The French post office, La Poste, released a stamp featuring Ada Lovelace on Ada Lovelace Day. The stamp costs €1.65 and is for use on priority international letters. A full sheet comprises 15 stamps.

La Poste’s page says (translation thanks to Google):

Ada Lovelace 1815-1852

“The Analytical Engine will weave algebraic patterns as Jacquard looms weave flowers and leaves.” – Ada Lovelace, Note A, 1843

Ada King, née Byron, Countess Lovelace, was born on December 10, 1815 in London. At a very young age, she began to study mathematics. It rises to a sufficient level to appreciate the work of a talented inventor, Charles Babbage. He has just developed an automatic calculator. Ada bends over these complex cogs and an intuition comes to her: what if, instead of handling only numbers, this machine also deals with symbols? She puts her intuition to work: it will be the famous “Note G”, published in 1843, the first computer program in the world. Ada will never know she was awesome. She died at age 36, on November 27, 1852.

Almost a century later, an American physicist named Howard Aiken makes a machine from Babbage’s gears and Ada Lovelace’s notes: the Mark I. This one will have many descendants: computers. In 1978, the new computer language of the US Department of Defense was called Ada. Ada Lovelace finally ceases to be a footnote in her father’s biographies. Ada ardently defended the idea of ​​“poetic science”. Fusing science and poetry within the same vision, she dreamed of a machine that would be able to speak previously unknown languages. She imagined IT, she pulled it out of nothing at a time when our modernity was barely waking up. His work, a fragile flower blooming within the mists of romanticism, rose like a sun over the second half of the 20th century and illuminates the third millennium. By shaping our future, Ada Lovelace marked our civilization as much as Pasteur, Einstein or Fleming. – Catherine Dufour

The stamp is issued on “Ada Lovelace day” Every year, on the 2nd Tuesday of October, this event celebrates innovative women in computing.

Here are just some of the Twitter highlights from this year’s Ada Lovelace Day:

Dr Elizabeth Rona

Dr Elizabeth Rona was a nuclear chemist who became an internationally renowned expert on isotope separation and polonium preparation. She also confirmed the existence of “Uranium-Y”, known as thorium 231.

Rona was born in 1890 in Budapest. She studied chemistry, geochemistry, and physics at the Philosophy Faculty at the University of Budapest, earning her PhD in 1912. After graduation she worked at the Kaiser Wilhelm Institute, Karlsruhe University and then University College London before returning to Budapest when World War I started.

She joined Budapest’s Chemical Institute, working on the diffusion of radon in water before being asked to investigate a new element known as Uranium-Y, ie thorium 231, which she successfully separated from other elements. She confirmed that it emitted beta radiation and had a half-life of 25 hours. Her work formed the basis of later mass spectrography and heavy water studies.

She worked with chemist George von Hevesy, using radioactive elements as tracers so that they could more easily study chemical reactions. They studied the diffusion of radioactive tracers through different materials, gathering the data required to calculate an atom’s size. Von Hevesy eventually won the Nobel Prize for his work on tracers, and they are now used to help diagnose cancer, heart disease and other conditions.

She became the first woman to teach chemistry at a university level in Hungary, but the communist invasion of Hungary and the subsequent anti-communist White Terror made life and work there untenable. She moved to the Kaiser Wilhelm Institute to work with Otto Hahn on separating ionium (now thorium 230) from uranium until she was transferred to a more practical role in the Textile Fibre Institute. She returned to Hungary in 1923, to work in a textile factory, but disliked the work and left to join the Institute for Radium Research of Vienna in 1924.

Rona learnt how to separate polonium from Irène Joliot-Curie in Paris, returning to the Radium Institute as a well-respected expert whose skills were much in demand. She worked with several collaborators, and her work with Berta Karlik on the half-lives of uranium, thorium and actinium decay, radiometric dating, and alpha particles won them both the Austrian Academy of Sciences Haitinger Prize in 1933. She returned to Paris to work with Joliot-Curie, who died not long after. Rona herself became ill, but later went to Vienna to share what she’d learnt with a group of other researchers who were working on a wide variety of research projects.

She spent some of World War II working in Sweden and Norway, but returned to Budapest to work at the Radium-Cancer Hospital where she prepared radium for medical use.

In 1941, however, she fled to the USA, eventually finding a teaching job at Trinity College in Washington, DC before being awarded a Carnegie Fellowship, and she began studying radium seawater and sediments at the Geophysical Laboratory of the Carnegie Institute. She assisted the Manhattan Project, giving them her method for extracting polonium.

