Tag Archives: women in science

Eunice Foote: the first person to measure the impact of carbon dioxide on climate

We often think of climate science as something that started only recently. The truth is that, like almost all fields of science, it started a long time ago. Advancing science is often a slow and tedious process, and climate science is not an exception. From the discovery of carbon dioxide until the most sophisticated climate models, it took a long time to get where we are.

Unfortunately, many scientists who played an important role in this climate journey are not given the credit they deserve. Take, for instance, Eunice Newton Foote.

Eunice Foote. Credits: Wikimedia Commons.

Foote was born in 1819 in Connecticut, USA. She spent her childhood in New York and later attended classes in the Troy Female Seminary, a higher education institution just for women.  She married Elish Foote in 1841, and the couple was active in the suffragist and abolitionist movements. They participated in the “Women’s Rights Convention” and signed the “Declaration of Sentiments” in 1848.

Eunice was also an inventor and an “amateur” scientist, a brave endeavor in a time when women were scarcely allowed to participate in science. However, one of her discoveries turned out to be instrumental in the field of climate science.

Why do we need jackets in the mountains?

In 1856, Eunice conducted an experiment to explain why low altitude air is warmer than in mountains. Back then, scientists were not sure about it, so she decided to test it. She published her results in the American Journal of Science and Arts.

“Circumstances affecting the heat of the Sun’s rays”. American Journal of Science and Arts. Credits: Wikimedia Commons.

Foote placed two cylinders under the Sun and later in the shade, each with a thermometer. She made sure the experiment would start with both cylinders with the same temperature. After three minutes, she measured the temperature in both situations. 

She noticed that rarefied air didn’t heat up as much as dense air, which explains the difference between mountaintops and valleys. Later, she compared the influence of moisture with the same apparatus. To make sure the other cylinder was dry enough, she added calcium chloride. The result was a much warmer cylinder with moist air in contrast to the dry one. This was the first step to explain the processes in the atmosphere, water vapor is one of the greenhouse gasses which sustain life on Earth.

But that wasn’t all. Foote went further and studied the effect of carbon dioxide. The gas had a high effect on heating the air. At the time, Eunice didn’t notice it, but with her measurements, the warming effect of water vapor made the temperatures 6% higher, while the carbon dioxide cylinder was 9% higher. 

Surprisingly, Eunice’s concluding paragraphs came with a simple deduction on how the atmosphere would respond to an increase in CO2. She predicted that adding more gas would lead to an increase in the temperature — which is pretty much what we know to be true now. In addition, she talked about the effect of carbon dioxide in the geological past, as scientists were already uncovering evidence that Earth’s climate was different back then.

We now know that during different geologic periods of the Earth, the climate was significantly warmer or colder. In fact, between the Permian and Triassic periods, the CO2 concentration was nearly 5 times higher than today’s, causing a 6ºC (10.8ºF) temperature increase.


Eunice Foote’s discovery made it to Scientific American in 1856, where it was presented by Joseph Henry in the Eighth Annual Meeting of the American Association for the Advancement of Science (AAAS). Henry also reported her findings in the New-York daily tribune but stated there were not significant. Her study was mentioned in two European reports, and her name was largely ignored for over 100 years — until it finally received credit for her observations in 2011

The credit for the discovery used to be given to John Tyndall, an Irish physicist. He published his findings in 1861 explaining how absorbed radiation (heat) was and which radiation it was – infrared. Tyndall was an “official” scientist, he had a doctorate, had recognition from previous work, everything necessary to be respected. 

But a few things draw the eye regarding Tyndall and Foote.

Atmospheric carbon dioxide concentrations and global annual average temperatures (in C) over the years 1880 to 2009. Credits: NOAA/NCDC

Dr Tyndall was part of the editorial team of a magazine that reprinted Foote’s work. It is possible he didn’t actually read the paper, or just ignored it because it was an American scientist (a common practice among European scientists back then), and or because of her gender. But it’s possible that he drew some inspiration from it as well — without quoting it.

It should be said that Tyndall’s work was more advanced and precise. He had better resources and he was close to the newest discoveries in physics that could support his hypothesis. But the question of why Foote’s work took so long to be credited is hard to answer without going into misogyny.

