Plum Pudding

The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote.... Our future discoveries must be looked for in the sixth place of decimals.
- Albert. A. Michelson, speech at the dedication of Ryerson Physics Lab, U. of Chicago 1894

The following year, Roentgen discovered X-rays; a year later, in 1896, Becquerel discovered radioactivity; and J.J. Thomson electrified physics in 1897 when he announced that cathode "rays" were really beams of electrons or what he called "corpuscles."

Thomson knew as much as anyone about electricity and its conduction--that electricity could flow here and there like invisible water and it could even be tamed and put to use. The electron, named after the Greek word for amber, had even been proposed before but had remained safely ensconced in matter. Thomson disclosed it. Disrobed it. What the electron lost in privacy, it gained in primacy and notoriety. Alone and naked for the first time, the electron succumbed to further scrutiny--first its mass-to-charge ratio was measured by Thomson. Soon after, it was actually weighed by Millikan (ironically at the University of Chicago--see quote above). But the real shocker at the time was that atoms were divisible--they were not a-tomos. This destroyed a comfortable notion of integrity.

JJ Thomson. Note the photograph (second from right) which is an early X-ray of the hand of Frau Roentgen

Knowing that he could strip off little negative bits, but not having a working notion of the countervailing positive portion which was surely left behind, Thomson theorized that electrons were uniformly sprinkled in a positively-charged, amorphous medium. The model was dubbed Plum Pudding. And why not? Thompson went with what he knew.  He would have overreached any data to have proposed anything else. And so, for the interregnum roughly corresponding to the Edwardian era—until Ernest Rutherford undid it—the atomic model looked like this:

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Suggested reading: history of the electron

This story continues here: link

Crystalline Rot

When Marie Curie coined the term "radioactivity," a competing term--hyperphosphorescence--was thankfully never adopted. Hyperphosphorescence, while descriptively accurate--lacks simplicity.  Metamictization is another concept that needs a simpler term.

Crystals are highly ordered structures. The word "metamictization" refers to internal destruction, usually caused by radioactive uranium or thorium inclusions--their radiation destroys the crystal's integrity in a sort of rotting from within. "Stone cancer" might seem appropriate, but remember that cancer is unchecked growth.

"Crystalline rot" might work as a simpler term than metamictization because it conveys the notion of havoc wreaked from within--like an organized nation's structure.

The man-made sun on earth...

...was first preceded by a moment of darkness. Nuclear weapons were contrived invention, but the phenomena behind them are quite natural. The Sun is our main source of energy--directly or indirectly--and at first its light was thought necessary for radioactivity.

Henri Becquerel (1852-1908)

Henri Becquerel was fascinated by phosphorescent materials--materials which glowed in the dark after exposure to sunlight--including uranium salts. In 1896, he knew of Roentgen's discovery the previous year--the discovery of X-rays--and he wondered if phosphorescent uranium would give off penetrating rays after exposure to light.* Here he describes his eureka moment:

One wraps a Lumière photographic plate with a [Ag] bromide emulsion in two sheets of very thick black paper, such that the plate does not become clouded upon being exposed to the sun for a day. One places on the sheet of paper, on the outside, a slab of the phosphorescent substance, and one exposes the whole to the sun for several hours. When one then develops the photographic plate, one recognizes that the silhouette of the phosphorescent substance appears in black on the negative. If one places between the phosphorescent substance and the paper a piece of money or a metal screen pierced with a cut-out design, one sees the image of these objects appear on the negative...

The shadow of a small copper cross is visible

One must conclude from these experiments that the phosphorescent substance in question emits rays which pass through the opaque paper and reduce silver salts.

But further experiments led him to doubt the necessity of sunlight and to abandon this hypothesis. Later, he reported:

I will insist particularly upon the following fact, which seems to me quite important and beyond the phenomena which one could expect to observe: The same crystalline crusts [of potassium uranyl sulfate], arranged the same way with respect to the photographic plates, in the same conditions and through the same screens, but sheltered from the excitation of incident rays and kept in darkness, still produce the same photographic images.  March 2, 1896

Becquerel's students, Pierre and Marie Curie, went on to discover two new elements, radium and polonium. Marie Curie coined the term "radioactivity" to describe the elements' natural property of begetting penetrating rays.

[story continues]
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*Becquerel may have been aware of Niepce de Saint-Victor's near discovery of the same phenomenon a generation earlier. link

Blessed Are The Wealth Makers

Wallace Hume Carothers (1896-1937)

DuPont made a fortune selling things like gunpowder and nitrocellulose to warring governments (mainly to our own) up through and including the First World War. During the roaring 1920s (and flush with cash before the crash) they decided to pursue pure research into material science and established a new division at their fledgling Experimental Station located near Wilmington, Delaware.

The company hired a young PhD chemist named Wallace Carothers to start up a new group. Carothers was fascinated by long chain macromolecules ubiquitous in nature but which had only recently been recognized as "polymers." With the exception of Bakelite, the first synthetic plastic,* other synthetic polymers were unheard of, let alone commercially successful.

DuPont's research gamble paid off and Carothers and his group brought the company enormous success, first with the serendipitous discovery of neoprene, the first synthetic rubber, and then with nylon. Neoprene and nylon were tangible wealth creation: making things of value from what were, at the time, essentially waste products.

Nylon was Carothers' baby. Not only did he invent a synthetic replacement for silk, he purposefully developed a new method of making polymers called step-growth polymerization. He used the same durable type of linkages used by proteins (amide bonds), mimicking nature. Nylon was the first synthetic fabric and was commercialized around 1938, just in time to replace Asian silk which, along with natural rubber, went missing during the Second World War.

We have a lot to thank Carothers for but he didn't stick around. He checked out early, killing himself in 1937.
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* I have two items made from Bakelite: One is a late 1940's era Viewmaster device and the other is my father's old Kit-Cat clock which I described here. Both of these items have the characteristic fragility and tendency to chip common to Bakelite.