Tables of Contents

for the green-flash, mirage, and refraction pages

 

Introduction

These hundred-odd Web pages have accumulated over several years, without any overall organization. I had no particular scheme in mind as I wrote them; when a topic seemed both mature enough and small enough to be covered in a page, I just wrote it up. When topics were related, I added links.

This, in a way, is the way the Web was designed: you can cross-reference anything from anywhere. The links show how seemingly disparate topics are actually related. The ability to make this non-sequential structure of the real world visible in written material gives the writer a degree of freedom that's denied in journal publications, where items necessarily follow one another in some one-dimensional ordering. I enjoyed the possibility of making my writing show the inter-related nature of physical science, where everything is somehow connected to everything else.

I've complained elsewhere about the limitations of my paper filing system, where a photocopy of some article has to be put into a particular file folder, even though it's related to several other topics. For a while, I tried making multiple copies and filing them in the various appropriate places; but the files are unmanageably large already, and it's too easy to misplace annotations that way. So I keep a single, linear set of paper files, and use grep and its parent, the search facility of the vi editor, to locate items on demand in their machine-readable counterpart. The bibliography is full of cross-references that I can follow to sift out a single topic, when I need to.

Problems arise

On the other hand, this real-world complexity is — in a way — the difficulty that “reductionism” was devised to vanquish: by focusing on one little piece of the puzzle at a time, we can eventually get them all in hand.

Before I knew it, complexity had taken over: the result was complete chaos. After I'd written a few dozen pages, I began having trouble remembering where a particular subject had been treated. My first attempt to organize this was the alphabetical index, which is still a useful finding tool.

Early in 2006, Les Cowley urged me to create a hierarchical contents page for my website. This isn't it; I tried to organize the material that way, after the fact, but found it was impossible. There are too many pages with single links from 5 or 10 others scattered throughout my directory tree. And the directory tree, while hierarchical, doesn't strictly follow the logical structure of things, either. So I gave up.

However, there are chunks of stuff here that do follow a system. For example, the simulations are arranged systematically. There's a general progression from low-level explanations at the first page of many categories to more technical, detailed explanations. So it's possible to produce partial “tables of contents” for various subsets. It's only impossible if you ask that everything be included in a single scheme.

LINK forces my hand

Mozilla's support of the LINK tag made me reconsider this problem. The site-specific toolbar is too handy a navigational aid to ignore. So I've introduced its compulsory hierarchy for certain groups of pages. In general, my choices were made with the beginner in mind; so this system isn't quite the way things are in my own head.

The basic drawback is that the allowed relations between pages must be one-to-one, whereas the actual links between pages are multiply-connected. Furthermore, some things don't fit into such a scheme. So I've included some alternative arrangements.

If you don't have the link-bar running, see here or here for instructions on how to activate it.

Here's the hierarchy the toolbar offers you:

Already, I have bent the rules a bit in fitting so many pages into a single scheme. For example, the links to sub-headings under simulations in fact point to markers within a single file, which means I couldn't make separate “previous” and “next” links for each of them.

Alternatives

Also, several pages have been rather arbitrarily placed. For example, the realistic color simulations of inferior-mirage flashes could have gone before the Omega pages, instead of after them. The simple models for astronomical refraction might well have gone under the “Calculating astronomical refraction” heading instead of under “Astronomical refraction”. (For that matter, the whole “Calculating …” group could as well have been a sub-topic under “Understanding astronomical refraction”.) And, logically, we should have the temperature profiles before the “calculating” group; you have to know the temperature profile before you can calculate refraction. The Reading page could have gone beneath the Bibliography; and the papers I've written could go there, too. I shoehorned the dip diagram page in after the one on the refractive invariant, because they're so closely related; but that forced dip, which is affected only by terrestrial refraction, to fall under the “astronomical refraction” heading.

More serious is the lack of a good place for several important pages that cut across the categories outlined above. For example, there's no place for the classification of green flashes or the glossary or the alphabetical index or the typographical style explanation in the hierarchical scheme. (However, the toolbar provides places for the glossary and the index.) My comments on O'Connell's pictures don't quite belong under the “Reading” category, and don't fit anywhere else, either. And what about odd pages like the ones on green ray displays, or centesimal (not to mention sexagesimal) angular measures?

The page on terrestrial and astronomical refractions really should be a bridge between astronomical refraction and mirages, instead of being stuck at the end of the “astronomical” group. Worse, the dip-diagram page logically should follow the one on dip; but there's no good place for the dip page itself. And dip is closely related to the distance to the horizon, which is affected by terrestrial refraction (like dip); but isn't itself really a refraction phenomenon. All of these are involved in predicting the time of sunset.

Horizon grouping

This suggests making a group of pages about either the horizon, or about terrestrial refraction. A “horizon” group might look like this:

but that last item should follow the Cassini-model page, which is out of place in this group.

Terrestrial-refraction grouping

A group centered on terrestrial refraction might be:

and then we might put all of Green Flashes under “Astronomical refraction”. But then there's no place for the general overview of refraction phenomena.

Meteorological grouping

A boundary-layer meteorologist would look at things from a different point of view. There, the subject of heat transfer and the thermal profile would be of primary importance; all these optical phenomena would be just a means of sensing them remotely. That might lead to this system:

Then everything else would follow that.

Optical grouping

An opticist, however, would start out with the Optics page, putting all the sunset phenomena after “Refractivity of air”, as above — leaving out, I suppose, everything related to thermal structure.

Pages related to O'Connell's book

If you have access to a copy of O'Connell's book, you might arrange the pages that mention it like this:

Color

Another serious problem is where to put the several pages related to colors. An opticist might put them together in a group after Geometrical and Physical Optics.

Here's a possible ordering of pages with color information:

Maybe there should be some intermediate headings to separate the photographs at the beginning from the theory in the middle, and the detailed simulations (which apply that theoretical understanding) at the end.

Leftovers

I also have some groups of pages that are only weakly connected to the rest. For example, in compiling the bibliography, I needed a multi-lingual spell-checker, and wrote it up. Other compositional tools related to LaTeX form a small group:

These don't have much to do with green flashes, although I do use an example from the green-rim page in the PS-conversion page.

Similarly, there are a few pages devoted to the debian flavor of Linux, on which these pages have been developed:

Finally, a number of adventures in the library relate some peripheral events loosely connected with this work.

And there are the pages explaining who I am, and how to email me.

 

Copyright © 2006 – 2012, 2015 – 2017 Andrew T. Young


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