Unexplained Nature Phenomenon: Do You Know Some?

[zoobyshoe]

Also, and maybe SA or other can help here, I don't believe we can model a spark gap so as to predict when an "electric wind" becomes spark.

I have a little book called The Electric Arc which deals with this. If you know all the variables it can be predicted. The current actually goes through several phases before becoming an arc: 1.Townsend dark discharge, 2. transition, 3. Normal Glow Discharge, 4. Abnormal Glow, 5. Transition, 6 Arc

Some of the variables are obvious. This book does a lot of study of discharge through non-air gasses at non-atmospheric pressure. It is packed with tedious formulas. It's by J.M. Sommerville, Professor of Physics, University of New England, N.S.W. Australia (I guess they have a New England as well) Methuen & Co. LTD., London. 1959

 

[Ivan Seeking]

I have a little book called The Electric Arc which deals with this. If you know all the variables it can be predicted. The current actually goes through several phases before becoming an arc: 1.Townsend dark discharge, 2. transition, 3. Normal Glow Discharge, 4. Abnormal Glow, 5. Transition, 6 Arc

Some of the variables are obvious. This book does a lot of study of discharge through non-air gasses at non-atmospheric pressure. It is packed with tedious formulas. It's by J.M. Sommerville, Professor of Physics, University of New England, N.S.W. Australia (I guess they have a New England as well) Methuen & Co. LTD., London. 1959

Are you sure that these are predictive models and not curve fitting techniques? The date makes me really suspicious. Can you cite some of the formulas used?

I'm not really disagreeing with you since I'm not even sure where I read about this, but it is easy to mistake formulas based on emperical data with predictive, fundamental, purely theoretical models; models that are in principle void of emperical data in their derivations.

 

[Ivan Seeking]

What guns are you sticking to?

I read a book about flight a few years ago that went into a lot of detail about insects and birds. It didn't menion anything about insect flight being inexplicable, or that it ever had been. Insect wings are relatively flat when not in flight. When insects fly their wings take on a camber, just like the old, early aeroplanes. They are curved on top, and hollow beneath. The same thing happens to sails on a sailboat. Slow motion film of insects in flight shows this.

I think sometimes scientists research the answers to questions that have already been answered by other researchers they're unaware of.

I saw a one hour show about the first person to replicate insect flight. According to that and past discussions, no one could explain the lift or the power needed for some of the large insects. They key was found in I think some complex motion of the wing... The defense department wants robotic, spy insects so that you can be a fly on the wall!

I would say that several possibilities exist. First, as you suggested maybe some people had figured this out and others simply did not know, or perhaps the author had a theory that never passed the mustard of peer review, or it was never tested, or when tested it failed to produce the expected results. Also, your book may have been written after this was all figured out.

 

[zoobyshoe]

Are you sure that these are predictive models and not curve fitting techniques?

No, since I don't know what a "curve fitting technique" is.

The date makes me really suspicious.

I'm not sure why, but assuming you mean it is too old for them to have been able to study it accurately by todays standards, that may or may not be true. On the other hand, the newer a topic of study is in science, the more minds are on it, and all kinds of effects are found and data gathered, that eventually becomes obscure since no one has any particular use for it. Take conics. No one studies conics anymore in any detail.

Can you cite some of the formulas used?

Not unless I master the LaTeX. It is Greek to me. (See my recent thread "Weird Physics Symbols" in General Physics. The formulas in this book are pretty complex and full of all those symbols.

I'm not really disagreeing with you since I'm not even sure where I read about this, but it is easy to mistake formulas based on emperical data with predictive, fundamental, purely theoretical models; models that are in principle void of emperical data in their derivations.

From skimming through it, it is clear that everything is based on both experiment and theory. He cites a lot of studies done by others on specific gasses under specific conditions, the use of schlieren photography, and other experimental setups.

It is clear that the variables are manifold. If you're talking about a spark through air at atmospheric pressure in an uncontrolled environment, the variables will be changing moment by moment: air pressure, moisture content, particulate matter floating in the air, temperature, etc. If you had no way to monitor these, of course the result would be unpredictable. The statement may have been made concerning this type of uncontrolled condition.

I would suppose that if you googled you would find this has been studied in excruciating detail, and is as predictable as any electrical phenomenon. I don't think it is on a par with fluid turbulence, it seems to be much more predictable.

 

[zoobyshoe]

I saw a one hour show about the first person to replicate insect flight. According to that and past discussions, no one could explain the lift or the power needed for some of the large insects.

On the question of lift, the knowledge that their wings take on a camber when they are flapping isn't a theory, but an observation made from high speed photography and slow motion film. So the only lift problem I can imagine is that the wing area must appear to be too small for the weight of the bug.
The book I read didn't address this, or the problem of power. It simply stated that the wings, which are flat like boards at rest, take on a camber when in flight. The question being answered with this is how an insect can fly with what appear to be flat wings.

If, even with cambered wings, it is determined the insect shouldn't have the power or wing area to fly, that is a different problem. I'm glad they discovered how the dragonfly obviates these limits.

 

[Ivan Seeking]

No, since I don't know what a "curve fitting technique" is.

We can use some tricks in math - for one, the Fourier expansion - to reproduce nearly any empirically derived curve.

Fourier theorem: A mathematical theorem stating that any function may be resolved into sine and cosine terms with known amplitudes and phases - [provided function meets certain [the Dirichlet] conditions.

This typically produces an infinite series of sin and cos terms, each with less and less significance [decreasing amplitudes], that approximates the empirical curve as precisely as we like - depending on how many terms that we use. I for one use this common technique to produce useful approximations of empirically derived [data] curves, or to approximate other mathematical expressions that can't solved directly by the algorithms available [industrial computers].

I'm not sure why, but assuming you mean it is too old for them to have been able to study it accurately by todays standards,

I meant that this definitely predates any complete solutions...according to what I read.
In fact, the more I think about this the surer I am. I am going to check my bookshelves and see if I can find my source. I am thinking that this may have even been in Feynman's lectures.

 

[Ivan Seeking]

On the question of lift, the knowledge that their wings take on a camber when they are flapping isn't a theory, but an observation made from high speed photography and slow motion film.

The program that I saw discussed HS video or film as the key. My take is that in the past, assumptions were made about the characteristics of the wings that made the lift generated too small. Given the new information made possible by modern video [maybe high speed film], the lift needed could then be explained; so I think our stories may be running parallel to each other. I'm not sure about the year, but I think this has all been within the last ten years.

 

[zoobyshoe]

I meant that this definitely predates any complete solutions...according to what I read.
In fact, the more I think about this the surer I am. I am going to check my bookshelves and see if I can find my source. I am thinking that this may have even been in Feynman's lectures.

OK. I'm vaguely aware of Fourier analysis because it is mentioned so often when I read about sound. I'm slowly working toward the point where I will understand how it is used to represent sound as a sine curve (I think).

At any rate, I have no idea if that is what this book is about. I don't see any equations with sine and cosine in them, though.

I am sure that the book I read about flight was at least 15 years ago. I am remembering it was when I was very interested in helicopters, and I remember that was about '87 or '88. I got it out of the library. (There was, and maybe still is, a 30,000.00 dollar prize being offered for the first human powered helicopter. I was reading about them dreaming up plans for that.)

The heyday of high speed photography was the 50s and early 60s. They were snapping pictures of every fast thing you can think of, including bullets going through things. I'm sure someone shot bugs in flight at that point and someone noticed the wings were cambered. I suspect that to make a mechanical replica of an insect flying there are a lot more sophisticated problems to solve than cambered wings, though, such as how the front and rear wings work together.

 

[quddusaliquddus]

What about this? I read somewhere a long time ago that the birth of either girls or boys (one of them ...all the time) increases dramatically after wars - I never checked the statistics so I'm wondering if this is true or not...and then if any1 has solved it by now :D

 

[Ivan Seeking]

http://news.bbc.co.uk/2/hi/science/nature/2450407.stm





http://www.physicsweb.org/article/news/05/6/10

A related thought on freak waves:

Clathrates as a cause of tsunamis

During the formation of gas hydrates, methane and water become immobilized within the sediment pore spaces. Because of the presence of these solids (instead of pore waters and gas), the sediment can not become consolidated because the water can not be expulsed with increasing overburden as more sedimentation occurs. Cementation of the sediments does not occur when pore spaces are filled with hydrates (solid ice) rather than with water, from which minerals such as calcite can be precipitated. Gas hydrate rich sediments are thus cemented by the hydrates, which may occupy much of the sedimentary section, but which are not stable when the temperature rises or the pressure falls.

This may lead to problems during continued sedimentation and further burial of the gas hydrates: the hydrates will become buried so deeply that the temperature will increase according to the regional geothermal gradient. The hydrates will then no longer be stable, and will disintegrate into a liquid water and gas mixture. The basal zone of the gas hydrate becomes under-consolidated, possibly over-pressured because of the release of the methane, leading to the development of a zone with low shear strength where failure could be triggered and massive landslides could occur. With the landslides, more gas could escape.

Several examples of possibly gas-hydrate linked extremely large slumps have been described, e.g., on the Norwegian continental margin (Bugge et al., 1987), where debris from the giant, three-part Storegga slide, over 450 m thick, is spread over a distance of 800 km. One of the Storegga slides caused a tsunami to deposit sediment up to 4 m above the high water line in Scotland (Nisbet and Piper, 1998). There are more of these mega slides in the same region (Laberg et al., 2000).

http://ethomas.web.wesleyan.edu/ees123/clathrate.htm