# Why is indeterminism assummed popular ?

1. Jun 29, 2010

### Ushtabalakh

Why is indeterminism assummed "popular"?

Hi

This is quoted from

"Popular belief (even among most physicists) holds that phenomena such as radioactive decay, photon emission and absorption, and many others are such that only a probabilistic description of them can be given."

http://plato.stanford.edu/entries/determinism-causal/#QuaMec

And A textbook I have also says

"The vast majority of physicists do accept quantum mechanics and the probabilistic view of nature. This view which is presented here is the generally accepted one, is called "Copenhagen interpretation" of quantum mechanics in honor of Niels Boher's home, since it was largely..."

Physics, principles with applications, Douglas C.Giancoli, Fifth Edition, Prentice Hall, Upper Saddle River, New Jersey 07458, Page 868

I need to know on what basis indeterminism is considered more popular, are there any surveys regarding this issue or studies of some kind?

2. Jun 29, 2010

### DrChinese

Re: Why is indeterminism assummed "popular"?

There have been a few surveys, I don't have a reference. However, the main reason this is popular is that no evidence has ever been found for an underlying cause. If a cause was discovered, that would change everything. In the meantime: if you want a really good random sequence, use observations of quantum particles.

3. Jun 29, 2010

### dx

Re: Why is indeterminism assummed "popular"?

I'm afraid 'indeterminism' is an inescapable fact of quantum mechanics, and all good physicists know this. That the feature of classical descriptions called 'causality' must be renounced follows logically from the existance of the quantum of action.

To understand this, we must first recognize that our description of our experiments must necessarily be in classical terms, i.e. the approximation h = 0 must on principle be assumed in the description of experimental apparatus. This is similar to the necessity in special relativity of the assumption c = ∞ in the interpretation of scale and clock readings that define the spacetime frame of an observer.

In fact, the feature of indivuduality implied by the quantum of action is completely foreign to the classical description, most transparently embodied in Hamilton's formulation, since there is no determining circumstance for a fundamental quantity of action in that description. This is related to the fact mentioned above that 'h = 0' is a necessary assumption on principle in the description of experimental arrangements, since they must be described classically.

These facts entail that we must, in any well defined application of the quantum formalism, always make a distiction between the experimental apparatus and the 'system' under observation, whose description must transcend the classical framework if it must manifest the fact of h = finite. As I have emphasized, the former must be described classically,

This is a peculiar position, since our tools of description are essentially classical pictures. It was recognized early by Niels Bohr that what we should do is not replace the classical pictures by other abstractions, but to modify our use of the classical pictures in a way that respects the fact symbolized by h. An early form of this was his 'correspondence principle', which was so important for the early progress in understanding the structure of the atom. However, a rational formulation of thewider perspective implied by the correspondence principle evaded Bohr at first. This problem was solved by Heisenberg, who discovered that the description of atomic systems using classical pictures, at the same time incorporating h, was possible if one subjects the classical variables p and q to a non-commutative algebra:

pq - qp = ih/2π

while retaining unchanged the canonical equations of motion

p' = -∂H/∂q

q' = ∂H/∂p

where H is the usual Hamiltonian function of the classical system. The canonical commutation relation in fact implies that only half the of the variables {pi,qi} can be fixed at any given time. The physical clarification of this situation was achieved by Niels Bohr in his paper 'The Quantum Postulate and the Recent Development of Atomic Theory' where he introduced the principle of complementarity, which must be regarded as a replacement of the paradigm of causality.

Complementarity can be illustrated by consideration of simple experimental arrangements such as the double-slit experiment. Here it is especially important to recognize the role of the experimental arrangement in gauging the possibilities of various forms of description. Indeed, in an experimental arrangement suited for the application of conservation laws in its analysis, no spacetime description is possible. This is a consequence of the fact that pq - qp = h implies that only half the canonical coordnates can be fixed. The de Broglie wave, whose mavenumber determines the momentum, embodies this fact in the circumstance that the definition of the wavenumber implies an ambiguity in the 'location', whereas a wavepacket which is localized in a small reagion does not have a definite wavenumber; these are essentially consequences of fourier analysis of the wave.

Various counterintuitive features of the quantum mechanical description can be rationally understood using the viewpoint of complementairty.

For example, in the description of the atom, the assmption of stationary states is needed in the comprehension of spectroscopic data. In the analysis of the experimets, no time description of the atom is possible, and this fact alone supplies the foundation of the assumption of the supramechanical stability of stationary states, and the assignment of definite energy values to these stationary states.

Even more profound implications of complementairty are revelaled in the analysis of observations that can test the quantum mechanical formalism of electrodynamics (Bohr and Rosenfeld, 'Field and Charge Measurements in Quantum Electrodynamics'), and are likeley to be revealved in the search for quantum gravity. Whatever the result of such investigations, it is clear the the classical mode of causal description cannot be revived.

Last edited: Jun 29, 2010
4. Jul 2, 2010

### snoopies622

Re: Why is indeterminism assummed "popular"?

I've wondered: Have there been many attempts over the decades to find patterns in these sequences / observations ?