She continued her work after the war, at the United States Atomic Energy Commission and then the Oak Ridge Institute of Nuclear Studies, where she worked as a chemist and senior scientist in nuclear studies. She discovered that uranium levels in seawater are globally constant, but that thorium collects in sediments, so the decay of uranium to thorium can be used to date core samples. This method of dating is still used today.

She continued working despite two retirements, first from Oak Ridge and then from the University of Miami, returning to Tennessee in the 1970s.

Rona became aware of the dangers of radium early in her career, but her warnings of the dangers and requests for protective equipment such as gas masks were ignored and she had to supply her own. She managed to avoid radiation exposure, however, and survived at least two lab explosions.

She died in 1981, aged 91.

Further Reading

• Elizabeth Rona, Wikipedia
• Overlooked No More: Elizabeth Rona, Pioneering Scientist Amid Dangers of War, Veronique Greenwood, The New York Times, 28 August 2019
• Elizabeth Rona, the wandering polonium woman, changed radiation science forever, Brittney G. Borowiec, Massive Science, 29 December 2019

Inge Lehmann

Inge Lehmann was a seismologist and geophysicist who discovered that the Earth has a solid inner core and a molten outer core.

Born in Copenhagen in 1888, in 1907 she began studying mathematics, chemistry and physics at the University of Copenhagen and University of Cambridge, but had to take a break due to ill-health. She resumed her study of mathematics at Cambridge in 1910, before exhaustion enforced another break, eventually restarting her education at Copenhagen University in 1918, graduating in 1920.

Her interest in seismology began when she got a job as an assistant to Niels Erik Nørlund, a geodesist. She was tasked with setting up seismological observatories in Denmark and Greenland, which prompted her to study seismology. She earnt her magister scientiarum, equivalent to a master’s degree, in geodesy in 1928 and took a position as a geodesist and head of the department of seismology at the Geodetical Institute of Denmark. She was responsible for analysing the seismograph data, recording the seismic wave arrival times ready for publication in international bulletins. This data was fundamental to much of the era’s seismological research.

In 1936, she found evidence of P-waves appearing in the shadow of the Earth’s core, which she interpreted as showing that there was an inner core. At the time, it was thought that the Earth’s core was liquid, but an earthquake in New Zealand resulted in P-waves arriving at seismic stations that should have been blocked by this liquid core. Lehmann’s theory was that these P-waves had been refracted by some sort of boundary, which had to mean that there was a solid inner core and a liquid outer core.

Although this interpretation was adopted within a few years, it was not shown to be correct until 1971 when computer calculations using data from more sensitive seismographs could verify her work. Lehmann had to do all of her data collection and calculations by hand, creating boxes of cards, each with data from earthquakes around the world.

Although her work was interrupted by World War II, she served as Chair of the Danish Geophysical Society in both 1940 and 1944.

In the early 1950s, she moved to the US and began investigating the Earth’s crust and upper mantle. A decade later, she discovered a seismic discontinuity, where seismic waves change speeds, at between 190 and 250 km which is now known as the Lehmann Discontinuity. This discovery was made through “exacting scrutiny of seismic records by a master of a black art for which no amount of computerization is likely to be a complete substitute”, as geophysicist Francis Birch put it.

Lehmann received many awards over the years. She was elected as a Fellow of the Royal Society in 1969, was the first woman to win the William Bowie Medal in 1971, and was awarded the Medal of the Seismological Society of America in 1977. The American Geophysical Union began awarding the Inge Lehmann Medal to honour “outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth’s mantle and core” in 1997. In 2015, the asteroid 5632 Ingelehmann was named after her, as was a new beetle species, Globicornis (Hadrotoma) ingelehmannae.

She died in 1993, aged 104.

Further Reading

• Inge Lehmann, Wikipedia
• Inge Lehmann: Discoverer of the Earth’s Inner Core, American Museum of Natural History
• Inge Lehmann, Meg Rosenburg, Trowelblazers, 16 October 2014
• How Inge Lehmann used earthquakes to discover the Earth’s inner core, Joseph Stromberg, Vox, 13 May 2015
• What Google’s doodle about Inge Lehmann is all about, Nick Statt, CNET, 13 May 2015
• Happy Birthday to Inge Lehmann, the Woman Who Discovered Earth’s Inner Core, Danny Lewis, Smithsonian Magazine, 13 May 2015
• The female scientist who discovered the core of the Earth, Lif Lund Jacobsen, Science Nordic, 15 May 2017
• Inge Lehmann: the Danish scientist who discovered Earth has a solid inner core, Brian Clegg, BBC Science Focus, 29 May 2020
• Inge Lehmann: Danish seismologist rocks Google’s earth, The Guardian, 13 May 2015