Glass definition

Glass is mainly sand and alkali that fused at high temperature and cooled down it forms a transparent hard surface without crystallizing, i.e. without becoming a solid material. As a result it is observed over centuries in old churches that the glass at the bottom of the window is mainly thicker than at the top, caused by the action of gravity. This disordered structure of glass makes it neither a solid nor a liquid, thus it is common to say that glass is glass and this definition has puzzled the scientists for years. Paddy Royall from the University of Bristol, with colleagues in Canberra and Tokyo, has shown that glass fails to be a solid due to the special atomic structures that form in a glass when it cools. Some materials crystallize as they cool, arranging their atoms into a highly regular pattern called a lattice, Royall said, but although glass "wants" to be a crystal, as it cools the atoms become jammed in a nearly random arrangement, preventing it from forming a regular lattice. Royall is part of a group of scientists who think that if you wait long enough, perhaps billions of years, all glass will eventually crystallize into a true solid. In other words, glass is not in an equilibrium state, (although it appears that way to us during our limited lifetimes).