Video below:
Rattlebacks, sometimes called rollerbacks or celts, have been around since antiquity. The first examples were found in the tombs of Egyptian mummies, and were believed to have been formed in the Nile river over time. The first published paper explaining their peculiar behavior appeared in 1896 and was written by G T Walker. Despite the fact that these oddly shaped semi-ellipsoid materials seem to defy the physical fact of angular momentum, the secret lies in the off center "ellipsoid bump". This misplaced symmetry causes the instability and interesting movement. They are now sold as toys and demonstrate physical instability in ellipsoids. There is a lot of information on rattlebacks and a good start is on the Wikipedia entry here. Although they can be purchased in many location I found these at American Science and Surplus. Although I could not link to the actual page, just enter "rattlebacks" in the search. I buy several toys and odd objects here. Just check the prices and have some fun with science...

It is the end of my first year of hosting this site and I thought that the honeysuckle photo that I posted here in an earlier post might be a nice image to show. And images are the subject of this post and the labor of love that some people display with their web efforts. Most of my images are original and I do the photography and drawing as required. But there are times that I really want an image that says it better than I can, so I have to search for good quality, public domain images. After all, this site is a labor of love and I have no intention of making money with it at all. But, I am not really able to afford image fees, so public domain fits the bill nicely. And that is where WPClipart comes in! A gentleman named Paul Sherman has had this site for several years and it is covered with a lot of public domain images that are safe and very effective. He puts in significant effort to share his collection with schools, businesses, and individuals like me. Here is an excerpt from his site on the collection:
The project started as a "safe" collection of clipart for my kids. Their middle school used AbiWord, and they were often searching for clipart that was both safe and copyright-free. Since this proved to be both difficult and hazardous (since image searches often yielded some very untoward photos) I decided to create a simple collection for their use. My background as both a photographer and a programmer lent itself well to the project, I put it online with my software for others to download and as the months passed it became very popular.
I made thumbnail pages and put up some Google ads, (made a bit of change every day), then suddenly the Google image search engine spidered the site and my server was a bit overwhelmed. After fielding 20-30k hits a day for a year or so I ended up putting the collection on a dedicated remote server, and the ad revenue takes care of the expense. And by using good image tagging and submitting XML sitemaps to Google with each update, the custom search function really helps track images down.
I did not expect to MAKE any money with the collection, so you won't see tons of ads and deceptive links or anything "tricky" to try to get clicks. The collection is self-supporting, and making it safe, useful and quick-loading are the ultimate goals. There is a Google ad atop each page clearly marked as such, so kids and everyone else can come by and find what they are looking for without being forced or tricked into viewing product information they are not interested in.
I would LIKE to do this full-time, but I am not sure I could "pay the bills" with the amount of revenue that comes from ads on an image site -- not without turning it into a ad-fest, and that would defeat the purpose of having the site in the first place . . .  The shear volume of traffic, however, may someday make this possible. -- I'm not complaining!

To me, this is a website that I can endorse and recommend to our readers. It is after all, another site done as a "labor of love". And, by the way Mr. Sherman, if you see an image here that you want to use, you have my blessing. Good work and a tip of the hat! The website is here.