Chapter 2 Motion Flashcards

Question

State six features of the Ptolemaic model.

Answer 1

1. All seven of the heavenly bodies are perfectly spherical. 2. All heavenly bodies move in circular orbital regions, called spheres. 3. All the spheres are centered on the earth, so this system is a geocentric system. 4. Corruption and change only exist on earth. All other places in the universe are perfect and unchanging. 5. All the spheres containing the heavenly bodies and all the stars rotate completely around the earth every 24 hours. 6. Epicycles are used to explain retrograde motion.

Answer 2

Copernicus proposed a detailed heliocentric model, with the earth rotating on an axis, all the planets moving in circular orbits around the sun, and the moon orbiting the earth.

Answer 3

He observed a conjunction between Jupiter and Saturnthat he predicted the date using Copernicus’ new heliocentric model. He observed what he called a new star which challenged the idea that the heavens are unchanging.

Answer 4

The sun and moon orbit the earth. All the other planets orbit the sun, which orbits the earth.

Answer 5

Each of the planetary orbits is an ellipse, with the sun at one focus.

Answer 6

Tycho Brahe was a Danish nobleman and astronomer who made two important observations. First, in 1563 he observed a conjunction between Jupiter and Saturn. A conjunction is when two planets are in a straight line with the earth, so that from earth they appear to be in the same place in the sky. Tycho closely predicted the date for this conjunction using Nicolaus Copernicus’ new heliocentric model. Second, in 1572 Tycho observed what he called a “nova” (what we would now call a supernova) and proved that it was a new star. This discovery was strong evidence that the stars were not perfect and unchanging as Aristotle had thought and as theologians also assumed.

Answer 7

Galileo Galilei was an Italian scientist who made many ground-breaking discoveries such as that all falling objects accelerate at the same rate. He also made significant improvements to the telescope and used it to discover four of the moons around Jupiter, which was in conflict with the seven heavenly body idea. Galileo was tried by the Holy Office in 1633 because he disobeyed an injunction not to hold, defend or teach the Copernican system as true. Galileo repented of his error, but still had to live the final nine years of his life under house arrest as a result of the trial.

Answer 8

Johannes Kepler was a German astronomer who used Tycho Brahe’s massive body of research data to develop his famous three laws of planetary motion, which were published between 1609 and 1619. Kepler took his faith very seriously, even though he was caught in the middle during a time of serious disagreement between Roman Catholics and Protestants. He also developed some of the major principles of gravity later synthesized by Isaac Newton, and he was the first to hypothesize that the sun exerted a force on the earth.

Answer 9

Nicolaus Copernicus was a Polish astronomer who proposed a detailed heliocentric model. In this model with the earth rotates on its axis, all the planets move in circular orbits around the sun and the moon orbits the earth. Copernicus’ model used circular orbits, and like the Ptolemaic model, used epicycles to make the models work. Still, Copernicus’ model was much closer to today’s understanding than the Ptolemaic model was.

Answer 10

Newton theorized that every object in the universe pulls on every other object in the universe. In Newton’s model, the gravitational attraction depends on each object having mass, because the force of gravity has both masses in it multiplied together. The effect is that everything in the universe pulls on everything else.

Answer 11

Einstein’s theory explains gravity in terms of the curvature of space around a massive object (that is, an object with mass), such as the sun or a planet. Since Einstein’s theory is about curving space, even phenomena without mass, such as rays of light, are affected by it. In Einstein’s theory, gravity is caused by curvature in space-time, and its effect is that starlight bends as it travels through space when it passes near a massive object such as the sun.