drop-off wasn't calculated properly during initial facility design, or it changed. Walking through the wrong door can have consequences as the news has reported.
    - nullc 1y ago
      You normally hear it describes as the "field falls off according to inverse cube" but the consider what that means about how the field increases. The effect for magnetic fields is that generally once the field is enough to obviously move an object it's already accelerating uncontrollably.
  - Aeolun 1y ago
    It’s probably of the “if it’s in your head, it can’t be anything other than titanium” variety. It’s not like they’re going to break open your head to check.
    - Karawebnetwork 1y ago
      From what I gather, it's between the 80's and 90's that titanium became the norm.
- zimpenfish 1y ago
  > "What if my leg bone actually has metal in it for some reason?!" I had that constant thought for the 15 minutes of my knee MRI (except s/leg bone/body/). Most discombobulating.
  - Aeolun 1y ago
    I had two head MRI’s, and both times I was equally terrified my metal fillings would start bouncing around my head.
  - xattt 1y ago
    Wait till you learn about Peripheral Nerve Stimulation effects: https://www.robarts.ca/scholl_group/research/peripheral_nerve_stimulation.html https://www.robarts.ca/scholl_group/research/peripheral_nerv...
  - mcv 1y ago
    There's lots of ways we could have metal in our body. A hip replacement, a forgotten piercing, old tooth fillings, maybe you accidentally swallowed some piece of metal. If MRI scanners are this deadly, everybody should be really thoroughly screened and scanned to be allowed into the room. And even into the room next to it. How can the door of that room open while the machine is still turned on? (Edit: apparently the magnets in these machines usually can't be turned off, which changes the question to: how was he allowed to enter the room at all?) But wearing such a heavy chain while accompanying your spouse to an MRI scan, is also not the best move.
    - mystraline 1y ago
      The walls are usually made from mu-metal. This is a metal mixture that blocks/attenuates magnetic energy. Spinning rust hard drives are also made with mu-metal as well.
    - bapak 1y ago
      Indeed. The hospital will pay a lot of money. Metal detectors are insanely cheap, there's no reason why there shouldn't be one before reaching the door as a default cautionary measure.
- Workaccount2 1y ago
  There are people who flock towards information about technology (probably almost everyone here as well as many in their social circles) and there are people who run from information about technology. I know people who if you tried to explain an MRI to them, would become visibly uncomfortable and search for any way to change the topic.
  - balamatom 1y ago
    >I know people who if you tried to explain an $X to them, would become visibly uncomfortable and search for any way to change the topic. Expected behavior. Explanations of complex topics are to be rejected if explainer does not have sufficient authority to make behaver hold-still-and-listen. I know such folk, too, and this is among the thing about people which annoys me to no end. If a MRI tech tried to explain the shit to one such acquaintance, they would try to change the subject like you say. OTOH, if the doctor in charge tries the same, the listener will instead have to zone out. But zoning out is a more expensive operation, as any zooner knows. (Which is why they hold doctors, lawyers, and other semi-priests in high reverence, up to pushing kids to take up these rather joyless professions to the exclusion of all sense.) Peeps here equally well-behaved other way round tho. C-f "mal" = 0. Geez I really needed to witness the absolute by-the-book Freudian slip that can be found at 1:55 of one of the probably infinite interview cuts, then have MRI safety explained to me by hacker noosers on their Monday morning.
    - pfannkuchen 1y ago
      Is law really joyless? IANAL but it seems like competitive puzzle solving, essentially.
      - balamatom 1y ago
        And medicine might, to some, seem like the use of science to save lives, but hey -- a shooting war is also a kind of competitive puzzle solving, and I assume there are people who find joy in that, too.
