2018’s Top 10 science anniversaries

With each new year, science offers a fresh list of historical occasions ideally suited for a Top 10 list.

Science’s rich history guarantees a never-ending supply of noteworthy anniversaries. Centennials of births, deaths or discoveries by prominent scientists (or popular centennial fractions or multiples) offer reminders of past achievements and context for appreciating science of the present day. To keep the holiday spirit pleasant, we’ll omit the plagues and natural disasters (so no mention of the centennial of the Spanish flu pandemic or the tricentennial of the Gansu earthquake in the Qing Empire). But that leaves plenty of math, medicine, astronomy and quantum stuff. Such as:

10. Quantum teleportation (25th anniversary)

At a physics meeting in Seattle in March 1993, Charles Bennett of IBM thrilled science fiction fans everywhere by revealing the theory of quantum teleportation. (A few days later, a paper by Bennett and his teleportation collaborators appeared in Physical Review Letters.) Bennett described how quantum experimentalists Alice and Bob could use quantum entanglement to erase the identity of a quantum particle at one location and restore it at a remote location — just like Captain Kirk disappearing in the Enterprise transporter and reappearing on some dangerous alien planet. It’s not magic, though. Alice and Bob must each possess one of a pair of entangled quantum particles. If Alice wants to teleport a quantum particle to Bob, she must let it interact with her entangled particle and send the result to Bob by e-mail (or text, or phone call, or snail mail). That interaction destroys Alice’s copy of the particle to be teleported, but Bob can reconstruct it using his entangled particle after Alice e-mails him. In 1993, it was just an idea, but a few years later it was successfully demonstrated in the lab.

9. Arnold Sommerfeld (150th birthday)

Born in Königsberg, Prussia, (now part of Russia) on December 5, 1868, Arnold Sommerfeld played a major role in advancing early quantum theory in the years after Niels Bohr introduced the quantum version of the hydrogen atom. Sommerfeld showed how to extend quantum ideas from circular to elliptical electron orbits, making him kind of like a Kepler to Bohr’s Copernicus. Earlier Sommerfeld had been one of the first strong supporters of Einstein’s special theory of relativity. Sommerfeld also mentored an all-star cast of 20th century physicists, his students including Wolfgang Pauli, Werner Heisenberg and Hans Bethe.

8. Jean Fourier (250th birthday)

Jean Baptiste Joseph Fourier, born March 21, 1768, survived multiple arrests during the French Revolution and ended up working for Napoleon, who made him a baron. With Napoleon’s demise, Fourier struggled to regain political favor and acceptance in the academic world, and eventually succeeded, but his political and diplomatic embroilments consumed much of his time when he should have been doing math. Nevertheless he did important work on the mathematics of heat diffusion and developed useful techniques for solving equations. His most famous achievement, Fourier’s theorem, allows complex periodic processes to be broken down into a series of simpler wave motions. It has wide application in many realms of physics and engineering.

7. James Joule (200th birthday)

James Joule was born into a family of brewers on December 24, 1818. The brewery provided a laboratory where he developed exceptional experimental skills. Despite no formal scientific training and no academic job, he still became one of England’s leading scientists. His experimental skill led him to precisely establish the amount of work needed to produce a quantity of heat and the relationship between heat and electricity.

Most famously, he demonstrated the law of conservation of energy. Whether mechanical, electrical or chemical, energy’s quantitative relationship to heat remained the same, regardless of the substances used in conducting the measurements, Joule showed. In other words, energy is conserved — a truth now known as the First Law of Thermodynamics. There were no Nobel Prizes in those days, so Joule’s main reward was the designation of the standard unit of energy as the joule.

6. Henrietta Swan Leavitt (150th birthday)

Born in Massachusetts on July 4, 1868, Henrietta Swan Leavitt attended Oberlin College in Ohio and then Radcliffe College, where she studied astronomy. Her excellent academic record impressed Edward Pickering, the director of the Harvard Observatory, where she volunteered to be a research assistant and soon earned a permanent job. She worked on mapping stars with the latest photographic and spectroscopic methods, eventually measuring the brightnesses of thousands of stars. Some of those stars varied in brightness over time (one of them, Delta Cephei, gave such stars the name Cepheid variables). Leavitt analyzed these Cepheids more thoroughly than her predecessors and noticed that the stars’ brightness varied on a regular schedule that depended on their intrinsic brightness. Leavitt worked out the “period-luminosity relationship” in 1908, giving astronomers a powerful tool for measuring the distance to stars and other astronomical objects.

Distance to a Cepheid nearby could be determined by parallax, enabling the determination of its intrinsic brightness based on its brightening-dimming schedule. Then, using nearby Cepheids’ intrinsic brightness, the bright-dim period for a more distant Cepheid could be used to infer its intrinsic brightness. That made it possible to calculate the star’s distance. Leavitt’s work made much of the 20th century’s dramatic revision of humankind’s conception of the cosmos possible. “Her discovery of the period-luminosity relationship in Cepheid variable stars is absolutely fundamental in transforming people’s ideas about first, our own galactic system and second, providing the means to demonstrate that galaxies do in fact exist,” historian Robert Smith said in a talk last January.

