Words about Dark Matter is not full of heavy paticles as scientists thought. Full of X-ray emissions from Hot gas.  Hundreds to thousands of galaxies collected & pulled by gravity together.  Collision of two huge cluster galaxies hold majority of the Dark matter.

Some of the puzzles that people list for the public get indexed by the search engines (like Google). Some people find those puzzles and cannot figure out how to make a puzzle of their own. So this page now has the navigation sidebar.

There are now buttons on the puzzle so that you can get a clean page, in either HTML or PDF, that you can use your browser's print button to print. The PDF format allows the web site to know how large a printer page is, and the fonts are scaled to fill the page. The PDF takes awhile to generate. Don't panic!