[Stonehenge]

Dr James B. Calvert

Associate Professor Emeritus of Engineering, University of Denver
Registered Professional Engineer, State of Colorado No.12317

Latest revision 1 September 2015

Recent Additions and Revisions

There is a new article on the physical cause of the thermoelectric effects. The article on the Catenary curve has been revised showing how to find the curve when the supports are not at the same height. The article on Parabolas has a better expression for the length of the curve, and a construction with T-squar and string is included. There is a new article on electromagnetic fields. Pages on PIC and AVR microcontrollers have been added, with pages on applications to digitally controlled potentiometers and accelerometers. There are new pages on making a digital compass, a humidity meter, and a barometric pressure transducer, using the I2C and SPI interfaces, as well as the PIC ADC. There is an article on the Bianchi and Servettaz hydraulic power interlocking in Railways, as well as an article on Italian Signals, with an explanation of the coupled home and distant semaphores. The Trigonometry article now includes spherical triangles, and gives all the derivations.

How To Use This Website

For a discussion of Stonehenge, click on the illustration above. Times and dates on this site are GMT or Zulu 24-hour time, unless otherwise stated.

Welcome. These pages are intended to be viewed with Internet Explorer 4 or better running in Windows 98, on a full screen 800x600 pixels. This was by far the most common browser configuration. Currently, I myself am using WindowsXP and Internet Explorer 7.0 with a 17-inch flat panel monitor, and things look OK. I do not have the resources to design for a variety of platforms, so a compromise must be made. If you see α as a Greek letter alpha, fine. If you see an ampersand followed by alpha; your browser does not interpret these characters, unfortunately. Many of the pages with mathematics depend heavily on these special characters. Panels and colored backgrounds appear on this index page only. Pages can be printed out, or read with Lynx, with little difficulty. Graphics, however, are often important. There are quite a few links to external sites. If you find one that is broken, I would be grateful for notification of the fact. Sometimes sites are only temporarily down. Press F11 to toggle a full-screen view without toolbars and status bar. This site is free of cookies, new screens (except when you command it), textured and colored backgrounds, useless panels and animation, and other juvenilia seen on commercial sites. It is mainly text-oriented, since I have limited space on the server. I use JavaScript in a few places, but mainly only as an example of this feature, or for informative pop-ups. To edit a page, display it and use View/Source and the source text will be loaded into Notepad. Loading the page into Word 2003 will make editing nearly impossible, and ruin your page when it is saved again.

Some weblinks are included, but a search by, for example, the BBC search engine, will reveal more. Websites are ephemeral, and it is difficult to keep them up to date. I appreciate hearing about broken links, since I cannot check them all regularly. Sites from the domains .edu, .org and .gov are normally not vicious, and contain most of the useful information. The domain .com contains very nasty sites, normally with very poor information, that should be visited with care. The appearance of multiple cookies is a giveaway of criminal or commercial intent, so set your browser security at least to Medium. Internet information can be very disappointing. It is a shame that such a powerful medium has been so debased.

My spam blocker is working pretty well these days. I delete rather quickly, so if you do not get an answer to your email, try to make it look less like spam. I delete all emails from Brazil automatically, due to unstoppable spam.

The Classics pages that have been unavailable because of an error in moving the files are again available. Most recent additions and changes: new pages showing how to use the HP-48G calculator for matrices, statistics, and iterative solving (see Economics, Mathematics, and Physics), conformal maps (Lambert and Mercator) and theory of analytic functions in Math (Complex Variables), as well as the complex inversion integral for Laplace transforms. Greek for Euclid has been revised and corrected, and a Greek font is available there (Jun 02). Latin for Mountain Men has also been revised. There are many new illustrated articles based on the chemical elements under Physics/Chemistry, and the Geology section has recently been enhanced. Some selected direct links are given below.

Some suggestions for reading (return here with the Back button on your browser, since the return links will not know where they are starting from):

Many more internet links are being included on these pages, since in many areas internet resources are interesting and valuable. I have found that websites with .edu, .org or .gov addresses are not predatory, and usually have the best information. Some .com sites, especially those outside the United States, and including the excellent www.bbc.co.uk, with not only news, but an excellent and noncommercial search engine, are also safe. They may write one or two cookies, but this is usually not excessive. However, many American websites, even those directed towards children, are pernicious, and can be detected by the excessive number of cookie requests (your security level should be at Medium), and failed scripts--these include all kinds of vermin and low hucksterism, and attempts to load robots on your site and to make other messes. It is best to exit these sites as soon as possible. Unfortunately, they may act as hosts for good websites, who are not responsible for the trash. When I give such a link, I include a warning. I very much appreciate being advised of broken links, so that I can remove them.

Please select your field of interest from the headings in the index at the left. The links will lead you to an index page for the particular topic, from which you can select articles to read. The longer articles have a table of contents with links that may help you find what you want. There is no search facility, unfortunately, since I have not found one that I can set up easily, and do not have the time to write one. At the end of the articles, there is a link back to the index page, and at the bottom of that page, a link back to here. Of course, your browser's Back button can also be used when convenient. The level of the pages ranges from elementary to advanced, mainly the latter, but there is much curious information, and it is not "written down" to the reader as so much is today. In many cases, I have tried to explain complicated matters for the nonspecialist, but never without rigor. You will find mathematics here, unlike most other places, and Greek and Latin as well. Mathematics is not avoided, since it is essential to understanding what I wish to present. There is no personal information or editorializing except under Miscellaneous, where I hope it may be permitted. The general content does, of course, reflect my views on topics, but is not intended to attack or offend. Fortunately, most scientific articles are utterly noncontroversial. At present, Miscellaneous also includes web authoring notes. Pages are continually reviewed and updated as I learn more, and correct my errors. When they first appear, they may be very incomplete and tentative, but improve with age, I hope. All the information may be freely used noncommercially, but I would appreciate the customary attribution if you publish it. Please do not use material that is credited to other sources, but contact these sources directly, to see their requirements. Most reputable sites will allow you to use material noncommercially if you give proper credit. All commercial rights reserved.


"Y con esto, Dios te dé salud, y a mí no olvide. Vale."
M. de Cervantes Saavedra

[Sunset]
Sunset at Land's End, Cornwall, England.

Composed by J. B. Calvert
e-mail: jcalvert@du.edu
All opinions are those of the author alone, and I beg tolerance if you do not agree.
All errors are my own responsibility, and I appreciate being advised of them.
All graphics and audio are my own, and were prepared by me, unless otherwise noted and credited.
www.du.edu/~jcalvert/