In its pure form, glass is a transparent, relatively strong, hard- wearing, essentially inert, and biologically inactive material which can be formed with very smooth and impervious surfaces. These desirable properties lead to the very many uses. Glass is, however, brittle and will break into sharp shards. These properties can be modified, or even changed entirely, with the addition of other compounds. Glasses are uniform amorphous solid materials, usually produced when a suitably viscous molten material cools very rapidly, thereby not giving enough time for a regular crystal lattice to form. Glasses can be made from many materials, although only a few varieties are in common use. Common glass is mostly amorphous silicon dioxide, which is the same chemical compound as quartz, or, in its polycrystalline form, sand.

Read the rest of this article: http://en.wikipedia.org/wiki/Glass

Today's selected anniversaries:

* 1787 - The text of the United States Constitution was finalized in Philadelphia. (http://en.wikipedia.org/wiki/United_States_Constitution)

* 1809 - The Treaty of Fredrikshamn concluded the Finnish War between Russia and Sweden, and Finland became an autonomous Grand Duchy under Czar Alexander I. (http://en.wikipedia.org/wiki/Treaty_of_Fredrikshamn)

* 1894 - Japanese and Chinese navies clashed at Battle of Yalu River, the largest naval engagement of the First Sino-Japanese War. (http://en.wikipedia.org/wiki/Battle_of_Yalu_River_%281894%29)

* 1976 - The first Space Shuttle, Enterprise, was unveiled by NASA. (http://en.wikipedia.org/wiki/Space_Shuttle)

* 1978 - The Camp David Accords were signed by Egyptian President Anwar Sadat and Israeli Prime Minister Menachem Begin. (http://en.wikipedia.org/wiki/Camp_David_Accords_%281978%29)

Wikiquote of the day:

"The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one." -- Wilhelm Stekel (http://en.wikiquote.org/wiki/Wilhelm_Stekel)