Welcome to the Glass Age

195 U 13. Glass beyond Glass L othar W ondraczek nderstanding glasses has always had its metaphorical aspects. Among the earliest efforts to capture the nature of glass, 9 th century cleric Hrbanus Maurus [1] was fascinated by visual transparency, which enabled clarity of view but also, at the same time, solid confinement. In some sense, this reflects our present understanding, where we see glasses all around us, but yet, recognize only a small fraction of the full versatility offered by this particular state of matter. Furthermore, we still do not understand the fundamental process and constraints which lead to the formation of glasses from their liquid parent states; 25 years after Phillip W. Anderson’s widely cited statement, glasses remain one of the greatest problems in solid-state physics (P. W. Anderson, 1996). Universality of the glassy state Beyond their material manifestations, optical or mechanical properties, glasses are sometimes understood as representing infinity: neither truly solid nor liquid, they are assumed to flow on infinite timescales; the dependence of glass (and liquid) viscosity on temperature is one of the strongest known to physicists. Spanning more than 25 orders of magnitude, it translates into relaxation times which range from the smallest fractions of a second to centuries, millennia and aeons. Similarly, the other characteristic of the glassy state. Spatial disorder has occupied generations of scientists in their quest for correlations, tools and physical relationships which would help