The Wave Function Of The Universe

[Demystifier]

I thought wave function collapse was real under Copenhagen?

As bhobba mentioned, there are several different variants of Copenhagen:
https://www.physicsforums.com/showthread.php?t=332269

 

[bhobba]

I'm trying to understand some things that have been told... but I feel lost...
First of all, the collapse does not happen when a HUMAN makes the measurement...The measurement can be done anytime by the nature itself... The particles don't understand a human is looking at them, they just interact with some matter (a photon let us say) and their "wavefunction" collapses...

Actually that's closer to the correct view than some of the gibberish you get in the populist press.

The modern view is to use decoherence to explain APPARENT collapse and to consider an observation to have occurred once decoherence has happened. For example a few stray photons will decohere a dust particle and its sensible to think that has given it a definite location, this being how the classical world emerges.

You might find the following article by Wienberg interesting (see the section on Contra Quantum Mechanics):
http://scitation.aip.org/content/aip/magazine/physicstoday/article/58/11/10.1063/1.2155755
'The other mistake that is widely attributed to Einstein is that he was on the wrong side in his famous debate with Niels Bohr over quantum mechanics, starting at the Solvay Congress of 1927 and continuing into the 1930s. In brief, Bohr had presided over the formulation of a “Copenhagen interpretation” of quantum mechanics, in which it is only possible to calculate the probabilities of the various possible outcomes of experiments. Einstein rejected the notion that the laws of physics could deal with probabilities, famously decreeing that God does not play dice with the cosmos. But history gave its verdict against Einstein—quantum mechanics went on from success to success, leaving Einstein on the sidelines.

All this familiar story is true, but it leaves out an irony. Bohr’s version of quantum mechanics was deeply flawed, but not for the reason Einstein thought. The Copenhagen interpretation describes what happens when an observer makes a measurement, but the observer and the act of measurement are themselves treated classically. This is surely wrong: Physicists and their apparatus must be governed by the same quantum mechanical rules that govern everything else in the universe. But these rules are expressed in terms of a wavefunction (or, more precisely, a state vector) that evolves in a perfectly deterministic way. So where do the probabilistic rules of the Copenhagen interpretation come from?

Considerable progress has been made in recent years toward the resolution of the problem, which I cannot go into here. It is enough to say that neither Bohr nor Einstein had focused on the real problem with quantum mechanics. The Copenhagen rules clearly work, so they have to be accepted. But this leaves the task of explaining them by applying the deterministic equation for the evolution of the wavefunction, the Schrödinger equation, to observers and their apparatus. The difficulty is not that quantum mechanics is probabilistic—that is something we apparently just have to live with. The real difficulty is that it is also deterministic, or more precisely, that it combines a probabilistic interpretation with deterministic dynamics.'

That considerable progress has to do with decoherence. You can read about it implications for this issue here:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

It sheds light on the issue - but whether it resolves the central issue is controversial.

Thanks
Bill