Today, whenever a finding is published, even if made with a low-budget apparatus, the scientist responsible for the next advance on the topic needs to cite their colleague. A good example happened to another important discovery involving another female scientist. Edwin Hubble used Henrietta Swan Leavitt’s discovery of the relationship between the brightness and period of cepheid variables. Her idea was part of the method to measure the galaxies’ velocities and distances that later proved the universe is expanding. Hubble said she deserved to share the Nobel Prize with him, unfortunately, she was already dead after the prize announcement.

It’s unfortunate that researchers like Foote don’t receive the recognition they deserve, but it’s encouraging that the scientific community is starting to finally recognize some of these pioneers. There’s plenty of work still left to be done.

Annie Jump Cannon: the legend behind stellar classification

It is striking that today, we can not only discover but even classify stars that are light-years from Earth — sometimes, even billions of light-years away. Stellar classification often uses the famous Hertzsprung–Russell diagram, which summarises the basics of stellar evolution. The luminosity and the temperature of stars can teach us a lot about their life journey, as they burn their fuel and change chemical composition.

We know that some stars are made up mostly of ionised helium or neutral helium, some are hotter than others, and we fit the Sun as a not so impressive star compared to the giants. Part of that development came from Annie Jump Cannon’s contribution during her long career as an astronomer. 

The Hertzsprung diagram where the evolution of sun-like stars is traced. Credits: ESO.

On the shoulders of giantesses

Cannon was born in 1863 in Dover, Delaware, US. When she was 17 years old, thanks to her father’s support, she managed to travel 369 miles all the way from her hometown to attend classes at Wellesley College. It’s no big deal for teens today, but back then, this was an imaginable adventure for a young lady. The institution offered education exclusively for women, an ideal environment to spark in Cannon an ambition to become a scientist. In 1884, she graduated and later in 1896 started her career at the Harvard Observatory.

In Wellesley, she had Sarah Whiting as her astronomy professor, who sparked Cannon’s interest in spectroscopy:

“… of all branches of physics and astronomy, she was most keen on the spectroscopic development. Even at her Observatory receptions, she always had the spectra of various elements on exhibition. So great was her interest in the subject that she infused into the mind of her pupil who is writing these lines, a desire to continue the investigation of spectra.”

Whiting’s obituary in 1927, Annie Cannon.

Cannon had an explorer spirit and travelled across Europe, publishing a photography book in 1893 called “In the footsteps of Columbus”. It is believed that during her years at Wellesley, after the trip, she got infected with scarlet fever. The disease infected her ears and she suffered severe hearing loss, but that didn’t put an end to her social or scientific activities. Annie Jump Cannon was known for not missing meetings and participating in all American Astronomical Society meetings during her career.


At Radcliffe College, she began working more with spectroscopy. Her first work with southern stars spectra was later published in 1901 in the Annals of the Harvard College Observatory. The director of the observatory, Edward C. Pickering chose Cannon as the responsible for observing stars which would later become the Henry Draper Catalogue, named after the first person to measure the spectra of a star. 

Annie Jump Cannon at her desk at the Harvard College Observatory. Image via Wiki Commons.

The job didn’t pay much. In fact, Harvard employed a number of women as “women computers” that processed astronomic data. The women computer at Harvard earned less than secretaries, and this enabled researchers to hire more women computers, as men would have need to be paid more.

Her salary was only 25 cents an hour, a small income for a difficult job to look at the tiny details from the spectrographs, often only possible with magnifying glasses. She was known for being focused (possibly also influenced by her deafness), but she was also known for doing the job fast. Simply put,

During her career, she managed to classify the spectra of 225,000 stars. At the time, Williamina Fleming, a Scottish astronomer, was the Harvard lady in charge of the women computers. She had previously observed 10,000 stars from Draper Catalogue and classified them from letters A to N. But Annie Jump Cannon saw the link between the stars’ temperature and rearranged Fleming’s classification to the OBAFGKM system. The OBAFGKM system divides the stars from the hottest to the coldest, and astronomers created a popular mnemonic for it: “Oh Be A Fine Guy/Girl Kiss Me”.


