Dreams.

I had a dream about a black hole today. The main idea was that entering a black hole allows you to travel to the future. But not literally; it's more like when a planet enters a black hole, it's as if it's taken out of time, as if it's been removed from the universe and placed in a cell where there is no time and nothing changes. After that, you exit the black hole and find yourself in a universe where changes have occurred, but on the planet, everything remains the same.
Although, maybe time simply slowed down significantly there; I'm not sure.