Glossary
Black Hole
What a Tangent Universe becomes if it is not resolved: it collapses on itself and destroys the Primary Universe with it. Visualised in the film as the storm vortex over Middlesex.
Sparrow: "Eventually it will collapse upon itself, forming a black hole within the Primary Universe capable of destroying all existence." This is the "end of the world" Frank announces. The swirling storm that forms over the Darko house in the final act is its visual form, and the plane carrying Rose and Samantha flies straight into it.
Defined in The Philosophy of Time Travel