As a much younger person I collected the Asimov non-fiction books and reviews of his books and short stories, he was quoted in one of them as rating this book, Poul Anderson’s Tau Zero, as being excellent, not least because its science was up-to-date and the best known at that point. That’s always stuck with me but I’d never found the book until it turned up in the SF Masterworks list of publications in 2006.
The idea is simple, if you have a ship that accelerates for half your journey, what happens if you then can’t stop it and decelerate at the halfway point? The answer, as posited in this book, is that you will get nearer and nearer to the speed of light until you finally reach Tau Zero, Tau being the rate that time is dilated for external observers. Without spoiling too much, the crew of 50, half male, half female, have to deal with a future of either dying instantaneously if they hit a star (or lots of dust) or continuing an eternal journey.
I really like this book, its dark, psychological and tense. The main character “Charles Reymont” is the constable, reponsible for keeping order both during the journey and while they are setting up the new colony. When this falls apart and the project is abandoned while they try to find a solution to the problems they have, he becomes the only stable, positive influence on the rest of the crew.
Naturally, with this being a Poul Anderson book, the majority of the characters are fairly one-dimensional, they turn up, have their scene and then wander off again. Reymont himself suffers his own stress while helping others out and a couple of the female crew help him along. This is a relatively adult book for 1960s sci-fi, there are bedroom scenes, infidelity, arguments and (soft) violence, its not Barbarella or Alien, but its not a Lucky Starr kids book either.
The reason for this book though is the science, Anderson drops out of the story a number of times to explain the nut and bolts of the Bussard Drive (I guess todays version would be the Ion Drive, low power but continuous drive), time dilation and how the ship is dealing with stresses it was never designed for. If you liked the Appendices in Lord Of The RIngs as much as the book, or get excited by the technical details of your new phone, this will be a book you will appreciate. It’s hard science fiction at its’ best, nice and techy and doesnt end up with a superhero saving the day.