Poul Anderson's Tau Zero, published in 1970, is a landmark of hard SF which pushes out far further, beyond the Milky Way and into the frightening emptiness of intergalactic space. It also deals memorably with time dilation, and a vast spain of eons.  Significantly, Anderson does all of this in a scientifically convincing way, with a plot strongly grounded in his understanding of phyics at the time. This episode takes a close look at the novel, and the reasons why it remains a classic of its type over 50 years later. Support the Show. For lots more writing on classic science fiction, other books, video games, and more check our my site andyjohnson.xyz and follow me on Twitter: @andyjohnsonuk