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"Invisible Electrostatic Wall" at 3M adhesive tape plant (1996) (amasci.com)
271 points by alvivar on Nov 24, 2011 | hide | past | web | favorite | 46 comments

We did this experiment in physics back in college. If you get sufficient charge you repelled by charge of the same polarity. I would speculate that the charge on people was the same as the charge being created in the spooling area (it is a giant Van DeGraff generator type apparatus after all). That would also correlate with the humidity component as the humid air would have a lower dielectric effect and you would get a lower max charge due to leakage into the surrounding environment.

The edge of that electric field would feel to you exactly like you were a magnet of the same pole trying to move into it.

Per some other comments here the biggest risk would no doubt be creating a conductive path for the charge to dissipate. At those levels it can and does ionize air and create lightning.

Would be great to get a picture of the factory setup. I bet you could trace the charge sources. In physics 101 we had to compute how much charge you would have to have on your body to levitate off the ground. It was a lot less then you might imagine, the challenge of course was keeping it on your body and not zapping things nearby in the occasional ionizing discharge. I was busily thinking up high K clothing concepts for a while to try to solve that issue but alas, nothing came of it.

I bought a fairly large (750 KV) VDG kit on eBay a couple of years ago just for the lulz, and I soon came to appreciate how unpredictable and unintuitive electrostatic phenomena can really be. Not only was the charge-transfer mechanism between the belt, rollers, and brushes completely different from what I'd always assumed, but the macro-level effects were sometimes downright confusing. In some ways, the operation of a Van de Graaff generator is even harder to internalize than that of a Tesla coil.

I expected longer discharges in dry weather -- nope, it does better in moderate humidity. I expected styrofoam peanuts to be consistently attracted (or maybe repelled) when thrown at the sphere, not to be attracted at first and then rapidly repelled at some small distance from the sphere. I expected the strongest discharges to occur when the generator was operated with no large objects nearby; instead, positioning it within a few feet of a tall wooden bookcase results in sparks (in any direction) at least 25% longer.

So I'm not too surprised at tales of strange force fields in a cellophane-tape factory. I am surprised that the rollers didn't have grounding brushes all over the place... but given my experiences with the VDG, for all I know that would have made things worse.

From what I was told in high school when they used to bring out the VDG's was that it would take a voltage potential in the millions to be harmful.

What my guess would be is that the mechanical energy from forcing the charged cellophane into compact rolls was forcing the free-electrons off of the cellophane belt and they were simply carrying on travelling. By the description it sounds like the rolling phase was giving the electrons a downward motion if it was a "tent" shape operation.

My guess it that it was simply a voltage-potential field. If the energy had found a way to ground itself it would have, and anyone walking around on a concrete floor wasn't going to provide a quicker route to ground. Probably similar to how a pigeon doesn't explode sitting on a power line, because despite sitting on a line with millions of watts of potential energy, until it comes actual energy (like when a tree branch hits across the lines) it's not dangerous.

Rather than a "force field," another possibility was Taser effect, where numerous tiny sparks to the skin will cause muscles to clench, making it impossible to walk. Search keywords: tetanizing beam

There is some more info from David Swenson:


key quote:

> I think the best explanation has to do with the film being at or vaery near the theoretical charge density limit and just the right combination of resistance between the person and floor. With the electric field at its maximum at the center of the tent formed by the film, the conductive body (person) approaching the center was actually pinned to the floor. Had the floor been more conductive, the person would have been closer to ground and probably would have received a massive shock from a propagating brush discharge. But being isolated from ground, no charge separation occured resulting in the electrostatic "pinning" effect.

From the article: "He could lean all his weight forward but was unable to pass." With that one, I imagine if his shoes were stuck to the ground, he'd just fall down, or at least noticed the resistance came from the shoes rather than body.

15 year old discussion, unfortunately. Makes it pretty likely this didn't stand up to scrutiny.

Could the OP please add [1996] to the title?

Reasoning based on zero information? Heh. We could say "Pretty likely it was declared National Security and hushed up."

Or we could say "Pretty likely that D. Swenson installed electrodes to quench the effect ...which task he was called in to perform." And Murphy's Law for experimental replication is that the desired phenomenon refuses to emerge except under identical conditions using only the original equipment.

It's time to look for MythBusters suggestions email, I guess... If anyone has a budget to replicate that setup as a one-time funny activity, it's going to be them ;)

Isn't this "invisible wall" basically a force field like they show on various Sci-Fi shows? Can it be replicated and used on a spacecraft to protect it from radiation and more importantly, small meteorites? That would be really cool...

did you see the speculation about recreating the effect but horizontally instead of vertically? you could effectively have an invisible platform!

did you see the speculation about recreating the effect but horizontally instead of vertically? you could effectively have an invisible trampoline!

Corrected that for you. ;-)

future tech of awesomeness. loving it!

Ah Ok, why isn't anybody trying to replicate and sell this ? it would be worth more than gold, and it's sitting there in an old maillist ? come on...

"why isn't anybody trying to replicate and sell this ?"

Because it can kill you, that's it.

Electrostatic motors(capacitive) are older than electromagnetic(inductive), but using way more voltage than current means touching it will kill you.

