Midterm Guide for Philosophy

What is diurnal rotation and what celestial bodies display it?

The pattern of motion exhibited by the stars, and the sun, moon, and planets against the background of the stars. For the stars it suggests that they are embedded on a sphere rotating around the earth because the stars are all moving as one unit around the north star, rather than having individual paths. All bodies in the celestial sphere display it.

What is bounded elongation and which bodies engage in it?

When planets, as they are in retrograde motion, stay a (close) specific distance from the sun at all times. Only Mercury and Venus engage in it.

How did Eudoxus explain retrograde motion?

Eudoxus’ system of retrograde motion says that four different spheres are used to generate retrograde motion, as well as the motion of a planet around the earth, and diurnal rotation.

What were Aristotle’s counterturners?

More spheres (for a total of 56) that have the same axis and speed of the previous body’s spheres but in the opposite direction, so that they undo the motion of the previous body.

How did Ptolemy explain retrograde motion?

Ptolemy used an epicycle/deferent system. Instead of just rotating around the earth, the planets rotate around a point that then rotates around the earth as well. It explains retrograde motion because the motion of the planet around the point while it rotates around the earth creates a looping motion.

What is the equant and why did Copernicus hate it?

The equant is a point on the line that connects the center of the earth and the center of the deferent arm. Copernicus hated it because it violated the Aristotelian view of uniform circular motion.

What is Copernicus’ explanation of bounded elongation?

Copernicus’ explanation is that from our standpoint Mercury and Venus will never be further than the distance of the respective radius of their orbits around the sun.

What is the objection to Copernicus’ view that concerns stellar parallax?

That there is no stellar parallax which means that the stars would have to be absurdly huge, even bigger than the solar system.

What is Newton’s explanation of the orbiting of the planets around the sun?

The sun’s gravity attracts the planets and, combined with their forward motion, keeps them moving in largely elliptical orbits around it.

What does Darwin mean by “survival of the fittest”?

Within a generation a particular trait varies, and some provide access to resources better than others. Those animals with traits that provide greater access survive and the others die off.

What is Kepler’s first law of planetary motion? According to that law, where is the sun located with respect to the planet’s orbit?

Planets move around the sun in elliptical orbits. The sun is located at one of the two focal points of the elliptical orbit of a planet.

What did Galileo notice when he looked at the stars through the telescope, and what was its
relevance for the Copernican account?

Galileo observed that Venus goes through a complete set of phases, from new crescent to full, which is the same as the heliocentric Copernican account.