inertiain
Inertiain is a term used in speculative physics and science fiction to denote a hypothetical substance or field that couples to ordinary matter to modify its inertial resistance to acceleration. In many depictions, a body within an inertiain medium experiences a change in effective inertial mass, allowing higher accelerations for a given force. Other variants describe a tunable coupling that can reduce or increase inertia. It is not an established material; it functions as a thought-experiment and plot device.
Properties and theoretical context: In fictional treatments, inertiain is typically portrayed as extremely dense and stable
Theoretical significance and usage: Inertiain is often used to explore the limits of the equivalence principle
See also: inertia; Higgs field; equivalence principle; Mach's principle; inertial frame.