According to our current understanding of physics, each electron in the universe is indistinguishable from one another. Electrons are elementary particles, and they belong to a class of particles called fermions, which obey the Pauli exclusion principle. This principle states that no two identical fermions can occupy the same quantum state simultaneously.
In practice, this means that while electrons share similar properties, such as mass and charge, they can occupy different quantum states and energy levels within atoms, molecules, or other systems. These different states allow electrons to have distinct positions, momenta, and other observable properties.
However, it's important to note that electrons are fundamental particles that can exist independently in various locations and interact with other particles. So, while there are countless electrons distributed throughout the universe, they are all identical in nature.
It's also worth mentioning that the concept of "particle" in quantum physics can be subtle due to the wave-particle duality. In certain circumstances, electrons can exhibit wave-like behavior and exist in superposition, where they can occupy multiple states simultaneously. The precise behavior of electrons is described by quantum mechanics, which is a probabilistic theory that provides statistical predictions about the behavior of particles at the microscopic level.