\chapter{The Magic of Glass}

To see a world in a grain of sand\ldots

\EmDash{} William Blake

Upon reflection, glass is really an extraordinary substance. When malleable that temperature range between solid and liquid\EmDash{}it can be manipulated as easily as clay by the potter, it can be cut with scissors like cloth, or drawn into threads thinner and stronger than silk. It can be rolled into plates, drawn into sheets, and poured or blown into molds.
Its transparent optical qualities have made lenses possible. Think of the countless people who would have been 'too blind' to contribute to society without eyeglasses (including this author)\EmDash{}how many geniuses (such as Franklin) have needed eyeglasses, whose contributions would have been thwarted without them. In fact, the explosion of learning in the Renaissance may be due in part to spectacles, in wide use in the 15th century (about the time the printing press was invented), which added decades of reading to human life.\footnote{Mumford, L. Technics and Civilization, p.126}

And the optical properties of glass have opened both the infinitely large Cosmos (with telescopes) and the infinitely small realm of the microbe and smaller  (with microscopes) to human view. Without glass, we would still believe that the sun revolved around the earth, and would still have no clue as to the cause of the Plague.

It's also impossible to imagine modern chemistry and medicine without glass: it is extremely chemically inert, making it possible for chemists to have test tubes and other apparatus that don't chemically react to their contents. Medical researchers have Petri dishes and other apparatus that are too inert for the bacteria and drugs under study to react with. And being transparent, scientists can see what's going on inside. (Perhaps using a microscope, with its glass lenses.) And glass is easy to clean, easy to seal, and easy to transform in shape.
Nor would modern electronics have been possible without glass. The first generation of radio and television, as well as early computers\EmDash{}all used 'vacuum tubes', which were made of glass. High-end audio equipment still uses glass 'tubes'. Picture tubes of glass are still in wide use in televisions and computer monitors. Glass globes can withstand the pressure of the atmosphere when the air is removed, and glass is also an excellent electrical insulator.

Or consider the simple windowpane\EmDash{}in your house and your car: glass lets the light in but keeps the elements out. Until the invention of plastics in very modern times there was no other choice but glass, and even today it is still generally the most economic choice. Imagine a house in northern climates before glass\EmDash{}your only light would be open windows that let in the elements, or candles. 

And let's not forget the light bulb\EmDash{}in\-can\-de\-scent, fluorescent, and neon.

And then there are the artistic uses of glass, from stained glass windows to incredible creations of glass\EmDash{}blown and otherwise\EmDash{}by millennia of artisans.

And as humanity inevitably adopts a more renewable economy, glass is likely to continue to play an important role: usually when substances (like plastic) are re-melted to be reused, they degrade. Glass, however, can be remelted and reused countless times without any measurable degradation.

And if all of that weren't enough, you can also make \textit{music} with glass! As we shall see\ldots