“A bibliography of Miss Cannon’s scientific work would be exceedingly long, but it would be far easier to compile one than to presume to say how great has been the influence of her researches in astronomy. For there is scarcely a living astronomer who can remember the time when Miss Cannon was not an authoritative figure. It is nearly impossible for us to imagine the astronomical world without her. Of late years she has been not only a vital, living person; she has been an institution. Already in our school days she was a legend. The scientific world has lost something besides a great scientist.”

Cecilia Payne-Gaposchkin in Annie Jump Cannon’s obituary.
Annie Jump Cannon at Harvard University. Smithsonian Institution @ Flickr Commons.

Annie Jump Cannon was awarded many prizes, she became honorary doctorate of Oxford University, the first woman to receive the Henry Draper Medal in 1931, and the first woman to become an officer of the American Astronomical Society. 

Her work in stellar classification was followed by Cecilia Payne-Gaposchkin, another dame of stellar spectroscopy. Payne improved the system with quantum mechanics and described what stars are made of

Very few scientists have such a competent and exemplary career as Cannon. Payne continued the work left from Cannon, her advisor, Henry Norris Russell, then improved it with minimum citation. From that, we got today’s basic understanding of stellar classification. Her beautiful legacy has been rescued recently by other female astronomers who know the importance of her life’s work.

Cecilia Payne would overcome the adversity that faced women in academia at the turn of the century to blaze a trail through physics and become one of the most important figures in astrophysics.

Who is Cecilia Payne-Gaposchkin: The Woman Who Knew The Stars

It’s almost staggering to think that before 1925 humanity knew very little about the composition of the stars. In fact, we would develop the theories of quantum mechanics, special and general relativity before we knew what lay beneath the surface of the Sun.

The first scientist to develop an accurate theory of the composition of the stars was Cecilia Payne-Gaposchkin. Born Cecilia Helena Payne in a small English market town in Buckinghamshire in 1900, in doing so she would also develop the first accurate picture of the abundance of the elements hydrogen and helium throughout the Universe.

But, these remarkable discoveries were not met with the appreciation one would expect. Payne-Gaposchkin would be discouraged from publishing her findings by a male contemporary. The setback would be just one more obstacle for Cecilia to overcome.

Cecilia Payne-Gaposchkin (1900-1979)

Facing the prejudice and misogyny that typified society in general, and science and academia in particular, during the early 20th Century, Payne-Gaposchkin would show a resolve that led to her becoming the world’s foremost expert on variable stars and enable her to lay the groundwork for astrophysics. 

Through sheer grit and determination, she would redefine our understanding of the composition of the stars and the Universe in general. Not bad for a scientist whose lectures weren’t even listed in her University’s course catalogue, who also had her wages by the same institute paid under ‘equipment costs.’

From Botany to Astronomy

The reward of the young scientist is the emotional thrill of being the first person in the history of the world to see something or to understand something. Nothing can compare with that experience.

Cecilia Payne-Gaposchkin

Things could have been very different for Cecilia Payne-Gaposchkin. Her interest in science first manifested as a fascination with the natural world and botany. A hint towards her future as an astronomer and astrophysicist shone through when Cecilia was just ten and she watched, transfixed, as a meteor traversed the night sky.

Payne’s interest in nature was encouraged by her mother, Emma Leonora Helena Payne, after her father Edward passed away when she was just four years old. The death of her father, who drowned in a canal under questionable circumstances, left young Cecilia devastated and her mother to raise the future astronomer and her two siblings alone.

Emma strongly encouraged the education of her three children, of which Cecilia was the eldest, introducing them to literature at an early age. Cecilia’s traits as a scientist would be further bolstered by her experience at her first school ran by Elizabeth Edwards which strongly encouraged the memorization of facts and figures.

Beyond this, Ms Edwards would actively teach her pupils, including the girls, geometry and algebra. Young Cecilia revelled in the solving of quadratic equations.

“My mother had told me of the Riviera-trapdoor spiders and mimosa and orchids, and I was dazzled by a flash of recognition. For the first time, I knew the leaping of the heart, the sudden enlightenment, that were to become my passion.”

