874012938 Prepared by Gilberto Berríos May 2, 2008 Reading Selections for ID1113, p. 10 Pre-reading activity After reading the introduction, answer the following questions. 1. What is the Doppler Effect? The change in wavelength perceived by an observer who moves with respect to the wave source 2. What phenomena are related to the Doppler Effect? The so-called blueshift and redshift 3. What is the connection between the Doppler Effect and the universe? That we can perceive the direction of universe motion by looking at the spectra of stars Reading Selections for ID1113, p. 12-14 Exercises Working with the text Read carefully the following topics and indicate the number of the paragraph where they are stated: M. Humason’s story ____3_____ Explanation of the red-shift of galaxies ____6_____ Doppler Effect and sound ____1_____ M. Humason and E. Hubble’s discoveries ____5_____ Doppler Effect and light ____2_____ M. Humason and E. Hubble’s relationship and work ____4_____ Vocabulary 1. Match the words in column A with their corresponding equivalent in column B. A B Match 1. to be used to (par. 1, line 2) a. moving back, becoming distant 1. _g__ 2. stretch out (par. 1, line 8) b. lengthen 2. _b__ 3. figure out (par. 4, line 5) c. consternation 3. _e__ 4. nearby (par. 5, line 6) d. running away, flying, escaping 4. _f__ 5. amazement (par. 5, line 7) e. understand, solve 5. _c__ 6. receding (par. 6, line 2) f. adjacent, neighboring 6. _d__ 7. fleeing (par. 6, line 3) g. to be familiar with 7. _a__ 874012938 Prepared by Gilberto Berríos May 2, 2008 2. Complete the following summary of the text using the words form the chart below. Working in Mount Wilson, Humason and Hubble found that distant galaxies are red-shifted and interpreted this in terms of the Doppler Effect: galaxies are receding from us; the more distant galaxies are receding faster than the near ones in proportion to their distance. This discovery led to the notion of the expansion of the universe and to the Big Bang theory. Understanding the text these two questions are too difficult for me; we’ll comment on them Choose the best alternatives to complete the following statements. 1. The Doppler Effect in astronomy can be used to explain __b__. a. the movement of galaxies away from the Earth I also think this is an answer b. the expanding movement of the universe best answer; see paragraph 6 c. the gravitational attraction of stars 2. This text can be seen in terms of: Perhaps the question should be, “This text presents…” a. a suggestion of a new hypothesis. b. a restatement of accepted theories. c. a rejection of a hypothesis. After reading activity Answer the following questions. 1. Why are galaxies said to be red-shifted? Because they have red light spectra, suggesting that they are withdrawing from us (according to a Doppler effect interpretation). 2. What would happen if the light from a galaxy were blue-shifted instead of red? It would mean that the galaxy is approaching us. 3. Why is the red shift of galaxies used in support of the Big Bang theory? Because it shows that galaxies are moving away from us and thus supports the idea that they were closer together in the past. 4. How does the expansion of the universe fit into the Big Bang theory? The expansion is a consequence of the initial explosion.