Basically, many-worlds proposes the idea that the quantum system doesn't actually decide. Rather, that at every junction where large everyday stuff interacts with the quantum system, the timeline of history splits and both possibilities happen on different alternate branches.

Scientists estimate that there are hundreds of billions of galaxies throughout our universe. When you think about them, the numbers are staggering, and scientists believe the possibilities are endless. More and more, scientists are beginning to believe that we are not alone.

It is only within this specific imaginary scenario that a person finds themselves surviving. Most experts believe that the experiment would not actually work in the real world. Max Tegmark now believes that from their own point of view, the person in the thought experiment should not expect immortality.

The many-worlds interpretation implies that there are most likely an uncountable number of universes. It is one of a number of multiverse hypotheses in physics and philosophy. MWI views time as a many-branched tree, wherein every possible quantum outcome is realized.