Tau Zero is one of those books that I had always meant to read, but never really got around to it. It recently came up (somewhere) and I remembered how I had wanted to add it to my collection, but this time decided to do something about it. Book acquired, I set down to read it.
This book, like a lot of Poul Anderson’s work, comes from a different era of SF: to borrow a term from the Comics industry, it is best described as the Silver Age (around 1950 to the mid-to-late 70s). This is the era that most of the big names in SF did their most productive work. Characterization takes a back seat to the Idea of the book (indeed, the Idea could be considered to be one of the characters) as the author uses the cast of characters as a vehicle for exploring whatever Idea they are presenting.
Tau Zero refers to the ratio of time dilation a traveler experiences as they approach the speed of light. Tau Zero is the speed of light (and thus is unachievable), but theoretically one can come very close to it.
The premise of the book is that a Bussard Ramjet spaceship, traveling to a star only 32 light years away (a there-and-back journey of 64 years, though the crew only experiences around 10 years of travel). During this trip, the ship encounters a hazard and is no longer able to decelerate. Furthermore, at the speeds they are traveling at, they cannot deactivate the magnetic scoop, as the hard radiation generated by even the sparse matter in interstellar space will kill them in a matter of hours, nor can the EVA while under acceleration due to the hard radiation emanating from the engines. So in short they are stuck in constant acceleration, going faster and faster, while Tau gets smaller and smaller. While they hatch a plan to shoot for intergalactic space (where hopefully the vacuum is more rarefied than the space between stars), in order to present the crew with a reasonable time-frame, they have to build their acceleration even higher. Soon, minutes inside the ship equal years in the background time-frame, and 10,000 years pass in the universe.
Finding Intergalactic space is not rarefied enough, they shoot instead for the space between galactic clusters, before they can affect repairs. Worse however, is that their journey – expected to be less than 100 years in their original mission, is now taking hundreds of millions of years. Further problems arise…how to decelerate in time to NOT miss a galactic cluster (or galaxy for that matter). The only thing to do is to keep accelerating. Soon billions upon billions of years pass, while it has only been months aboard ship. The crew witness the death of the universe: new stars fail to form, and old stars gutter and die out. They encounter galaxies – now passing through them a few minutes at a time – populated by red dwarfs. Soon even their light fades away.
Worse still the universe undergoes a retrograde, contracting under the influence of gravity, to form a new singularity from which a new universe can be born. The crew survives this (I guess they’re just going too fast), and use the expansion of this new universe as a brake upon their speed. Tau drops, they find a suitable planet – timed to be old enough in its evolution to support an industrial civilization, but still very young in the stellar neighborhood that reborn Humanity could be the first on the scene of intelligent, starfaring civilizations.
Overall, the book is very effective in exploring the phenomenon of time dilation. The story is interspersed with descriptive text exploring time dilation. But it is definitely a product of an earlier generation of Science Fiction: I found the characters in some places forced; the dialogue awkward. Still, the central character in this story is the science, and its affect upon the crew, so perhaps that can be forgiven.
This book was first published in 1970, so the march of science has continued since then. Anderson proposes a contractionary period leading up to a new Big Bang, but current thinking on the problem suggests this is not correct: evidence suggests that the universe is expanding at an increasing rate – galaxies and clusters are moving away from each other at an increasing rate – so the eventual death of the universe will not be in a new Big Bang, but rather in a degenerate era of star-corpses, radiating the last of their heat into space, where the focus of energy is not through stellar fusion, but rather the activity of black holes as they rip apart the dark, brown dwarfs left in the universe.
Still, if one reads this book in the context of when it was written, it can be forgiven that the science is not up-to-date, and the story can still be enjoyed. While I personally would be utterly fascinated with a story set in this degenerate era, as the human crew struggles to survive in an era without light, that might be a story for another time.