We all
know the role of Johannes Kepler in the revolution of astronomy. The
theoretical explanation of the motion of all planets and celestial bodies in
space comes from Kepler’s three laws. But it was the astronomer Maria Cunitz
who played a pioneering role in making Kepler’s theory more precise and easier
to understand. Maria Cunitz was an extraordinary, yet often underestimated,
figure of the astronomical revolution and a contemporary of Johannes Kepler.
Astronomy
began with an Earth-centred view of the universe. In the second century, Claudius
Ptolemy proposed that everything in the universe revolved around the Earth.
For nearly fourteen hundred years, Ptolemy’s theory dominated, and all
observational research in this field was conducted within the framework of his
geocentric model.
But in
1543, after the publication of Nicolaus Copernicus’s theory, Ptolemy’s
model was shaken. After many struggles and controversies, Copernicus’s
heliocentric astronomy was eventually established. We came to understand that
the Earth rotates once on its axis every twenty-four hours—causing day and
night—and revolves around the Sun once a year, resulting in the change of
seasons. The other planets of the solar system also revolve continuously around
the Sun in their respective orbits at definite speeds.
Naturally,
the question then arose—how do they revolve? What are the theoretical laws
governing the motion of the planets and stars?
Through
continuous observation of the planets, the German scientist Johannes Kepler
formulated three revolutionary laws concerning the orbits of the planets, their
motion within those orbits, and their total periods of revolution. He published
the first two laws in 1609 and the third law in 1619.
Kepler’s
First Law:
According to the law of elliptical orbits, every planet revolves around the Sun
in an elliptical path, with the Sun at the centre. We know that a circle has
only one centre, but an ellipse has two centres, called foci. The Sun is
located at one of these two foci, and the planets move around it in elliptical
paths.
The
shorter the distance between the two foci, the more the ellipse resembles a
circle. When the distance between the two foci becomes zero, they merge into a
single point—this point becomes the centre of a circular path, and the ellipse
becomes a perfect circle. At that time, the eccentricity of the ellipse is at
its minimum (zero). Conversely, as the distance between the two foci increases,
the ellipse becomes more flattened, and its eccentricity increases.
Among the
planets, Mercury has the most elongated (flattened) orbit; therefore, it has
the greatest eccentricity. As a result, Mercury sometimes comes very close to
the Sun and at other times moves far away from it. The point at which a planet
is closest to the Sun is called perihelion, and the point at which it is
farthest from the Sun is called aphelion. This law of orbits is applied
when determining the paths of modern satellites.
Kepler’s
Second Law:
According to the law of equal areas, if a straight line is drawn between the
Sun and a planet, that line sweeps out equal areas in equal intervals of time
as the planet moves along its orbit.
In the
diagram, Area-1 = Area-2. Therefore, the time required to move from P1 to P2 is
equal to the time required to move from P3 to P4. However, the distance from P1
to P2 is greater than the distance from P3 to P4. So, to travel from P1 to P2,
the planet must move faster than it does from P3 to P4.
Thus, a
planet’s speed is not the same at all points in its orbit. When a planet comes
closer to the Sun, it moves faster; and when it moves farther away from the
Sun, it moves more slowly.
Kepler’s
Third Law:
According to the law of periods, the closer a planet is to the Sun, the faster
it moves in its orbit. The square of a planet’s orbital period (T²) is
proportional to the cube of its average distance (R³) from the Sun.
Here it
should be remembered that the unit of the orbital period must be years,
and the unit of the average distance of a planet from the Sun must be the astronomical
unit (AU). The distance from the Earth to the Sun is taken as one
astronomical unit. The Earth–Sun distance is about 150 million kilometres.
Therefore,
1 AU =
150,000,000 km.
Based on
the laws governing the motion of planets and stars, Johannes Kepler
published a set of tables to help scientists accurately determine the positions
of celestial bodies in space. In honor of Emperor Rudolf II (then King
of Hungary and Bohemia), who had patronized astronomical research, Kepler named
these tables the Rudolphine Tables.
Although
the tables were published in 1627, they were extremely difficult to understand.
However, the self-taught astronomer Maria Cunitz recognized their
importance and far-reaching usefulness. Over the next twenty-three years, she
worked on Kepler’s theories and tables, corrected their errors, and transformed
them into a clearer and more user-friendly form.
