In 1903, a young physicist named Marie Curie submitted her doctoral thesis Recherches sur les substances radioactives— Research on Radioactive Substances—to the Faculty of Science at the University of Paris. This work, based on her meticulous and painstaking investigation of radioactive materials, would not only earn her a doctorate with distinction but also pave the way for one of the most remarkable scientific careers in history. Curie ’s thesis marks a seminal moment in the understanding of radioactivity and laid the foundation for modern nuclear physics and chemistry.
A Woman in Science at the Turn of the Century Marie Curie, born Maria Skłodowska in Warsaw, Poland, in 1867, arrived in Paris in 1891 to pursue higher education in a society and an era where women were severely underrepresented in the sciences. Overcoming gender and financial obstacles, she earned degrees in physics and mathematics from the University of Paris ( Sorbonne ). Her scientific path took a decisive turn when she began working with physicist Pierre Curie , who would become both her husband and collaborator.
By the time she began her doctoral research, Marie Curie was already captivated by the mysterious phenomenon of radiation—a term that had only recently entered scientific discourse following Henri Becquerel ’s 1896 discovery that uranium salts emitted invisible rays capable of exposing photographic plates.
The Thesis: Recherches sur les substances radioactives Curie’s thesis, Recherches sur les substances radioactives, was defended on June 25, 1903. It was among the first major works to establish the field of radioactivity as a legitimate and independent area of scientific study. The thesis is structured around systematic experimentation, rigorous observation, and quantitative analysis. Her primary objective was to understand the nature of “uranic rays” discovered by Becquerel and to determine whether this property was unique to uranium or shared by other elements.
In her introduction, Curie writes:
Her experiments revealed that thorium, like uranium, emitted rays capable of ionising air. This was a critical discovery that expanded the understanding of radioactivity beyond uranium.
But her most famous breakthrough came from studying the mineral pitchblende, a uranium-rich ore. Curie observed that the radiation emitted by pitchblende was significantly greater than what could be explained by its uranium content alone. This led her to hypothesise the existence of new, more intensely radioactive elements.
Through laborious chemical separation processes—often conducted under physically taxing conditions in an ill-equipped shed—Marie and Pierre Curie isolated two new elements: polonium (named after her native Poland) and radium. Both elements were far more radioactive than uranium, and their discovery would transform the periodic table and the broader scientific landscape.Also read: Why Marie Curie’s coffin lined with lead and still remains radioactive even after 100 years
Terminology and the birth of a new science Marie Curie coined the term “radioactivity” to describe the phenomenon whereby certain elements spontaneously emit radiation. This was not merely a linguistic contribution but a conceptual leap: it established a new category of physical behaviour that defied conventional chemical and physical understanding.
At the time, the prevailing atomic theory still conceived atoms as indivisible. Curie’s work—and the spontaneous emission of energy from supposedly stable atoms—suggested otherwise. Her thesis implicitly challenged existing theories of matter and opened the door to atomic models that would later be developed by Rutherford, Bohr , and others.
Impact and recognition Marie Curie’s thesis was received with great acclaim. The faculty awarded her the degree of Doctor of Science with the highest possible distinction. That same year, in recognition of her work, she was jointly awarded the 1903 Nobel Prize in Physics alongside Pierre Curie and Henri Becquerel. The Nobel Committee honoured her “in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena.”
This recognition was historic in more ways than one: Curie became the first woman to win a Nobel Prize. Later, in 1911, she would also become the first person to win two Nobel Prizes—this time in Chemistry, for her isolation of pure radium and further studies into its properties.
A Lasting scientific legacy Marie Curie’s doctoral thesis not only catalogued new radioactive elements but also introduced a framework for future research. Her emphasis on rigorous quantification, controlled experimentation, and theoretical modesty made her work a model of scientific excellence.
The discovery of radium and polonium had wide-ranging implications. Radium, in particular, found early application in medicine, notably in cancer treatment, and later in industrial products and consumer goods—though this would eventually lead to increased awareness of radiation hazards. Curie herself suffered the long-term effects of radiation exposure, and her notebooks are still stored in lead-lined boxes to this day.
Beyond the lab, Curie’s achievements inspired generations of scientists, especially women, who saw in her an example of intellectual brilliance and resilience. In a field long dominated by men, she stood alone at first—but never quietly.
Marie Curie’s Recherches sur les substances radioactives stands as one of the most influential doctoral theses in the history of science. With calm persistence and extraordinary intellect, she transformed a newly discovered curiosity—uranic rays—into the foundation of a new scientific discipline. Her work not only redefined our understanding of the atom but also helped usher in the atomic age.
PDF of Marie Curie’s doctoral thesis ‘Recherches sur les substances radioactives’
'Instant Scholar' is a Times of India initiative to make academic research accessible to a wider audience. If you are a Ph.D. scholar and would like to publish a summary of your research in this section, please share a summary and authorisation to publish it. For submission, and any question on this initiative, write to us at instantscholar@timesgroup.com
A Woman in Science at the Turn of the Century Marie Curie, born Maria Skłodowska in Warsaw, Poland, in 1867, arrived in Paris in 1891 to pursue higher education in a society and an era where women were severely underrepresented in the sciences. Overcoming gender and financial obstacles, she earned degrees in physics and mathematics from the University of Paris ( Sorbonne ). Her scientific path took a decisive turn when she began working with physicist Pierre Curie , who would become both her husband and collaborator.
