It is commonly claimed that Galileo did not perceive the rings of Saturn because the telescope he was using was not capable of magnifying the image. That is not true. After Galileo, astronomers needed another 50 years to think about the problem and re-imagine it. They needed to ask the right questions. Christiaan Huygens was the first to perceive the structure as a ring. However, it was another 200 years before the ring was understood as a system of particles, rather than a rigid body. The problem was epistemology, not optics.
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Galileo’s Images of Saturn 1610 and 1616
https://attic.gsfc.nasa.gov/huygensgcms/Shistory.htm |
“Galileo Galilei was the first to observe Saturn with a telescope in 1610. Because of the crudeness of his telescope, he couldn't determine what the rings were. He incorrectly guessed that there were two large moons on either side of Saturn. Two years later when he viewed Saturn again, the "moons" had disappeared. We know now this is because Galileo was viewing the rings edge-on so that they were invisible, but at the time it was very confusing to Galileo. After another two years, Galileo viewed Saturn again and found that the "moons" had returned. He concluded that the rings were “arms” of some sort.
“Many years later, in 1659, a Dutch astronomer named Christiaan Huygens solved the mystery of Saturn's "arms." Because of improved telescope optics, he correctly deduced that the "arms" were actually a ring system. Huygens also discovered Saturn's moon, Titan, and for this reason, the probe exploring Titan is named after him.”
From NASA’s Cassini-Huygens Mission website (no longer current) here https://attic.gsfc.nasa.gov/huygensgcms/Shistory.htm
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“Galileo’s Sketch of Saturn”
from Galileo and the Scientific Revolution
by Laura Fermi and Gilberto Bernardini,
Basic Books, 1961. |
“When he turned his telescope on the planet Saturn, he found that this did not always look like a round body but seemed of strangely variable shape. He thought it to be “three-bodied; that is it … was an aggregate of three stars arranged in a straight line parallel to the ecliptic, the central star being much larger than the others.” His telescope was not sufficiently powerful to let him to distinguish the three, possibly four, rings we now know are around Saturn. It was the Dutch astronomer Christian Huygens (1625-1695) who discovered Saturn’s rings.” -- Galileo and the Scientific Revolution by Laura Fermi and Gilberto Bernardini, Basic Books, 1961.
“Galileo continued his telescopic observations from his new home in Florence. Here he discovered that Saturn sports a pair of curious appendages, but his telescope was not powerful enough to reveal their true nature. (They were Saturn’s rings.)” Parallax: the Race to Measure the Cosmsos by Alan Hirshfeld, W. H. Freeman and Company, 2001.
“1610 - Galileo Galilei becomes the first to observe Saturn's rings with his 20-power telescope. He thought the rings were “handles” or large moons on either side of the planet. He said “I have observed the highest planet [Saturn] to be tripled-bodied. This is to say that to my very great amazement Saturn was seen to me to be not a single star, but three together, which almost touch each other”.
“1612 - Galileo was astounded when he found that the rings he first observed a couple of years earlier had now disappeared. He wrote "I do not know what to say in a case so surprising, so unlooked for and so novel". The rings were, in fact, edge-on from Earth's perspective. Galileo inadvertently became the first person to observe a Saturn ring plane crossing.
“1616 - Galileo now observes the rings as two half ellipses. He wrote “The two companions are no longer two small perfectly round globes ... but are present much larger and no longer round ... that is, two half ellipses with two little dark triangles in the middle of the figure and contiguous to the middle globe of Saturn, which is seen, as always, perfectly round.”
From Views of the Solar System Copyright © 1995-2015 by Calvin J. Hamilton. https://solarviews.com/eng/saturnbg.htm
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Museo Galileo, Florence
https://catalogue.museogalileo.it/indepth/SaturnsRings.html |
“In some observations conducted in 1610, Galileo (1564-1642) saw Saturn as tricorporeo [three-bodied], i.e.,composed of a central body and two lateral bulges, which he mistakenly thought to be satellites. In 1655, Christiaan Huygens (1629-1695), thanks to a more powerful telescope, observed Saturn's rings for the first time. He described them accurately in Systema Saturni (The Hague, 1659). The Accademia del Cimento was concurrently investigating the nature of the rings. Between 1671 and 1684, Giovanni Domenico Cassini (1625-1712) discovered four satellites of Saturn, in addition to the one previously found by Huygens. Cassini also observed and studied the divisions between the rings. Recently, the Voyager space probes have revealed that the many concentric rings are thin bands consisting of countless rock and ice fragments that orbit the planet and reflect sunlight.”
