A little while back, I was put in touch with a Wall Street Journal writer who was looking into a new-ish health fad called "earthing," which involves people sleeping on special grounded mats and that sort of thing. The basis of this particular bit of quackery is the notion that spending time indoors, out of contact with the ground, allows us to pick up a net positive charge relative to the Earth, and this has negative health consequences. Walking barefoot on the ground, or sleeping on a pad that is electrically connected to ground via your house's wiring, allows you to replace your lost electrons with electrons from the Earth, curing all manner of ills.
I'm quoted briefly in a column about this, but in preparing to talk about the physics, I drew up a more extensive list of reasons why this "earthing" business is a bunch of crap than could really fit in a single column. Luckily, I have this blog where I can post this sort of thing; thus, a collection of physics reasons why this fad is nonsense.
Of course, like most health fads, there's a tiny grain of truth at the center of a giant ball of crap. It is, in fact, perfectly true that we can build up a potential difference between our bodies and the Earth, due to brushing against materials that tend to grab electrons. It's also true that contact with the Earth, or with grounded conductors, will equalize the potential by allowing electrons to flow between your body and the Earth. There's nothing particularly wrong about those two statements; it's just, you know, everything else that follows after them. They're true, but basically meaningless, for the following reasons, among others:
1) Electrons are electrons. The sites I looked at are full of talk about "beneficial electrons from the Earth" and that sort of thing, which is garbled nonsense. Electrons are electrons are electrons-- there's nothing that singles out or sets apart an electron from the Earth as opposed to from some synthetic material, or, for that matter, an electron that came blasting in from outer space.
How do we know this? Basically because chemistry works. The Periodic Table of the elements is set up the way it is because of the arrangement of electrons within atoms-- as you increase the number of electrons in a given atom, you "fill up" energy states, with the last electron added going into a particular state that determines the binding properties of the atom in question. That "filling up" is a consequence of the Pauli Exclusion Principle, which says that no two electrons can be found in exactly the same state. The Exclusion Principle, in turn, is a consequence of the indistinguishability of electrons-- two electrons aren't allowed to occupy the same state because electrons are perfectly indistinguishable, and that puts some constraints on their properties.
If there were a difference between electrons from the Earth and from other sources, then chemistry would be a mess. Electrons that originated in the ground would "fill up" one set of states, while electrons that originated somewhere else would "fill up" a different set of states. You'd end up with carbon atoms that could only form two chemical bonds, instead of the usual four, or solids that ought to be conductors but act as insulators, and all sorts of other screwy results. We don't see those things, which means that all electrons are truly identical to a very high degree.
2) Potential Differences Are Transient and Meaningless. Shuffle your feet across a carpet, and then touch a doorknob. Feel a spark? Congratulations, you've established a significant potential difference between yourself and the Earth, and then eliminated it.
It's perfectly true that ordinary interactions with many materials will strip electrons off your body. But that never lasts all that long, as the doorknob-spark illustrates. In the process of shuffling across a carpeted floor, you lose (or gain, depending on the materials involved) several billion electrons, but as soon as you touch a metal object, you get them all back (or give them all up).
It's simply not possible to build up and maintain a significant charge imbalance between your body and the rest of the world, because everything we interact with contains electrons, and they move back and forth between objects all the time. If nothing else, the charge on an object will eventually dissipate into the air-- back when I was doing sticky tape experiments, I had to periodically recharge the tapes, because the charge goes away over time. A net positive charge will attract negative ions from the air, and eventually neutralize, and the same thing happens to your body.
3) The Potential Measurements Made by "Earthing" Advocates Are Worthless. One of the many sites out there promoting this stuff (I'm not going to dignify them with a link) suggests that you can demonstrate the severity of the problem by getting a voltmeter from Radio Shack and putting one of the leads into the ground socket of an electrical outlet in your house. Then touch the other to your body, and you'll see a voltage reading that's a measure of how much your potential differs from that of the Earth.
