Saturday, March 20, 2010

More Astrophysics & Quantum Mechanics Connections

While researching my initial response, “Scott Rebuttal III. The Importance of Quantum Mechanics”, I discovered yet another fascinating connection which illustrates how researchers in quantum mechanics developed techniques important in astrophysics and semiconductor physics.

As I mentioned in  “Scott Rebuttal III”, Alan H. Wilson was a physicist who initially explored applying quantum mechanics in nuclear astrophysics before writing the two foundational papers of semiconductor electronics using the same quantum mechanical principles.  Dr. Wilson was a student of Ralph H. Fowler.  

Those familiar with electronics might recognize Ralph Fowler as one of the authors of the Fowler-Nordheim equation.
This paper was a landmark work which solved the problem of understanding cold-cathode emission, sometimes called field-effect emission (Wikipedia).  Cold-cathodes could emit electrons at room temperature through the application of a strong electric field.  In contrast, hot-cathodes emit electrons by heating the metal with a filament.   The cold-cathode mechanism defied explanation by classical electromagnetism for many years.

Prior to this, Dr. Fowler had worked on issues surrounding the effect of the Pauli Principle (Wikipedia), on the mass structure in stellar interiors.  The Pauli Principle states that no two fermions (Wikipedia) can occupy the same quantum state at the same time.  This principle is responsible for the energy-level structure in atoms.   By applying the fundamental principles of hydrostatic pressure combined with the gas laws (Wikipedia), and the Pauli Principle, Fowler demonstrated that  the density in stellar interiors could far exceed that available in Earth laboratories due to the weight (pressure) of overlying mass of the star.  Eventually, the electrons would fill all the available energy states in the stellar core and would become degenerate (Wikipedia). 

Here's some of the papers by Fowler on this topic available through the Astrophysical Data Service.  Some of the full papers are available for free through these links:
Fowler solved these two very different problems, cold-cathode emission in Earth  laboratories, and the other deep in stellar interiors, using the exact same quantum mechanical mathematics!

Electromagnetism by itself was unable to explain the process of cold-cathode emission beyond defining a few simple mathematical relationships from simple experimentss.  It took the intervention of physics and particularly the development of quantum mechanics to connect those simple experiments to more fundamental processes.  Electromagnetism had the same difficulty explaining the photoelectric effect (Wikipedia). 

The development of quantum mechanics turned cold-cathode emission from a mysterious behavior into a well-understood process which enabled others to use the idea in developing more sophisticated technologies such as modern flat-panel displays, etc.  It is the same quantum mechanics that predicts 'exotic' states of matter under extreme conditions such as the center of stars.


tangiblezero said...

That's very interesting, thanks for posting. I always love hearing about ways quantum mechanics has impacted modern technology. It's so poorly understood by the lay population (I include myself in that group), that it's easy to marginalize and, in the case of some EU advocates demonize, as a field. Posts like this help to illustrate just how pivotal QM is.

W.T."Tom" Bridgman said...

I forgot to include a link to my paper on the Cornell preprint server that illustrates some of the practical implications from astronomy. I include other quantum mechanics connections as well as other fundamental theories in physics. The Cosmos In Your Pocket: How Cosmological Science Became Earth Technology. I