# Paul Dirac

## Theories of the Atom

- J.J. Thomson's 'currant bun' theory
Problem
- Atoms seems to be mostly empty space

- Bohr's 'planetary' Model
Problems
- What keeps similarly charged particles together in the nucleus?
- A moving electron would be an electric current and should lose all its kinetic energy in radiation

- Quantised Planetary Model
Problem
- Only works for hydrogen

- Heisenberg's quantum account
- No picture, just tabulate the observables
- Equivalent to matrix algebra

- Dirac reformulated the theory using Poisson brackets