steady state
noun
- an unvarying condition in a physical process, especially as in the theory that the universe is eternal and maintained by constant creation of matter稳恒态, 稳态。
The steady state theory postulates that the universe maintains a constant average density, with more matter continuously created to fill the void left by galaxies that are receding from one another. The theory has now largely been abandoned in favour of the big bang theory and an evolving universe.