Xeelee Sequence

Lore & Background

Baxter first conceived of the Xeelee while writing a short story in the summer of 1986 as a hobby, eventually published in Interzone as 'The Xeelee Flower' the following year. He introduced powerful off-stage aliens to explain the story's titular artifact. In developing the backstory, he began to outline the elements that would later define the Sequence: a universe populated by intelligent species living in the shadow of the incomprehensible Xeelee.

The series introduces several notable species and civilizations, including the Squeem, a group-mind aquatic species; the Qax, whose biology depends on the interactions of convection cells; and the Silver Ghosts, colonies of symbiotic organisms encased in reflective skins. Several stories explore humans and posthumans in extreme environments: at the heart of a neutron star (Flux), in a parallel universe where gravity is much stronger (Raft), and within eusocial hive societies (Coalescent).

The overarching plot involves an intergalactic war between humanity and the Xeelee, as well as a cosmic conflict between the Xeelee and the Photino Birds. The Xeelee are described as symbiotic entities composed of spacetime defects, Bose–Einstein condensates, and baryonic matter. The Photino Birds are a species based on dark matter that live in the gravity wells of stars. To avoid losing their habitats to supernovae and stellar evolution, the Photino Birds interfere with nuclear fusion in stellar cores, prematurely aging stars into stable white dwarfs, threatening the Xeelee and their cosmic projects.

Reader's Guide

The Xeelee Sequence is a landmark in hard science fiction, noted for its rigorous engagement with theoretical physics and futurology, including artificial wormholes, time travel, exotic-matter physics, naked singularities, closed timelike curves, multiple universes, advanced computing, faster-than-light travel, spacetime engineering, quantum wave function entities, and the higher levels of the Kardashev scale. Thematically, the series addresses existential and philosophical issues such as the struggle for survival in an unknowable universe, the impact of war and militarism on society, and the consequences of an unpredictable technological future for humanity.

As of August 2018, the series comprises nine novels and 53 shorter works, most collected in three anthologies. An omnibus edition of the first four novels (Raft, Timelike Infinity, Flux, and Ring), entitled Xeelee: An Omnibus, was released in January 2010. In August 2016, the entire series of novels and stories (up to that date) was released in a single e-book volume, Xeelee Sequence: The Complete Series. Baxter's Destiny's Children series is also part of the Xeelee Sequence. The series has been praised by science fiction author Paul J. McAuley for its mind-bending scope and meticulous mapping onto cutting-edge speculations about the universe.

Did You Know?

• The Xeelee are described as symbiotic entities composed of spacetime defects, Bose–Einstein condensates, and baryonic matter.
• The Photino Birds are a species based on dark matter that interfere with nuclear fusion in stellar cores to create stable white dwarf habitats.
• The series includes a colossal ring-like structure made of cosmic strings, known as Bolder's Ring, which enables escape to other universes.
• Baxter first conceived of the Xeelee while writing a short story in the summer of 1986 as a hobby, published in Interzone as 'The Xeelee Flower' the following year.