Study Figures 4-11 and 4-16 and describe the phases that Venus would have displayed to Galileo’s telescope if the Tychonic universe had been correct.
Figure 4-11 Tycho’s model of the Universe retained the first principles of classical astronomy; it was geocentric with the Sun and Moon revolving around Earth, but the planets revolved around the Sun. All motion was along circular paths.
Figure 4-16 (a) If Venus moved in an epicycle centered on the Earth-Sun line (see Figure 3b in the Chapter 2 Concept Art: An Ancient Model of the Universe), it would always appear as a crescent. (b) Galileo observed through his telescope that Venus goes through a full set of phases, proving that it must orbit the Sun.
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Chapter 4 Solutions
Foundations of Astronomy (MindTap Course List)
- In Ptolemys model, how do the epicycles of Mercury and Venus differ from those of Mars, Jupiter, and Saturn?arrow_forwardWhat two factors made it difficult, at first, for astronomers to choose between the Copernican heliocentric model and the Ptolemaic geocentric model?arrow_forwardAccording to Kepler’s second law, where in a planet’s orbit would it be moving fastest? Where would it be moving slowest?arrow_forward
- Why might Tycho Brahe have hesitated to hire Kepler? Why do you suppose he appointed Kepler his scientific heir? What is limited about Keplers third law P2 = a3, where P is the time in units of years a planet takes to orbit the Sun and a is the planets average distance from the Sun in units of AU? (Hint: Look at the units.) What does this tell you about Kepler and his laws?arrow_forwardWhy did Copernicus want to develop a completely new system for predicting planetary positions? Provide two reasons.arrow_forwardWhat phases would Venus show if the geocentric model were correct?arrow_forward
- What is P for Earth? What is a for Earth? Do these values support or disprove Keplers third law?arrow_forwardHow many precession periods are in one cycle of Earths axis inclination variation? In one cycle of Earths orbit eccentricity variation? In the time span shown in Figure 2-11b, how many periods or fractions of periods did the Earths axis precess, nod, and Earths orbit change shape? Of the three periods, which is likely to have the most effect on the changes shown in Figure 211?arrow_forwardUse the figure below to explain how the Ptolemaic model treated some planets differently from the rest. How did the Copernican model treat all of the planets the same?arrow_forward
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