Someone hands you a seashell and tells you to listen. You raise it to your ear, perhaps standing on a beach, perhaps sitting in a room hundreds of kilometres from the nearest coast, and there it is: a soft, hollow rushing sound. As a child, you may have accepted the explanation that the shell remembers …
There is something almost irresistible about discovering an echo. Walk into an empty tunnel, stand beneath a great dome, or find yourself facing a distant mountain wall, and sooner or later someone will call out. Often, it is nothing meaningful—just a loud “Hello!” or someone calling their own name into the distance. Then everyone waits. …