That seems very convincing, as long as you've never been an easily bored physics major (as if there's any other kind). I was an easily bored physics major, though, so I've played with voltmeters lots of times in the past, and tried measuring the potential difference between myself and lots of things. As a result, I know that these results are gibberish.
But, just to be fair, I did what they suggested, and plugged the meter into the ground socket, then touched my thumb with the other lead. I measured a potential difference that fluctuated a bit, between about 0.03V and 0.15V. I then took the lead out of the electrical socket, and touched both leads to my left thumb, about an inch apart. Where I measured a potential difference that fluctuated between 0.03V and 0.15V. Those measurements are basically meaningless-- it's noise in the meter, fluctuating local fields, and other garbage effects.
Their literature talked about potential differences of multiple volts, which I didn't see, but have occasionally managed in past screwing around with voltmeters. But even that is completely insignificant-- if you shuffle your feet across the rug and then throw a spark touching a metal object, the potential difference between you and the metal thing was probably around 1,000V. It takes an electric field around 1,000,000 V/m to make a spark in air (give or take a factor of ten or so; the textbook we used to use had a long discussion of sparks), and a typical spark from everyday static electricity will jump around a millimeter. So, a potential difference across that gap of 1,000V will get the job done.
You build up and discharge potential differences of hundreds of volts all the time, without particularly noticing.
4) Their Own Safety Devices Undermine Their Claims. The literature I looked at reassured potential customers that there was no danger of electric shock from using their products, because the cord used to connect the "Earthing" mats to the ground of your house's electrical system contains a 100,000 Ω resistor as a precaution. That made me bust up laughing.
Why? Because the definition of a resistor is that it resists the flow of current. Which means it will impede the flow of harmful current from a faulty appliance of some sort, true, but it will also act to impede the flow of beneficial electrons from the Earth by exactly the same amount.
How big a difference are we talking? Well, the connection between the ground plug of your electrical system and actual ground (generally either a metal spike driven into the ground, or something like a metal water pipe coming into the house) should have a resistance of a few ohms (see, for example, this discussion). So if you drop a 100,000 Ω resistor in there, you're increasing the resistance by nearly a factor of 100,000, which reduces the rate at which electrons flow in from the Earth by the same factor.
What's that mean? Well, in order to get the same health benefit of one second of electron flow between you and the Earth due to direct contact-- standing barefoot on the ground, for example-- you would need to spend 100,000 seconds in contact with their mat. 100,000 seconds is about 27 hours, a bit more than a day. Their literature talks about the health benefits of multiple hours spent "Earthing" yourself, which would require hundreds of thousands of hours on the protected mat, and 100,000 hours is over 11 years.
And that, right there, ought to be enough to, well, bury this whole silly idea. Their "safety" precaution should obliterate the effectiveness of their devices. The fact that they advertise this as a positive feature indicates just how little real physics there is at work here.
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This isn't the silliest bit of medical nonsense I have encountered (if you have read Orac's blog regularly, as I do, you will know what I mean), but it's up there.
There are people who believe that you can take a substance, dilute it by anywhere from one part in 10^60 to one part in 10^200, and obtain something that can treat a particular medical condition. Avogadro's number is just a trivial detail to people who are into homeopathy.
At least earthing and homeopathy are merely silly. There is other quackery out there which is actually harmful.
Chad, perhaps you don't understand the physics of the remarkable earthing mat. as Eric pointed out above, homeopathy is involved. the 100KΩ resistor has a homeopathic effect, lowering the current by 10^5 actually INCREASES the effectiveness! if you lined the matt with 80% Ni-Fe-Mo alloy, you could shield the user from magnetic fields too!11!! it would be a Quantum Earthing Matt!!!11!!
p.s. if anyone actually makes money using my Quantum Earthing Matt idea, I expect to receive royalties which I will use to set up scholarships for science education.
