Objectives

1. Chapter 26 Section 1 Viewing the Universe Objectives • Describe characteristics of the universe in terms of time, distance, and organization • Identify the visible and nonvisible parts of the electromagnetic spectrum • Compare refracting telescopes and reflecting telescopes • Explain how telescopes for nonvisible electromagnetic radiation differ from light telescopes

2. Chapter 26 Section 1 Viewing the Universe The Value of Astronomy astronomy the scientific study of the universe • Scientists who study the universe are called astronomers • Astronomers have made exciting discoveries, such as new planets, stars, black holes, and nebulas. • By studying these objects, astronomers have been able to learn more about the origin of Earth and the processes involved in the formation of our solar system.

3. Chapter 26 Section 1 Viewing the Universe The Value of Astronomy, • Studies of how stars shine may one day lead to improved or new energy sources on Earth. • Astronomers may also learn how to protect us from potential catastrophes, such as collisions between asteroids and Earth.

4. Chapter 26 Section 1 Viewing the Universe Where does the Value of Astronomy come into play? • Astronomical research is supported by federal agencies, such as the National Science Foundation and NASA. • Private foundations and industry also fund research in astronomy. • We can all gain from what they learn.

5. Chapter 26 Section 1 Viewing the Universe Characteristics of the Universe • The evolution of the universe is called cosmology. • Most astronomers believe the universe began about 14 billion years ago. • We study the stars to see the past and predict the future.

6. Chapter 26 Section 1 Viewing the Universe Organization of the Universe • The solar system includes the sun, Earth, the other planets, and many smaller objects such as asteroids and comets. • The solar system is part of a galaxy. • galaxy a collection of stars, dust, and gas bound together by gravity • The galaxy in which the solar system resides is called the Milky Way galaxy. • The nearest part of the universe to Earth is our solar system.

7. A Galaxy

8. The Same Galaxy

9. Chapter 26 Section 1 Viewing the Universe Measuring Distances • What are some ways we measure distances?

10. Chapter 26 Section 1 Viewing the Universe Measuring Distances in the Universe • astronomical unit the average distance between the Earth and the sun; approximately 150 million kilometers (symbol, AU) • Astronomers also use the speed of light to measure distance.

11. Chapter 26 Section 1 Viewing the Universe Measuring Distances in the Universe • Light travels at 300,000,000 m/s. In one year, light travels 9.4607 x 1012 km. This distance is known as a light-year. • Aside from the sun, the closet star to Earth is 4.2 light-years away.

12. Chapter 26 Section 1 Viewing the Universe Observing Space • What we see in the universe is light that was formed a long time ago. • It take light from the sun about 8 min. to reach the earth.

13. Chapter 26 Section 1 Viewing the Universe Electromagnetic Spectrum • electromagnetic spectrum all of the frequencies or wavelengths of electromagnetic radiation. • Light, radio waves, and X rays are all examples of electromagnetic radiation. • The radiation is composed of traveling waves of electric and magnetic fields that oscillate at fixed frequencies and wavelengths.

14. Chapter 26 Section 1 Viewing the Universe Visible Electromagnetic Radiation • Though all light travels at the same speed, different colors of light have different wavelengths. These colors can be seen when visible light is passed through a spectrum. • The human eye can see only radiation of wavelengths in the visible light range of the spectrum.

15. Chapter 26 Section 1 Viewing the Universe Visible Electromagnetic Radiation • Electromagnetic radiation shorter or longer than wavelengths of violet or red light cannot be seen by humans. • The shortest visible wavelength of light are blue and violet, while the longest visible wavelength of light are orange and red.

16. The Electromagnetic Spectrum

17. Section 1 Viewing the Universe Reading check Which type of electromagnetic radiation can be seen by humans?

18. Chapter 26 Section 1 Viewing the Universe Reading check Which type of electromagnetic radiation can be seen by humans? The only kind of electromagnetic radiation the human eye can detect is visible light.