- xattt 1y ago
  Both can be true. We learn to fear and respect modern technology because of training and reinforcement that might occur as part of learning. Consider the “Things I Won’t Work With” column. There is a healthy degree of respect for various compounds that’s learned with experience. This is similar to the way that (properly trained) electricians work with electricity, and nuclear plant techs work around radioactive material.
- moralestapia 1y ago
  Hehe, in my case I used to have a metal filling that was removed, but I was still worried about a missing piece of it or something. Apparently it's not an issue, even if you do have them.
  - conradludgate 1y ago
    My first MRI I confirmed I have no metal on my body to the technician, but by the time I was inside I suddenly remembered I have metal fillings. I was so stressed by the time the machine turned on, but yeah no problems at all
    - itishappy 1y ago
      The machine was already on by the time you were in it. The magnet does not get turned off.
      - jpeloquin 1y ago
        True, but the RF coils do get turned on & off. Heating of non-magnetic metal from the radio waves used for scanning is another concern, not just magnetic force.
- bapak 1y ago
  I think people are just not aware of how bad it is. People might think it's "fork in microwave" oopsie bad, not "fire at the gas station" fatal bad.
  - Velorivox 1y ago
    It’s certainly bad enough that you shouldn’t be able to enter a room with an operational MRI machine just like that, as a normal guest with no training and no escort. One cheap RFID reader could have saved a life here.
colechristensen 1y ago
The other side is also true though, "man gets killed by cobra venom" isn't sensational international news because it's an intuitive rational thing we expect to happen. A man getting killed by an MRI machine doesn't fit into our intuition so it gets much more interest than a snake bite.
nancyminusone 1y ago
To be fair, most people aren't going to know what they means. If anything it's going to sound more like "only 3 huh? That doesn't sound very dangerous." Only 3 miles per hour isn't very fast. Only 3 degrees outside is cold, but it probably won't kill you. 30,000 gauss sounds a lot scarier.
- mpreda 1y ago
  Not to mention that "gauss" sounds deadlier than "tesla" to begin with. Talking about choosing the right units.
  - littlestymaar 1y ago
    Cars are quite deadly though.
- snewman 1y ago
  Obligatory xkcd: https://xkcd.com/3106/ https://xkcd.com/3106/
- littlestymaar 1y ago
  Same for 2°C of global warming…
- nullc 1y ago
  The field strength isn't a fair measure of the danger in any case. It's as dangerous as it is because of the size. A little rare earth magnet can easily have a 1T field at its surface, but some inches away the field is negligible.
meindnoch 1y ago
And yet, Koreans are afraid of fans.
- unsupp0rted 1y ago
  The current generations aren’t. It stopped being a thing a decade back.
raverbashing 1y ago
Honestly yeah, why do you need your "workout chain" while taking your wife to a medical exam? Sounds like Darwin Awards material
- shawabawa3 1y ago
  > Honestly yeah, why do you need your "workout chain" while taking your wife to a medical exam? sounds like people wear them all day, so it would more be a case of "why would i take this off?" I would have thought the dozens of huge warning signs around the MRI room would have tipped him off but i guess warning fatigue is a thing
  - raverbashing 1y ago
    "Main Character syndrome" is a thing
- rbanffy 1y ago
  I'd make sure to look into life insurance and abuse complains.
rbanffy 1y ago
We don't have a sense for detecting 3 Tesla magnets because they don't happen in nature. People can see a tarantula, and, depending on the snake, hear it as well. But you need to seriously piss off the tarantula for it to engage in a fight with an opponent our size. Most of them are sweet and just want to get on with their tiny lives. They are well aware we are not food. Poisonous snakes, on the other hand, tend to be much less chill. Much like wasps, they seem to enjoy causing pain and suffering.
