Part of the Casswiki article series Natural science
One interpretation of quantum theory is that each time a measurement is made, all possible outcomes of the measurement occur, each in its own parallel world. There is no need of an underlying order which determines which of the possible outcomes of a measurement is actualized because in fact all are actualized.
This interpretation has little practical consequence however since one split, the worlds remain apart and cannot communicate or interact.
The idea of branching universes is itself not without merit but we need to qualify the idea of measurement and splitting further for this to become a useful model. The transactional interpretation of quantum physics states that observation draws the world into existence, as it were: The act of looking at a star causes a back action through thousands of years of time and an equal amount of light years of space, causing the photon to be emitted in the past of the star. This seems unintuitive but is consistent with quantum theory itself. It is often thought that observation by some form of consciousness is necessary for causing a definite measurement, in other words collapsing the probability wave. There is thus a link of sorts between quantum theory and consciousness, although what constitutes measurement and what constitutes consciousness is not exactly defined.
Transactionally, we may view the present as a result of futures observing their past. In this sense we can think of each moment as a point of branching. This does not however mean that all possible branches happen, or at least does not mean that they happen at equal probability or equal frequency across all possible worlds. If we add an element of consciousness and a sort of feedback loop between pasts and presents that can strengthen or weaken various timelines, the many worlds interpretation becomes a more useful mental device for picturing the universe.