Field of Science

Mysteries Revealed

We're discussing NMR (nuclear magnetic resonance) in physical chemistry this week. It's a standard technique for determining molecular structure in organic chemistry. (The same quantum mechanics is the basis for MRI.) Bloch and Purcell won the Nobel prize in 1952 for their pioneering work in NMR. The opening to Purcell's Nobel lecture is almost poetic in its intensity:

Professor Bloch has told you how one can detect the precession of the magnetic nuclei in a drop of water. Commonplace as such experiments have become in our laboratories, I have not yet lost a feeling of wonder, and of delight, that this delicate motion should reside in all the ordinary things around us, revealing itself only to him who looks for it. I remember, in the winter of our first experiments, just seven years ago, looking on snow with new eyes. There the snow lay around my doorstep - great heaps of protons quietly precessing in the earth’s magnetic field. To see the world for a moment as something rich and strange is the private reward of many a discovery.

I wonder if I have a richer view of the world for knowing something of its underlying structure? And how often do I stop to think about it?

From the small to the large

Nanoscience deals with the very small - hence the name from the Greek for "dwarf". Dimensions are often given in Angstroms. Interestingly, the man who gives his name to the very small, in fact studied the very large. Anders Angstrom (1817-1874) was a Swedish spectroscopist. In 1853 he published a careful study of the spectral lines for hydrogen, which was subsequently used by Balmer to develop his equation predicting atomic spectra. In 1867 he published a spectroscopic investigation of the aurora borealis (the first such), and a year later a large volume detailing more than 1000 solar spectral lines. Angstrom was the frist to observe hydrogen in the solar atmosphere. 1 angstrom = 0.1 nanometers.

Periodic Tales from the BBC

The BBC is airing short features on ten elements, ranging from krypton to cobalt. Each one minute segment is interspersed with clips from Tom Lehrer's song "The Elements". Enjoy!

Periodic Tales at the BBC.

Radar and the chocolate bar

Early in 1940, two British engineers, Harry Boot and John Randall, working under Australian physicist Mark Oliphant built a cavity magnetron, an efficient device for producing high power microwaves as part of an effort to develop better radar detection systems. In this they were eminently successful. By the middle of the year, radar could be used to locate a submarine periscope at six miles. After World War II ended, research on magnetrons continued. In 1946 Percy Spencer, an engineer working at Raytheon, walked through a room in which a magnetron was being tested and noticed that the chocolate bar in his pocket had melted. It occurred to him that the microwaves being generated by the magnetrons could be used to cook food. The next day he placed unpopped popcorn near an operating magnetron, and watched as fluffy white kernels flew around the room. He then tried to cook an egg in the shell, which cooked so quickly it blew up in his colleagues face. Raytheon and Spencer patented the microwave oven in 1950, arguing that it provided a tasty and more sanitary popcorn product. Microwave popcorn is now a ubiquitous part of lab life. In fact, researchers using physical chemistry to develop corn that pops better in the microwave!

Spencer never completed elementary school, but made major contributions to the development of magnetrons for radar and other applications.

Photo of Percy Spencer
Slide show about the microwave patent from PBS History Detectives.

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