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
Robotic-are spacecraft that carry only instruments and computers
Humans never went past moon
, 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. Ellipse-closed curve, shape is determined by 2 pts w/in ellipse
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