19. Chapter 26 Section 1 Viewing the Universe Invisible Electromagnetic Radiation • Invisible wavelengths include infrared waves, microwaves, radio waves, ultraviolet rays, X rays, and gamma rays, and are detected only by instruments. • In 1852, a scientist named Sir Frederick William Herschel discovered infrared, which means “below the red.”Infrared is radiation that has waves longer than waves of visible light. • Ultravioletmeans “beyond the violet” and has wavelengths shorter than waves of visible light.

20. Chapter 26 Section 1 Viewing the Universe Telescopes • telescope an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation. • In 1609, an Italian scientist, Galileo, heard of a device that used two lenses to make distant objects appear closer. • Telescopes that collect only visible light are called optical telescopes.

21. Chapter 26 Section 1 Viewing the Universe Telescopes • The two types of optical telescopes are refracting telescopes and reflecting telescopes.

22. Optical Telescopes • Refractors • Focus light with refraction: bend light path in transparent medium • Use lenses • First kind made • Kind used by Galileo • Reflectors • Focus light by reflection: bounce light off a solid medium • Use mirrors • First designed and created by Sir Isaac Newton • Many different designs

23. Chapter 26 Section 1 Viewing the Universe Refracting Telescopes • refracting telescope a telescope that uses a set of lenses to gather and focus light from distant objects • The bending of light is called refraction. • Refracting telescopes have an objective lens that bends light that passes through the lens and focuses the light to be magnified by an eyepiece.

24. Chapter 26 Section 1 Viewing the Universe Refracting Telescopes

25. Image of source is formed on focal plane and magnified by eyepiece. First Optical Telescopes:Refractors

26. Chapter 26 Section 1 Viewing the Universe Refracting Telescopes • One problem with refracting telescopes is that the lens focuses different colors of light at different distances causing the image to distort. • Another problem is that objective lenses that are too large will sag under their own weight and cause images to become distorted.

27. Dispersion of light through optical material causes blue component of light passing through lens to be focused slightly closer to lens than red component. Known as chromatic aberration. Chromatic Aberration

28. Chapter 26 Section 1 Viewing the Universe Reflecting Telescopes • In the mid-1600s Isaac Newton solved the problem of color separation that resulted from the use of lenses. • reflecting telescopes a telescope that uses a curved mirror to gather and focus light from distant objects

29. Chapter 26 Section 1 Viewing the Universe Reflecting Telescopes

30. Reflecting Telescopes

31. Chapter 26 Section 1 Viewing the Universe Reflecting Telescopes • When light enters a reflecting telescope, the light is reflected by a large curved mirror to a second mirror. The second mirror reflects the light to the eyepiece, where the image is magnified and focused. • Unlike refracting telescopes, reflecting telescopes can be made very large without affecting the quality of the image.

32. Chapter 26 Section 1 Viewing the Universe Reading check What are the problems with refracting telescopes?

33. Chapter 26 Section 1 Viewing the Universe Reading check, continued What are the problems with refracting telescopes? Images produced by refracting telescopes are subject to distortion because of the way different colors of visible light are focused at different distances from the lens and because of weight limitations on the objective lens.

34. Chapter 26 Maps in Action Maps in Action Light Sources

35. Chapter 26 Section 1 Viewing the Universe Telescopes for Invisible Electromagnetic Radiation • Scientists have developed telescopes that detect invisible radiation, such as a radiotelescope for radio waves. • Ground-based telescopes work best at high elevations, where the air is dry.

36. Chapter 26 Section 1 Viewing the Universe Telescopes for Invisible Electromagnetic Radiation • The only way to study many forms of radiation is from space because the Earth’s atmosphere acts as a shield against many forms of electromagnetic radiation.

37. Chapter 26 Section 1 Viewing the Universe Space-Based Astronomy • Space telescopes have been launched to investigate planets, stars, and other distant objects • In space, Earth’s atmosphere cannot interfere with the detection of electromagnetic radiation.

38. Chapter 26 Section 1 Viewing the Universe Reading check Why do scientists launch spacecraft beyond Earth’s atmosphere?