"The literature I looked at reassured potential customers..." Exquisite wording, Chad :-)
You inspired me to use my multimeter to measure the level of AC on my body: circa 3 volts at 50 Hz. So, why aren't the promoters of grounding mats raising deep concerns about the "awful deleterious effects" of having huge numbers of electrons pumped backwards and forwards through one's body 50 or 60 times per second when using an Earthing mat.
Being serious for a moment: I thoroughly enjoy my anti-static carpets because I'm old enough to have become totally fed up with being zapped by doorknobs and taps (faucets). The years of zapping was a constant reminder of Pavlov's dogs and it very nearly led me to developing a serious obsessive-compulsive disorder (OCD).
Very sadly, I have to conclude that vendors (and promoters) of Earthing products are fear-mongering for the sole purpose of inducing OCD into those who are susceptible to it, then selling "The only known cure". This is still one of the most commonly used methods used in advertising (because it has solid evidence efficacy).
You have missed the obvious point that living, and especially sleeping, without connection to the earth is well known to cause severe health problems in vampires. Does everything have to be demonstrated in randomized trials before the evidence of our senses can be accepted? How many vampires would have to be randomized to suffering and death before the essential health value of connection to their native earth was acknowledged?
There used to be a fashion a few years back for earth strips on cars. These were basically just a conducting strip connected to the car's bodywork that dangled onto the road surface. They were supposed to prevent the build-up of static electricity on a moving car, and many people swore that fitting one completely cured their travel sickness. Haven't seen one recently though.
@Rachel: Most modern vehicle tyres are now designed to be electrically conductive enough to render the strips redundant. Nothing to do with the travel sickness myth: it is to eliminate the very unpleasant electric shock received when one touches the vehicle after getting out of it without maintaining electrical contact with the bodywork during the process. Ouch!
Most modern vehicles also have their carpets and seats treated with an anti-static agent to reduce the chance of occupants receiving a noticeable electric shock when touching the bodywork. I would guess that it is also used to help prevent the static build up from zapping the electronics used in steering wheel buttons, steering column stalks, and in-car entertainment systems.
I sincerely hope that you enjoy this:
http://www.core77.com/blog/photography/helicopter_rotor_galaxy-like_vis…
The driver that delivered gas to our farm when I was a kid - early to mid 60s - had a couple small chains dangling from the rear of his truck, dragging on the road, and said they were to get rid of the static electricity. Same idea, earlier implementation.
Million dollar idea. Market slippers that make you positive. You should feel great! (And the marketers could pun on "positive" all the way to the bank.)
I am always entertained the first time students use an AC voltmeter. When they ask "why isn't it reading zero", I tell them to touch ONE lead and see what happens!
So the question is, what would you read if you touched one lead to that mat, isolated as it is by 100 kOhm from the earth. Is it an even better antenna for 60 Hz, WiFi, and everything else than we are by ourselves?
Strangely, I had never heard of this until some days ago when I accidentally stumbled over a whole bunch of related websites, trying to figure out how to get the static noise off my microphone. I have an external microphone hooked up to the USB port, awesome microphone, but after 30 seconds or so, it starts building up static which drives you nuts if you get it on the headphones. In any case, as I was trying to figure out if there is a way to put a ground line between the USB port and the external hardware, I came across all kind of instruction information for 'earthing' your computer and screen and dog and yourself. (None of which looked very useful to my end.) It seems to be mostly a US phenomenon though?
The driver that delivered gas to our farm when I was a kid – early to mid 60s – had a couple small chains dangling from the rear of his truck, dragging on the road, and said they were to get rid of the static electricity.
The "delivering gas" bit is key here. I have obviously not done the experiment myself, but ISTM that one might reasonably fear that such a spark in the presence of gasoline could cause a fire, particularly if the shutoff valve weren't working properly, or if you were carrying large amounts of gasoline as cargo.
