
"Invisible Electrostatic Wall" at 3M adhesive tape plant (1996) - alvivar
http://amasci.com/weird/unusual/e-wall.html
======
ChuckMcM
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.

~~~
CamperBob
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.

~~~
electromagnetic
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.

~~~
wbeaty
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

------
yread
There is some more info from David Swenson:

[http://boards.straightdope.com/sdmb/showpost.php?s=b06561cd9...](http://boards.straightdope.com/sdmb/showpost.php?s=b06561cd9b21d94322e22d4b0705566f&p=4212704&postcount=22)

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.

~~~
viraptor
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.

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

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

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viraptor
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 ;)

~~~
viraptor
And I was too late, already submitted:
[http://community.discovery.com/eve/forums/a/tpc/f/9701967776...](http://community.discovery.com/eve/forums/a/tpc/f/9701967776/m/20419888901)

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jakeonthemove
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...

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

~~~
jackgavigan
_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. ;-)

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cfontes
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...

~~~
forgottenpaswrd
"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.

~~~
einhverfr
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?

~~~
wbeaty
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.

------
Hacktivist
Here is some more information on the phenomenon that causes this

<http://en.wikipedia.org/wiki/Triboluminescence>

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

[http://www.npr.org/templates/story/story.php?storyId=9613962...](http://www.npr.org/templates/story/story.php?storyId=96139621)

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

~~~
yread
Are you sure? There is no light involved

~~~
ars
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>

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jeggers5
This happens because of this: <http://en.wikipedia.org/wiki/Coulomb%27s_law>.

Mythbusters should definitely try this!

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

------
unabridged
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?

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astangl
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.

~~~
jff
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!

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

~~~
aperiodic
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.

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

~~~
ars
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.

~~~
CamperBob
_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.

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

~~~
CamperBob
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.

~~~
ars
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.

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cantbecool
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.

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

~~~
joezydeco
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.

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

