Our universe is incredibly young, relative to its total life span. How young? Well, it contains stars. Giant balls of readily fusing hydrogen and helium that give off a pleasant glow, suitable for igniting the formation of life forms on planets orbiting at optimal distances with healthy chemical compositions.
About 100 trillion years from now, the universe will look very different. All hydrogen burning stars will have exhausted their fuel, and all pockets of free floating gasses large enough to form into new stars will have done so, and then those stars will have all run out of fuel. The only remaining stars in this future universe will be degenerate ones: white dwarfs, neutron stars, and black holes. The universe will have entered what's known as the Degenerate Era.
Assuming that there are chemically ideal planets for it to evolve on (these will stick around for a few hundred trillion more years after the stars have all burned away), could life evolve in such a universe? How would life in the Degenerate Era differ from life in the current universe?
What is life?
When considering the question of the evolution of life, we must first answer an important question: what is life? While there are many working definitions of life, here's a simple one that may work for the purpose of this question. In order to be considered "life", something must meet these four criteria:
- Reproduce - Life must be able to reproduce in a manner which passes on the traits of the parent organism(s).
- Grow - Life must consume matter and use this matter to grow in size.
- React to stimuli - Life must be capable of reacting to external stimuli.
- Metabolize - Life must be able to utilize chemicals and energy to change its structure and physical state.