World Science Scholars
2.2 The Granular World
Quantum mechanics established the discrete nature of light.drop-down

  • Quantum mechanics began after observations of atomic emission spectra showed that atoms do not emit light at any arbitrary frequencies but rather at specific well-defined frequencies.
  • This eventually led to the notion that light, in addition to being a wave, is also a particle, and that particles of light can only have energies that are discrete multiples of a fundamental value.
  • In the case of electromagnetism, the continuous electromagnetic field is replaced with the photon.

Heisenberg's interpretation of quantum theorydrop-down

  • According to Heisenberg, we cannot assume that particles exist continuously between observations. Reality itself is discrete, not continuous.
  • Just as there is a minimum fundamental value for the energy of photons, there too exists a minimum fundamental distance of space. Particles do not move smoothly through space but rather “jump” from one segment to the next.
  • Furthermore, in standard quantum theory, there is no strong deterministic law that predicts when and where particles will next appear. Quantum mechanics only provides probabilities about particle locations and behavior.
  • Finally, one way to interpret quantum theory is that reality is relational — particles only become well-defined during interactions, and they are defined in relation to the system they interact with.

Almost every aspect of reality has proven to be fundamentally discrete.drop-down

  • Quarks and leptons are the class of elementary particles that compose matter. Quarks can combine to create protons and neutrons, while the electron is the most commonly known lepton.
  • As mentioned above, the photon is the quantum of the electromagnetic force.
  • The quantum particles of the strong and weak nuclear forces have also been discovered. The strong force is mediated by gluons, while W and Z bosons mediate the weak force.
  • The only fundamental force for which no quantum particle has yet been discovered is gravitation. The best current description of gravitation, general relativity, is a purely classical field theory.

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