How do you find meaning in the universe?
Peter Apian was a sixteenth century mathematician, physician, and astronomer.
When he produced a gift for his patrons,
Emperor Charles the fifth, and his brother Ferdinand the first, Apian turned to this question.
In his printing house in Ingolstadt, Germany,
he commissioned illustrator Michael Ostendorfer to embark on a project that might provide an answer.
In 1540, after a decade of work, they were finally done.
Apian’s masterpiece features vivid, hand-colored illustrations
of the sky, constellations, eclipses, and moons,
on thin paper disks, accented by silk threads with seed pearl markers.
A manual suitable for emperors to decode the stars.
This is the Astronomicum Caesareum.
In this video, I will be guiding you through this magnificent book,
discovering together how sixteenth century nobles
navigated an uncertain world by interpreting the skies.
Apian and Ostendorfer produced over a hundred copies of the book,
each made as gifts for high-ranking officials in both Catholic and Protestant courts across Europe.
The book illustrates the beautiful integration of art and science at court.
The pages calculate the placements of stars
to determine fate, medical diagnoses, and travel and military conflict in the noblemen’s everyday lives.
Apian based his calculations on the sixteenth century geocentric model of the universe,
in which the planets, the sun, and the moon, rotated around the earth.
The sun’s apparent orbit around the earth was called the ecliptic.
When the moon crossed the ecliptic at the same point as the Sun, an eclipse occured.
The two intersection points between the moon and sun’s orbits are called lunar nodes,
illustrated by a dragon’s head and a dragon’s tail.
To perform calculations about the eclipses most efficiently,
Apian designed thinly stacked paper disks called vovelles.
For example, this vovelle is used to calculate the position of lunar nodes during times of the year.
On the far left are instructions for calculating the positions using the birthdays of Apian’s patrons as examples.
The central table lists the node positions at the beginning of each century.
One of the nobles who received a copy of the Astonomicum Caesarium was King Henry the eighth.
Apian’s gift most likely arrived at the English court in the year 1545.
If King Henry wanted to calculate the position of the lunar nodes on his birthday of that year, June 28, 1545,
he could use this page to do so.
First, he would locate the year 1500 on the table,
in the column labeled Capits Draco, or Dragon’s Head, in the sub-column post Christum, or AD.
We can see here listed the values 1, 25, and 45, the sign, degree, and minutes of the Dragon’s head in 1500.
We begin with our first value, number 1, which stands for the first sign in the zodiac: Taurus.
We move the dragon’s head into the sign of Taurus.
Next, the degree indicates that the dragon’s head should be moved to 25.
This is where the dragon’s head would have been in the year 1500.
To find the year 1545, look to this golden band and find the number 45, somewhere in Sagittarius.
Use the silk thread to mark that place, and turn the dragon’s head there.
To find the day of Henry’s birth, June 28th, find June on the small calendar to the left of the dragon’s head
and mark the silk thread close to the end of the month, and then move the tab accordingly.
Therefore, on June 28, 1545, the dragon’s head would be about fifteen degrees of Sagittarius,
and the dragon’s tail would be around fifteen degrees of Gemini.
These node positions can then be used on some of the book’s other pages
in calculations for the phases of the moon, the timing of eclipses, and more.
Many scholars believed that the earthly world was dependent on the heavens.
From the seasons to the onset of illness,
everyday experiences of change were causally linked to the movement of the celestial spheres.
For example, if Henry the eighth fell ill on his birthday,
his physicians might use the moon’s longitude, latitude, and node locations to schedule a treatment regime.
When Peter Apian made this book in the 1500s, everything he knew and believed in was radically changing.
His world was upended by the influx of information from voyages of exploration and conquest,
the surge of religious wars in the wake of the Protestant Reformation,
and the growing dominance of the heliocentric model.
In a time of extreme uncertainty and change, Apian used the Astronomicum Caesareum
to visualize his understanding of the universe,
in which meaning and guidance could be found in the stars.