93000000mi / 186000(mi/s) _____________________ 60(sec/min)

1. Drill: Earth is roughly 93,000,000 miles from the Sun. Light travels 186,000 miles per sec. How long does it take for light leaving the sun to reach the earth? 93000000mi / 186000(mi/s) _____________________ 60(sec/min) =8.3 min

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

3. Section 1 Viewing the Universe Chapter 26 The Value of Astronomy astronomy the scientific study of the universe • Scientists who study the universe are called astronomers • In the process of observing the universe, 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.

4. Section 1 Viewing the Universe Chapter 26 The Value of Astronomy, continued • 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. • Astronomical research is supported by federal agencies, such as the National Science Foundation and NASA. Private foundations and industry also fund research in astronomy

5. Chapter 26 Section 1 Viewing the Universe Characteristics of the Universe Organization of the Universe Galaxy: a collection of stars, dust, and gas bound together by gravity • 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. • 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.

6. Chapter 26 Section 1 Viewing the Universe Measuring Distances in the Universe astronomical unit the average distance between the Earth and the sun; approximately 93 million miles or 150 million kilometers (symbol, AU) • Astronomers also use the speed of light to measure distance. • Light travels at 186,000mi/sec or 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.

7. Section 1 Viewing the Universe Chapter 26 Observing Space 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.

8. Chapter 26 Section 1 Viewing the Universe Observing Space, continued 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. • 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.

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

10. Chapter 26 Section 1 Viewing the Universe Invisible Electromagnetic Radiation • Invisible wavelengths cannot be seen by the human eye. They 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 electromagnetic radiation that has waves longer than waves of visible light. Ultraviolet means “beyond the violet” and has wavelengths shorter than waves of visible light.

13. Visible spectrum

14. Infra Red Spectrum

15. X-Ray Spectrum

16. Micro / Radiowave spectrum

17. Ultraviolet Spectrum

19. Left shows ancient terrain of Egypt using radar

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. • The two types of optical telescopes are refracting telescopes and reflecting telescopes.

21. 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. • 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.

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

23. Chapter 26 Section 1 Viewing the Universe Telescopes, continued The diagram below shows reflecting and refracting telescopes.

24. 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.

25. 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. • 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.

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

27. Chapter 26 Section 1 Viewing the Universe 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.

28. 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.

29. 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 Galileo spacecraft 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.

30. 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 Challenger in 1986 and the Columbia in 2003, have focused public attention on the risks of human space exploration.

31. 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.