QUANTUM METAPHYSICS - E-thesis

dependent on the chosen group of observables. The concept of a wave was essential, but on its
own it was not enough. Already de Broglie had shown that a moving body could be described
with wave packets constituted from different component waves: the group velocity for matter
waves was the same as the velocity of the body. In collisions, however, wave packets behaved
differently to material particles. They passed through each other, interfering only temporarily,
while particles typically bounce away from one another. Furthermore, wave packets connected to
atomic particles soon dissipate because of the different velocities of the component waves. 470
As the concept of the wave was not able to provide an exhaustive description for all the relevant
features, the wave function was generally seen as no more than a mathematical instrument
suitable for calculating probabilities. It provided a comprehensible image of the mathematical
function, but probability waves were not waves in physical reality. When the usefulness of the
probability waves was limited to the calculation of probabilities, they were not seen as actual
waves in reality, but only as a means to produce an illustrative image of a mathematical function.
Nonetheless, Max Born himself was prone to see these waves as something more real. He
thought that even if particles followed indeterministic laws of probabilities, these probabilities
were still something real that followed laws of causality in the configuration space. 471 Albert
Einstein also preferred fields and waves. He never accepted the probability interpretation, but
tried to reduce all particles to field equations. Because of discontinuity his goal was not generally
adopted. Accustomed discourse concerning particles went on, even if they were no longer
considered the bodies of classical mechanics which could be idealised as point masses. 472
Schrödinger's equation, not unlike those of Newton and Maxwell, produces an absolutely
deterministic time development. After a wave function has been determined, its time
development at the atomic level is, in principle, fully predictable. 473 On the other hand, this only
applies at the atomic level where there is interference, superposition, and probabilities. When one
wants to know something about the real world, the system must be measured. While this
470 Laurikainen 1973, 138-139.
471 Born 1963, 234.
472 Laurikainen 1973, 155, 185.
473 With respect to the quantum-mechanical state-description defined by the Psi-function, quantum mechanics is a
fully deterministic theory. Nagel 1961, 306. In quantum mechanics, however, the state Ψ is totally different to the
state in classical mechanics which gives the exact position and velocity of particles, since it only provides the
possibility of calculating the statistical distribution of expected values. Laurikainen 1973, 165.
183