The 20th century irrevocably changed people's ideas about knowledge, space, time, the cosmos, the psyche, society, progress, and art. It was also a profoundly strange era, in which it is not so easy to distinguish a visionary from a madman. Without understanding it, we are unlikely to be able to comprehend what is happening now. Historian and journalist John Higgs suggests looking at the past century from the perspective of the history of ideas and the gradual penetration of the concept of relativity into all spheres of life. Why did a century of discord and disunity end in universal networking? What can science fiction and pop culture tell us about its philosophy and psychology? How did scientists and artists, without collusion, arrive at similar images? And finally, what can we expect from the 21st century if the previous one was full of wars and tragedies?