A Notable Life In Quantum Physics

Chien-Shiung Wu was one of the pioneers of quantum mechanics and high energy physics, and was a female Chinese physicists in an era where women still made up only a tiny percentage of scientists in the field. 

If something remembers you with a speech like this, one hundred and ten years after you were born, when you have long passed away, then you did something right in life.

In 1950, Chien-Shiung Wu and her student published a coincidence experiment on entangled photon pairs that were created in electron-positron annihilation. This experiment precisely verified the prediction of quantum electrodynamics. 

Additionally, it was also the first instance of a precisely controlled quantum entangled state of spatially separated particles, although Wu did not know about this at the time. 

In 1956, Wu initiated and led the so-called Wu experiment, which discovered parity nonconservation, becoming one of the greatest experiments of the 20th century. 

As Chen Ning Yang said, Wu's experiments were well known for their precision and accuracy. Experimental precision and accuracy manifested Wu's scientific spirit, which we investigate here in some detail. 

Yu Shi, "Scientific Spirit of Chien-Shiung Wu: From Quantum Entanglement to Parity Nonconservation" arXiv:2504.16978 (May 31, 2022) (This paper is the translated transcript of the speech the author made at the International Symposium Commemorating the 110th Anniversary of the Birth of Chien-Shiung Wu, on May 31, 2022 in Chinese. The above abstract is the translation of the original abstract of the speech.)

She earned her undergraduate degree in physics (which had a thesis requirement at the time) in China in 1934, prior to the Maoist Revolution, and earned a PhD working under a professor only three years older than her who had studied under Madame Curie, and under the first female PhD in Physics in China, who earned that degree at the University of Michigan (where I also earned my graduate degree). Wu earned her PhD at the University of California at Berkley in 1940 (thirty years before my father earned his PhD at Stanford).

Wu was admitted by the University of Michigan to study at her own expense, and was financially supported by her uncle. On her way to Michigan, Wu visited Berkeley, where she was so impressed, especially by Ernest O. Lawrence’s cyclotron, that she wanted to stay in Berkeley. The cyclotron had been invented by Lawrence, so it was an ideal place for studying physics. Another important factor that influenced Wu’s decision was that she cared a lot about gender equality, and there was gender discrimination at the University of Michigan. In addition, there were a lot of Chinese students at the University of Michigan at the time, and Wu didn’t want her socializing be dominated by fellow Chinese students. So she stayed in Berkeley. Her decision reflected her devotion to physics as a woman.

She then taught at Smith (from which my sister-in-law graduated), and then Princeton, and then she worked at Columbia University as part of the Manhattan Project. 

She was highly productive (publishing more than fifty papers in the early 1950s when a huge share of U.S. women were homemakers in the Baby Boom), and her early post-war research agenda involved the verification of Fermi’s theory of β decay.

Chien-Shiung Wu served as the President of the American Physical Society from 1975 to 1976.

James W. Cronin, who won the 1980 Nobel Prize for his discovery of charge conjugation-parity (CP) nonconservation, once said, “The great discovery of Chien-Shiung Wu started the golden age of particle physics.” 

She continued to publish through at least 1980, and died in February of 1997. The author of the paper had met her.

The Hunger Stones And Their Antecedents

This is a notable genre of historically expression that I've only encountered once before, an an inscription from the arid period of ca. 2200 BCE in Mesopotamia that toppled the Akkadian Empire.* 

A lengthy drought in Europe has exposed carved boulders, known as "hunger stones," that have been used for centuries to commemorate historic droughts — and warn of their consequences. 

The Associated Press reports that hunger stones are newly visible in the Elbe River, which begins in the Czech Republic and flows through Germany. 

"Over a dozen of the hunger stones, chosen to record low water levels, can now be seen in and near the northern Czech town of Decin near the German border," the AP writes.

One of the stones on the banks of the Elbe is carved with the words "Wenn du mich siehst, dann weine": "If you see me, weep." 

A team of Czech researchers described that stone in detail in a 2013 paper about the history of droughts in Czech lands. 

The stone is also chiseled with "the years of hardship and the initials of authors lost to history," the researchers wrote:

"It expressed that drought had brought a bad harvest, lack of food, high prices and hunger for poor people. Before 1900, the following droughts are commemorated on the stone: 1417, 1616, 1707, 1746, 1790, 1800, 1811, 1830, 1842, 1868, 1892, and 1893." 

. . .

Tree-ring research in north-central Europe has found evidence of repeated "megadroughts" in the 15th through 19th centuries. 

And an article in Nature earlier this summer compared recent droughts in Europe to droughts over the last 250 years. The scientists found that the 21st century droughts were indeed extreme, but not as long-lasting or as massive as the worst of the historic ones. 

However, the same study noted that the more recent droughts are also linked to record-breaking temperatures. That appears to be causing "unprecedented drying trends" for the soil, which hurts crops. 

This trend "raises concerns about the consequences of extreme meteorological droughts" as the climate continues to warm, the researchers note. 

The drought in northern and central Europe this year is "one of the most intense regional droughts in recent memory," The Guardian wrote in July, and it is paired with abnormally hot temperatures.

From National Public Radio.

The drought of 1790 coincides with the French Revolution. The last several coincide with considerable surges in migration to New World.

* These inscriptions are known as the Curse of Akkad:

For the first time since cities were built and founded, 

The great agricultural tracts produced no grain, 

The inundated tracts produced no fish, 

The irrigated orchards produced neither syrup nor wine, 

The gathered clouds did not rain, the masgurum did not grow. 

At that time, one shekel's worth of oil was only one-half quart, 

One shekel's worth of grain was only one-half quart. . . . 

These sold at such prices in the markets of all the cities! 

He who slept on the roof, died on the roof, 

He who slept in the house, had no burial, 

People were flailing at themselves from hunger.

A more complete version can be found here.

The same drought may also have been responsible for the demise of the Sarasvati River and collapse of Harappan civilization the opened the door for Indo-Europeans to advance into South Asia. The Old Kingdom in Egypt (2686 BCE – 2181 BCE) collapsed around the same time, giving rise to the First Intermediate Period in which the Egyptian empire collapsed into two kingdoms, each with declining central authority after having been united in one, that ended around 2080 BCE. And, this drought may have weakened the states in Anatolia, allowing the first Hittite city-state to establish itself there.

It may even had led to the demise of a civilization in China: "The drought may have caused the collapse of Neolithic Cultures around Central China during the late 3rd millennium BCE. At the same time, the middle reaches of the Yellow River saw a series of extraordinary floods related to the legendary figure of Yu the Great. In the Yishu River Basin, the flourishing Longshan culture was affected by a cooling that severely reduced rice output. This led to substantial decrease in population and fewer archaeological sites. In about 2000 BCE, Longshan was displaced by the Yueshi culture, which had fewer and less sophisticated artifacts of ceramic and bronze."

This drought may be responsible for the prohibitions on pig eating that survive today in Jewish Kosher rules and Islamic halal dietary restrictions according to William J. Burroughs, "Climate Change in Prehistory: The End of the Age of Chaos" (2005). 

A volcanic eruption is one possible explanation for this drought also known as the 4.2 kiloyear climate event, although a 2013 paper fingered an asteroid impact. The 4.2-kiloyear BP aridification event was one of the most severe climatic events of the Holocene period. It defines the beginning of the current Meghalayan age in the Holocene epoch.