5. Spontaneous Generation, Not (350th anniversary)

Casual observations of nature had led the ancients to believe that life sometimes spontaneously generated itself from decaying organic matter — think maggots appearing in rotten meat. Francesco Redi, an expert on the effects of snake venom, thought otherwise. Born in Italy, educated at the University of Pisa and then medical school in Florence, Redi conducted various experiments on the effects of snakebites, realizing that the danger stemmed from venom entering the bloodstream. In his masterwork Experiments on the Generation of Insects, published in 1668, he described clever experiments that showed maggots could appear only if flies had access to the meat to lay their eggs. He didn’t close the case on all claims of spontaneous generation, but his work was a major first step toward eliminating received dogma in biology and replacing it with experiment and reason.

4. Discovery of helium (150th anniversary)

On August 18, 1868, French astronomer Jules Janssen witnessed a total eclipse of the sun in Guntur, India, and recorded the colors in the spectrum of solar prominences. He realized that he could record the colors even without an eclipse, and in the following days he observed a curious bright yellow line. He wrote a paper and sent it off to the French Academy of Sciences. Later that year, English astronomer Joseph Lockyer observed the same spectral line, wrote a paper and also sent it to the French Academy of Sciences. Legend (apparently true) has it that the papers arrived within minutes of each other, so Janssen and Lockyer shared in the discovery of the yellow line, whatever it was.

Lockyer soon argued that it was the signature of a new chemical element, unknown on Earth. He called it helium, for Helios, the Greek god of the sun. Some experts doubted that the line signified a new element or insisted that such an element must exist only on the sun and would never have any usefulness on Earth. But their balloon burst in 1895 when William Ramsay in London found helium gas within a uranium-containing mineral. (Others working in Sweden found the gas at about the same time.) Uranium emits alpha particles, the nuclei of helium atoms, so all those alpha particles need to do is find some stray electrons buzzing around to become helium atoms. But nobody understood that at the time because radioactivity hadn’t been discovered yet.

3. Ignaz Semmelweis (200th birthday)

Born on July 1, 1818, in Hungary, Ignaz Semmelweis almost single-handedly (or maybe dual-handedly) showed how to bring public health out of the dark ages and into modernity by identifying the importance of washing your hands. After attending medical school in Vienna, he practiced midwifery for a while and then studied surgery and statistics. He then joined the staff at a teaching hospital, where he noticed a large (statistically suspicious) difference between two clinics in deaths of mothers or their babies from puerperal fever. He eventually realized that in one of the clinics doctors conducted autopsies and apparently carried cadaver contamination to the birthing room. Semmelweis concocted a solution for cleansing hands after autopsies; the puerperal fever death rate then dropped dramatically. But his insight was widely resisted by the medical establishment. It was only much later, after Louis Pasteur established the importance of germs in transmitting disease, that Semmelweis’ method could be successfully explained and then adopted.

2. Richard Feynman (100th birthday)

One of the most nonconformist of theoretical physicists, Richard Feynman (born May 11, 1918) gained public notoriety late in life as a member of the Presidential Commission investigating the space shuttle Challenger explosion. He was also skilled at playing bongo drums. Among physicists, he was most highly regarded for his original approach to quantum mechanics and formulation of quantum field theory (work earning a share of the 1965 Nobel Prize in physics). Later he was an early leading advocate of research into quantum computing. Hans Bethe, another physics Nobel laureate, considered Feynman to be a most unusual kind of genius. “He was a magician,” Bethe once said. “Feynman certainly was the most original physicist I have seen in my life.”

1. Noether’s theorem (centennial)

On any list of history’s great mathematicians who were ignored or underappreciated simply because they were women, you’ll find the name of Emmy Noether. Despite the barricades erected by 19th century antediluvian attitudes, she managed to establish herself as one of Germany’s premier mathematicians. She made significant contributions to various math specialties, including advanced forms of algebra. And in 1918, she published a theorem that provided the foundation for 20th century physicists’ understanding of reality. She showed that symmetries in nature implied the conservation laws that physicists had discovered without really understanding.

Joule’s conservation of energy, it turns out, is a requirement of time symmetry — the fact that no point in time differs from any other. Similarly, conservation of momentum is required if space is symmetric, that is, moving to a different point in space changes nothing about anything else. And if all directions in space are similarly equivalent — rotational symmetry — then the law of conservation of angular momentum is assured and figure skating remains a legitimate Olympic sport. Decades after she died in 1935, physicists are still attempting to exploit Noether’s insight to gain a deeper understanding of the symmetries underlying the laws of the cosmos. On any decent list of history’s great mathematicians, regardless of sex or anything else, you’ll find the name of Emmy Noether.

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