Galileo, Renaissance Astronomer and Artist

 

 

Galileo, Renaissance Astronomer and Artist by Vicky L. Oldham, December 1, 2021

Many historians consider Galileo Galilei (1564–1642) the "Father of Modern Science" (Biography.com Editors, 2021).  Galileo's discoveries defied long-held beliefs that began with the Greek philosopher Aristotle (384–322 BCE) and the geocentric model of the Solar System that places the Earth at its center.  By redesigning the "spyglass," an already-existing telescope limited to just three times magnification, Galileo improved its capacity to greater than 20 times magnification (Helden, n.d.).

The night Galileo turned his custom telescope to the sky, the world of astronomy would never be the same again.  He recorded firsthand observations of the Moon, planets, and stars and drew elegant and precise sketches to accompany his reports.  Through this process, Galileo accumulated evidence that conclusively supported the heliocentric view of the Solar System, a model defined by Copernicus, who intended to revise and improve the centuries-old, often capricious geocentric model by Ptolemy.

Claudius Ptolemy (90-168 CE) defined the Earth-centered, geocentric model in the Almagest.  He published hundreds of years of astronomical observations and tables for predicting the motions of planets and stars.  He devised "epicycles" to make sense of the retrograde motion of planets, for which Aristotle's earlier geocentric model could not account.  The Almagest became the standard reference and represented the foundation of astronomy for the next 1000 years (Library of Congress, n.d.a). 

Nicolas Copernicus (1473–1543) lived when astronomy and astrology combined were considered the same science (Westman, n.d.).  However, disagreement prevailed regarding the order of planets or their positions in the sky during times of the year.  Copernicus set out to solve these problems; the effort led him to confirm the simpler yet more accurate Sun-centered or heliocentric model published in his Revolution of the Heavenly Spheres.

The Starry Messenger

Galileo became the first person in history to use a telescope to study astronomy (NASA Science, 2019).  Observations made through his telescope confirmed the belief that the heliocentric, or Sun-centered view of the Solar System was the correct model.  Already partial to the Copernican perspective, Galileo quickly realized flaws in the Earth-centered model using his telescope.  Instead of seeing the Moon as a "perfect pearl," as described by the Church, it was pockmarked with craters.  He also learned that Venus had phases like the Moon, indicating its revolution around the Sun.

Galileo discovered that Jupiter had moons, too; clearly, these four satellites did not revolve around the Earth (Biography.com Editors, 2021).  He published his findings as fast as he could and included sketches he drew during his observation.  His publication, Starry Messenger (Sidereus Nuncius, 1610) was the first monograph about using the telescope for astronomy.  Galileo quickly gained fame, and demand grew for his lectures and demonstrations of the new telescope.  He soon excited others to use telescopes to study the skies (Library of Congress, n.d.b).

Chiaroscuro

Galileo was considered a "polymath," meaning one who excels or is knowledgeable in many disciplines (The Max Planck Society, n.d.).  In addition to his accomplishments as a philosopher, astronomer, mathematician, physicist, engineer, lecturer, and author, he was also trained in the Renaissance art of chiaroscuro.  Chiaroscuro is a technique that allows painters to create the illusion of realism by accurately depicting light and shadow on objects (Library of Congress, n.d.b).   For instance, Galileo knew how shadows cast from one sphere onto another should appear, with the characteristic rounding of the edge, contributing to his understanding when observing planets and moons.

The Moon

Viewing the Moon through his specially designed, custom telescope, Galileo observed features like mountains and craters and recognized their physical nature based on his artistic training in chiaroscuro (Library of Congress, n.d.b). 

Figure 1. Galileo's sketches of the moon from Sidereus Nuncius, published in March 1610.

 

Note: Galileo's sketches of the moon from Sidereus Nuncius, published in March 1610. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Galileo%27s_sketches_of_the_moon.png. In the public domain.

 

The observation of a pitted and scarred Moon refuted the conception of heavenly spheres by Aristotle and Ptolemy adhered to by the Church which insisted that the Moon is like a perfect pearl.  Galileo eloquently notes, "…that the Moon certainly does not possess a smooth and polished surface, but one rough and uneven, and, just like the face of the Earth itself, is everywhere full of vast protuberances, deep chasms, and sinuosities" (Galileo et al., 1610/2014, loc. 144).  Galileo preserved his observations by hand-drawn sketches of the surface of the Moon in phases, sparing no detail to share what he really saw.