For similar reasons you are not supposed to use your cell phone while pumping gas, although in this case I'm not so sure the fear is reasonable. It has long been a safety precaution in the rocketry business that you are supposed to avoid RF when people are working on the launch pad, and when you pass through a construction zone where blasting work is involved, you are supposed to turn off your two-way radio. At one time it was reasonable to fear that RF could accidentally set something off. I don't know if that is still true, but the tradition persists.
Eric Lund;
I could see that, but I also wondered whether the possibility of sparking caused by the chain dragging on the road wouldn't be more of a danger than having no chain at all.
Re chains dangling from a gasoline tanker truck (petrol bowser):
This is 100% mainstream stuff here, not woo-woo crap. It was standard practice at least through the 1960s, I haven't noticed if it's still done but I'm curious enough to ask the next time I fill up.
The risk is that the truck picks up a static charge, and if there are gasoline _fumes_ present, a spark could set off an explosion. This could happen a) when the tanker is being filled at the refinery, b) when it's on the highway if its tank is mostly empty but fumes are still present, c) when the tanker is filling the underground tank at the gas station.
The dangers involved also occur when someone handles a gasoline pump without first touching a metallic ground. The typical instance is a person who puts the nozzle in their tank and lets it fill while they climb back into their seat in the car. Then they get out of their seat, picking up static electricity via friction between their clothing and the seat, and they go back to remove the nozzle from the tank. But a small amount of gasoline vapor is present around the opening, and when they touch the gasoline pump nozzle, they produce a spark, that ignites the vapor and causes a fire or explosion.
I've verified this for myself, as I always touch a metallic part of the gasoline pump (away from the nozzle) before handling the nozzle: more than once I've felt the unmistakable little "zap" of static electricity.
Re. radios and blasting:
Blasting for civil engineering operations such as highway construction, used to (and may still) involve long wires connected between the blasting engineer's control box and the detonator caps that in turn set off dynamite in drill holes in the rock. Under certain conditions that are not easy to predict on a construction site, those wires can act as antennae to pick up radio signals and convert them to current at the point of contact with the ground (in other words, the detonator cap atop the dynamite stick in the drill hole). That can set off a detonator, thereby setting off the dynamite.
The types of two-way radios those signs are warning about are the commercial types that are used in construction vehicles such as concrete trucks, construction foremen's pickup trucks, and the like. Those radios require FCC licenses and are substantially more powerful than hand-held walkie talkies. They are designed to cover the large distances between e.g. a concrete batch plant and a highway construction site. The signage is a warning to the drivers of those trucks to not use the radios during blasting operations.
The transmitted power of those radios can be picked up by the long wires at the blasting site, and set off the detonators, thereby setting off the dynamite. If workers are not cleared to a safe distance when the dynamite is set off, they can die or be seriously injured directly from the explosions or indirectly from shrapnel.
(Nowadays, for routine blasting on small projects, there is a much nicer & safer alternative to dynamite: keyword search "expanding mortar," and look for videos. It's basically a powder you mix with water, and then pour into a drill hole in a boulder. Over the course of about a day, it expands as it hardens, and in a manner analogous to ice, the pressure of its expansion fractures the rock in place. It also goes by the nickname "Chinese dynamite", possibly because it was first widely used in China or was invented there.)
Re. "Earthing":
Ha ha ha haaaa, good grief what silly horse-stuff. They had to use the British term "earthing" instead of the US term "grounding," because it sounds so much more, well you know, Earthy! That and because nowadays when someone says "I need to get grounded," they either mean connect themselves to a frame ground when working on sensitive electronic equipment, or they mean have a beer or a few puffs of pot to de-stress after work.
To ignite gasoline (and many other fuels), the vapour in the spark region must be somewhere near the stoichiometric ratio and the spark must have sufficient impact to start ignition at that air-fuel ratio. E.g. gas cookers and central heating boilers require multi-strike electric discharge ignition systems in order to reasonably guarantee ignition of the gas within around 10 seconds.
