Invisible Infrastructure: Radio Waves and Material Knowledge in Early Twentieth Century Japan.

How do humans engage with infrastructure whose major components are invisible and poorly understood? While many studies assume that infrastructure's materiality is known and stable, early twentieth-century radio communication presented a striking exception: radio waves were new and possessed properties beyond human knowledge. The limited frequencies available for medium- and long-wave wireless transmission sparked anxieties over international competition, while growing reliance on shortwave communication raised the stakes for understanding how radio waves behaved, especially in relation to the ionosphere. Focusing on Japan, a late-industrializing country, this article shows how shifting knowledge of materiality-shaped by political, scientific, and industrial contexts-profoundly shaped infrastructure development. Because much of the physical world remains unknown and human knowledge constantly evolves, this study underscores the mediated nature of materiality in all infrastructure.