- unsupp0rted 1y ago
  Another good question is why do we have a sense for detecting things that appear vaguely human but aren't (uncanny valley)?
- vunderba 1y ago
  Tarantulas covers A LOT of spiders (around 1100 different species). You still have to at least be a bit careful around them since they have urticating hairs. > Poisonous snakes, on the other hand, tend to be much less chill. Much like wasps, they seem to enjoy causing pain and suffering. Eh, I don't know about that. For example, sea snakes, despite being incredibly venomous, are actually pretty timid creatures. Also: https://www.britannica.com/story/whats-the-difference-between-venomous-and-poisonous https://www.britannica.com/story/whats-the-difference-betwee...
- throwanem 1y ago
  Wasps aren't sadists.
  - codyb 1y ago
    Agreed, most wasps are super chill if you're not a jackass to 'em. Watching 'em lick up some sugar water is pretty neat in my experience, what with the way they clean their little legs.
    - int_19h 1y ago
      My mom would actually feed wasps by pouring sweet syrup or the like in her palm and letting them land and drink it from there. She never got stung.
gadders 1y ago
Similarly: https://www.fox5ny.com/news/courtney-edwards-piedmont-airlines-sucked-into-engine https://www.fox5ny.com/news/courtney-edwards-piedmont-airlin... Intellectually, you can think that "If a jet can move a plane, it can move me through space", but you never experience a fan even close to that in real life.
cjbgkagh 1y ago
Fear of heights is ingrained, fear of snakes is learned. We can definitely do better to educate people on the fear of magnets, I figure it’s not a priority since we’re not going to encounter many MRI machines in the wild. How difficult would it be to install metal detectors to give an alarm to people who enter. I have had a few MRIs and they did seem too trusting that I properly remembered to remove anything magnetic.
- unsupp0rted 1y ago
  I'd say about 1/5 of the MRI centers I've been to had metal detectors before entry. And 0/5 had ones that were turned on.
- kjkjadksj 1y ago
  Fear of snakes is also biological. Look up the cat cucumber videos.
  - cjbgkagh 1y ago
    For some species that makes a lot of sense, but humans do not react the same way to cucumbers. I'm going by; https://www.youtube.com/watch?v=3L4lxusff1c https://www.youtube.com/watch?v=3L4lxusff1c "The Surprising Reason Babies Are NOT Afraid of Snakes | Secret Science"
codyb 1y ago
Maybe if you instead phrased it as "there's a magnetic field in there that will shear anything magnetic straight through your body if you're holding it on the wrong side of you" that might help folk get the picture a bit better? I mean sheesh, I've got a B.S. in Computer Engineering and a 3 Tesla magnetic field doesn't mean much to me either
- Aeolun 1y ago
  It won’t shear it straight through your body though. The path of least resistance is to spin you around and then fly off. That doesn’t quite work if the thing is around your neck though.
- JKCalhoun 1y ago
  Just a sensitive metal detector around the doorway where you enter the MRI room. It sounds like this guy would have had the metal detector blaring before he even crossed the threshold.
  - lostlogin 1y ago
    As would staff shoes, bra, jewellery, access card, ring etc etc.
    - unsupp0rted 1y ago
      You can have a metal detector that detects a 20 lb chain and not a pair of nurse's shoes
      - lostlogin 1y ago
        So the patient with the tiny, unsafe aneurysm clip on a cerebral artery gets in. They are an imperfect solution. They may help, but dependence on good practice remains.
- lumpa 1y ago
  "There's a huge evil magnet that will tear you apart if you have any metal on you" sounds much easier to grasp and less likely to lose the listener's attention. Then, when you have them listening: "It can grab you from outside the room and hurl you into the machine where the evil magnet lives! Any metal, be it coins, necklaces, pins in your bones, belt buckles, bra wiring, dog tags. Anything can be the end of you, be damn sure you don't have any metal on you." Oh, wait, you still want them willing to go near the machine? That complicates things a bit ;)

