If the Big Bang started the Universe, the Big Rip might end it in just 20 Billion Years!
In 1998, an accelerating expanding universe was discovered.
Meaning, something like Dark energy was involved in this.
If dark energy plays a role, today, it could even more so tomorrow and completely overwhelm gravity....
And end the Universe in a Big Rip!
In 20 Billion years!
Caldwell's theory.