Engineer – Russian Chi-Yuen Ai-Ling, Planetologist – Chinese; after Reymont's break-up with Ingrid, she and Reymont begin a long-term relationship. Lars Telander, Ship's Captain – Swedish; a devout Protestant and a strong leader, but the dangers, uncertainties and responsibilities piled on him following the disaster seem to slowly erode him. Johann Friewald, Machinist – German; a man of courage and good nature; after the disaster, he becomes Reymont's right-hand man in maintaining order and ensuring survival. Elof Nilsson, Astronomer – Swedish; a brilliant scientist, but arrogant, physically unattractive and completely lacking in social graces to the point where he is unable to maintain relationships with people; his relationship with Sadler quickly self-destructs, but later he and Ingrid begin a partnership. Jane Sadler, Bio-Technician – Canadian; after a brief relationship at the book's beginning and her failed relationship with Nilsson, she and Friewald become permanent partners. Emma Glassgold, Molecular Biologist – Nationality not stated, lived most of her life in Israel; apparently (though not specifically stated) a devout Christian; as the story develops, she develops a deep (but non-sexual) relationship with Norbert Williams. Norbert Williams, Chemist – American; brash and somewhat loud-mouthed and hot-headed, but capable of deep feeling (proved by his relationship with Emma Glassgold). Origin of the title The novel's title is derived from the value of the time contraction factor Tau (), where where v is the velocity of the ship and c the speed of light. At a given velocity, the duration that is experienced on the non-accelerating Earth may be multiplied by tau to yield the duration experienced on board the ship. Therefore, as Anderson writes, "the closer that [the ship's velocity] comes to [the speed of light], the closer tau comes to zero", and the longer the time that passes outside the ship for a duration inside. The ship in the story intended to attain a tau of 0.015, but as they continue to accelerate beyond the original schedule, it decreases much further. This usage of tau is somewhat idiosyncratic. In physics, tau is more usually used to represent the total elapsed time of the moving clock, so Anderson's "tau factor" is what would conventionally be written d/dt. Physicists also prefer to use gamma (γ) to represent the Lorentz factor in time dilation, which in Anderson's terminology would be 1/. Themes The social themes in this book are much lighter than the scientific themes. The