CHAPTER 3: THE TWO-SPHERE UNIVERSE IN ARISTOTELIAN THOUGHT
THE ARISTOTELIAN UNIVERSE
What is aether?
- It is the celestial element, a crystalline solid, which is pure and unalterable as well as transparent and weightless. (79)
What are the planets and stars made of?
- They are made up of aether, the celestial element. (79)
What is a crystalline sphere?
- It’s a shell made up of aether, that altogether (the 55 shells in the Aristotelian universe), create the motion of the planets. (80)
Why does Aristotle think the Earth stands still?
- Because its natural position is to go to the center of the universe because of what it is composed of.
What is the Aristotelian universe?
- “For Aristotle the entire universe was contained within the sphere of the stars, or, more precisely, within the outer of the sphere. At every point inside the sphere there was some sort of matter – no holes or vacuums could exist. Outside the sphere there was nothing – no matter, no space, nothing at all.” (79)
Why did Copernicus fail to design an essentially Aristotelian universe?
- Because in the Aristotelian universe, the notion that the Earth would not be at the center of the universe and therefore be only one more planet, could not be conceived since that would alter the perfection of the celestial bodies and alter the sublunary region and its elements. (84)
Why was innovation difficult for an Aristotelian to accept?
- “Because the concept of a unique central earth was interwoven with so many other important concepts within the fabric of Aristotelian thought… it did not survive the modification that made the earth a planet.” (84)
Why did the Aristotelian conception of the universe not survive the modification that made Earth a planet?
- Same as above (84)
What is the role of the elements in the Aristotelian structure of the universe?
- The pure elements (Earth, Water, Fire, and Air) fill the sublunary region, where they remain undisturbed. But the terrestrial region is disturbed by the moving and mixture of these elements due to the moving sphere of the moon. (82)
THE ARISTOTELIAN LAWS OF MOTION
What is Aristotle’s proof that the Earth is a sphere?
- There are two main observations that prove the sphericity of the Earth. “First, if the earth were not spherical, eclipses of the moon would not exhibit segments of the shape they do, and second, that observation of the the stars also shows not only that the earth is spherical but that it is of no great size, since a small change of position on our part southward or northward visibly alters the circle of the horizon.” (85)
According to Aristotle, why is Earth at the center of the universe?
- The proof that earth is at the center of the Universe can be proved by observing the natural motion of heavy bodies. These tend to go to the center of the Universe, but we see that they also move to the center of the earth, therefore, both the Universe and the earth must have the same center. (85)
What is the Aristotelian explanation for terrestrial motion?
- Earth doesn’t move (i.e. it doesn’t rotate) and that’s why all objects thrown vertically return to their point of origin. “The natural motion of a stone is governed by space alone, not by the stone’s relation to other bodies.” (87)
What is Aristotle’s objection to the movement of the Earth?
- If earth were moving, things thrown vertically would not return to their place of origin (i.e. earth would leave behind those objects as it rotates). (87)
THE ARISTOTELIAN PLENUM
What is Horror Vacui?
- A principle that states that Nature will always act to prevent the formation of a vacuum. (88)
Why can’t a vacuum exist?
- According to Aristotle, a vacuum would be a contradiction, since space can only be defined in terms of volume occupied by body. Matter and space are inseparable. (88)
How could an infinite universe scarcely remain an Aristotelian universe?
- For two reasons: first, an infinite universe has no center; and second, that if there is no special center point, it is scarcely plausible that all the earth, water, air, and fire in the universe should have aggregated at one and only one point. (89)
What is a plenum?
- The conception of a full universe where there are no vacuums. (90)
Why didn’t the principle of horror vacui survive?
- Because it does not logically necessitate some of the main feature of the Aristotelian universe, namely the uniqueness, central position, or the immobility of the earth. (90)
Which features of the Ptolemaic and Aristotelian universe did Copernicus try to preserve?
- -__-
What essential Aristotelian functions did Copernicus drop?
- The immobility of earth, the sublunary region, earth uniqueness, that earth was the center of the universe.
What are the difficulties that an infinite universe poses to Aristotelian cosmology?
- That earth would remain to be the center of the Universe, since it won't have a center, eliminate earth uniqueness.
In the Aristotelian universe, what is the relationship between matter and space?
- They are inseparable, space can only be defined by the matter it has. There are no vacuums.
THE MAJESTY OF THE HEAVENS
What are the non-scientific arguments for Aristotle’s theory?
1. The integration of Aristotelian cosmology with Christian theology.
2. The “science” of astrology.
Why was the Copernican theory so threatening to Christian-Aristotelian cosmology?
- It was threatening because it would make the earth share the perfection of the heaven and the heaven would share the corruption of earth. In other words, it deprived the heavens of special power.
Why was the Copernican theory so threatening to astrology?
- It would made astrology obsolete, since astrology explains the perfection of the celestial bodies and therefore provides answers to the problem of the planets.
THE ARISTOTELIAN WORLD VIEW IN PERSPECTIVE
Did Galileo get his understanding of motion by looking at the world closer?
- He did made observations and experiments to understand somehow the motion of bodies, but he got most of his understanding through logical arguments and not observation.
Why is Galileo’s law more useful to science than Aristotle’s?
