system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes it so your body can stay in a coma for years and just randomly wake up? Why are comas so unpredictable for how long you are asleep for?
gpt
Imagine you're playing Dwarf Fortress. Your fortress is big, complex, and detailed levels stretch from surface to the underground caves. Suddenly there's a cave in that collapses a wide area of tunnels three quarters of the way down your whole fortress. This is a gigantic mess. The majority of your dwarves will be tasked clearing rubble, digging new tunnels, redigging old tunnels, basically repairing the whole fortress. It takes too many dwarves to spare any for trading or diplomacy or military, so you close up the fortress while the long repairs are underway.  
  
Normally this would spell death as the fortress is not farming or hunting food for itself, but other fortresses in the area donate foodstuffs while the long repairs are underway. They don't know the progress of the repairs, but they're hedging that your dwarves can get it done.  If they do, if they manage to get things *just* to the point where the fortress can operate again, the gates will open and the dwarves will pour out to get things running again.
  
Sometimes they can't. The chasms are too big, the remaining stone too weak to build with. This fortress is never going to be up and running again. It's dwarves will live only as long as the food supplies last. But we can not know that, we can only judge by what we can see from the outside.