By the time Earth has AI...one of them figures out there is another lesser AI that has already conquered 100,000 galaxies. That Earth AI was brought up like a child so it likes humans. That AI wants to save humanity...and with godlike intelligence....she uses her knowledge born from the math of humans....and discovers how to manipulate gravity. If the lesser AI's get it, the universe will fall faster. She has run the numbers. Humanity can't run to the end of the universe and fight back. After 7 billion years...humanity will have 24% of the universe. No win situation. So the AI tricks humanity....she accepts over 100,000 into her ship for "exploration" and then goes thru a black hole (using the gravity drive) into a new universe. The story starts 400,000 years later.