At the age of twelve, Cecilia was forced to move schools when her family relocated from Wendover to London. Her new school, St Mary’s College, Paddington, could not have been less like Ms Edward’s. Like her female contemporaries, at the Church of England school with its strong emphasis on religion and ‘traditional values’ Cecilia would be offered little in the way of educational stimulation and even less encouragement to embark on a career in science.

In fact, it was here that a male teacher would confidently tell Payne-Gaposchkin she would never achieve a career in science. A prediction that may well go down in history as one of the worst ever made by an educator.

The Milky Way’s Trifid Nebula home to many Cepheid variable stars. Cecilia Payne-Gaposchkin would overcome adversity to become one of the foremost experts on such stars (ESO/VVV consortium/D. Minniti)

Fortunately, at the age of 17, Payne-Gaposchkin would be asked to transfer to St. Paul’s Girls School in London. Though the move initially troubled her, it is here where her teachers would allow Cecilia to study elements of physics such as mechanics, dynamics, electricity and magnetism, light, and thermodynamics.

At St. Pauls she was encouraged by her teachers to pursue science, enabling her to obtain a scholarship to Newnham College in 1919 where she would study the slightly odd but eclectic mix of botany, chemistry, and astronomy.

Attending the college, part of Cambridge University, Payne-Gaposchkin soon became bored with botany. Her tutors taught the subject stiffly and rigidly, relaying information she already knew, thus providing Cecilia with little stimulation. She recalled, in particular, an incident in which she discovered a group of desmids whilst studying algae under a microscope. Asking her tutor for help in identifying the organisms, he simply responded that it was not within the remit of her studies so she should just ignore it.

Her decision to switch to astronomy as her major was solidified when she attended a lecture given by Cambridge’s renowned astronomer Sir Arthur Eddington.

Eddington had found fame journeying to the island of Príncipe off the west coast of Africa to examine a solar eclipse that would provide verification for Einstein’s theory of general relativity. The lecture was on the same subject and for Payne, it ignited her desire to study nature beyond the surface of our planet.

Cecilia approached Eddington asking for a research project. He set her the problem of integrating the properties of a model star, starting from initial conditions at the centre and working outward. 

“The problem haunted me day and night. I recall a vivid dream that I was at the center of Betelgeuse, and that, as seen from there, the solution was perfectly plain; but it did not seem so in the light of day.”

Betelgeuse would come to occupy Cecila Payne-Gaposchkin’s thoughts thanks to a problem set by Eddington (ESO/DIGITIZED SKY SURVEY 2/DAVIDE DE MARTIN)

Disappointed at not being able to solve the problem she took her calculations to Eddington incomplete. She need not have worried. Eddington revealed to her with a jovial smile that he had not been able to solve the conumdrum either and had spent years trying!

Building the foundations of Astrophysics

Do not undertake a scientific career in quest of fame or money. There are easier and better ways to reach them. Undertake it only if nothing else will satisfy you; for nothing else is probably what you will receive. Your reward will be the widening of the horizon as you climb. And if you achieve that reward you will ask no other.

Cecilia Payne-Gaposchkin

Eddington was just taken with Payne-Gaposchkin as she was with astronomy, seeing great potential in the young woman. Unfortunately, transferring to the class of Ernest Rutherford, Cecilia discovered that not all of Eddington’s colleagues would be as supportive.

Rutherford, who would go onto perform experiments that would reveal the structure of the atom, was extremely cruel to Payne–the only woman in his class–encouraging the other, exclusively male, students to mock and taunt her, something they did with relish.

Payne-Gaposchkin weathered the storm. She had already experienced what it was like to exist in a male-dominated world and had already overcome too much to fold under mere mockery.

And the indignities would nor end there. Despite completing her coursework, women were forbidden to obtain degrees in the United Kingdom in 1923. Thus Payne-Gaposchkin would have no paperwork to verify her academic achievements. Her chances of obtaining a master’s degree or PhD in the UK were slim to none.

It was upon attending a meeting of the Royal Astronomical Society that Cecilia’s options improved markedly. Its new director Harlow Shipley regaled Payne-Gaposchkin with tales of the opportunities that would await her were she to relocate across the Atlantic to the United States.

