"Tau Zero" is a science fiction novel written by Poul Anderson, first published in 1970. The story follows the crew of the spaceship Beltane, which is on a mission to reach another galaxy. Due to a malfunction, the ship accelerates to near-light speed, causing time to slow down for the crew while time on Earth continues to pass. As the crew grapples with the effects of time dilation, they face challenges related to survival and the nature of existence. The novel explores themes of human perseverance, the passage of time, and the vastness of the universe, making it a thought-provoking read for science fiction enthusiasts.