The Many Worlds Theorem of Quantum Mechanics,
a mainstream contender in particle science,
proposes for every event that can happen
all other events that can happen do too
but each of the many exist in their own world,
no link between any can ever occur.

The theory says worlds split off from our own
whenever there's change, no matter how small.
In quantum mechanics, time can reverse,
and, backwards in time, such worlds, they would merge.
Theories elsewhere say time could be travelled,
so worlds navigation perhaps could occur.
                          [poetic license applied for]