The behavior of particles like electrons in the double-slit experiment is indeed intriguing and can be described using wave-particle duality. When the electron is observed or detected, it exhibits particle-like behavior, appearing as a localized particle at a specific position on the screen. However, when not observed, it exhibits wave-like behavior, leading to an interference pattern on the screen.
The interpretation of this phenomenon has been a subject of debate in quantum mechanics. One interpretation is the Copenhagen interpretation, which suggests that the act of measurement or observation collapses the wave function, causing the electron to "choose" a specific position and behave as a particle. In this interpretation, the wave-like behavior is described as a probability distribution that determines the likelihood of finding the particle at different positions.
Regarding your mention of "probabilities" being alternate realities, it is important to note that interpretations of quantum mechanics differ. While some interpretations, such as the Many-Worlds interpretation, propose the existence of multiple parallel realities or universes to account for the probabilistic nature of quantum mechanics, this is not universally accepted. The Many-Worlds interpretation is just one of the interpretations attempting to explain the phenomena observed in quantum mechanics.
It's worth noting that interpretations in quantum mechanics go beyond empirical observation and involve philosophical and metaphysical considerations. They are subject to ongoing research and discussion in the scientific community. Different interpretations can offer different ways of conceptualizing and understanding the nature of quantum phenomena, but there is no definitive consensus on which interpretation is the correct one.