Could the universe ever get so densly packed that it caved in on itsself?

Question: Could the universe ever get so densly packed that it caved in on itsself?
- Keywords:
  density,
  universe
Asked by mylifeisacatalyst to Claire, Kate, Matt, Rob, Sam on 21 Jun 2013.
- Sam Geen answered on 21 Jun 2013:
  
  In theory, sure – if the universe was different, it could collapse again (this idea is called the “Big Crunch” because everything crunches together). But we think that there’s enough energy in our universe for it to keep expanding forever.

Question: Could the universe ever get so densly packed that it caved in on itsself?