Quantum Mechanics
The branch of physics describing the behaviour of matter and energy at the smallest scales — atoms, electrons, photons. Predicts probabilities rather than certainties.
Quantum mechanics is the most accurate physical theory ever developed, describing the behaviour of matter and energy at atomic and subatomic scales. Unlike classical physics, it predicts probabilities rather than certainties, and includes counterintuitive phenomena such as wave-particle duality, superposition, and entanglement.
At quantum scales, particles can exist in multiple states simultaneously (superposition) until measured, after which they appear in one specific state. Entangled particles share information instantaneously regardless of distance — a phenomenon Einstein called "spooky action at a distance."
Quantum mechanics underpins modern technology including semiconductors, lasers, MRI machines, atomic clocks, and emerging quantum computers. Despite its predictive accuracy, the question of *why* quantum mechanics works the way it does remains philosophically unresolved.