A reader writes:
Do you ride motorcycles or know anything about them? Please take a look at the RiderSaver™ EMF Shielding for Motorcycle Seats.
It's a bit of a long read, and I will not cover my nutts with aluminium foil anyway so you don't need to read it, but in case you do, is there really some bad radiation on motorcycles that could harm my precious balls?
This remarkable item appears to be the product of one Randall Dale Chipkar, who has a Web site for the product and his "Motorcycle Cancer Book" here. And whaddaya know - yet again, here's a proudly-displayed patent for a device, once again exploiting the general public's belief that you can't patent a thing unless it works. (You can actually patent pretty much anything you like, however crazy, as long as it's sufficiently different from other patented things.)
The nutty-sounding stuff on the RiderSaver product page about how the "outstanding magnetic field attenuation results from a unique heating/cooling process within a hydrogen reactive atmosphere" means that RiderSaver EMF Shielding is - or is at least supposed to be - "mu-metal", which is indeed commonly used for magnetic shielding.
There are some problems with using it for this purpose, though.
Problem one: Mu metal doesn't just "soak up" magnetism, like heavy drapes soak up sound. To use mu-metal to "contain" a magnetic field, you have to form the metal into a casing right around the field source. (You can do the same thing with ordinary mild steel, by the way - it just won't work as well.)
Just putting a mu-metal "hat" on top of a field source won't do this, though. It'll do something, but it's quite possible that you'll actually end up with the magnetic field lines being pulled down and concentrated right where your arse meets the seat, which I'm given to understand includes a piece of the anatomy known technically as the Bollockular Region.
(There's more info on all sorts of shielding as it applies to electronics, with helpful diagrams, here.)
Problem two: Mu-metal is for screening low-frequency, or static (i.e. just a permanent magnet) magnetic fields. The higher the frequency at which a field is oscillating, the less effective mu-metal will be.
If you've got a two-cylinder four-stroke motorcycle chugging along at 3000 RPM, its spark-plugs will be firing fifty times per second, giving an electromagnetic field around the plug wires that oscillates at that same 50Hz. And changes shape too, depending on the ignition-system layout.
50Hz isn't high-frequency - it actually qualifies as "extremely low frequency", or ELF, and ELF magnetic fields are what bother a significant portion of the people who're worried about the effects of non-ionising radiation on health. Mu-metal is often used to shield EMR in the 50-60Hz range, which is what you get from mains electricity.
[Although, as commenters point out below, the radio-frequency energy emitted from spark-plugs and their wires is broadband RF noise from DC to daylight, because that's what sparks do.]
The 50-60Hz fields from overhead power lines are a big concern for the EMR-avoiders, though I don't think anybody's ever demonstrated there to be any real risk. Yes, people who live under power lines have a higher incidence of many diseases including cancer. But people who live under power lines also tend to be poorer than people who live somewhere more picturesque, and poor people get many diseases, including cancer, at higher rates than rich people. If you do a proper test that controls for these "confounders", the health "effects" of power lines approach zero.
When you start digging into stuff like this, you'll soon find people using for support reports that say things like "the risk was elevated but not statistically significant". This is an unfortunate choice of words, because to Joe Average it means "the risk was only a bit higher". Statistical significance is actually what tells you if a result is likely to reflect reality, or just be due to chance.
A lot of medical studies use a "confidence interval" of 0.95. If something is statistically significant to this degree, there's only a one in twenty chance that it's just a fluke (and if different 0.95-interval studies all find the same thing, the probability of error drops rapidly).
Something that isn't statistically significant is something that doesn't achieve a decent confidence interval. A measurement with a confidence interval of 0.6, for instance, is only 60% likely to be a real result not due to chance. It's not wise to make decisions based on lousy confidence intervals, and what you should say if you're talking about dubious results like this is "there was no statistically significant difference in risk".
Getting back to engines, it's easy for them to produce magnetic fields at higher frequencies. If you've got a four-cylinder four-stroke bike pushing a bit hard at 8000RPM, for instance, the spark-plug field will now be oscillating 266.7 times per second, and mu-metal shielding will be less effective.