HelloUsername 1y ago

https://en.wikipedia.org/wiki/Darwin_Awards https://en.wikipedia.org/wiki/Darwin_Awards

sippeangelo 1y ago

This doesn't track to me. People have been irrationally afraid of things since the dawn of time, based purely on hearsay (see religion). And surely even the simplest of language serves to warn about unseen dangers. Entering the MRI room myself I was very familiar with the dangers of bringing metal inside, to the point where I would second guess myself and my own body. "What if my leg bone actually has metal in it for some reason?!"

Karawebnetwork 1y ago
> "What if my leg bone actually has metal in it for some reason?!" I have a titanium plate in my head, so it's not magnetic. When the MRI tech asked if I had any metal in me, I said I had titanium on my skull. She asked if I was sure it was titanium. I knew it was, but I was nervous, so I said, "I think so." She half-joked, "Well, if it's not, we'll find out real quick." It was titanium. But they never really double-checked or anything. Part of me thinks that because of my age, she could tell it wasn't iron or anything dangerous. But another part of me feels like she honestly didn't care that much and meant it when she said we'd find out fast.
- octopoc 1y ago
  Wouldn’t your head have started to get pulled towards it as you approached, so maybe you could stop approaching once you felt something weird going on in your head?
  - trod1234 1y ago
    Powerful electromagnets don't work like that. They may switch on and off, and if you are in range, the motion is almost instantaneous. Its not like in the movies where you have to be right up on it, and certain materials may attract at higher rates depending on the amount of ferromagnetic materials affected by the flux. Field flux lines may also be warped depending on the geometry so its possible the drop-off wasn't calculated properly during initial facility design, or it changed. Walking through the wrong door can have consequences as the news has reported.
  - nullc 1y ago
    You normally hear it describes as the "field falls off according to inverse cube" but the consider what that means about how the field increases. The effect for magnetic fields is that generally once the field is enough to obviously move an object it's already accelerating uncontrollably.
- Aeolun 1y ago
  It’s probably of the “if it’s in your head, it can’t be anything other than titanium” variety. It’s not like they’re going to break open your head to check.
  - Karawebnetwork 1y ago
    From what I gather, it's between the 80's and 90's that titanium became the norm.
zimpenfish 1y ago
> "What if my leg bone actually has metal in it for some reason?!" I had that constant thought for the 15 minutes of my knee MRI (except s/leg bone/body/). Most discombobulating.
- Aeolun 1y ago
  I had two head MRI’s, and both times I was equally terrified my metal fillings would start bouncing around my head.
- xattt 1y ago
  Wait till you learn about Peripheral Nerve Stimulation effects: https://www.robarts.ca/scholl_group/research/peripheral_nerve_stimulation.html https://www.robarts.ca/scholl_group/research/peripheral_nerv...
- mcv 1y ago
  There's lots of ways we could have metal in our body. A hip replacement, a forgotten piercing, old tooth fillings, maybe you accidentally swallowed some piece of metal. If MRI scanners are this deadly, everybody should be really thoroughly screened and scanned to be allowed into the room. And even into the room next to it. How can the door of that room open while the machine is still turned on? (Edit: apparently the magnets in these machines usually can't be turned off, which changes the question to: how was he allowed to enter the room at all?) But wearing such a heavy chain while accompanying your spouse to an MRI scan, is also not the best move.
  - mystraline 1y ago
    The walls are usually made from mu-metal. This is a metal mixture that blocks/attenuates magnetic energy. Spinning rust hard drives are also made with mu-metal as well.
  - bapak 1y ago
    Indeed. The hospital will pay a lot of money. Metal detectors are insanely cheap, there's no reason why there shouldn't be one before reaching the door as a default cautionary measure.
Workaccount2 1y ago
There are people who flock towards information about technology (probably almost everyone here as well as many in their social circles) and there are people who run from information about technology. I know people who if you tried to explain an MRI to them, would become visibly uncomfortable and search for any way to change the topic.
- balamatom 1y ago
  >I know people who if you tried to explain an $X to them, would become visibly uncomfortable and search for any way to change the topic. Expected behavior. Explanations of complex topics are to be rejected if explainer does not have sufficient authority to make behaver hold-still-and-listen. I know such folk, too, and this is among the thing about people which annoys me to no end. If a MRI tech tried to explain the shit to one such acquaintance, they would try to change the subject like you say. OTOH, if the doctor in charge tries the same, the listener will instead have to zone out. But zoning out is a more expensive operation, as any zooner knows. (Which is why they hold doctors, lawyers, and other semi-priests in high reverence, up to pushing kids to take up these rather joyless professions to the exclusion of all sense.) Peeps here equally well-behaved other way round tho. C-f "mal" = 0. Geez I really needed to witness the absolute by-the-book Freudian slip that can be found at 1:55 of one of the probably infinite interview cuts, then have MRI safety explained to me by hacker noosers on their Monday morning.
  - pfannkuchen 1y ago
    Is law really joyless? IANAL but it seems like competitive puzzle solving, essentially.
    - balamatom 1y ago
      And medicine might, to some, seem like the use of science to save lives, but hey -- a shooting war is also a kind of competitive puzzle solving, and I assume there are people who find joy in that, too.
xattt 1y ago
Both can be true. We learn to fear and respect modern technology because of training and reinforcement that might occur as part of learning. Consider the “Things I Won’t Work With” column. There is a healthy degree of respect for various compounds that’s learned with experience. This is similar to the way that (properly trained) electricians work with electricity, and nuclear plant techs work around radioactive material.
moralestapia 1y ago
Hehe, in my case I used to have a metal filling that was removed, but I was still worried about a missing piece of it or something. Apparently it's not an issue, even if you do have them.
- conradludgate 1y ago
  My first MRI I confirmed I have no metal on my body to the technician, but by the time I was inside I suddenly remembered I have metal fillings. I was so stressed by the time the machine turned on, but yeah no problems at all
  - itishappy 1y ago
    The machine was already on by the time you were in it. The magnet does not get turned off.
    - jpeloquin 1y ago
      True, but the RF coils do get turned on & off. Heating of non-magnetic metal from the radio waves used for scanning is another concern, not just magnetic force.
bapak 1y ago
I think people are just not aware of how bad it is. People might think it's "fork in microwave" oopsie bad, not "fire at the gas station" fatal bad.
- Velorivox 1y ago
  It’s certainly bad enough that you shouldn’t be able to enter a room with an operational MRI machine just like that, as a normal guest with no training and no escort. One cheap RFID reader could have saved a life here.

