
Clue to earthquake lightning mystery - ColinWright
http://www.bbc.co.uk/news/science-environment-26462348
======
tehwalrus
preface: I'm doing a PhD in granular physics.

I was at a conference two years ago where this experiment (flash of light from
a tub of flour) was discussed. This is not new, or news.

It was also linked, by another speaker at the conference, to earthquake
lightning in the following discussions.

~~~
cperciva
It may not be news to experts in the field, but I think it's news to most of
us.

~~~
disputin
Unless I've missed something, it also seems to be news to Professor Troy
Shinbrot of Rutgers University.

~~~
Jach
No, Troy is the link. [http://phys.org/news/2012-06-rutgers-granular-slip-
documents...](http://phys.org/news/2012-06-rutgers-granular-slip-documents-
voltage-video.html) (So after 2 years he still has no idea on how it's
happening?)

~~~
tehwalrus
Ah, if they were writing about it 2 years ago already, then their result may
be the one that was repeated in front of me - curse the mainstream media's
"new! new!" language in their copy.

the abstract from that paper is very informative as to the context:

 _" It has been known for over a century that electrical signals are produced
by material failure, for example during crack formation of crystals and
glasses, or stick-slip motion of liquid mercury on glass. We describe here new
experiments revealing that slip events in cohesive powders also produce
electrical signals, and remarkably these signals can appear significantly in
advance of slip events. We have confirmed this effect in two different
experimental systems and using two common powdered materials, and in a third
experiment we have demonstrated that similar voltage signals are produced by
crack-like defects in several powdered materials."_

~~~
samstave
Interesting that this is likely also very related (or the exact same) as when
peeling scotch tape, that mechanical action produces x-rays.

What about the thought of Chi; could the electric impulses commonly thought of
for centuries by martial artists and meditators be an electrical output of
some mechanical function of the body?

~~~
tehwalrus
Chi - only of breaking your arm.

The energy being released is from fracture, i.e. bonds breaking, in all but
the granular case. Indeed, even granular pack breakup could well involve
sympathetic local charging, especially for packs gradually compressed and
stressed like soils.

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rikkipitt
Tupperware tends to be plastic, the BBC article doesn't really mention if they
tested different container materials with the same substrate. For example,
would a wooden container yield the same results with flour as the "soil"?

Their abstract mentions the use of 3 types of "soil" \- organic powders,
polymeric disks and glass particles. Does anyone have access to the full
article to see if they repeated the experiment with differing containers?

~~~
throwaway_yy2Di
I had the same thought. The box in the photograph looks like acrylic, which
has a strong triboelectric potential.

[https://en.wikipedia.org/wiki/Triboelectric_effect](https://en.wikipedia.org/wiki/Triboelectric_effect)

Here's a paper by the authors:

[http://arxiv.org/abs/1307.2489](http://arxiv.org/abs/1307.2489)

 _" The shear cell is nominally 125 cm × 26 cm in size, and the particles are
weakly confined by either a 0.5 mm clear flexible PVC or 1.4 mm thick acrylic
sheet in order to suppress out-of-plane buckling. The sheet is wiped with a
damp cloth before the experiment to minimize triboelectrification."_

~~~
rikkipitt
Exactly. Also, it's a bit hard to determine but the container looks closed. In
my mind that would provide another surface to enhance the triboelectric
potential you mentioned.

Edit: Thanks for that link. Why don't they remove the triboelectric
contribution altogether by using a more sensible container for obtaining
reliable results?

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dshankar
Interesting. I'd like to see further research done to test if large voltage
spikes like this could explain animal behavioral patterns before earthquakes
and tsunamis.

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asgard1024
What kind of equipment is required to detect those spikes? Can it be done at
home as an experiment?

~~~
jmpe
Check out "The Scientific American Book Of Projects For The Amateur Scientist"
\- C. L. Strong describes quite a bit of this in the section "The earth
sciences". The schematics date from 1960 (tubes, not transistors) but you'll
find updates around the web.

[http://www.sciencemadness.org/library/books/projects_for_the...](http://www.sciencemadness.org/library/books/projects_for_the_amateur_scientist.pdf)

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sudhirj
If this is a phenomenon, could it used to generate electricity? What the lower
layer of ships were filled with a flour like substance? Would that produce
anything useful as the ship rolled? Or what if we float tubs of this stuff on
waves?

~~~
Xylakant
> If this is a phenomenon, could it used to generate electricity?

In theory yes. You could gain electricity by rubbing millions of plastic rods
on cats. Whether that's an efficient way to produce electricity is a different
matter: Power plants that use the power of waves exist, at least in
experimental stages and they're probably much more efficient than a boat
filled with flour.

~~~
bagosm
Also, note that although producing Volts means electricity it doesn't mean
necessarily that you have any significant amount of energy.

You may have an incredibly large amount of volts from a source that's not even
capable to light a bulb for a few seconds.

~~~
Xylakant
see for example a zamboni pile:
[http://en.wikipedia.org/wiki/Zamboni_pile](http://en.wikipedia.org/wiki/Zamboni_pile)
potential is in the KV range while the current is in the nano ampere range.
That thing is weaker than most most modern batteries when it comes to powering
things.

