system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What's the connection between entropy and the end of the universe ?
gpt
Imagine the universe is a box, a really big box.  The box is full of water, with a bunch of packing peanuts suspended in the water.  The peanuts dissolve in the water over time.  It's slow process, but sooner or later all of the peanuts will be completely dissolved in the water.  It's like they were never there at all. 

This is entropy, and the end of the universe.  All the stuff in the universe is slowly dissolving away - through processes ranging from gigantic explosions that scatter star-stuff through the void to physical matter literally vaporizing back into energy over a long, long time.  

Once everything is scattered/dissolved, the universe will be "dead", because there won't be enough energy left for anything interesting to happen ever again. 

In the analogy, you can't get the packing peanuts back out of the water without cracking open the box and adding energy (in the form of a filter or something).  So the packing peanut leftovers will just float in the water forever, not doing anything.