Unexplained Nature Phenomenon: Do You Know Some?

[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