In 1650,
her important book Urania Propitia was published—a work that came to be
recognized as the first accurate and reliable book in astronomy.
Maria
Cunitz was born around 1610 in Silesia of the Holy Roman Empire, a region that
today lies between Poland and the Czech Republic. Her father, Heinrich Cunitz,
was a physician. At that time, formal education for women was still prohibited
in Europe. However, seeing Maria’s enthusiasm for learning, her father
encouraged her to study mathematics, science, philosophy, and various
languages.
Gradually,
Maria read nearly all the scientific books available at the time—especially
those on astronomy. Latin was the formal language of science then; important
scientific papers were written in Latin, which she mastered. In addition, to
follow scientific research published in other languages, she learned Greek,
German, Polish, Italian, and Hebrew. Her fluency in multiple languages,
combined with strong mathematical skills, gave her access to the most complex
scientific knowledge. She created this opportunity for herself.
Maria
Cunitz absorbed everything related to the research of Johannes Kepler. Although
Kepler’s Rudolphine Tables were filled with extremely complex mathematical
calculations, she had no difficulty understanding them. When the tables were
published in 1627, Europe was engulfed in war. From 1618 to 1648, the Thirty
Years’ War raged across Europe between Catholics and Protestants, bringing
insecurity and instability to everyday life.
Amid this
turmoil, Maria continued her studies and research. In 1629, she married Elias
von Löwen, a learned physician and amateur astronomer. He became her principal
supporter. Since women were barred from formal education and research
institutions, Maria received no institutional assistance. Undeterred, she began
re-examining all the data in Kepler’s tables from her home.
Maria
discovered several errors in Kepler’s logarithmic calculations. Moreover, his
methods for determining planetary positions over time were extremely complex.
She began correcting these errors and simplifying the methodology. There were
inconsistencies in Kepler’s calculations of perihelion and aphelion, which she
corrected. She replaced the highly difficult logarithmic procedures with more
straightforward arithmetic methods and improved tables. As a result, not only
professional astronomers but also amateur astronomers could determine planetary
positions more easily. Even the preparation of astronomical almanacs (used by
astrologers) became more feasible through her work.
After more
than a decade of research, she completed the manuscript of her book by 1645.
However, due to the war, it was published five years later. In 1650, she
released her book Urania Propitia.
Until
then, science had largely remained inaccessible to the general public because
it was written in Latin. Maria sought to change this. Following convention, she
wrote her book in Latin for scholars, but she also wrote it in German for
ordinary readers. Gradually, alongside Latin, German became an important
language of science in Europe.
In Maria
Cunitz’s time, women were not only barred from formal education but were also
denied recognition for their achievements. Her husband, Elias von Löwen,
understood this reality. When no publisher agreed to print Urania Propitia,
he arranged its publication himself and wrote a preface clearly stating that
the entire work was Maria’s own research—because many people at the time
assumed that any intellectual work attributed to a woman must actually have
been done by a man.
With just
one research book, Maria Cunitz achieved lasting recognition in astronomy. For
several centuries, astronomers followed her tables and methods. In recognition
of her contributions, a minor planet—12624 Mariacunitia—was named after her,
and a crater on Mercury also bears her name.
Maria was
an ideal seeker of knowledge. She never demanded recognition nor engaged in
self-promotion. She devoted her time and dedication entirely to the pursuit of
knowledge. She died in 1664.
For many
years, her contributions to astronomy were largely forgotten. As barriers to
women’s formal education gradually diminished and women’s participation in
scientific research increased in the twentieth century, the history of science
began to be re-examined. In that reassessment, the overlooked scientists of
earlier centuries have regained recognition. Today, we can better appreciate
Maria Cunitz’s contribution—she made Kepler’s theories practically usable and
accessible.
References
- Astronomy & Geophysics:
The Journal of the Royal Astronomical Society, August 2024, Vol. 65 (4),
pp. 4–4.26.
- Anna Reser and Leila McNeill, Forces
of Nature, Frances Lincoln Publishing, London, 2021.
- Magdolna Hargittai, Meeting
the Challenge: Top Women in Science, Oxford University Press, 2023.