colechristensen 1y ago

The other side is also true though, "man gets killed by cobra venom" isn't sensational international news because it's an intuitive rational thing we expect to happen. A man getting killed by an MRI machine doesn't fit into our intuition so it gets much more interest than a snake bite.

nancyminusone 1y ago

To be fair, most people aren't going to know what they means. If anything it's going to sound more like "only 3 huh? That doesn't sound very dangerous." Only 3 miles per hour isn't very fast. Only 3 degrees outside is cold, but it probably won't kill you. 30,000 gauss sounds a lot scarier.

mpreda 1y ago
Not to mention that "gauss" sounds deadlier than "tesla" to begin with. Talking about choosing the right units.
- littlestymaar 1y ago
  Cars are quite deadly though.
snewman 1y ago
Obligatory xkcd: https://xkcd.com/3106/ https://xkcd.com/3106/
littlestymaar 1y ago
Same for 2°C of global warming…
nullc 1y ago
The field strength isn't a fair measure of the danger in any case. It's as dangerous as it is because of the size. A little rare earth magnet can easily have a 1T field at its surface, but some inches away the field is negligible.

meindnoch 1y ago

And yet, Koreans are afraid of fans.

unsupp0rted 1y ago
The current generations aren’t. It stopped being a thing a decade back.

raverbashing 1y ago

Honestly yeah, why do you need your "workout chain" while taking your wife to a medical exam? Sounds like Darwin Awards material

shawabawa3 1y ago
> Honestly yeah, why do you need your "workout chain" while taking your wife to a medical exam? sounds like people wear them all day, so it would more be a case of "why would i take this off?" I would have thought the dozens of huge warning signs around the MRI room would have tipped him off but i guess warning fatigue is a thing
- raverbashing 1y ago
  "Main Character syndrome" is a thing
rbanffy 1y ago
I'd make sure to look into life insurance and abuse complains.

rbanffy 1y ago

We don't have a sense for detecting 3 Tesla magnets because they don't happen in nature. People can see a tarantula, and, depending on the snake, hear it as well. But you need to seriously piss off the tarantula for it to engage in a fight with an opponent our size. Most of them are sweet and just want to get on with their tiny lives. They are well aware we are not food. Poisonous snakes, on the other hand, tend to be much less chill. Much like wasps, they seem to enjoy causing pain and suffering.

