The document discusses four possible scenarios for the future of the universe: 1. The Big Freeze - the universe expands forever and stars burn out, leaving everything dark and cold. 2. The Big Crunch - the universe stops expanding and starts collapsing back in on itself due to gravity. 3. The Big Rip - the universe expands so rapidly that galaxies, stars, planets, atoms, and everything else gets torn apart. 4. Steady State - the universe expands but matter is continuously created to keep the density of matter constant over time.