Physics and Philosophy - Notes on Heisenberg's course

- The central lesson of the theory of relativity is that space and time are not merely the arena in which the drama of  the universe is acted out but part of the cast (part of the physical universe as matter).

- Heisenberg's uncertainty: all physical quantities that can be observed are subject to unpredictable fluctuations, so that their values are not precisely defined.

- Consider, for example, the position x and the momentum p (p=mv) of a quantum particle such as an electron. The experimenter is free to measure either of these quantities to arbitrary precision, but they cannot possess precise values  simultaneously (in one observation or mesurement).

- Quantum mechanics is a statistical theory. Where it differs from other statistical theories is that the chance element is inherent in the nature of the quantum system and not merely imposed by our limited grasp of all the variables that affect the system.

- In a classical world our observations do not create reality: they uncover it. Thus atoms and particles continue to exist with well-defined attributes even when we do not observe them.

- By contrast, in quantum mechanics one cannot meaningfully talk about what an electron is doing between observations because it is the observations alone that create the reality of the electron. Thus a measurement of an electron's position creates an electron-with-a-position; a measurement of its momentum creates an electron-with-a-momentum. But neither entity can be considered already to be in existence prior to the measurement being made.

- A particle is an abstract encodement of a set of potentialities or possible outcomes of measurements. But the reality is in the observations, not in the electron.

- 'What actually happens inside a piece of measuring apparatus when a measurement of a quantum particle is made?' 

=> The combined system of apparatus + particle adopts a state that still represents a range of potential possibilities. These potential possibilities should be mesured (observed) themselves (circular raisoning).

Deails: "Measurement problem" by John von Neumann

- Radiation: releasing energy (in form of waves or particles).
- Atom with more or less neutrons (than the proton's number) is called "unstable" or "radioactive".
- Unstable atom ==release_energy==> Stable atom.
Released energy  is either alpha, beta or gamma

- Break: wave simulation https://phet.colorado.edu/

- Standing/Stationary Waves: superposition of a wave and its reflection
- Golden rule of a wave: Speed = WaveLength* Frequency
- Richard Feynman on Energy :
http://www.feynmanlectures.caltech.edu/I_04.html