Quantum mechanics is weird, man. Particles can exist in multiple places at once. Like this function: Wavefunction Example 2 shows us how it works.
Here's a simple example of a wavefunction in action:
Try clicking on the wavefunction above to see how it "collapses" into a single point.
Back to Quantum Superposition Quantum Superposition Example 3 Quantum Superposition Example N (for advanced users)