Despite its solid appearance, glass is actually a 'jammed' state of matter that moves very slowly. Like cars in a traffic jam, atoms in a glass can't reach their destination because the route is blocked by their neighbours, so it never quite becomes a 'proper' solid.
For more than 50 years most scientists have tried to understand just what glass is. Work so far has concentrated on trying to understand the traffic jam, but now Dr Paddy Royall from the University of Bristol, with colleagues in Canberra and Tokyo, has shown that the problem really lies with the destination, not with the traffic jam.
Publishing June 22, 2008, in Nature Materials, the team has revealed that glass 'fails' to be a solid due to the special atomic structures that form in a glass when it cools (ie, when the atoms arrive at their destination).