39. Chapter 26 Section 1 Viewing the Universe Reading check, continued Why do scientists launch spacecraft beyond Earth’s atmosphere? Scientists launch spacecraft into orbit to detect radiation screened out by Earth’s atmosphere and to avoid light pollution and other atmospheric distortions.

40. Chapter 26 Section 1 Viewing the Universe Space-Based Astronomy • A space telescope does not have to view the stars through the earths atmosphere. • The same telescope in space will see many times further than on earth.

41. Chapter 26 Section 1 Viewing the Universe Space Telescopes • The Hubble Space Telescope collects electromagnetic radiation from objects in space. • The Chandra X-ray Observatory makes remarkably clear images using X rays from objects in space, such as remnants of exploded stars. • The Compton Gamma Ray Observatory detected gamma rays from objects, such as black holes. • The James Webb Space Telescope will detect infrared radiation from objects in space after it is launched in 2011.

42. Hubble Space Telescope • Launched from the Space Shuttle in 1990. • Largest telescope in space: 2.4 meter mirror. • Mirror has an optical flaw (spherical aberration). • Hubble was fixed by astronauts in 1994. • Hubble has higher resolution and gathers more light than most Earth-based telescopes.

43. Our Sun in Different Wavelengths Visible (BBSO) X-Ray (Yohkoh) Ultraviolet (SOHO) Infrared (NSO) Radio (Nobeyama)

44. x-ray far UV near UV infrared radio visible Crab Nebula at Different Wavelengths

45. Chapter 26 Section 1 Viewing the Universe Other Spacecraft • Since the early 1960s, spacecraft have been sent out of Earth’s orbit to study other planets. • The Voyager 1 and Voyager 2 spacecraft investigated Jupiter, Saturn, Uranus, and Neptune, and collected images of these planets and their moons. • The Galileospacecraft orbited Jupiter and its moons from 1995 to 2003. • The Cassini-Huygens spacecraft will study Titan, Saturn’s largest moon. Like Earth, Titan has an atmosphere that is rich in nitrogen. Scientists hope to learn more about the origins of Earth by studying Titan.

46. Chapter 26 Section 1 Viewing the Universe Human Space Exploration • Spacecraft that carry only instruments and computers are described as robotic and can travel beyond the solar system. • The first humans went into space in the 1960’s. Between 1969 and 1972, NASA landed 12 people on the moon. Humans have never gone beyond Earth’s moon. • The loss of two space shuttles and their crews, the Challengerin 1986 and the Columbia in 2003, have focused public attention on the risks of human space exploration.

47. Chapter 26 Section 1 Viewing the Universe Spinoffs of the Space Program • Satellites in orbit provide information about weather all over Earth. • Other satellites broadcast television signals from around the world or allow people to navigate cars and airplanes. • Even medical equipment, like the heart pump, have been improved based on NASA’s research on the flow of fluids through rockets.

48. Section 2 Movements of the Earth Chapter 26 Objectives • Describe two lines of evidence for Earth’s rotation. • Explain how the change in apparent positions of constellations provides evidence of Earth’s rotation and revolution around the sun. • Summarize how Earth’s rotation and revolution provide a basis for measuring time. • Explain how the tilt of Earth’s axis and Earth’s movement cause seasons.

49. Section 2 Movements of the Earth Chapter 26 The Rotating Earth rotationthe spin of a body on its axis • Each complete rotation takes about one day. • The Earth rotates from west to east. At any given moment, the hemisphere of Earth that faces the sun experiences daylight. At the same time, the hemisphere of Earth that faces away from the sun experiences nighttime. • These movements of Earth are also responsible for the seasons and changes in weather.

50. Section 2 Movements of the Earth Chapter 26 The Foucault Pendulum • In the 19th century, the scientist Jean-Bernard-Leon Foucault, provided evidence of Earth’s rotation by using a pendulum. • The path of the pendulum appeared to change over time. However, the path does not actually change. Instead, the Earth moves the floor as Earth rotates on its axis.