Ch 26-Studying Space

1. Ch 26-Studying Space • Objectives • Describe the characteristics of the universe in terms of time, distance, organization • Visible and nonvisible parts of electromagentic spectrum • Refracting and reflecting teloscopes • Explain how telescopes for nonvisible electromagnetic radiation differ from light telescopes • 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

2. Characteristics of Universe • How have people studied the sky in the past? What is astronomy? • Scientific study of the universe • Astronomers • Why is astronomy important? • Cosmology-study of origin, properties, processes, and evolution of universe • Big bang-big explosion 14 billion yrs ago • Universe-large and objects far apart • What tools are used to see distant objects?

3. Organization of Universe • What makes up the solar system? • Sun, Earth, other planets, asteroids and comets • Galaxy-collection of stars, dust, and gas bound together by gravity • What galaxy do reside in? • Milky Way • Beyond are billions of other galaxies

4. Measuring Distances in Universe • Approximately 150 million km between Earth and sun-this is known as astronomical unit • Use speed of light to measure distance • Travels at 300,000 km/s • Light yr-light travels 9.46 x 10^12 km • Closet star other than the sun to Earth=4.22 light yrs away

5. Observing Space • Electromagnetic spectrum-all frequencies or wavelengths of electromagnetic radiation • Light, radio waves, x rays • Visible electromagnetic radiation-different colors result because each color of light has characteristic wavelength • Shortest wavelengths-blue and violet, longest-red and orange • Wavelengths not visible-infrared waves, microwaves, radio waves, ultraviolet rays, x rays, gamma rays

6. Models of Solar System • Aristole-model in which Earth was center, everything revolved around Earth • Ptolemy-planets moved in small circles-epicycles, revolved around in larger circles around Earth • Copernicus-sun centered, planets revolved around sun in same direction but at different speeds and distances from sun

7. Kepler’s Laws • Law of ellipses-Each planet orbits the sun in a path called a ellipse, not a circle • Elliptical orbits can vary in shape • Eccentricity-degree of elongation of an elliptical orbit • Law of equal areas-objects travel at different speeds in their orbits, equal areas are covered in equal amounts of time as an object orbits the sun • Mars travels fastest when closet to sun • Law of periods-describes the relationship between average distance between planet and sun and orbital period of planet • What is orbital period?

8. Newton • Hypothesized moving objects will keep moving and resist change in speed until acted upon by outside force • Inertia-tendency of an object to resist being moved or resist change in speed or direction until outside force acts on object • Newton’s Model of Orbits-gravity causes the orbit to curve • Gravity pulls object toward sun, inertia keeps object moving forward in straight line • Weaker gravitational pull further away from sun • Longer orbits=outer planets

9. Telescopes • Who constructed the 1st telescope? • Galileo, 1609, viewed craters on moon and Milky Way • Instrument that collects electromagnetic radiation from the sky and concentrates it for better observation • Optical telescopes-only collect visible light • Refracting telescopes-uses a set of lenses to gather and focus light from distant objects • Focuses different colors of light at different distances • Reflecting-uses curved mirror to gather and focus light from distant objects • Issac Newton • Gather more light than refracting

10. Telescopes for Invisible Electromagnetic Radiation • Telescopes that detect invisible radiation • Earth’s atmosphere acts as shield against many forms of electromagnetic radiation • Prevents short wavelengths from reaching Earth’s surface • Only way to study many forms of radiation is from space

11. Space Based Astronomy • Space telescopes-launched into space to collect electromagnetic radiation from objects in space • Examples-Hubble Space Telescope, Chandra X-ray Observatory, Compton Gamma Ray Observatory, Spitzer Space, James Webb Space Telescope • Voyager 1 and 2 investigated Jupiter, Saturn, Uranus, Neptune in 1977 • Galileo investigated Jupiter and moons from 1995-2000 • Robotic-are spacecraft that carry only instruments and computers • Humans never went past moon • 1969-1972, 12 people landed on moon by NASA • Mars • Welcome to Discovery Education Player • Challenger and Columbia

12. Sec 2-Movements of Earth • Rotation-spin of a body on its axis, complete rotation= 1 day • How do scientists know Earth rotates? • Foucault pendulum-evidence of Earth’s rotation by using pendulum • Jean Bernard Leon Foucault • Coriolis Effect-movement of ocean surface currents and wind belts by rotation of Earth • Revolution-motion of a body that travels around another body in space

13. Orbit-the path that a body follows as it travels around another body in space • Ellipse-closed curve, shape is determined by 2 pts w/in ellipse • Earth orbits the sun in a ellipse • Perihelion-pt in orbit of a planet at which planet is closest to sun • Aphelion-pt in orbit of a planet at which the planet is farthest from sun

14. Constellations and Earth’s Moon • What is a constellation? • Group of stars organized in recognizable pattern • 88 constellations • Greek names-2000 yrs ago • Earth moves, constellations do not. Rotation of Earth on its axis causes change in position • Earth’s revolution, causes positions to change over several weeks • Different constellations will appear in night sky as seasons change

15. Measuring Time • Day and yr are based on periods of Earth’s motion • Rotation=1 day • Revolution=365 ¼ days • Formation of calendar-created for measuring long intervals of time by dividing time into periods of days, weeks, months, and yrs • Who created calendar? • Egyptians, Bablonians, Aztecs • Extra ¼ day added to February, leap yr • Modern calendar-keep calendar aligned w/ seasons-Pope Gregory XIII

16. Time zones- Earth divided into 24 time zones • Earth’s time zones cover about 15 deg each • International date line-runs N to S through P ocean. Friday west, Thursday east • No islands or continents • Day light saving time-clocks set 1 hr ahead of standard time in April, set back to standard time in october • No daylight savings time in equatorial region-12 hrs of day

17. Seasons • Axis tilted at 23.5 deg • Sun rays change as Earth moves toward orbit • Seasonal Weather-changes in angle at which the sun’s rays strike Earth’s surface cause the seasons • N Pole tilted away from sun in winter • Equinoxes-moment when sun appears to cross the celestial equator-line drawn on sky directly overhead from equator on Earth • Autumnal equinox-Sept 22 or 23 • Vernal equinox-Mar 21 or 22 • Summer solstices-pt at which sun is as far N or as far S of equator as possible. June 21 or 22 • 24 hrs of daylight during summer solstice at Arctic Circle, opposite at Antarctica • Winter solstices-N Pole is titled to farthest pt away from sun. Dec 21 or 22