It’s easy to assume that the digital world is just pixels and code – lacking the physical form of books or stone tablets. But Brewster Kahle knows otherwise. “Digital is not as immaterial as most people think,” he says. And he’s in a good position to comment. Kahle is the founder of the Internet Archive, an online repository of digital information. From scanned magazine articles to books, video, audio and websites – the data amassed is now over 20 petabytes – 20 million gigabytes.

It’s all stored on physical media like hard drives or magnetic tape reels, and the Internet Archive has warehouses full of them in a number of locations worldwide. But the space they take up is not the only problem. Hard drives don’t last that long. The materials and, in some cases, electronic components in these formats eventually decay or stop working. And discs are sometimes blighted by “CD rot”. The most conservative estimates suggest such media might only be reliable for 2-5 years before they risk losing data.