The theory of the end of the universe based on the second law of thermodynamics is indeed what you describe, known as "The Big Freeze", "The Big Chill" or "Heat Death". 

There are other theories, such as "The Big Rip", "The Big Crunch" and "The Big Bounce".
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence