The World Wide Web Is Woven Out Of Threads Of Glass

A crossbow, a lump of molten glass, and a revolution in human communications.

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This is a picture of me—a video still, technically—taken about seven years ago. The image comes from “Glass,” an episode of the PBS/BBC series, How We Got To Now, which I helped create back in 2014. I am in a glassworks shop in Berkeley, California, staring at a molten quartz fibre that I have just formed, seconds before, by blowtorching a chunk of glass and then firing it from a crossbow. As one does.

I’ve always liked this image, and so when I was searching around for some kind of icon to use for this newsletter—which I had only recently decided to call “Adjacent Possible,” borrowing a phrase coined by the complexity scientist Stuart Kauffman two decades ago—this was the image that immediately came to mind. Because that glass fiber I am gazing at with such wonder is a case study in how the adjacent possible works.

We’d planned the crossbow stunt as a kind of historical recreation, bringing to life the moment in 1887 when the physicist Charles Vernon Boys performed a similar feat. (The How We Got To Now producers recognized early on that there was something inherently comical about having me operate any kind of weapon or heavy machinery.) Charles Boys had been a professor London’s Royal College of Science, and a gifted designer of instruments for experimental physics. In the 1880s, as part of his research, Boys had hit up the idea of creating a very fine strand of silicon dioxide—also known as fused quartz, or just old-fashioned glass—to measure the effects of delicate physical forces on objects. He thought the glass could potentially be used as a balance arm, if he could just figure out how to manufacture the piece.

To create his thin string of glass, Boys ultimately built a special crossbow in his laboratory, and created lightweight arrows (or bolts) for it. To one bolt he attached the end of a glass rod with sealing wax. Then he heated glass until it softened, and he fired the bolt. As the bolt hurtled toward its target, it pulled a tail of fiber from the molten glass clinging to the crossbow. In one of his shots, Boys produced a thread of glass that stretched almost ninety feet long.

The feat was impressive enough just looking at it. But its true significance would take almost a century to become apparent. It was one of those ideas that suddenly made a whole other set of ideas thinkable for the first time.

“If I had been promised by a good fairy for anything I desired, I would have asked for one thing with so many valuable properties as these fibres,” Boys would later write. Most astonishing, initially, was how strong the fiber was: as strong, if not more so, than an equivalently sized strand of steel. For thousands of years, humans had employed glass for its beauty and transparency, and tolerated its chronic fragility. But Boys’s crossbow experiment suggested that there was one more twist in the story of this amazingly versatile material: using glass for its strength.

By the second half of the next century, glass fibers, now wound together in a miraculous new material called fiberglass, were everywhere: in home insulation, clothes, surfboards, yachts, helmets, and the circuit boards that connected the chips of a modern computer. The fuselage of Airbus’s commercially troubled by technologically advanced A380 jumbo jet is built with a composite of aluminum and fiberglass, making it much more resistant to fatigue and damage than traditional aluminum shells.

Ironically, most of these applications ignored the strange capacity of silicon dioxide to transmit light waves. Most objects made of fiberglass do not look to the untutored eye to be made of glass at all. During the first decades of innovation with glass fibers, this emphasis on non-transparency made sense. It was useful to allow light to pass through a windowpane or a lens, but why would you need to pass light through a fiber not much bigger than a human hair?

The transparency of glass fibers became an asset only once we began thinking of light—specifically laser beams—as a way to encode information. In 1970, researchers at Corning Glassworks developed a type of glass that was so extraordinarily clear that if you created a block of it the length of a bus, it would be just as transparent as looking through a normal windowpane. (Today, after further refinements, the block could be a half-mile long with the same clarity.) Scientists at Bell Labs then took fibers of this super-clear glass and shot laser beams down the length of them, fluctuating optical signals that corresponded to the zeroes and ones of binary code. This hybrid of two seemingly unrelated inventions—the concentrated, orderly light of lasers, and the hyper-clear glass fibers—came to be known as fiber optics.

Using fiber optic cables was vastly more efficient than sending electrical signals over copper cables, particularly for long distances: light allows much more bandwidth and is far less susceptible to noise and interference than is electrical energy. Today, the backbone of the global Internet is built out of fiber-optic cables. A few dozen cables traverse the Atlantic Ocean, carrying almost all the voice and data communications between the continents. Each of those cables contains a collection of separate fibers, surrounded by layers of steel and insulation to keep them watertight and protected from fishing trawlers, anchors, and even sharks. Each individual fiber is thinner than a piece of straw.

Much of this was made possible by the molten silicon dioxide that Charles Boys fired from that crossbow. In a literal sense, the World Wide Web is woven together out of threads of glass. But this turns out to be only a small part of the debt that the digital age owes to silicon dioxide, and glassmaking innovators like Charles Boys. Think of that iconic, early-twenty-first-century act: snapping a selfie on your phone and then uploading the image to Instagram or Twitter, where it circulates to other people’s phones and computers all around the world. We’re accustomed to celebrating the innovations that have made this act almost second nature to us now: the miniaturization of digital computers into handheld devices, the creation of the Internet and the Web, the interfaces of social-networking software. What we rarely do is recognize the way glass supports this entire network: we take pictures through glass lenses, store and manipulate them on circuit boards made of fiberglass, transmit them around the world via glass cables, and enjoy them on screens made of glass. It’s silicon dioxide all the way down the chain.

So I guess I came back to the image of myself staring at that thin strand of glass because those are the kinds of moments that I hope to be investigating at Adjacent Possible. What’s the equivalent of Boys and his crossbow right now, the new idea that someone has just released into the world that will open as many new doors in the adjacent possible as those glass fibers did? To answer that question you can’t just be focused on the short-term, immediate applications. If you’d told Charles Boys that he’d just laid the groundwork for a communications platform that would allow people to send images instantaneously across oceans to thousands of other people, he would have thought you were insane. But the future would have been on your side. It’s just hard to imagine those kinds of futures, and extremely difficult to come up with definitive predictions about them, over any extended time scale. But it’s still a great question to ask, even if the answers are always a bit blurry: what new door in the adjacent possible just opened—what new glass-bearing crossbow has just been fired in a lab somewhere—and where might it lead us next?

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