Conversely, to guarantee an absence of unwanted ignition the sparks must be very much smaller. E.g. It would be extremely foolish to start pumping gas into one's vehicle before the metal pump nozzle was in electrical contact with the metal receptacle of the vehicle.
The main reason why it is extremely unwise to use a cellphone while pumping gas is not due to the risk of the RF inducing ignition, it is because pumping gas and driving the vehicle are both highly responsible tasks that require one's full concentration and attention to small, but literally vital, details.
The delivery procedures used in larger scale fuel delivery incorporate mechanisms to eliminate the risk of ignition via electrostatic discharge. It's totally obvious that dragging metal chains behind a fuel delivery vehicle would likely ignite the fuel in the event of a leak.
Best practice documents and legislation will never be enough to fully protect us from the hopelessly stupid members of society.
As part of the Earthing product line, they also have a car seat cushion that will "ground" you to your car, which of course is not a real ground at all (at least without the chains/strips mentioned above).
Oh, and on April 1 (note the date), I blogged about an even more important "scientific" discovery: Neutrining: The Most Important Health Discovery Ever.
Re. Ahcuah @ 14: Does the car seat also come with a built-in "whoopie cushion" device, to make an appropriately obnoxious noise when someone sits on it? Now _that_ would be an improvement.
Re. Pete A. @ 13: I've seen pics of gasoline tankers trailing chains, with the explanation that it's to conduct static charge away from the vehicle. Clearly a leaking tank would be a hazard, but the chain ground is intended to deal with the far more probable hazards of ignition during normal operation.
The risk of a leak in the tank itself, is negligible. Also it would not surprise me if the petroleum companies had internal regulations requiring drivers to do a walk-around of their truck before and after loading up with gasoline at a refinery, and to report any signs of a leak in the tank.
Clearly the air/fuel mix has to be right for ignition to occur, and of course the vast majority of times it does not occur, for example people touching gas nozzles after fueling their cars. But as with wearing seatbelts, the goal is to minimize risk by using a simple procedure.
BTW, I do not have distractions in my vehicle, and I do not have a mobile phone. They are personal surveillance devices wrapped up in shiny consumer packaging, and some of my clients prohibit them in certain areas of their buildings for security reasons. I use an old-fashioned beeper, which works everywhere, never runs out of battery, has no distracting consumer baubles in it, doesn't spy on me, and can't compromise sensitive client information.
General rule for driving, and for walking around in the city:
"Eyes on the scene, not on the screen."
I may be confused by the terminology, but if by ground plug you mean the 3 prong outlet then in my last residence some of the 2 prong outlets were replaced with 3 prong outlets but the ground was not connected to anything. So I guess in my last house if I plugged the earther in it wouldn't even not work?
Bob @ 16:
If the ground pin on an AC mains outlet is not connected to anything, what you have is a building code & fire code violation that will need to be remedied by a licensed electrician, otherwise there is a risk that a faulty appliance or tool could electrocute someone or start a fire.
G @ 15: Thanks for your interesting reply. I've seen many fuel tankers while I've been driving, but none having chains or any other easily visible grounding straps. Next time I see a tanker at my gas station I'll ask the driver about it. Most of our truck drivers enjoy having a short conversation with anyone who shows keen interest in their work.
While I'm in a vehicle (as a driver or passenger) my phone is either switched off or left at home. When I'm driving in congested traffic, and when parking, I find the task much easier when there is nobody talking in the car and the audio system is off. Perhaps this is just a rare quirk, but at least I'm aware of it and act accordingly.
While driving, I make the assumption that I'm probably a worse driver than everyone else on the road around me.
I think your "Eyes on the scene, not on the screen." could be turned into a very effective road safety advertising campaign.
My hubby's seen a couple of people lately huffing on e-cigarettes while pumping gas. I would think that if cell phones are a potential hazard, those things are just a fireball waiting to happen.