Knowledge: Finally, our collective need for knowledge was long constrained by capital. Making books, for instance, was expensive and time-consuming, and copies could only be made by humans, which introduced errors. The spread of knowledge was limited by the need to create and supply physical copies, constraints that we have now left behind. There were also other ways in which capital was scarce as far as knowledge was concerned. For instance, we had insufficient scientific instruments for inspecting matter, such as microscopes. Today, by contrast, we are able to build massive undertakings to support science, such as the Large Hadron Collider.