One of the great scientific achievements of the late twentieth and early twenty-first centuries has been to establish that the Universe did begin in a Big Bang, almost exactly 13.7 billion years ago, and has been expanding ever since in line with the description of space and time provided by the general theory of relativity.
If this is true, then the "Many Worlds" hypothesis says nothing to the cosmological argument. It represents every possible arrangement of matter created in the Big Bang, as it passes through cause and effect in finite time. It does not address the possibility of the Big Bang occurring in the first place or why there could be no personal cause involved.
