We must consider the possibility that the manifold of universes through which we wonder is in fact infinite. - Stephen Baxter

Cause and Effect, when Time Machines are about, are rather awkward concepts.

The last of the Qax had come sliding through the interstices of space and now hovered with him over the frigid surface of the star.
Human and Qax, huddled around the chill proton star, did not attempt to communicate. There was nothing more to say.
The river of time flowed, unmarked, towards the endless seas of timelike infinity.

In the hearts of a hundred billion worlds
Across a trillion dying realities in a lethal multiverse—
In the chthonic silence—
All that could have been done had been done.
In peace and satisfaction, minds diffuse and antique submitted to the End Time.