By the time she began her doctoral research, Marie Curie was already captivated by the mysterious phenomenon of radiation—a term that had only recently entered scientific discourse following Henri Becquerel ’s 1896 discovery that uranium salts emitted invisible rays capable of exposing photographic plates.
- 'Instant Scholar' is a Times of India initiative to make academic research accessible to a wider audience. If you are a Ph.D. scholar and would like to publish a summary of your research in this section, please share a summary and authorisation to publish it. For submission, and any question on this initiative, write to us at instantscholar@timesgroup.com
The Thesis: Recherches sur les substances radioactives Curie’s thesis, Recherches sur les substances radioactives, was defended on June 25, 1903. It was among the first major works to establish the field of radioactivity as a legitimate and independent area of scientific study. The thesis is structured around systematic experimentation, rigorous observation, and quantitative analysis. Her primary objective was to understand the nature of “uranic rays” discovered by Becquerel and to determine whether this property was unique to uranium or shared by other elements.
In her introduction, Curie writes:
“I have taken up the study of this question and have made a detailed investigation of the substances emitting these rays, in the hope of discovering some new radioactive substances.”Key findings and methodology One of the most striking aspects of Curie’s research was her reliance on empirical measurement. Using a sensitive electrometer (originally developed by Pierre Curie), she measured the ionisation produced by uranium compounds and later by other elements and minerals. These measurements allowed her to quantify the intensity of radiation and establish a scale of comparison.
Her experiments revealed that thorium, like uranium, emitted rays capable of ionising air. This was a critical discovery that expanded the understanding of radioactivity beyond uranium.
But her most famous breakthrough came from studying the mineral pitchblende, a uranium-rich ore. Curie observed that the radiation emitted by pitchblende was significantly greater than what could be explained by its uranium content alone. This led her to hypothesise the existence of new, more intensely radioactive elements.
Through laborious chemical separation processes—often conducted under physically taxing conditions in an ill-equipped shed—Marie and Pierre Curie isolated two new elements: polonium (named after her native Poland) and radium. Both elements were far more radioactive than uranium, and their discovery would transform the periodic table and the broader scientific landscape.Also read: Why Marie Curie’s coffin lined with lead and still remains radioactive even after 100 years
Terminology and the birth of a new science Marie Curie coined the term “radioactivity” to describe the phenomenon whereby certain elements spontaneously emit radiation. This was not merely a linguistic contribution but a conceptual leap: it established a new category of physical behaviour that defied conventional chemical and physical understanding.
At the time, the prevailing atomic theory still conceived atoms as indivisible. Curie’s work—and the spontaneous emission of energy from supposedly stable atoms—suggested otherwise. Her thesis implicitly challenged existing theories of matter and opened the door to atomic models that would later be developed by Rutherford, Bohr , and others.
Impact and recognition Marie Curie’s thesis was received with great acclaim. The faculty awarded her the degree of Doctor of Science with the highest possible distinction. That same year, in recognition of her work, she was jointly awarded the 1903 Nobel Prize in Physics alongside Pierre Curie and Henri Becquerel. The Nobel Committee honoured her “in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena.”
This recognition was historic in more ways than one: Curie became the first woman to win a Nobel Prize. Later, in 1911, she would also become the first person to win two Nobel Prizes—this time in Chemistry, for her isolation of pure radium and further studies into its properties.
A Lasting scientific legacy Marie Curie’s doctoral thesis not only catalogued new radioactive elements but also introduced a framework for future research. Her emphasis on rigorous quantification, controlled experimentation, and theoretical modesty made her work a model of scientific excellence.
The discovery of radium and polonium had wide-ranging implications. Radium, in particular, found early application in medicine, notably in cancer treatment, and later in industrial products and consumer goods—though this would eventually lead to increased awareness of radiation hazards. Curie herself suffered the long-term effects of radiation exposure, and her notebooks are still stored in lead-lined boxes to this day.
Beyond the lab, Curie’s achievements inspired generations of scientists, especially women, who saw in her an example of intellectual brilliance and resilience. In a field long dominated by men, she stood alone at first—but never quietly.
Marie Curie’s Recherches sur les substances radioactives stands as one of the most influential doctoral theses in the history of science. With calm persistence and extraordinary intellect, she transformed a newly discovered curiosity—uranic rays—into the foundation of a new scientific discipline. Her work not only redefined our understanding of the atom but also helped usher in the atomic age.
PDF of Marie Curie’s doctoral thesis ‘Recherches sur les substances radioactives’
'Instant Scholar' is a Times of India initiative to make academic research accessible to a wider audience. If you are a Ph.D. scholar and would like to publish a summary of your research in this section, please share a summary and authorisation to publish it. For submission, and any question on this initiative, write to us at instantscholar@timesgroup.com
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