Category: The Copenhagen Interpretation

Schroedinger’s cat has become a sort of diagnostic tool for testing all kinds of interpretations of quantum physics. It wasn’t the last such Gedankenexperiment, nor was it the first. It was preceded by a set of lively debates between the chief architect of the Copenhagen interpretation, Niels Bohr, and Albert Einstein, its fiercest critic. These… Continue reading The Bohr-Einstein Debates

The Copenhagen interpretation says that before a wave function is pinned down by a measurement, things that you might potentially measure, like position or energy state, can take many possible values. Some values may be more probable than others, as determined by the details of the wave function, but each remains possible. As we have… Continue reading Schroedinger’s Cat

A bigger issue may be the introduction of a conscious, self-aware observer into the processes of nature at a very fundamental level. The whole idea of measurement seems to require someone to do the measuring. Given the concept of wave function collapse, the act of measurement has a profound effect on nature itself. If no… Continue reading Measurement and Objective Reality

We explain that there is typically more than one solution to the Schroedinger equation for a given quantum system. Each solution is an Eigenfunction that we can denote as Ψi, and the various Eigenfunctions correspond to valid quantum states of the system. We also explained that any linear combination of Eigenfunctions is itself a valid… Continue reading Superposition and Collapse

One of the more difficult concepts is the exact nature of the wave function (Ψ) itself. We can easily represent wave functions with mathematical formulas, but what exactly are we representing? The standard Copenhagen interpretation doesn’t take a position on whether the wave function is a physical reality or not. Wave functions can include imaginary… Continue reading Wave Functions and Probability

When Heisenberg first unveiled his famous uncertainty relations, they were often misunderstood. Many experimental physicists actually took them as an affront to their skill and saw this as a challenge to be overcome. How dare the theorist Heisenberg, who has probably never been in a lab himself, tell them how precisely they can make their… Continue reading Uncertainty and Duality

We described quantum physics with the dominant interpretation, called the “Copenhagen interpretation,” in mind. This interpretation primarily reflects the views of Niels Bohr and Werner Heisenberg, but many other thinkers have contributed various parts over the years. It is named after the capital of Denmark because that is where Heisenberg and Bohr did their seminal… Continue reading The Basic Features

The quantum physics we have described so far has proven extremely successful at predicting all sorts of usual—and unusual—effects observed at the sub-atomic level. The old laws of classical physics, which work so well for objects of macroscopic size, utterly fail to predict these observations. But classical physics never required us to violate our intuition… Continue reading Introduction