Three Possible Theories in Which the Universe Dies.

https://www.youtube.com/watch?v=4_aOIA-vyBo

This is an animate video that explains three ways the Universe might die.
1.Big Rip
-The first of the three theories mentioned in the series is the Big Rip. This theory states that as the universe continues to expand and accelerate, particles will also accelerate. As the universe becomes bigger, it begins to accelerate faster. Eventually the universe is expanding faster than the speed of light. Galaxies begin breaking down to the most basic particles. As the universe continues to expand past the speed of light, particles will no longer be able to interact with one another and the universe will be dead.

2.Heat Death/Big Freeze
-Just like the first theory, the universe will continue to expand at the rate of that greater than the speed of light. The difference in this theory is that matter will stay intact instead of breaking down. Instead, matter will eventually come off as some sort or radiation. When the whole universe successfully finishes radiating, the universe is dead. They like to compare this to entropy stating that the end of the universe is the universe reaching maximum entropy.

3.Big Crunch and Big Bounce
-The third theory is the most interesting I believe. The theory states that dark matter, the apparent substance that expands the universe, will eventually deplete. When this occurs, gravity will eventually overcome all other forces. Blackholes will eventually combine together creating a super blackhole devouring everything including itself. Another Big Bang will occur and the universe will die again; this is known to be the Big Bounce.

Check out the video! It helps visualize everything!