A lot of people have died from industrial plastic bags electrostatic charge with friction, so it now uses wire to ground it.

My understanding, albeit somewhat limited, is that generally amperes are a larger issue than volts in determining what sorts of electricity is dangerous. (Low voltage high amp circuits can't initiate sufficient amperage through the body to be dangerous in this way due to ohm's law but could still kill you through other means, such as burning you, but high voltage, low amp circuits are far less dangerous.)

What am I missing?

Cap discharge? One story was the Robert VandeGraaff got the idea for his generator from a Boston printing plant, where the metal body of an ungrounded newspaper press on a wooden floor would give dangerous shocks to anyone approaching closely. If a machine is many meters across, and charges itself up to many tens of KV, the body capacitance may store lethal (joules) level of energy, e.g. 50KV at 1000pF.

We don't know that nobody is trying to replicate it. We can only be sure nobody found a commercial application for it.

Here is some more information on the phenomenon that causes this


The most interesting section is how UCLA researchers created such powerful results that they were able to x-ray fingers.


There are also a couple of videos on Youtube that show the effect in action.

Is this the same kind of light you can make from the static electricity in say a polyester blanket on the couch?

Are you sure? There is no light involved

If there are sparks there is light. A spark is a very wide band transmitter - it creates just about every single frequency of light possible.

See http://en.wikipedia.org/wiki/Spark_gap_transmitter

I guess I shouldn't have used such a strong word like "causes this" since the article was more about the force field and not the source of the ionized air.

The point is that if the tape spool can create such a strong field then there is more than likely a visible light being created at the interface of the spool and tape caused by the charged atmospheric nitrogen which releases a photon when leaving the excited state.

Photons mediate the electromagnetic force it's very likely there was light involved.

This happens because of this: http://en.wikipedia.org/wiki/Coulomb%27s_law.

Mythbusters should definitely try this!

I remember http://amasci.com/ from over 10 years ago. A fun website. The hand-drawn holograms, for example, are great.

If this actually happened, don't you think 3M engineers would be aware of the effect before it was making a wall the size of a room that could stop a human? They didn't notice small parts and dust being repelled? And they couldn't capitalize on it even just by making a small public display of hovering objects?

This is one of a couple tantalizing stories I've seen on that site over the years, something that sounds really promising but then leads nowhere, calling the whole story into question. The other one is the lawnmower engine retrofitted with a magnetron in place of the spark plug, turning the engine into a type of steam engine running on water. Poster acted like it was no big deal, and apparently moved on to more interesting things.

Ok, this magnetron-on-lawnmower thing is interesting me. The problem I'm seeing is that unless you run an extension cord to the mower, it's not actually going to do anything. Steam is a useful way to turn pure heat into something that can push a piston, but turning water into steam doesn't actually generate any new power. I think it would be really cool to do... but the end result would surely be no better than simply putting an electric motor into your lawnmower.

Also, this definitely reminds me of all those "free energy/orgone/powah of da pyramids" kind of things that people without a decent physics education get suckered into. Run your car on water!

If this effect were real, this would be ideal for scramjets and re-entry vehicles to reduce friction related heat.

Contrary to popular belief, the reason that spacecraft heat up upon re-entry is gas compression, not friction (remember the ideal gas law, PV = nRT). The gas would still be compressed by the electrostatic barrier, so the heating would still occur.

Is there really a difference between heat generated by friction and heat generated by gas compression, at the end of the day?

Of course. They work very differently.

If you have heat from friction you expect the heat along the length of the ship.

If you have heat from compression you expect it at any point where the ship is not parallel to the air - but not along the length of it.

Heat from friction can be aided by a low friction surface material.

Heat from compression can be aided by not having any surface very perpendicular to the air (spread out the change in angle over a distance).

With heat from friction you want a short ship - so just have the angled surface and be done with it.

Heat from compression would benefit from a longer ship so you have space to gradually change the angle of a surface.

If you have heat from friction you expect the heat along the length of the ship.

How in the world does that follow? Heat from friction will be generated in proportion to cos(angle) between the airflow and the surface at any given point, just like heat from compression would. It will flow along the ship's surface and soak into its interior volume just as if it were generated by compression.

Um, air can't flow at an angle to a surface. It can only flow parallel to it.

But what's important is the behavior of the airflow at the point where it hits the surface and is forced to both compress and diverge. That's where the majority of the heat is presumably generated, right? Maybe that's where I'm misunderstanding the issue.

That heat is created by compression, not by friction.

And I would not automatically say that's where the majority is. Some is created there from compression, some from friction by flowing along the length of the ship.

Wouldn't reducing friction also reduce the braking effect and make the spacecraft hit the ground at high speeds?

I wish smart phones were prevalent back in 96'. It would have been fascinating to view a video of the phenomenon described in this story, but I probably would have been skeptical thinking it was simply special effects.

So this is the kind of thing that's going to make our hovercars hover?

Sure. All you need is a 20-foot wide sheet of poly film moving 20 feet up,over,and down at 1000 feet per second.

No, this is how the Combine built those force fields that Gordon Freeman can't get through.

Probably would have better luck with super conductors

selling tickets might be nice....how i love product managers (even better sales managers) :)

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