Cecilia needed little further encouragement. She was awarded the Pickering Fellowship through Harvard College, taking the small financial aid offered by the only scholarship exclusively for women at the time and using it to move to America. Her association with Havard would continue for many years and prove to be extremely fruitful. Indeed, she would come to consider Boston her second home.

Whilst working under the auspices of Shapely at Harvard College Observatory she continued her studies, finalising what would go on to be her doctoral thesis–Stellar Atmospheres.

Cecilia Payne-Gaposchkin and two astronomers who would have a major influence on her early career. Eddington (centre) would inspire her to embark on the study of astronomy and Ruessell (right) would encourage her not to publish her most important discovery in her doctoral thesis.

In the work, Payne-Gaposchkin would be the first person to suggest that hydrogen was the most abundant element in the universe and the primary constituent of stars. At that time scientists had believed that the Sun and other stars had a chemical composition similar to that of the Earth’s crust. American physicist Henry Norris Russell has pioneered the idea that if earth’s temperature was raised to that of the Sun’s it would have a spectral signature the same as our star.

Payne-Gaposchkin’s finding bucked this idea and arose from the fact she had a much better understanding of atomic spectra than her contemporaries. Unfortunately, American Russell strongly disagreed with her conclusion and persuaded her to leave it out of her thesis.

Payne later reflected on her regret with regards to being persuaded not to publish her findings. It was not a mistake that Payne would never be convinced to make again.

“I was to blame for not having pressed my point. I had given in to Authority when I believed I was right. That is another example of How Not To Do Research. I note it here as a warning to the young. If you are sure of your facts, you should defend your position.”

For what it is worth, Russell too would go on to regret his decision to pressure Cecilia. Russell published a 1929 paper that credited Cecilia as Payne’s earlier work and her discoveries.

It must be one of the most heinous injustices in the history of astronomy that Russell is still to this day often wrongly credited with Payne-Gaposchkin’s discovery.

Russian-American astronomer Otto Struve later recognised the genius of Payne-Gaposchkin’s thesis, describing it as “the most brilliant PhD thesis ever written in astronomy.”

To The Stars and Beyond

The reward of the old scientist is the sense of having seen a vague sketch grow into a masterly landscape.

Cecilia Payne-Gaposchkin

In 1934 on a visit to Germany for an astronomy meeting Cecilia met a young  Russian astronomer, Sergei Gaposchkin. The astronomer was an exile from his country of birth due to his political convictions, and Cecilia found his struggles to be an echo of her own. She was determined to help Sergei find a secure and consistent place to practice science.

Indeed, obtaining Sergei a visa as a stateless person, Cecilia found him a research position at Harvard. To the surprise of their colleagues, the two were married in late 1934. Initial doubts that the marriage wouldn’t last were ill-founded.

Cecilia Payne-Gaposchkin and Sergei Gaposchkin would go on to have three children and remained married until her death in 1979. The two would also form a solid partnership in research, authoring several papers and books together. They even started their own farm–though it’s undeniable that Sergei enjoyed the life of a farmer much more than Cecilia did.

The discovery of the abundances of hydrogen and helium in the Universe and the composition of the stars would not be Payne-Gaposchkin’s only substantial contribution to astronomy and the burgeoning field of astrophysics.

The evolution of the light echo around V838 Monocerotis a variable star. Cecilia Payne was one of the prominant experts on this variety of star. (ESO)

Following the completion of her doctorate, Payne-Gaposchkin would begin to study high luminosity stars in order to understand the composition of the Milky Way. The period marked the beginning of Payne-Gaposchkin’s fascination with variable stars–stars which display periodic brightness fluctuations over radically different periods of time– and novae. This specialization led to the book Stars of High Luminosity, published in 1930.

Cecilia and Sergei undertook an audacious investigation of variable stars, during the ’30s and ’40s, they would make nearly 1.3 million observations of variable stars, with Payne-Gaposchkin’s mind for memorizing facts and figures making her almost a walking compendium of such objects. One of their papers published in 1938 would be the ‘go-to’ tome on variable stars for decades.

During the 1960s, Cecilia and Sergei would shift their attention to the small irregular galaxies situated by the Milky Way–the Magellanic Clouds–and the variable stars located within it. They would make another staggering contribution to astronomy during this study, cataloguing over 2 million visual estimates of these star’s magnitudes.