- It is more useful because it goes behind what appears a regularity observed through our senses. It needs more than observation, and therefore, logical arguments are needed.
What is aether?
- It is the celestial element, a crystalline solid, which is pure and unalterable as well as transparent and weightless. (79)
What are the planets and stars made of?
- They are made up of aether, the celestial element. (79)
What is a crystalline sphere?
- It’s a shell made up of aether, that altogether (the 55 shells in the Aristotelian universe), create the motion of the planets. (80)
Why does Aristotle think the Earth stands still?
- Because its natural position is to go to the center of the universe because of what it is composed of.
What is the Aristotelian universe?
- “For Aristotle the entire universe was contained within the sphere of the stars, or, more precisely, within the outer of the sphere. At every point inside the sphere there was some sort of matter – no holes or vacuums could exist. Outside the sphere there was nothing – no matter, no space, nothing at all.” (79)
Why did Copernicus fail to design an essentially Aristotelian universe?
- Because in the Aristotelian universe, the notion that the Earth would not be at the center of the universe and therefore be only one more planet, could not be conceived since that would alter the perfection of the celestial bodies and alter the sublunary region and its elements. (84)
Why was innovation difficult for an Aristotelian to accept?
- “Because the concept of a unique central earth was interwoven with so many other important concepts within the fabric of Aristotelian thought… it did not survive the modification that made the earth a planet.” (84)
Why did the Aristotelian conception of the universe not survive the modification that made Earth a planet?
- Same as above (84)
What is the role of the elements in the Aristotelian structure of the universe?
- The pure elements (Earth, Water, Fire, and Air) fill the sublunary region, where they remain undisturbed. But the terrestrial region is disturbed by the moving and mixture of these elements due to the moving sphere of the moon. (82)
THE ARISTOTELIAN LAWS OF MOTION
What is Aristotle’s proof that the Earth is a sphere?
- There are two main observations that prove the sphericity of the Earth. “First, if the earth were not spherical, eclipses of the moon would not exhibit segments of the shape they do, and second, that observation of the the stars also shows not only that the earth is spherical but that it is of no great size, since a small change of position on our part southward or northward visibly alters the circle of the horizon.” (85)
According to Aristotle, why is Earth at the center of the universe?
- The proof that earth is at the center of the Universe can be proved by observing the natural motion of heavy bodies. These tend to go to the center of the Universe, but we see that they also move to the center of the earth, therefore, both the Universe and the earth must have the same center. (85)
What is the Aristotelian explanation for terrestrial motion?
- Earth doesn’t move (i.e. it doesn’t rotate) and that’s why all objects thrown vertically return to their point of origin. “The natural motion of a stone is governed by space alone, not by the stone’s relation to other bodies.” (87)
What is Aristotle’s objection to the movement of the Earth?
- If earth were moving, things thrown vertically would not return to their place of origin (i.e. earth would leave behind those objects as it rotates). (87)
THE ARISTOTELIAN PLENUM
What is Horror Vacui?
- A principle that states that Nature will always act to prevent the formation of a vacuum. (88)
Why can’t a vacuum exist?
- According to Aristotle, a vacuum would be a contradiction, since space can only be defined in terms of volume occupied by body. Matter and space are inseparable. (88)
How could an infinite universe scarcely remain an Aristotelian universe?
- For two reasons: first, an infinite universe has no center; and second, that if there is no special center point, it is scarcely plausible that all the earth, water, air, and fire in the universe should have aggregated at one and only one point. (89)
What is a plenum?
- The conception of a full universe where there are no vacuums. (90)
Why didn’t the principle of horror vacui survive?
- Because it does not logically necessitate some of the main feature of the Aristotelian universe, namely the uniqueness, central position, or the immobility of the earth. (90)
Which features of the Ptolemaic and Aristotelian universe did Copernicus try to preserve?
- -__-
What essential Aristotelian functions did Copernicus drop?
- The immobility of earth, the sublunary region, earth uniqueness, that earth was the center of the universe.
What are the difficulties that an infinite universe poses to Aristotelian cosmology?
- That earth would remain to be the center of the Universe, since it won't have a center, eliminate earth uniqueness.
In the Aristotelian universe, what is the relationship between matter and space?
- They are inseparable, space can only be defined by the matter it has. There are no vacuums.
THE MAJESTY OF THE HEAVENS
What are the non-scientific arguments for Aristotle’s theory?
1. The integration of Aristotelian cosmology with Christian theology.
2. The “science” of astrology.
Why was the Copernican theory so threatening to Christian-Aristotelian cosmology?
- It was threatening because it would make the earth share the perfection of the heaven and the heaven would share the corruption of earth. In other words, it deprived the heavens of special power.
Why was the Copernican theory so threatening to astrology?
- It would made astrology obsolete, since astrology explains the perfection of the celestial bodies and therefore provides answers to the problem of the planets.
THE ARISTOTELIAN WORLD VIEW IN PERSPECTIVE
Did Galileo get his understanding of motion by looking at the world closer?
- He did made observations and experiments to understand somehow the motion of bodies, but he got most of his understanding through logical arguments and not observation.
Why is Galileo’s law more useful to science than Aristotle’s?
- It is more useful because it goes behind what appears a regularity observed through our senses. It needs more than observation, and therefore, logical arguments are needed.