Could scientists perfectly simulate the entire universe in a computer, down to the last atom?
On the fundamental level, the universe obeys quantum theory. Quantum theory is probabilistic and non-deterministic. This means that if you know everything there is to know about a certain electron at the current moment, and then perfectly apply all the equations of quantum theory to the electron, you cannot exactly predict where the electron will be in one minute. You can only predict the probability of the electron being at various locations. The probability distribution may give you a general idea of where the one electron will end up, and can even tell you the average location of many electrons, but quantum theory cannot tell you the actual, exact location of the electron. The problem is not with quantum theory. The problem is with the electron itself. Quantum objects like electrons are not hard little balls or classical waves. They are more complicated beasts that are somewhat particle-like and somewhat wave-like at the same time. Furthermore, quantum objects innately contain uncertainty in their properties. Electrons fundamentally don't have exact locations. They have locations that exist only up to a degree of definiteness as a result of their inherent uncertainty, which depends on the state of the electron.
