Friday, November 21, 2014

How to Weigh a Quantum: Randy and Jim talk about consistency

Why do we need quantum mechanics?

Is the way that physicists formulate quantum mechanics viable?

That's what Randy and Jim answer in this episode, talking about Aharonov and Rohrlich's Quantum Paradoxes. Including:

(1) Mathematical Consistency:

A set of mathematical postulates is consistent if they don't have contradictory implications.

(2) Black Body Radiation:

A black body is a hot object, like a kiln. Being hot, the cavity of the kiln has a large thermal energy. It transfers some of that energy to the electromagnetic field -- it glows.

In 1899, Max Planck proposed that the thermal energy from the black body can only transfer to the electromagnetic field in discrete chunks, called quanta.

(3) The Compton Effect

The Compton effect is one where a photon (a massless quantum particle of light) strikes and electron, but momentum is transferred from the photon to the electron -- meaning the massless photon has momentum to transfer.

(4) Uncertainty Relationships

In quantum mechanics, there are pairs of variables called conjugate variables that cannot be both simultaneously and and precisely measured together.

This is discussed in terms of the light from a microscope.

(5) Single Slit Diffraction

Light diffracts in a single slit experiment, not just a double slit like we talked about last time.

(6) The Clock in the Box Paradox

Einstein's last attempt to prove that the mathematical formulation of quantum mechanics is inconsistent.

Thanks to Neal Tircuit for our new theme music!

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We're reading Quantum Paradoxes by Yakir Aharonov and Daniel Rohrlich. This is a technical book that is making an argument for a specific interpretation of quantum theory. The first half of the book uses paradoxes to explore the meaning of quantum theory and describe its mathematics, then after interpretations are discussed in the middle chapter, an interpretation of quantum mechanics is explored with paradoxes based on weak quantum measurements.

A popular, and short, introduction to quantum mechanics that includes a lot of the topics in the first half of this books is Rae's Quantum Physics. If the equations in Quantum Paradoxes get you down, this might perk you up.