Rakesh, a man living on a computer in interstellar space in the distant future, feels that everything in the galaxy has been explored and there's nothing new to do. When he learns that the Aloof, the mysterious and uncommunicative civilization that controls the center of the galaxy, has found evidence of the existence of a new DNA-based biosphere and wants some other life forms to search for it, Rakesh and his friend Parantham travel into Aloof territory to investigate.
Meanwhile, a pre-industrial society of bug-like Starfish Aliens lives in tunnels in a chunk of rock called the Splinter, where gravity behaves in unusual ways, pushing them towards the center in some places and away from it in others. Two of the aliens, Roi and Zak, conduct experiments to determine the nature of their home.
Incandescence contains examples of:
- Alien Non-Interference Clause: The Amalgam, the alliance of star systems and species that spans most of the galaxy, has a policy of waiting for a species to develop interstellar travel before making First Contact, which is often an unpleasant and frightening experience for a more primitive society. Rakesh and Parantham make an exception for the aliens they find in their search because the center of the galaxy is so crowded and unstable that they could easily be wiped out, and the Amalgam can offer them safety.
- Alien Sky: Rakesh is struck by how bright and crowded the night sky is near the center of the galaxy.
- Alternative Number System: The people of the Splinter have six legs, and their number system is based on that. Their word for "very many" translates to "thirty-six times thirty-six."
- Anachronic Order: The story seems like it's being told in order, but Zak and Roi actually lived millions of years before Rakesh and Parantham.
- Centrifugal Gravity: The Aloof house Rakesh and Parantham in a habitat that spins around the meteor containing the DNA, creating enough gravity for them to walk around comfortably.
- Cyborg: Rakesh and Parantham have modifications that include infrared sensors in their fingertips and a Brain/Computer Interface that lets them communicate with each other and operate technology.
- Destructive Teleportation: People have their bodies digitized and destroyed before they travel long distances. When they reach their destination, a new body is built to their specifications. The technology for doing this has been so perfected that anyone can live indefinitely just by periodically transferring their minds from their old bodies to a younger one, and people will sometimes experiment by inhabiting bodies of different species. Parantham was created de novo on a computer and had no original body, so on the rare occasion that she takes on a body, she looks like whatever organisms she happens to be staying with at the moment.
- Earth-Shattering Kaboom: The Splinterites have a myth that their home broke off from a larger rock long ago. When Rakesh and Parantham discover a different splinter inhabited by similar beings, they theorize that when the species' home planet was destroyed, their ancestors designed this environment where they could live somewhat safely.
- A Form You Are Comfortable With: When someone is living on a computer, they see everyone they talk to as a member of their own species and hear all speech as their own language, no matter how many kinds of aliens are present. They also perceive the environment as something familiar from their home planet.
- Lost Tribe: The Splinterites make contact with the inhabitants of other members of their species who live in similar arks orbiting the same black hole. Eventually they develop interstellar travel and become the Aloof, discouraging other species from going near the center of the galaxy because it's too dangerous. But they failed to discover one ark, whose inhabitants lived for millions of years in total ignorance of the universe outside their little world until Rakesh and Parantham arrived.
- Panspermia: DNA-based lifeforms have evolved on many planets thanks to collision ejecta spreading the replicators between star systems. There are also ten other panspermias of different kinds of replicators. All are believed to have originated between twenty and thirty thousand light years from the center of the galaxy. The discovery of a meteor containing DNA in the central bulge of stars is surprising news partly because conditions there are believed to be too hostile to support the development of a biosphere.
- Remote Body: Rakesh and Parantham use remote bodies that resemble jelly babies to explore hostile environments. These bodies can be as large or small as necessary, can adjust their senses to perceive different kinds of stimuli, and can use ion thrusters to get around.
- Small, Secluded World: The Splinterites never visit the surface of their rock. They have everything they need inside - two species of less intelligent animals they can use for meat and other products, and fungi that not only feed them but also automatically repair damage to the walls. Although the Splinterites are intelligent enough to understand math and science, their ancestors genetically engineered themselves to be complacent and uninterested in the universe to stop them from going crazy with boredom in their tiny environment. However, they are also designed to regain their curiosity if an emergency situation requires them to develop solutions.
- Starfish Language: The Splinterites communicate by drumming their legs on their undersides.
- Switching P.O.V.: Rakesh narrates odd-numbered chapters and Roi narrates even-numbered ones, both in the third person limited.