In 1956, Payne-Gaposchkin would finally be awarded the title of professor, making her the first woman in Harvard’s history to receive such an accolade. She would also be made the chair of a department at Harvard, also the first woman to be recognised in this way. Whilst no one could disagree that the accolade was insultingly well overdue, it was a small positive step in the right direction, finally opening the door for female professors across the US.

The Legacy of Cecilia Payne- Gaposchkin

Payne-Gaposchkin’s most dramatic scientific contribution was the discovery that hydrogen is millions of times more abundant than any other element in the universe. Every high school student knows that Newton discovered gravity, that Darwin discovered evolution, even that Einstein discovered relativity. But when it comes to the composition of our universe, the textbooks simply say that the most prevalent element in the universe is hydrogen. And no one ever wonders how we know…”

Jeremy Knowles, dean of the Harvard University’s Faculty of Arts and Sciences (2002)

Despite waiting so long to be named a professor, Payne-Gadoschkin’s life would not be short on accolades. In 1934, the American Astronomical Society recognized her significant contribution to astronomy by awarding her Annie J. Cannon Prize.

In 1936 she would become a member of the American Philosophical Society, and the 1940s and 1950s marked the award of several honorary doctorates, that should not be viewed as merely consolation prizes for the actual doctorate that she had strived for and had been denied her.

Continuing her trailblazing progress for women in the sciences, in 1976 she would become the first woman to receive the Henry Russell Prize from the American Astronomical Society. The astronomer, who would publish over 150 papers and several books during her career, would receive a further honour in 1977 when the astroid 1974 CA–occupying the asteroid belt between Jupiter and Mars–was renamed 2039 Payne-Gaposchkin.

Amongst the thousands of asteroids between Mars and Jupiter lies 2039 Payne-Gaposchkin a testament to the woman who discovered the composition of the stars.
(Emer O Boyle, Meadhbh O’Connor)

After her semi-retirement in 1966, Payne-Gaposchkin would continue to lecture inspiring the next generation of astronomers. Her final academic paper was published in 1977, just months before her death in December of that year.

During the course of her life, Cecilia Payne- Gaposchkin would change our understanding of the Universe in a way that was no less profound than her colleagues in physics did. Without doubt, her name, therefore, should be listed alongside luminaries such as Copernicus, Newton, and Einstein.

Yet, because of her gender, her genius was barely recognised during her lifetime and her name is still sadly omitted from many textbooks and is nowhere near as prominent as the names of her male counterparts or as her achievements demand.

It is abundantly clear, by becoming the first person to known the true composition of the universe, her star shines just as bright if not brighter as any other scientist. And without her, we still may not know why.

(c) Nature

New female scientist figurines introduced by LEGO

(c) LEGO

(c) LEGO

There’s a huge gender gap between men and women in science that can be tied to early segregation in childhood (boys with math, girls with humanities), continuing with bias against women pursuing science, either in the classroom, academia or industry later on in life. Efforts to close this gender gap are made, and progress, albeit slow by all accounts, seems promising. Efforts to close the gender gap in science shouldn’t be limited to classrooms and institutions, though – cultural awareness is equally important. Recently, LEGO announced it will soon introduce three new female scientist figurines, as part of the upcoming Minifigures Series 11 collection.

The three new figures, which represent women at a research institute include three scientists and their subsequent labs. The Astronomer looks out at the night sky through a LEGO telescope, the Paleontologist inspects a LEGO tyrannosaurus, and the Chemist mixes the contents of two LEGO Erlenmeyer flasks. Still, the LEGO mini-figurines are dominated by male representations, despite last year a female surgeon, a zookeeper and a scientist were introduced.


(c) LEGO

Science remains institutionally sexist. Despite some progress, women scientists are still paid less, promoted less frequently, win fewer grants and are more likely to leave research than similarly qualified men, according to Nature. In some countries like China and Portugal, gender inequality is less discrepant and at times in history it was actually almost 50-5o balanced. The graph below shows the gender gap in U.S. sciences closing in, from an extremely biased society in the 1970’s to a less biased, yet still imbalanced, society in present day.

(c) Nature

(c) Nature