Quantum mechanics
Theory · 1925 to 1930s, Germany, Denmark, and Britain · Physics, stage 2: Map the theories
Quantum mechanics is the theory that replaced classical mechanics at atomic scale. Heisenberg produced one formulation in 1925 using arrays of numbers, Schrödinger produced another in 1926 using a wave equation, and the two were soon shown to be mathematically equivalent. The theory describes a system by a state that evolves smoothly and predicts probabilities rather than definite outcomes for individual measurements. Its predictions have never failed a test, and it underlies chemistry, semiconductors, lasers, and magnetic resonance imaging. What it means remains contested, because the theory does not explain why measurement produces a single definite result.
What it claims
- A quantum system is described by a state that can combine several classically exclusive possibilities.
- The theory predicts probabilities of outcomes, not individual results.
- Certain pairs of properties cannot both have definite values at once.
- Measurement yields one definite outcome, and the theory does not say why.
Key ideas
People
Sources
- Quantum mechanics English Wikipedia
- Quantum Mechanics Stanford Encyclopedia of Philosophy
- Quantum mechanics Britannica