© 2018 - 2020 Museo Galileo - Istituto e Museo di Storia della Scienza
https://catalogue.museogalileo.it/indepth/SaturnsRings.html
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https://www.bibliovault.org/thumbs
/978-0-8165-0829-7-frontcover.jpg |
“Telescopic studies of Saturn, its ring system, and its satellites from 1610 to about 1900 are surveyed. Early observations of the Saturn system and changing beliefs about the constitution of the rings are covered, showing that what an observer sees in the heavens depends not only on the quality of his instruments, but also on what he expects to see. The first observations of the Saturn system by Galileo, the development of the ring theory by Huygens, and the replacement of Herschel's and Laplace's solid ring theories by Maxwell's particle ring theory are recounted.”
Saturn Gehrels, Tom; Matthews, Mildred Shapley (Editors). Tucson, University of Arizona Press, 1984, p. 23-43.
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Introduction to Objectivist Epistemology
by Ayn Rand (2nd. edition) |
In Introduction to Objectivist Epistemology, Ayn Rand asserted that a sensation must be identified to become a percept. A set of percepts, identified and integrated by common attribute becomes a perception. A set of perceptions integrated by their common characteristics are given a name and thereby made into a concept. Concepts are further abstracted by their essential distinguishing characteristics, according to objective context, into wider (and more powerful) ideas. Without identification, a sensation alone is meaningless. Not knowing what to expect, Galileo could not perceive the rings of Saturn correctly.
Just as it took time for the nature of Saturn’s rings to be teased out from the observations, so, too, did someone 400 years after Galileo finally put 2 and 2 together. In 2005, the science of epistemology informed astronomy.
“Saturn was first seen through the telescope by Galileo in the summer of 1610. In the ensuing half century, Saturn's strange appearances became a celebrated puzzle. The problem was often not the poor quality of telescopes: a number of observers drew images that we would interpret as showing a ring around the planet. It was also a problem of concepts because for several decades observers had the wrong model in mind when they observed the planet. Thus we could say that their telescopes could show them the ring, but their preconceptions did not allow them to see it. The manner in which Christiaan Huygens arrived at the solution, in the winter of 1655-56, shows that more than good telescopes were necessary, although for rhetorical reasons Huygens maintained the opposite. And Huygens's ring-theory, [elegant] as it was, had several shortcomings that were slowly fixed--often by others.” -- “Saturn through the Telescope: The First Century” by Albert Van Helden. American Astronomical Society, DPS meeting #37, Bulletin of the American Astronomical Society, Vol. 37, p.620. Pub Date: August 2005
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Explore Scientific First Light 102
660 mm focal length |
Last night, I went out with my telescope to see what Galileo could or could not have perceived, had he held the identifying concept. Admittedly, the 102 mm objective of my Explore Scientific refractor has 16 times the area of his. However, I am inside a city, a mile from a major shopping center. He was in Florence, a city with smoke, perhaps, but no arc vapor street lights.
I tested three magnifications: 20.8x (32 mm), 26.4x (25 mm) and 38x (17 mm). At 21 power, it was a strong “maybe” given Galileo's patience. At 26.4 power the rings were discernable without question, and at 38x, they were undeniable. Although his 20x telescope was his primary instrument, it was not his only telescope. He had made a 30-power at the same time, but gave it to Cosimo Medici. I believe that Galileo’s instruments were good enough, but understanding of the taxonomy of the solar system required a conceptual leap that would have to wait for later astronomers.
PREVIOULSY ON NECESSARY FACTS
The Scientific Method
Feynman's Rainbow
Harriman's Logical Leap
Cosmos: a Spacetime Travesty
