3 ms·

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. Thi

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 13y ago
It may not be news to experts in the field, but I think it's news to most of us.
- disputin 13y ago
  Unless I've missed something, it also seems to be news to Professor Troy Shinbrot of Rutgers University.
  - Jach 13y ago
    No, Troy is the link. http://phys.org/news/2012-06-rutgers-granular-slip-documents-voltage-video.html http://phys.org/news/2012-06-rutgers-granular-slip-documents... (So after 2 years he still has no idea on how it's happening?)
    - tehwalrus 13y ago
      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 13y ago
        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 13y ago
        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.
- tehwalrus 13y ago
  I was referring to the Scientists describing their findings. They are clearly not already members of the granular community as I know it.
fractallyte 13y ago
I remember reading (a long time ago) that occasionally static electricity in deserts caused headaches, which could be dispelled by earthing oneself. I found this on Wikipedia just now (http://en.wikipedia.org/wiki/Desert#Dust_storms_and_sandstorms http://en.wikipedia.org/wiki/Desert#Dust_storms_and_sandstor...): "During a sandstorm, the wind-blown sand particles become electrically charged. Such electric fields, which range in size up to 80 kV/m, can produce sparks and cause interference with telecommunications equipment. They are also unpleasant for humans and can cause headaches and nausea. The electric fields are caused by collision between airborne particles and by the impacts of saltating sand grains landing on the ground. The mechanism is little understood but the particles usually have a negative charge when their diameter is under 250 μm and a positive one when they are over 500 μm." Do you know if these phenomena are connected?
- tehwalrus 13y ago
  Same origin: friction (just like the balloon and your hair) causes the particles to charge up. Where it earths itself is the only difference.
tehwalrus 13y ago
Update: OK, perhaps I should have googled Troy Shinbrot, as he was the guy who presented the work I saw. Apologies! I worked this out after a simple google image search for his name. The image from this article (sorry, it's more of an advert in fact) is the one that sparked my memory, you'll see why: http://www.nj.com/entertainment/index.ssf/2012/04/rutgers_day_2012.html http://www.nj.com/entertainment/index.ssf/2012/04/rutgers_da...

cperciva 13y ago

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

disputin 13y ago
Unless I've missed something, it also seems to be news to Professor Troy Shinbrot of Rutgers University.
- Jach 13y ago
  No, Troy is the link. http://phys.org/news/2012-06-rutgers-granular-slip-documents-voltage-video.html http://phys.org/news/2012-06-rutgers-granular-slip-documents... (So after 2 years he still has no idea on how it's happening?)
  - tehwalrus 13y ago
    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 13y ago
      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 13y ago
        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.
tehwalrus 13y ago
I was referring to the Scientists describing their findings. They are clearly not already members of the granular community as I know it.

fractallyte 13y ago

I remember reading (a long time ago) that occasionally static electricity in deserts caused headaches, which could be dispelled by earthing oneself. I found this on Wikipedia just now (http://en.wikipedia.org/wiki/Desert#Dust_storms_and_sandstorms http://en.wikipedia.org/wiki/Desert#Dust_storms_and_sandstor...): "During a sandstorm, the wind-blown sand particles become electrically charged. Such electric fields, which range in size up to 80 kV/m, can produce sparks and cause interference with telecommunications equipment. They are also unpleasant for humans and can cause headaches and nausea. The electric fields are caused by collision between airborne particles and by the impacts of saltating sand grains landing on the ground. The mechanism is little understood but the particles usually have a negative charge when their diameter is under 250 μm and a positive one when they are over 500 μm." Do you know if these phenomena are connected?

tehwalrus 13y ago
Same origin: friction (just like the balloon and your hair) causes the particles to charge up. Where it earths itself is the only difference.

tehwalrus 13y ago

Update: OK, perhaps I should have googled Troy Shinbrot, as he was the guy who presented the work I saw. Apologies! I worked this out after a simple google image search for his name. The image from this article (sorry, it's more of an advert in fact) is the one that sparked my memory, you'll see why: http://www.nj.com/entertainment/index.ssf/2012/04/rutgers_day_2012.html http://www.nj.com/entertainment/index.ssf/2012/04/rutgers_da...