unsupp0rted 1y ago
Another good question is why do we have a sense for detecting things that appear vaguely human but aren't (uncanny valley)?
vunderba 1y ago
Tarantulas covers A LOT of spiders (around 1100 different species). You still have to at least be a bit careful around them since they have urticating hairs. > Poisonous snakes, on the other hand, tend to be much less chill. Much like wasps, they seem to enjoy causing pain and suffering. Eh, I don't know about that. For example, sea snakes, despite being incredibly venomous, are actually pretty timid creatures. Also: https://www.britannica.com/story/whats-the-difference-between-venomous-and-poisonous https://www.britannica.com/story/whats-the-difference-betwee...
throwanem 1y ago
Wasps aren't sadists.
- codyb 1y ago
  Agreed, most wasps are super chill if you're not a jackass to 'em. Watching 'em lick up some sugar water is pretty neat in my experience, what with the way they clean their little legs.
  - int_19h 1y ago
    My mom would actually feed wasps by pouring sweet syrup or the like in her palm and letting them land and drink it from there. She never got stung.

gadders 1y ago

Similarly: https://www.fox5ny.com/news/courtney-edwards-piedmont-airlines-sucked-into-engine https://www.fox5ny.com/news/courtney-edwards-piedmont-airlin... Intellectually, you can think that "If a jet can move a plane, it can move me through space", but you never experience a fan even close to that in real life.

cjbgkagh 1y ago

Fear of heights is ingrained, fear of snakes is learned. We can definitely do better to educate people on the fear of magnets, I figure it’s not a priority since we’re not going to encounter many MRI machines in the wild. How difficult would it be to install metal detectors to give an alarm to people who enter. I have had a few MRIs and they did seem too trusting that I properly remembered to remove anything magnetic.

unsupp0rted 1y ago
I'd say about 1/5 of the MRI centers I've been to had metal detectors before entry. And 0/5 had ones that were turned on.
kjkjadksj 1y ago
Fear of snakes is also biological. Look up the cat cucumber videos.
- cjbgkagh 1y ago
  For some species that makes a lot of sense, but humans do not react the same way to cucumbers. I'm going by; https://www.youtube.com/watch?v=3L4lxusff1c https://www.youtube.com/watch?v=3L4lxusff1c "The Surprising Reason Babies Are NOT Afraid of Snakes | Secret Science"

codyb 1y ago

Maybe if you instead phrased it as "there's a magnetic field in there that will shear anything magnetic straight through your body if you're holding it on the wrong side of you" that might help folk get the picture a bit better? I mean sheesh, I've got a B.S. in Computer Engineering and a 3 Tesla magnetic field doesn't mean much to me either

Aeolun 1y ago
It won’t shear it straight through your body though. The path of least resistance is to spin you around and then fly off. That doesn’t quite work if the thing is around your neck though.
JKCalhoun 1y ago
Just a sensitive metal detector around the doorway where you enter the MRI room. It sounds like this guy would have had the metal detector blaring before he even crossed the threshold.
- lostlogin 1y ago
  As would staff shoes, bra, jewellery, access card, ring etc etc.
  - unsupp0rted 1y ago
    You can have a metal detector that detects a 20 lb chain and not a pair of nurse's shoes
    - lostlogin 1y ago
      So the patient with the tiny, unsafe aneurysm clip on a cerebral artery gets in. They are an imperfect solution. They may help, but dependence on good practice remains.
lumpa 1y ago
"There's a huge evil magnet that will tear you apart if you have any metal on you" sounds much easier to grasp and less likely to lose the listener's attention. Then, when you have them listening: "It can grab you from outside the room and hurl you into the machine where the evil magnet lives! Any metal, be it coins, necklaces, pins in your bones, belt buckles, bra wiring, dog tags. Anything can be the end of you, be damn sure you don't have any metal on you." Oh, wait, you still want them willing to go near the machine? That complicates things a bit ;)