The other significant electromagnetic-radiation source in a bike or car is the alternator, which is all made out of electromagnets (alternators are related to field-coil electric motors, which were the only game in town in the days before good permanent magnets). Half of the electromagnets in an alternator are whizzing round and round; the alternator therefore creates a complicated rapidly-changing high-frequency magnetic field which mu-metal is probably not very good at shielding at all.
Problem three: Mu-metal actually needs to be hydrogen-annealed when it's in its final form. This is part of the reason why mu-metal shielding is expensive; you can't just buy a flat sheet of it and wrap and hammer it around whatever you want to shield. But the Web site for the allegedly-mu-metal stick-on RiderSaver stuff says it "can be cut and is bendable and pliable to accommodate intricate motorcycle seat internal base pans". As soon as you cut or bend mu-metal, you'll work-harden it, and its magnetic permeability, from which comes its high shielding ability, will be decreased. If all you do is wrap mu-metal foil around a box then it'll still work pretty well, only failing on the bent edges, but if you change the shape of most of the surface so you can jam your seat back down on top of it, you may well end up with no better a result than you would have gotten from some cheap sheet steel.
(All modern hard drives have a couple of high-powered rare-earth permanent magnets inside them. There's close to zero field outside or even impinging on the platters right next to the magnets, though, because the magnets are on the inside of an iron pole-piece assembly. Mu-metal would work even better, but it's not needed.)
Problem four: There's not actually any good reason to suppose that any of the clearly-understood risks of sitting on a motorcycle seat, above a spark-ignition engine, have anything to do with magnetic fields or electromagnetic radiation.
Motorbikes are dangerous, but that danger comes from Newtonian, not electromagnetic, physics. (I like the observation that if motorcycles had only just been invented, there's no way they'd be legal.) Per distance travelled, motorcyclists are something in the order of 35 times as likely to die as car drivers. (These numbers are the aggregate for all motorcyclists, though; if you ride a sedate commuter or cruiser bike then you're actually pretty safe. Crotch-rocket sport-bike riders apparently have a death rate ten times that of other motorcyclists, and they affect the statistics accordingly.)
If I had a bike, I'd be focussing my attention more on heavily armoured clothing than on any theoretical danger to my precious bodily fluids from non-ionising radiation. A factory-fitted device that disabled a bike's ignition if it detected that the rider was only wearing jeans and a T-shirt would do quite a bit to reduce bike-related deaths and injuries.
There's no way to convince some people that non-ionising radiation from phones or powerlines or wireless networks or whatever does not seem to be a significant health risk. "It's still radiation, isn't it?", they say. "And I read that Wi-Fi causes autism, too!"
Similar reactions to "nuclear magnetic resonance imaging" are what caused the name to be shortened to just "magnetic resonance imaging", or MRI. MRI machines have nothing to do with nuclear weapons, of course, but "nuclear", just like "radiation", equals "bad" for most people. Explaining that visible light is also a form of radiation doesn't seem to help. It's all forms of non-visible radiation that're considered to be dangerous. (See also people who won't eat food that has "chemicals" in it.)
There's a whole family of bizarre products and books having to do with the terrible dangers allegedly posed by all kinds of invisible radiation, empirical evidence be damned. "Electrosensitivity" - the alleged deleterious effects of non-ionising radiation of one kind or another - is a big market at the moment. Look at those "radiation shield" stickers for cellphones, for instance, which work every bit as well as the "antenna stickers". There are also cellphone anti-radiation products that may actually work; there's just not much reason to suppose that they're necessary.
(L. Ron Hubbard was ahead of the radiation-scare trend, in his inimitable style.)
But there are also plenty of people who believe that static or pulsed magnetic fields are good for you. There's some actual very narrow scientific support for this - pulsed magnetic fields may have some effect on the healing of fractured bones, for instance - but it is largely a crock, about as believable as the old electric belts. (Though presumably less harmful than the old health devices that used ionising radiation.)
Over and over, alleged "electrosensitives" have failed to demonstrate that they can even perceive electromagnetic fields and radiation, much less that those phenomena cause any ill effects. But that doesn't stop them from buying products like the RiderSaver that claim to protect them.
I find the RiderSaver much more amusing than most bogus radiation-blocking doodads. Worrying about whether EMR is in some unknown-to-science way barbecuing your bottom while you ride your donorcycle strikes me as being like making sure you put on extra sunblock before you participate in the Running of the Bulls.