Chapter 28 Stars and the Universe

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710 CHAPTER 28: STARS AND THE UNIVERSE ET, Phone Earth Another attempt to discover extraterrestrial life is project SETI: the Search for Extra Terrestrial Intelligence. This program seeks to identify radio transmissions coming from outside the solar system. Considering the billions of stars in the universe, it seems possible that planets with conditions similar to those on Earth could be orbiting some stars. It also seems possible that on some of these planets there may be technological civilizations like our own. The huge distances in space may prevent anyone from traveling from one star system to another. However, radio waves, which are relatively easy to generate, travel at the speed of light. Large radio receivers, also known as radio telescopes, can pick up very faint radio transmissions. Large radio telescopes were built to explore the universe with long wavelengths of electromagnetic radiation that are not visible to our eyes. Radio waves can penetrate dust and clouds of gas that prevent visual observations. How would scientists know if they were receiving signals from another civilization? It seems likely that the signals would not be in a familiar language. If astronomers detect patterns in radio transmissions that have no known sources in natural sources, they may be listening to communications from another civilization. Some of the largest radio telescopes in the world have been used over the past several decades to listen for intelligent transmissions. At first, the job of analyzing these signals was a severe limitation. How could scientists separate intelligent communications from the great amount of radio noise generated by stars? This is where computers came to the aid of scientists. Computers can quickly analyze radio signals, looking for patterns. The development of faster and more powerful computers has enabled astronomers to scan far more observations than humans could ever analyze. However, since SETI began in about 1960 there have been no signals identified as likely forms of intelligent communication.
What Would We Answer? If scientists did detect intelligent communications, how could it affect Earth? Perhaps the information in the data would provide new insights into mathematics, science, or technology. Perhaps people could learn more about the promise and the dangers of a developing civilization. On the other hand, there is always the danger of conquest by a distant power. The future has always brought people into the unknown. Fortunately, people have learned to apply discoveries to improve their lives. Experience has taught that, in the long run, the developments of science seem to benefit humans. WHAT IS A STAR? A star is a massive object in space that creates energy and radiates it as electromagnetic radiation. The sun is a star. If you compare the sun with the thousands of stars known to astronomers, the sun appears to be a typical star. Actually, most of the stars visible in the night sky are larger and brighter than the sun. At the same distances as the visible stars, there are more stars too dim to be visible from Earth. Observations of the sun give astronomers insights into most other stars and their observations of other stars help them understand the sun. ACTIVITY 28-1 LIGHT INTENSITY AND DISTANCE WHAT IS ASTAR? 711 Using a light meter that measures the intensity of light, you can measure the change in the intensity with distance. Place a lightbulb in a dark room. Measure the intensity of the light at different distances from the lightbulb. Make a data table of the intensity of illumination at various distances from the lightbulb. Graph your data. What other factor shows a similar change of intensity with distance?
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Page 5 and 6: of energy. However, nuclear fusion
Page 7 and 8: Figure 28-3 When stars are plotted
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Page 11 and 12: HOW DO ASTRONOMERS STUDY STARS? Sta
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Page 15 and 16: colors. You may need to rotate the
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Page 19 and 20: Figure 28-9 The sun and nearby gala
Page 21 and 22: theory proposes that at the time of
Page 23 and 24: TERMS TO KNOW Therefore, the ultima
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Chapter 28 Stars and the Universe

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