Project 3: Astronomy

Much of what is currently known about the solar system can be traced back to Galileo and he is considered to be the father of observational astronomy. The Galileo museum contains instruments of his own design, which were used to gain an understanding of astronomy. This includes some of his original telescopes and the objective lens he used to discover the moons of Jupiter. The lens comes from Galileo’s improved telescope, which had a 20x magnification. The four largest moons; Io, Europa, Ganymede and Calisto, are now called the Galilean satellites in his honor. He originally called them Cosimo’s stars, dedicating them to the Medici family. Galileo had been hired as a math tutor for Cosimo de’ Medici before Cosimo became Grand Duke. 

One of the displays I was most drawn to in the Galileo museum were the Armillary spheres. I was impressed with the size and intricacy of them and was interested in what all of the rings represented. Armillary spheres act as models of the sky and of time measurement; they have either the earth or the sun in the center. The spheres were used to show the difference between the geocentric and heliocentric theories of the solar system. The rings represent celestial longitudes and latitudes, and the sphere contains rings for the ecliptic line, equator, polar circles and other features. In comparison to a celestial globe, Armillary spheres can show the movement of objects in space and demonstrate how they relate to each other.

The ecliptic line represents the apparent movement of the sun around the Earth. It is divided into 12 sections of 30 degrees for each sign of the zodiac. The constellations of the zodiac all lie 7 degrees above or below the ecliptic. I had decided to do my project on the zodiac constellations, and chose to place them into an Armillary sphere because of how well the ecliptic organizes the constellations. I also found it interesting that the ecliptic line was used at a time when the geocentric model was widely accepted, but is still relevant to modern astronomy. This provides a parallel between two time periods that differ immensely in the state of knowledge of astronomy.

The division of the ecliptic into the zodiac signs originates from Babylonian astronomy and were first recorded around 1000 BC. The modern constellations are a modification from this catalog. The Babylonian astronomers divided the ecliptic into twelve equal sections, creating the first ecliptic coordinate system. The Babylonian calendar then assigned a sign to each month. They assigned Aries as the first sign, as it was found at zero degrees at the vernal equinox. Even though the vernal equinox has moved away from the Aries constellation, we still consider it to be the first. The zodiacs started as a way to organize the sky and easily identify the longitude of planets, but have now evolved into something much more significant to many peoples lives in astrology.

There are 88 classified constellations, but all are made up and used simply as a way to identify certain stars. They originated from people who observed the stars and arbitrarily assigned a form to them, and are now commonplace in modern astronomy. Since constellations were made up as an organizational tool, I decided to abstract my zodiac constellations by mapping out the stars and using cut up paper to show their forms. I placed my constellations above and below the ecliptic, following their longitudinal order shown in the Armillary sphere in the museum.