Phases of Venus

When Galileo turned his telescope to the planet Venus, he noted its "phases" by the changes to rounded shadows on its surface similar to the phases of Earth's Moon (University of Rochester, n.d.).  The geocentric model previously tried to make sense of Venus' phases by placing it within its own epicycle, revolving in a small circle to prove that it moved along with the Sun around the Earth.  However, telescopic observations by Galileo magnified Venus to reveal the shadows of its phases (not evident with the naked eye), confirming it revolved around the Sun.  There was no need for the forced contrivance of epicycles with the heliocentric system.

Moons of Jupiter

Galileo observed Jupiter and found it accompanied by four "stars."  He realized these smaller objects were actually moons of Jupiter, tethered to their Jovian parent as they revolved around it.  A major argument against the heliocentric model had been that Earth could not possibly drag its own Moon along as it revolved around the Sun.  With the observation of moons revolving around Jupiter, Galileo proved that other planets not only have their own moons, but they do drag them along on their journey around the Sun (and do not revolve around the Earth) (Library of Congress, n.d.b).

Conclusion

Without Galileo and his expertise in so many areas, one may wonder if our modern understanding of the universe might have been postponed for a few more centuries.  He felt an urgency to publish his findings to others and even wrote advertising copy as lyrical prose to promote his Starry Messenger (DeSoysa, 1999).  Fortunately, the Renaissance provided the perfect medium for scientific and cultural development out of what seemed like centuries of relative darkness.  Despite the ongoing threats from the Inquisition, new ideas and improved tools reached a critical mass of awareness impossible to suppress indefinitely.  Thanks to Galileo and other great minds of his time, history experienced an unprecedented acceleration in scientific discovery and innovation, from which it continues to benefit to this day.

 

  

References

Biography.com Editors (2021, March 30). Galileo biography. Biography.com. https://www.biography.com/scholar/galileo

Galileo Galilei & Johannes Kepler (1610- ). Carlos, E.S. (Translator) (2014, June 24). The sidereal Messenger of Galileo Galilei and a part of the preface to Kepler's dioptrics containing the original account of Galileo's astronomical discoveries [eBook]. https://www.amazon.com/gp/product/B00LALINDE/ref=ppx_yo_dt_b_d_asin_title_o00?ie=UTF8&psc=1

Helden, A.V. (n.d.). Galileo. Encyclopedia Britannica. https://www.britannica.com/biography/Galileo-Galilei

Library of Congress (n.d.a). Ancient Greek astronomy and cosmology. Library of Congress. https://www.loc.gov/collections/finding-our-place-in-the-cosmos-with-carl-sagan/articles-and-essays/modeling-the-cosmos/ancient-greek-astronomy-and-cosmology/

Library of Congress (n.d.b). Galileo and the telescope. Library of Congress. https://www.loc.gov/collections/finding-our-place-in-the-cosmos-with-carl-sagan/articles-and-essays/modeling-the-cosmos/galileo-and-the-telescope/

NASA Science (2019, March 13). Galileo's observations of the Moon, Jupiter, Venus and the Sun. https://solarsystem.nasa.gov/news/307/galileos-observations-of-the-moon-jupiter-venus-and-the-sun/

DeSoysa, K. (1999). Sidereus Nuncius: The Starry Messenger. http://www.sites.hps.cam.ac.uk/starry/galsidnun.html

The Max Planck Society (n.d.). Galileo Galilei. Max-Planck-Gesellschaft. https://www.mpg.de/en/galileo-galilei

University of Rochester. (n.d.). Galileo: The telescope & the laws of dynamics. http://www.pas.rochester.edu/~blackman/ast104/galileo12.html

Westman, R. S. (n.d.). Nicolaus Copernicus. Encyclopedia Britannica. https://www.britannica.com/biography/Nicolaus-Copernicus

Wikimedia Commons (n.d.). Galileo's sketches of the moon from Sidereus Nuncius, published in March 1610 [Photo]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Galileo%27s_sketches_of_the_moon.png